Gene Summary

Gene:RBL2; RB transcriptional corepressor like 2
Aliases: Rb2, P130
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:retinoblastoma-like protein 2
Source:NCBIAccessed: 11 March, 2017


What does this gene/protein do?
Show (15)
Pathways:What pathways are this gene/protein implicaed in?
Show (2)

Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 11 March 2017 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Nasopharyngeal Cancer
  • Promoter Regions
  • Tumor Virus Infections
  • Transfection
  • Retinoblastoma
  • Cancer Gene Expression Regulation
  • Cell Differentiation
  • Melanoma
  • Genes, Retinoblastoma
  • Sequence Homology
  • Neuroblastoma
  • Trinucleotide Repeats
  • Cancer DNA
  • Immunohistochemistry
  • Cell Cycle Proteins
  • Tumor Suppressor Gene
  • RBL1
  • Xenograft Models
  • Base Sequence
  • Molecular Sequence Data
  • T-Lymphocytes
  • Signal Transduction
  • Retinoblastoma-Like Protein p130
  • DNA Mutational Analysis
  • Nuclear Proteins
  • Gene Expression Profiling
  • Chromosome 16
  • Survival Rate
  • Transcription
  • RB1
  • Transcription Factors
  • DNA Methylation
  • Down-Regulation
  • DNA-Binding Proteins
  • Lung Cancer
  • Proteins
  • Cell Cycle
  • Phosphoproteins
  • Thrombocytosis
  • Cell Proliferation
  • Mutation
  • Urinary Tract
  • Endometrial Cancer
Tag cloud generated 11 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (7)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: RBL2 (cancer-related)

Lee J, Jung JH, Chae YS, et al.
Long Noncoding RNA snaR Regulates Proliferation, Migration and Invasion of Triple-negative Breast Cancer Cells.
Anticancer Res. 2016; 36(12):6289-6295 [PubMed] Related Publications
AIM: We evaluated the role of long noncoding ribonucleic acid (lncRNA) in breast cancer cell lines by quantitative reverse transcription-polymerase change reaction.
MATERIALS AND METHODS: The effects of small NF90-associated RNA (snaR) with RNA interference on proliferation, migration and invasion of MDA-MB-231 cells were observed by 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide, wound healing and transwell assay.
RESULTS: Among 90 lncRNAs, E2F transcription factor 4, p107/p130-binding (E2F4) antisense, insulin-like growth factor 2 antisense (IGF2AS), snaR, and small nucleolar RNA host gene 5 (SNHG5) were up-regulated in MDA-MB-231 and 7SK, antisense noncoding RNA in the INK4 locus (ANRIL), IGF2AS, Nespas, p53 mRNA, and snaR were up-regulated in MCF-7 cells. Down-regulation of snaR inhibited the proliferation, migration, and invasion of MDA-MD-231 breast cancer cells.
CONCLUSION: LncRNA snaR was found to be up-regulated in breast cancer cells, and the cancer progression of MDA-MB-231 cells was significantly suppressed by down-regulation of snaR. Therefore, snaR knockdown has potential as a treatment modality for triple-negative breast cancer.

Fischer M, Quaas M, Nickel A, Engeland K
Indirect p53-dependent transcriptional repression of Survivin, CDC25C, and PLK1 genes requires the cyclin-dependent kinase inhibitor p21/CDKN1A and CDE/CHR promoter sites binding the DREAM complex.
Oncotarget. 2015; 6(39):41402-17 [PubMed] Free Access to Full Article Related Publications
The transcription factor p53 is central to cell cycle control by downregulation of cell cycle-promoting genes upon cell stress such as DNA damage. Survivin (BIRC5), CDC25C, and PLK1 encode important cell cycle regulators that are repressed following p53 activation. Here, we provide evidence that p53-dependent repression of these genes requires activation of p21 (CDKN1A, WAF1, CIP1). Chromatin immunoprecipitation (ChIP) data indicate that promoter binding of B-MYB switches to binding of E2F4 and p130 resulting in a replacement of the MMB (Myb-MuvB) by the DREAM complex. We demonstrate that this replacement depends on p21. Furthermore, transcriptional repression by p53 requires intact DREAM binding sites in the target promoters. The CDE and CHR cell cycle promoter elements are the sites for DREAM binding. These elements as well as the p53 response of Survivin, CDC25C, and PLK1 are evolutionarily conserved. No binding of p53 to these genes is detected by ChIP and mutation of proposed p53 binding sites does not alter the p53 response. Thus, a mechanism for direct p53-dependent transcriptional repression is not supported by the data. In contrast, repression by DREAM is consistent with most previous findings and unifies models based on p21-, E2F4-, p130-, and CDE/CHR-dependent repression by p53. In conclusion, the presented data suggest that the p53-p21-DREAM-CDE/CHR pathway regulates p53-dependent repression of Survivin, CDC25C, and PLK1.

Mileo AM, Mattarocci S, Matarrese P, et al.
Hepatitis C virus core protein modulates pRb2/p130 expression in human hepatocellular carcinoma cell lines through promoter methylation.
J Exp Clin Cancer Res. 2015; 34:140 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Hepatitis C Virus (HCV) infection is associated with chronically evolving disease and development of hepatocellular carcinoma (HCC), albeit the mechanism of HCC induction by HCV is still controversial. The nucleocapsid (core) protein of HCV has been shown to be directly implicated in cellular transformation and immortalization, enhancing the effect of oncogenes and decreasing the one of tumor suppressor genes, as RB1 and its protein product pRB. With the aim of identifying novel molecular mechanisms of hepatocyte transformation by HCV, we examined the effect of HCV core protein on the expression of the whole Retinoblastoma (RB) family of tumor and growth suppressor factors, i.e. pRb, p107 and pRb2/p130.
METHODS: We used a model system consisting of the HuH-7, HCV-free, human hepatocellular carcinoma cell line and of the HuH-7-CORE cells derived from the former and constitutively expressing the HCV core protein. We determined pRb, p107 and pRb2/p130 protein and mRNA amount of the respective genes RB1, RBL1 and RBL2, RBL2 promoter activity and methylation as well as DNA methyltransferase 1 (DNMT1) and 3b (DNMT3b) expression level. The effect of pRb2/p130 over-expression on the HCV core-expressing HuH-7-CORE cells was also evaluated.
RESULTS: We found that the HCV core protein expression down-regulated pRb2/p130 protein and mRNA levels in HuH-7-CORE cells by inducing promoter hyper-methylation with the concomitant up-regulation of DNMT1 and DNMT3b expression. When pRb2/p130 expression was artificially re-established in HuH-7-CORE cells, cell cycle analysis outlined an accumulation in the G0/G1 phase, as expected.
CONCLUSIONS: HCV core appears indeed able to significantly down-regulate the expression and the function of two out of three RB family tumor and growth suppressor factors, i.e. pRb and pRb2/p130. The functional consequences at the level of cell cycle regulation, and possibly of more complex cell homeostatic processes, may represent a plausible molecular mechanism involved in liver transformation by HCV.

Meng WJ, Pathak S, Ding ZY, et al.
Special AT-rich sequence binding protein 1 expression correlates with response to preoperative radiotherapy and clinical outcome in rectal cancer.
Cancer Biol Ther. 2015; 16(12):1738-45 [PubMed] Free Access to Full Article Related Publications
Our recent study showed the important role of special AT-rich sequence binding protein 1 (SATB1) in the progression of human rectal cancer. However, the value of SATB1 in response to radiotherapy (RT) for rectal cancer hasn't been reported so far. Here, SATB1 was determined using immunohistochemistry in normal mucosa, biopsy, primary cancer, and lymph node metastasis from 132 rectal cancer patients: 66 with and 66 without preoperative RT before surgery. The effect of SATB1 knockdown on radiosensitivity was assessed by proliferation-based assay and clonogenic assay. The results showed that SATB1 increased from normal mucosa to primary cancer, whereas it decreased from primary cancer to metastasis in non-RT patients. SATB1 decreased in primary cancers after RT. In RT patients, positive SATB1 was independently associated with decreased response to preoperative RT, early time to metastasis, and worse survival. SATB1 negatively correlated with ataxia telangiectasia mutated (ATM) and pRb2/p130, and positively with Ki-67 and Survivin in RT patients, and their potential interaction through different canonical pathways was identified in network ideogram. Taken together, our findings disclose for the first time that radiation decreases SATB1 expression and sensitizes cancer cells to confer clinical benefit of patients, suggesting that SATB1 is predictive of response to preoperative RT and clinical outcome in rectal cancer.

Ullah F, Khan T, Ali N, et al.
Promoter Methylation Status Modulate the Expression of Tumor Suppressor (RbL2/p130) Gene in Breast Cancer.
PLoS One. 2015; 10(8):e0134687 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Aberrant expression of tumor suppressor genes may correspond to the abnormal cell development and tumorigenesis. Rbl2/p130, a member of retinoblastoma family of proteins, has growth suppressive properties. Numerous studies reported de-regulation of Rbl2/p130 in various types of cancer as a consequence of a number of genetic alterations. However, role of epigenetic mechanisms like DNA methylation in Rbl2/p130 expression remains elusive.
METHODS: In the current study, 76 breast cancer tumors along with normal tissues (n = 76), blood (n = 76) of respective individuals and control blood (n = 50) were analyzed. Rbl2/p130 expression was analyzed by quantitative real time PCR (syber green method). Promoter methylation status was studied through methylation specific PCR of bisulfite converted genomic DNA. Data was analyzed using various statistical tests.
RESULTS: We report significantly reduced Rbl2/p130 expression (P = 0.001) in tumors tissues as compared to control samples. Similarly, Rbl2/p130 expression varies with age and disease stages (P = 0.022), which suggest its involvement in tumor progression. Aberrant promoter methylation (Δmeth) was found in almost all the diseased samples and that was significantly different (P<0.001) with control samples. Similarly, methylation status varies significantly with tumor progression stages (P = 0.022). Hyper-methylation was observed at -1, +3, +15 and +75 of Rbl2/p130 promoter flanking around the TSS. Statistical analysis revealed that Rbl2/p130 expression negatively correlates to its promoter methylation (r = -0.412) in tumor tissues. Our results reflect an epigenetic regulation of Rbl2/p130 expression in breast cancer. This highlights the importance of Rbl2/p130 promoter methylation in breast cancer pathogenesis.

Cai L, Ye Y, Jiang Q, et al.
Epstein-Barr virus-encoded microRNA BART1 induces tumour metastasis by regulating PTEN-dependent pathways in nasopharyngeal carcinoma.
Nat Commun. 2015; 6:7353 [PubMed] Free Access to Full Article Related Publications
Epstein-Barr virus (EBV), aetiologically linked to nasopharyngeal carcinoma (NPC), is the first human virus found to encode many miRNAs. However, how these viral miRNAs precisely regulate the tumour metastasis in NPC remains obscure. Here we report that EBV-miR-BART1 is highly expressed in NPC and closely associated with pathological and advanced clinical stages of NPC. Alteration of EBV-miR-BART1 expression results in an increase in migration and invasion of NPC cells in vitro and causes tumour metastasis in vivo. Mechanistically, EBV-miR-BART1 directly targets the cellular tumour suppressor PTEN. Reduction of PTEN dosage by EBV-miR-BART1 activates PTEN-dependent pathways including PI3K-Akt, FAK-p130(Cas) and Shc-MAPK/ERK1/2 signalling, drives EMT, and consequently increases migration, invasion and metastasis of NPC cells. Reconstitution of PTEN rescues all phenotypes generated by EBV-miR-BART1, highlighting the role of PTEN in EBV-miR-BART-driven metastasis in NPC. Our findings provide new insights into the metastasis of NPC regulated by EBV and advocate for developing clinical intervention strategies against NPC.

Kumbrink J, Soni S, Laumbacher B, et al.
Identification of Novel Crk-associated Substrate (p130Cas) Variants with Functionally Distinct Focal Adhesion Kinase Binding Activities.
J Biol Chem. 2015; 290(19):12247-55 [PubMed] Free Access to Full Article Related Publications
Elevated levels of p130(Cas) (Crk-associated substrate)/BCAR1 (breast cancer antiestrogen resistance 1 gene) are associated with aggressiveness of breast tumors. Following phosphorylation of its substrate domain, p130(Cas) promotes the integration of protein complexes involved in multiple signaling pathways and mediates cell proliferation, adhesion, and migration. In addition to the known BCAR1-1A (wild-type) and 1C variants, we identified four novel BCAR1 mRNA variants, generated by alternative first exon usage (1B, 1B1, 1D, and 1E). Exons 1A and 1C encode for four amino acids (aa), whereas 1D and 1E encode for 22 aa and 1B1 encodes for 50 aa. Exon 1B is non-coding, resulting in a truncated p130(Cas) protein (Cas1B). BCAR1-1A, 1B1, and variant 1C mRNAs were ubiquitously expressed in cell lines and a survey of human tissues, whereas 1B, 1D, and 1E expression was more restricted. Reconstitution of all isoforms except for 1B in p130(Cas)-deficient murine fibroblasts induced lamellipodia formation and membrane ruffling, which was unrelated to the substrate domain phosphorylation status. The longer isoforms exhibited increased binding to focal adhesion kinase (FAK), a molecule important for migration and adhesion. The shorter 1B isoform exhibited diminished FAK binding activity and significantly reduced migration and invasion. In contrast, the longest variant 1B1 established the most efficient FAK binding and greatly enhanced migration. Our results indicate that the p130(Cas) exon 1 variants display altered functional properties. The truncated variant 1B and the longer isoform 1B1 may contribute to the diverse effects of p130(Cas) on cell biology and therefore will be the target of future studies.

Chung YJ, Kim HJ, Park SH, et al.
Transcriptome analysis reveals that Müllerian inhibiting substance regulates signaling pathways that contribute to endometrial carcinogenesis.
Int J Oncol. 2015; 46(5):2039-46 [PubMed] Related Publications
Müllerian inhibiting substance (MIS) has been shown to inhibit growth of a number of tumors in vitro and/or in vivo, but the downstream pathways which it regulates are not fully understood. In the present study we show that MIS type II receptor was highly expressed in AN3CA cells, a cell line derived from human endometrial cancer cell in which MIS-treatment caused a reduction of cell viability, and induced cellular apoptosis and genes involved cell cycle arrest. To understand the genome-wide effects of MIS on gene regulation, we performed serial gene expression analyses from 0 to 96 h at 24 h intervals after treating AN3CA cells with MIS. Transcriptomic analysis of molecular changes induced by MIS identified 2,688 differentially expressed genes that were significantly up- or down-regulated during the 96 h study period. When the 2,688 differentially expressed genes were mapped to known biological processes, Wnt-, cancer-, proteolysis-, cytoskeleton-, cell cycle-, apoptosis-, and MAPK-signaling pathways emerged as the functions most significantly changed by MIS in AN3CA cells. Furthermore, western blot analysis validated that protein expression of cell cycle inhibitory genes, apoptotic protease activating factor-1 (APAF-1), β-catenin-interacting protein (ICAT), Rb related protein 130 (p130), and inhibitor of disheveled Dvl and Axin complex (IDAX), were gradually increased over the time of the study, whereas downstream cell cycle activating genes, cyclin-dependent kinase 2 (CDK2) and phospho-c-Jun were downregulated in MIS-treated AN3CA cells. These transcriptome analyses support previous observations that MIS functions as a tumor suppressor, potentially by regulating signaling pathways that could contribute to endometrial carcinogenesis, and indicating that MIS should be considered as a potential treatment for endometrial cancer.

Schwentner R, Papamarkou T, Kauer MO, et al.
EWS-FLI1 employs an E2F switch to drive target gene expression.
Nucleic Acids Res. 2015; 43(5):2780-9 [PubMed] Free Access to Full Article Related Publications
Cell cycle progression is orchestrated by E2F factors. We previously reported that in ETS-driven cancers of the bone and prostate, activating E2F3 cooperates with ETS on target promoters. The mechanism of target co-regulation remained unknown. Using RNAi and time-resolved chromatin-immunoprecipitation in Ewing sarcoma we report replacement of E2F3/pRB by constitutively expressed repressive E2F4/p130 complexes on target genes upon EWS-FLI1 modulation. Using mathematical modeling we interrogated four alternative explanatory models for the observed EWS-FLI1/E2F3 cooperation based on longitudinal E2F target and regulating transcription factor expression analysis. Bayesian model selection revealed the formation of a synergistic complex between EWS-FLI1 and E2F3 as the by far most likely mechanism explaining the observed kinetics of E2F target induction. Consequently we propose that aberrant cell cycle activation in Ewing sarcoma is due to the de-repression of E2F targets as a consequence of transcriptional induction and physical recruitment of E2F3 by EWS-FLI1 replacing E2F4 on their target promoters.

Vilas JM, Ferreirós A, Carneiro C, et al.
Transcriptional regulation of Sox2 by the retinoblastoma family of pocket proteins.
Oncotarget. 2015; 6(5):2992-3002 [PubMed] Free Access to Full Article Related Publications
Cellular reprogramming to iPSCs has uncovered unsuspected links between tumor suppressors and pluripotency factors. Using this system, it was possible to identify tumor suppressor p27 as a repressor of Sox2 during differentiation. This led to the demonstration that defects in the repression of Sox2 can contribute to tumor development. The members of the retinoblastoma family of pocket proteins, pRb, p107 and p130, are negative regulators of the cell cycle with tumor suppressor activity and with roles in differentiation. In this work we studied the relative contribution of the retinoblastoma family members to the regulation of Sox2 expression. We found that deletion of Rb or p130 leads to impaired repression of Sox2, a deffect amplified by inactivation of p53. We also identified binding of pRb and p130 to an enhancer with crucial regulatory activity on Sox2 expression. Using cellular reprogramming we tested the impact of the defective repression of Sox2 and confirmed that Rb deficiency allows the generation of iPSCs in the absence of exogenous Sox2. Finally, partial depletion of Sox2 positive cells reduced the pituitary tumor development initiated by Rb loss in vivo. In summary, our results show that Sox2 repression by pRb is a relevant mechanism of tumor suppression.

Rashid NN, Yusof R, Watson RJ
A B-myb--DREAM complex is not critical to regulate the G2/M genes in HPV-transformed cell lines.
Anticancer Res. 2014; 34(11):6557-63 [PubMed] Related Publications
BACKGROUND/AIM: It is well-established that HPV E7 proteins, encoded by human papillomavirus (HPV) genes, frequently associated with cervical cancers bind avidly to the retinoblastoma (RB) family of pocket proteins and disrupt their association with members of the E2F transcription factor family. Our previous study showed that the repressive p130-dimerization partner, RB-like, E2F and multi-vulval class (DREAM) complex was disrupted by HPV16 E7 proteins in order to maintain the viral replication in CaSki cells. However, we would like to address whether the activator B-myb-DREAM complex is critical in regulating the replication and mitosis phase since our previous study showed increased B-myb-DREAM expression in HPV-transformed cell lines when compared to control cells.
RESULTS: The association of B-myb with both LIN-54 and LIN-9 was equally decreased by depleting LIN-54 in CaSki cells. Flow cytometry analysis showed that LIN-54 depletion caused an increased proportion of G2/M cells in T98G, SiHa and CaSki cells. The mRNA levels of certain S/G2 genes such as cyclin B, aurora kinase A and Polo-like kinase 1 have demonstrated a marginal increased in CaSki-Lin-54-depleted cells when compared to SiHa- and T98G-Lin-54-depleted cells. We further confirmed this experiment by depleting the B-myb itself in CaSki cells and the results showed the same pattern of cell cycle and mRNA levels for S/G2 genes when compared to LIN-54- and LIN-9-depleted cells.
CONCLUSION: The B-myb-DREAM complex might not be vital for progression through mitosis in cells lacking a G1/S checkpoint and not as crucial as the p130-DREAM complex for the survival of the HPV virus.

Xu XL, Singh HP, Wang L, et al.
Rb suppresses human cone-precursor-derived retinoblastoma tumours.
Nature. 2014; 514(7522):385-8 [PubMed] Free Access to Full Article Related Publications
Retinoblastoma is a childhood retinal tumour that initiates in response to biallelic RB1 inactivation and loss of functional retinoblastoma (Rb) protein. Although Rb has diverse tumour-suppressor functions and is inactivated in many cancers, germline RB1 mutations predispose to retinoblastoma far more strongly than to other malignancies. This tropism suggests that retinal cell-type-specific circuitry sensitizes to Rb loss, yet the nature of the circuitry and the cell type in which it operates have been unclear. Here we show that post-mitotic human cone precursors are uniquely sensitive to Rb depletion. Rb knockdown induced cone precursor proliferation in prospectively isolated populations and in intact retina. Proliferation followed the induction of E2F-regulated genes, and depended on factors having strong expression in maturing cone precursors and crucial roles in retinoblastoma cell proliferation, including MYCN and MDM2. Proliferation of Rb-depleted cones and retinoblastoma cells also depended on the Rb-related protein p107, SKP2, and a p27 downregulation associated with cone precursor maturation. Moreover, Rb-depleted cone precursors formed tumours in orthotopic xenografts with histological features and protein expression typical of human retinoblastoma. These findings provide a compelling molecular rationale for a cone precursor origin of retinoblastoma. More generally, they demonstrate that cell-type-specific circuitry can collaborate with an initiating oncogenic mutation to enable tumorigenesis.

Cito L, Indovina P, Forte IM, et al.
pRb2/p130 localizes to the cytoplasm in diffuse gastric cancer.
J Cell Physiol. 2015; 230(4):802-5 [PubMed] Related Publications
pRb2/p130 is a key tumor suppressor, whose oncosuppressive activity has mainly been attributed to its ability to negatively regulate cell cycle by interacting with the E2F4 and E2F5 transcription factors. Indeed, pRb2/p130 has been found altered in various cancer types in which it functions as a valuable prognostic marker. Here, we analyzed pRb2/p130 expression in gastric cancer tissue samples of diffuse histotype, in comparison with their normal counterparts. We found a cytoplasmic localization of pRb2/p130 in cancer tissue samples, whereas, in normal counterparts, we observed the expected nuclear localization. pRb2/p130 cytoplasmic delocalization can lead to cell cycle deregulation, but considering the emerging involvement of pRb2/p130 in other key cellular processes, it could contribute to gastric tumorigenesis also through other mechanisms. Our data support the necessity of further investigations to verify the possibility of using pRb2/p130 as a biomarker or potential therapeutic target for diffuse gastric cancer.

Shi J, Zhuang Y, Liu XK, et al.
TGF-beta induced RBL2 expression in renal cancer cells by down-regulating miR-93.
Clin Transl Oncol. 2014; 16(11):986-92 [PubMed] Related Publications
PURPOSE: TGF-beta can induce G1 arrest via many mechanisms including up-regulating p21, p27, and Rb. However, as the member of Rb family, whether RBL2 is induced by TGF-beta treatment remains exclusive.
METHODS: The expression of RBL2 and miR-93 after TGF-beta treatment was determined by quantitative real-time PCR and western blot. The growth of renal cancer cells was determined by CCK-8 assays and cell cycle was determined by PI staining. The binding of miR-93 on RBL2 3'-UTR was determined by double luciferase system.
RESULTS: In renal cancer cells, TGF-beta treatment induced expression of RBL2 in a time- and concentration-dependent manner, and RBL2 mediated TGF-beta induced growth inhibition and cell cycle arrest in renal cancer cells. Furthermore, we found that miR-93 directly targeted RBL2 by binding to its 3'-UTR in renal cancer cells. Over-expression of miR-93 significantly reduced the expression of RBL2, whereas knock down of miR-93 up-regulated the expression of RBL2. More importantly, TGF-beta treatment inhibited miR-93 expression, which resulted in up-regulation of RBL2 after TGF-beta treatment.
CONCLUSION: TGF-beta induced RBL2 expression through down-regulating miR-93 in renal cancer cells. The newly identified TGF-beta/miR-93/RBL2 signal pathway reveals a new mechanism of TGF-beta induced growth arrest in renal cancer.

Butcher LD, Garcia M, Arnold M, et al.
Immune response to JC virus T antigen in patients with and without colorectal neoplasia.
Gut Microbes. 2014; 5(4):468-75 [PubMed] Related Publications
JC virus (JCV) is a polyomavirus that infects approximately 75% of the population and encodes a T antigen (T-Ag) gene, which is oncogenic and inactivates the p53 and pRb/p107/p130 protein families. Previous work in our lab has identified the presence of T-Ag in colorectal neoplasms. While JCV remains in a latent state for the majority of those infected, we hypothesized that a disturbance in immunological control may permit JCV to reactivate, which may be involved in the development of colorectal neoplasia. Our aim was to determine the cell mediated immune response to JCV T-Ag, and determine if it is altered in patients with colorectal adenomatous polyps (AP) or cancers (CRC). Peripheral blood mononuclear cells (PBMCs) isolated from the blood of patients undergoing colonoscopy or colorectal surgery were stimulated by a peptide library covering the entire T-Ag protein of JCV. Cytokine production and T cell proliferation were evaluated following T-Ag stimulation using Luminex and flow cytometry assays. JCV T-Ag peptides stimulated secretion of IL-2, which induced T cell expansion in all three groups. However, stronger IL-10 and IL-13 production was seen in patients without colorectal neoplasms. IP-10 was produced at very high levels in all groups, but not significantly differently between groups. Most patients exhibited CD4(+) and CD8(+) T cells in response to stimulation by the T-Ag clusters. The combination of IL-2 and IP-10 secretion indicates the presence of T-Ag-specific Th1 cells in all patients, which is higher in patients without carcinoma.

Murali A, Nalinakumari KR, Thomas S, Kannan S
Association of single nucleotide polymorphisms in cell cycle regulatory genes with oral cancer susceptibility.
Br J Oral Maxillofac Surg. 2014; 52(7):652-8 [PubMed] Related Publications
Alterations in the regulation of the cell cycle are strongly linked to tumorigenesis, so genetic variants in genes critical to control of the cycle are good candidates to have their association with susceptibility to oral cancer assessed. In this hospital-based, case-control study of 445 patients who had been newly-diagnosed with oral cancer and 449 unaffected controls, we used a multigenic approach to examine the associations among a panel of 10 selected polymorphisms in the pathway of the cell cycle that were possibly susceptible to oral cancer. Six of 9 single nucleotide polymorphisms in the cell cycle showed significant risks for oral cancer, the highest risk being evident for p27 (rs34329; Odds ratio 3.05, 95% CI 2.12 to 4.40). A significant risk of oral cancer was also evident for individual polymorphisms of cyclin E (rs1406), cyclin H (rs3093816), cyclin D1-1 (rs647451), cyclin D2 (rs3217901) and Rb1-2 (rs3092904). The risk of oral cancer increased significantly as the number of unfavourable genotypes in the pathway increased, and so the results point to a stronger combined effect of polymorphisms in important cell cycle regulatory genes on predisposition to oral cancer.

Kleinman CL, Gerges N, Papillon-Cavanagh S, et al.
Fusion of TTYH1 with the C19MC microRNA cluster drives expression of a brain-specific DNMT3B isoform in the embryonal brain tumor ETMR.
Nat Genet. 2014; 46(1):39-44 [PubMed] Related Publications
Embryonal tumors with multilayered rosettes (ETMRs) are rare, deadly pediatric brain tumors characterized by high-level amplification of the microRNA cluster C19MC. We performed integrated genetic and epigenetic analyses of 12 ETMR samples and identified, in all cases, C19MC fusions to TTYH1 driving expression of the microRNAs. ETMR tumors, cell lines and xenografts showed a specific DNA methylation pattern distinct from those of other tumors and normal tissues. We detected extreme overexpression of a previously uncharacterized isoform of DNMT3B originating at an alternative promoter that is active only in the first weeks of neural tube development. Transcriptional and immunohistochemical analyses suggest that C19MC-dependent DNMT3B deregulation is mediated by RBL2, a known repressor of DNMT3B. Transfection with individual C19MC microRNAs resulted in DNMT3B upregulation and RBL2 downregulation in cultured cells. Our data suggest a potential oncogenic re-engagement of an early developmental program in ETMR via epigenetic alteration mediated by an embryonic, brain-specific DNMT3B isoform.

Tokuhisa Y, Lidsky ME, Toshimitsu H, et al.
SRC family kinase inhibition as a novel strategy to augment melphalan-based regional chemotherapy of advanced extremity melanoma.
Ann Surg Oncol. 2014; 21(3):1024-30 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Src kinase inhibition has been shown to augment the efficacy of chemotherapy. Dasatinib, a dual Src/Abl kinase inhibitor approved for the treatment of CML, is under investigation as monotherapy for tumors with abnormal Src signaling, such as melanoma. The goal of this study was to determine if Src kinase inhibition using dasatinib could enhance the efficacy of regionally administered melphalan in advanced extremity melanoma.
METHODS: The mutational status of c-kit and patterns of gene expression predictive of dysregulated Src kinase signaling were evaluated in a panel of 26 human melanoma cell lines. The effectiveness of dasatinib was measured by quantifying protein expression and activation of Src kinase, focal adhesion kinase, and Crk-associated substrate (p130(CAS)), in conjunction with in vitro cell viability assays using seven melanoma cell lines. Utilizing a rat model of regional chemotherapy, we evaluated the effectiveness of systemic dasatinib in conjunction with regional melphalan against the human melanoma cell line, DM443, grown as a xenograft.
RESULTS: Only the WM3211 cell line harbored a c-kit mutation. Significant correlation was observed between Src-predicted dysregulation by gene expression and sensitivity to dasatinib in vitro. Tumor doubling time for DM443 xenografts treated with systemic dasatinib in combination with regional melphalan (44.8 days) was significantly longer (p = 0.007) than either dasatinib (21.3 days) or melphalan alone (24.7 days).
CONCLUSIONS: Systemic dasatinib prior to melphalan-based regional chemotherapy markedly improves the efficacy of this alkylating agent in this melanoma xenograft model. Validation of this concept should be considered in the context of a regional therapy clinical trial.

Suzuki K, Sakaguchi M, Tanaka S, et al.
Prolyl oligopeptidase inhibition-induced growth arrest of human gastric cancer cells.
Biochem Biophys Res Commun. 2014; 443(1):91-6 [PubMed] Related Publications
Prolyl oligopeptidase (POP) is a serine endopeptidase that hydrolyzes post-proline peptide bonds in peptides that are <30 amino acids in length. We recently reported that POP inhibition suppressed the growth of human neuroblastoma cells. The growth suppression was associated with pronounced G0/G1 cell cycle arrest and increased levels of the CDK inhibitor p27(kip1) and the tumor suppressor p53. In this study, we investigated the mechanism of POP inhibition-induced cell growth arrest using a human gastric cancer cell line, KATO III cells, which had a p53 gene deletion. POP specific inhibitors, 3-({4-[2-(E)-styrylphenoxy]butanoyl}-l-4-hydroxyprolyl)-thiazolidine (SUAM-14746) and benzyloxycarbonyl-thioprolyl-thioprolinal, or RNAi-mediated POP knockdown inhibited the growth of KATO III cells irrespective of their p53 status. SUAM-14746-induced growth inhibition was associated with G0/G1 cell cycle phase arrest and increased levels of p27(kip1) in the nuclei and the pRb2/p130 protein expression. Moreover, SUAM-14746-mediated cell cycle arrest of KATO III cells was associated with an increase in the quiescent G0 state, defined by low level staining for the proliferation marker, Ki-67. These results indicate that POP may be a positive regulator of cell cycle progression by regulating the exit from and/or reentry into the cell cycle by KATO III cells.

Chung J, Karkhanis V, Tae S, et al.
Protein arginine methyltransferase 5 (PRMT5) inhibition induces lymphoma cell death through reactivation of the retinoblastoma tumor suppressor pathway and polycomb repressor complex 2 (PRC2) silencing.
J Biol Chem. 2013; 288(49):35534-47 [PubMed] Free Access to Full Article Related Publications
Epigenetic regulation mediated by lysine- and arginine-specific enzymes plays an essential role in tumorigenesis, and enhanced expression of the type II protein arginine methyltransferase PRMT5 as well as the polycomb repressor complex PRC2 has been associated with increased cell proliferation and survival. Here, we show that PRMT5 is overexpressed in three different types of non-Hodgkin lymphoma cell lines and clinical samples as well as in mouse primary lymphoma cells and that it up-regulates PRC2 expression through inactivation of the retinoblastoma proteins RB1 and RBL2. Although PRMT5 epigenetically controls RBL2 expression, it indirectly promotes RB1 phosphorylation through enhanced cyclin D1 expression. Furthermore, we demonstrate that PRMT5 knockdown in non-Hodgkin lymphoma cell lines and mouse primary lymphoma cells leads to RBL2 derepression and RB1 reactivation, which in turn inhibit PRC2 expression and trigger derepression of its CASP10, DAP1, HOXA5, and HRK pro-apoptotic target genes. We also show that reduced PRMT5 expression leads to cyclin D1 transcriptional repression via loss of TP53K372 methylation, which results in decreased BCL3 expression and enhanced recruitment of NF-κB p52-HDAC1 repressor complexes to the cyclin D1 promoter. These findings indicate that PRMT5 is a master epigenetic regulator that governs expression of its own target genes and those regulated by PRC2 and that its inhibition could offer a promising therapeutic strategy for lymphoma patients.

Liu F, Gong J, Huang W, et al.
MicroRNA-106b-5p boosts glioma tumorigensis by targeting multiple tumor suppressor genes.
Oncogene. 2014; 33(40):4813-22 [PubMed] Related Publications
Aberrant expression of microRNAs (miRNAs) has been implicated in cancer initiation and progression. However, little is known about the potential role of miRNAs in glioma tumorigenesis. In this study, we found that miRNA-106b-5p was significantly upregulated in glioma tumor samples and cell lines compared with normal brain tissues, and its expression level correlated with the pathological grading. Overexpression of miR-106b-5p in glioma tumor cells significantly promoted cell proliferation, although inhibited cell apoptosis in vitro and in vivo. In contrast, knockdown of miR-106b-5p significantly inhibited cell proliferation, although enhanced cell apoptosis. Mechanistic study revealed that two target genes, retinoblastoma-like 1 (RBL1) and RBL2, were involved in miR-106b-5p's regulation of cell proliferation and one target gene, caspase-8 (CASP8), mediated miR-106b-5p's regulation of apoptosis. We also investigated the function of the three targets in glioma tumorigenesis by RNA interference manipulation and demonstrated that knockdown of these target genes led to cell proliferation enhancement or cell apoptosis inhibition in vitro. More interestingly, the expression levels of these targets were significantly downregulated in glioma samples and knockdown of these targets in glioma cells inhibited the xenograft tumor formation in vivo. Moreover, we verified the regulation function of miR-106b-5p and its targets on cell proliferation and apoptosis of the primary cultured astrocytes isolated from glioma tumor samples and healthy controls. Collectively, our findings show the critical roles of miR-106b-5p and its targets, RBL1, RBL2 and CASP8, in glioma tumorigenesis and provide potential candidates for malignant glioma therapy.

DeCaprio JA
Human papillomavirus type 16 E7 perturbs DREAM to promote cellular proliferation and mitotic gene expression.
Oncogene. 2014; 33(31):4036-8 [PubMed] Free Access to Full Article Related Publications
The study of the small DNA tumor viruses continues to provide valuable new insights into oncogenesis and fundamental biological processes. Although much has already been revealed about how the human papillomaviruses (HPVs) can transform cells and contribute to cervical and oropharyngeal cancer, there clearly is much more to learn. In this issue of Oncogene, Pang et al., doi:10.1038/onc.2013.426, demonstrate that the high-risk HPV16 E7 oncogene can promote cellular proliferation by interacting with the DREAM (DP, RB-like, E2F and MuvB) complex at two distinct phases of the cell cycle. Consistent with earlier work, HPV16 E7 can bind to the retinoblastoma tumor suppressor (RB) family member p130 (RBL2) protein and promote its proteasome-mediated destruction thereby disrupting the DREAM complex and can prevent exit from the cell cycle into quiescence. In addition, they demonstrate that HPV16 E7 can bind to MuvB core complex in association with BMYB and FOXM1 and activate gene expression during the G2 and M phase of the cell cycle. Thus, HPV16 E7 acts to prevent exit from the cell cycle entry and promotes mitotic proliferation and may account for the high levels of FOXM1 often observed in poor-risk cervical cancers.

Paquin MC, Leblanc C, Lemieux E, et al.
Functional impact of colorectal cancer-associated mutations in the transcription factor E2F4.
Int J Oncol. 2013; 43(6):2015-22 [PubMed] Related Publications
The transcription factor E2F4 plays a critical role in cell cycle progression of normal and cancerous intestinal epithelial cells. Contrary to other E2Fs, the coding region of the E2F4 gene contains a longer spacer segment of a CAG trinucleotide repeat sequence encoding 13 consecutive serine residues, which is highly vulnerable to frameshift mutations in situations of genetic instability. Mutations in this region of the E2F4 gene have been observed in colorectal tumors with microsatellite instability. However, the effect of these changes on its function in colorectal cancer cells is currently unknown. We generated E2F4(CAG)₁₂ and E2F4(CAG)₁₄ mutants and compared their activity to the E2F4 wild-type, E2F4(CAG)₁₃. Luciferase assays with the thymidine kinase-luc reporter gene revealed that the mutants were more transcriptionally active than wild-type E2F4. The mechanism of increased activity of E2F4 was primarily related to protein stability, due to a significantly enhanced half-life of E2F4 mutants comparatively to that of wild-type E2F4. However, the association with the pocket protein p130/RBL2 did not account for this increased protein stability. Sequencing analysis of the endogenous E2F4 gene in a series of colorectal cancer cell lines showed that the microsatellite-unstable cell line SW48 exhibited a serine deletion in this gene. Accordingly, E2F4 half-life was much more elevated in SW48 cells in comparison to Caco-2/15, a microsatellite-stable cell line. Notably, in soft-agar assays, both mutants more potently increased anchorage-independent growth in comparison to wild-type E2F4. In conclusion, our data demonstrate that cancer-associated E2F4 mutations enhance the capacity of colorectal cancer cells to grow without anchorage, thereby contributing to tumor progression.

Liu Z, Gersbach E, Zhang X, et al.
miR-106a represses the Rb tumor suppressor p130 to regulate cellular proliferation and differentiation in high-grade serous ovarian carcinoma.
Mol Cancer Res. 2013; 11(11):1314-25 [PubMed] Free Access to Full Article Related Publications
UNLABELLED: The degree of differentiation in human cancers generally reflects the degree of malignancy, with the most undifferentiated cancer being also the highest grade and the most aggressive. High-grade serous ovarian carcinomas (HGSOC) are poorly differentiated and fast-growing malignancies. The molecular mechanisms underlying the poor differentiation of HGSOC has not been completely characterized. Evidence suggests that miRNA, miR are dysregulated in HGSOC. Therefore, we focused on those miRNAs that are relevant to tumor differentiation. Expression profiling of miRNAs in HGSOC, indicated miR-106a and its family members were significantly upregulated. Upregulation of miR-106a was further validated by real-time reverse transcriptase PCR (qRT-PCR) and miRNA in situ hybridization in a large cohort of HGSOC specimens. Overexpression of miR-106a in benign and malignant ovarian cells significantly increased the cellular proliferation rate and expanded the side-population fraction. In particular, SKOV3 cells with miR-106a overexpression had significantly higher tumor initial/stem cell population (CD24- and CD133-positive cells) than control SKOV3 cells. Among many miR-106a predicated target genes, p130 (RBL2), an retinoblastoma (Rb) tumor suppressor family member, was not only confirmed as a specific target of miR-106a but also related to tumor growth and differentiation. The importance of mir-106a and RBL2 was further demonstrated in vivo, in which, SKOV3 cells overexpressing miR-106a formed poorly differentiated carcinomas and had reduced RBL2 levels. To our knowledge, this is the first study of miR-106a mediating proliferation and tumor differentiation in HGSOC.
IMPLICATIONS: The current study suggests that the RB tumor suppressor pathway is a critical regulator of growth and differentiation in HGSOC.

Yi C, Shen Z, Stemmer-Rachamimov A, et al.
The p130 isoform of angiomotin is required for Yap-mediated hepatic epithelial cell proliferation and tumorigenesis.
Sci Signal. 2013; 6(291):ra77 [PubMed] Free Access to Full Article Related Publications
The Hippo-Yap signaling pathway regulates a number of developmental and adult cellular processes, including cell fate determination, tissue growth, and tumorigenesis. Members of the scaffold protein angiomotin (Amot) family interact with several Hippo pathway components, including Yap (Yes-associated protein), and either stimulate or inhibit Yap activity. We used a combination of genetic, biochemical, and transcriptional approaches to assess the functional consequences of the Amot-Yap interaction in mice and in human cells. Mice with a liver-specific Amot knockout exhibited reduced hepatic "oval cell" proliferation and tumorigenesis in response to toxin-induced injury or when crossed with mice lacking the tumor suppressor Nf2. Biochemical examination of the Amot-Yap interaction revealed that the p130 splicing isoform of Amot (Amot-p130) and Yap interacted in both the cytoplasm and nucleus, which involved binding of PPxY and LPxY motifs in Amot-p130 to WW domains of Yap. In the cytoplasm, Amot-p130 prevented the phosphorylation of Yap by blocking access of the WW domains to the kinase Lats1. Within the nucleus, Amot-p130 was associated with the transcriptional complex containing Yap and Teads (TEA domain family members) and contributed to the regulation of a subset of Yap target genes, many of which are associated with tumorigenesis. These findings indicated that Amot acts as a Yap cofactor, preventing Yap phosphorylation and augmenting its activity toward a specific set of genes that facilitate tumorigenesis.

Su S, Minges JT, Grossman G, et al.
Proto-oncogene activity of melanoma antigen-A11 (MAGE-A11) regulates retinoblastoma-related p107 and E2F1 proteins.
J Biol Chem. 2013; 288(34):24809-24 [PubMed] Free Access to Full Article Related Publications
Melanoma antigen-A11 (MAGE-A11) is a low-abundance, primate-specific steroid receptor coregulator in normal tissues of the human reproductive tract that is expressed at higher levels in prostate cancer. Increased expression of MAGE-A11 enhances androgen receptor transcriptional activity and promotes prostate cancer cell growth. Further investigation into the mechanisms of MAGE-A11 function in prostate cancer demonstrated interactions with the retinoblastoma-related protein p107 and Rb tumor suppressor but no interaction with p130 of the Rb family. MAGE-A11 interaction with p107 was associated with transcriptional repression in cells with low MAGE-A11 and transcriptional activation in cells with higher MAGE-A11. Selective interaction of MAGE-A11 with retinoblastoma family members suggested the regulation of E2F transcription factors. MAGE-A11 stabilized p107 by inhibition of ubiquitination and linked p107 to hypophosphorylated E2F1 in association with the stabilization and activation of E2F1. The androgen receptor and MAGE-A11 modulated endogenous expression of the E2F1-regulated cyclin-dependent kinase inhibitor p27(Kip1). The ability of MAGE-A11 to increase E2F1 transcriptional activity was similar to the activity of adenovirus early oncoprotein E1A and depended on MAGE-A11 interactions with p107 and p300. The immunoreactivity of p107 and MAGE-A11 was greater in advanced prostate cancer than in benign prostate, and knockdown with small inhibitory RNA showed that p107 is a transcriptional activator in prostate cancer cells. These results suggest that MAGE-A11 is a proto-oncogene whose increased expression in prostate cancer reverses retinoblastoma-related protein p107 from a transcriptional repressor to a transcriptional activator of the androgen receptor and E2F1.

Sadasivam S, DeCaprio JA
The DREAM complex: master coordinator of cell cycle-dependent gene expression.
Nat Rev Cancer. 2013; 13(8):585-95 [PubMed] Free Access to Full Article Related Publications
The dimerization partner, RB-like, E2F and multi-vulval class B (DREAM) complex provides a previously unsuspected unifying role in the cell cycle by directly linking p130, p107, E2F, BMYB and forkhead box protein M1. DREAM mediates gene repression during the G0 phase and coordinates periodic gene expression with peaks during the G1/S and G2/M phases. Perturbations in DREAM complex regulation shift the balance from quiescence towards proliferation and contribute to the increased mitotic gene expression levels that are frequently observed in cancers with a poor prognosis.

Kurimchak A, Haines DS, Garriga J, et al.
Activation of p107 by fibroblast growth factor, which is essential for chondrocyte cell cycle exit, is mediated by the protein phosphatase 2A/B55α holoenzyme.
Mol Cell Biol. 2013; 33(16):3330-42 [PubMed] Free Access to Full Article Related Publications
The phosphorylation state of pocket proteins during the cell cycle is determined at least in part by an equilibrium between inducible cyclin-dependent kinases (CDKs) and serine/threonine protein phosphatase 2A (PP2A). Two trimeric holoenzymes consisting of the core PP2A catalytic/scaffold dimer and either the B55α or PR70 regulatory subunit have been implicated in the activation of p107/p130 and pRB, respectively. While the phosphorylation state of p107 is very sensitive to forced changes of B55α levels in human cell lines, regulation of p107 in response to physiological modulation of PP2A/B55α has not been elucidated. Here we show that fibroblast growth factor 1 (FGF1), which induces maturation and cell cycle exit in chondrocytes, triggers rapid accumulation of p107-PP2A/B55α complexes coinciding with p107 dephosphorylation. Reciprocal solution-based mass spectrometric analysis identified the PP2A/B55α complex as a major component in p107 complexes, which also contain E2F/DPs, DREAM subunits, and/or cyclin/CDK complexes. Of note, p107 is one of the preferred partners of B55α, which also associates with pRB in RCS cells. FGF1-induced dephosphorylation of p107 results in its rapid accumulation in the nucleus and formation of larger complexes containing p107 and enhances its interaction with E2F4 and other p107 partners. Consistent with a key role of B55α in the rapid activation of p107 in chondrocytes, limited ectopic expression of B55α results in marked dephosphorylation of p107 while B55α knockdown results in hyperphosphorylation. More importantly, knockdown of B55α dramatically delays FGF1-induced dephosphorylation of p107 and slows down cell cycle exit. Moreover, dephosphorylation of p107 in response to FGF1 treatment results in early recruitment of p107 to the MYC promoter, an FGF1/E2F-regulated gene. Our results suggest a model in which FGF1 mediates rapid dephosphorylation and activation of p107 independently of the CDK activities that maintain p130 and pRB hyperphosphorylation for several hours after p107 dephosphorylation in maturing chondrocytes.

Agrelo R, Kishimoto H, Novatchkova M, et al.
SATB1 collaborates with loss of p16 in cellular transformation.
Oncogene. 2013; 32(48):5492-500 [PubMed] Free Access to Full Article Related Publications
Tumor progression is associated with invasiveness and metastatic potential. The special AT-rich binding protein 1 (SATB1) has been identified as a key factor in the progression of breast cancer cells to a malignant phenotype and is associated with progression of human tumors. In normal development, SATB1 coordinates gene expression of progenitor cells by functioning as a genome organizer. In contrast to progenitor and tumor cells, SATB1 expression in nontransformed cells is not compatible with proliferation. Here we show that SATB1 expression in mouse embryonic fibroblasts induces cell cycle arrest and senescence that is associated with elevated p16 protein levels. Deletion of p16 overcomes the SATB1-induced senescence. We further provide evidence for an interaction of SATB1 with the retinoblastoma (RB)/E2F pathway downstream of p16. A combined deletion of the RB proteins, RB, p107 and p130 (triple-mutant; TM), prevents SATB1-induced G1 arrest, which is restored upon the reintroduction of RB into SATB1-expressing TM fibroblasts. SATB1 interacts with the E2F/RB complex and regulates the cyclin E promoter in an E2F-dependent manner. These findings demonstrate that p16 and the RB/E2F pathway are critical for SATB1-induced cell cycle arrest. In the absence of p16, SATB1 causes anchorage-independent growth and invasive phenotype in fibroblasts. Our data illustrate that p16 mutations collaborate with the oncogenic activity of SATB1. Consistent with our finding, a literature survey shows that deletion of p16 is generally associated with SATB1 expressing human cell lines and tumors.

Nande R, Greco A, Gossman MS, et al.
Microbubble-assisted p53, RB, and p130 gene transfer in combination with radiation therapy in prostate cancer.
Curr Gene Ther. 2013; 13(3):163-74 [PubMed] Related Publications
Combining radiation therapy and direct intratumoral (IT) injection of adenoviral vectors has been explored as a means to enhance the therapeutic potential of gene transfer. A major challenge for gene transfer is systemic delivery of nucleic acids directly into an affected tissue. Ultrasound (US) contrast agents (microbubbles) are viable candidates to enhance targeted delivery of systemically administered genes. Here we show that p53, pRB, and p130 gene transfer mediated by US cavitation of microbubbles at the tumor site resulted in targeted gene transduction and increased reduction in tumor growth compared to DU-145 prostate cancer cell xenografts treated intratumorally with adenovirus (Ad) or radiation alone. Microbubble-assisted/US-mediated Ad.p53 and Ad.RB treated tumors showed significant reduction in tumor volume compared to Ad.p130 treated tumors (p<0.05). Additionally, US mediated microbubble delivery of p53 and RB combined with external beam radiation resulted in the most profound tumor reduction in DU-145 xenografted nude mice (p<0.05) compared to radiation alone. These findings highlight the potential therapeutic applications of this novel image-guided gene transfer technology in combination with external beam radiation for prostate cancer patients with therapy resistant disease.

Further References

Raschellà G, Tanno B, Bonetto F, et al.
The RB-related gene Rb2/p130 in neuroblastoma differentiation and in B-myb promoter down-regulation.
Cell Death Differ. 1998; 5(5):401-7 [PubMed] Related Publications
The retinoblastoma family of nuclear factors is composed of RB, the prototype of the tumour suppressor genes and of the strictly related genes p107 and Rb2/p130. The three genes code for proteins, namely pRb, p107 and pRb2/p130, that share similar structures and functions. These proteins are expressed, often simultaneously, in many cell types and are involved in the regulation of proliferation and differentiation. We determined the expression and the phosphorylation of the RB family gene products during the DMSO-induced differentiation of the N1E-115 murine neuroblastoma cells. In this system, pRb2/p130 was strongly up-regulated during mid-late differentiation stages, while, on the contrary, pRb and p107 resulted markedly decreased at late stages. Differentiating N1E-115 cells also showed a progressive decrease in B-myb levels, a proliferation-related protein whose constitutive expression inhibits neuronal differentiation. Transfection of each of the RB family genes in these cells was able, at different degrees, to induce neuronal differentiation, to inhibit [3H]thymidine incorporation and to down-regulate the activity of the B-myb promoter.

Raschellà G, Tanno B, Bonetto F, et al.
Retinoblastoma-related protein pRb2/p130 and its binding to the B-myb promoter increase during human neuroblastoma differentiation.
J Cell Biochem. 1997; 67(3):297-303 [PubMed] Related Publications
Neuroblastoma cells can undergo neural differentiation upon treatment with a variety of chemical inducers and growth factors. During this process, many cell cycle-related genes are downregulated while differentiation-specific genes are triggered. The retinoblastoma family proteins, pRb, p107, and pRb2/p130, are involved in transcriptional repression of proliferation genes, mainly through their interaction with the E2F transcription factors. We report that pRb2/p130 expression levels increased during differentiation of neuroblastoma cell line LAN-5. On the other hand, both pRb and p107 decreased and underwent progressive dephosphorylation at late differentiation times. The expression of B-myb and c-myb, two targets of the retinoblastoma family proteins, were downregulated in association with the increase of pRb2/p130, which was detected as the major component of the complex with E2F on the E2F site of the B-myb promoter in differentiated cells. Interestingly, E2F4, a preferential partner of p107 and pRb2/p130, was upregulated and underwent changes in cellular localization during differentiation. In conclusion, our data suggest a major role of pRb2/p130 in the regulation of B-myb promoter during neural differentiation despite the importance of cofactors in modulating the function of the retinoblastoma family proteins.

Minimo C, Bibbo M, Claudio PP, et al.
The role of pRb2/p130 protein in diagnosing lung carcinoma on fine needle aspiration biopsies.
Pathol Res Pract. 1999; 195(2):67-70 [PubMed] Related Publications
The retinoblastoma gene family is composed of three members: the retinoblastoma gene, one of the most studied tumor suppressor genes, and two related genes: p107 and pRb2/p130. These proteins are also known as the pocket proteins due to a unique structural and functional domain composed of subdomains A and B separated by a spacer region that is highly conserved among each of the proteins. These proteins exhibit unique growth suppressive properties that are cell type specific, suggesting that although the pocket proteins may complement each other, they are not fully functionally redundant. With the development of antibodies recognizing these three proteins it is now possible to detect expression in formalin-embedded specimens. Recent studies on 235 lung cancers, using immunohistochemical techniques, suggested an independent role for Rb2/p130 in the development and/or progression of human lung carcinoma. We found a statistically significant inverse relationship between the histological grading (degree of malignant potential) and the expression of pRb/p105, p107 and pRb2/p130 in squamous cell carcinomas, meaning that an increase in grading resulted in a significant decrease in protein expression. This phenomenon was particularly evident for pRb2/p130 (p < .0001) which had the highest percentage of undetectable levels in all the specimens examined and the tightest inverse correlation (p value) with both the histological grading and PCNA expression in the most aggressive tumor types, suggesting an important role for pRb2/p130 in the pathogenesis and progression of certain lung cancers. We further explored the expression of pRb2/p130 protein in routine archival FNAB cytological material from 30 Patients with lung cancer using immunocytochemical techniques, comparing protein expression with tumor type. Two pathologists evaluated the staining pattern and scored the percentage of positive cells. Of the 30 neoplasms, 27 displayed a positive staining for pRb2/p130. In particular, we detected pRb2/p130 in 9 (100%) squamous carcinomas, 11 (84%) adenocarcinomas, 5 (100%) BAC, and 2 (66%) SCC. The percentage of positive nuclei varied in different tumors with the highest expression level in adenocarcinomas. Immunocytochemistry represents a sensitive method for detection of pRb2/p130 expression in cytological or archival specimens, and the level of detection seems to be comparable to paraffin sections. Therefore, this methodology could be used in the preoperative evaluation of routine cytological specimens in order to improve the diagnostic and prognostic evaluation of lung cancer patients.

Baldi A, Esposito V, De Luca A, et al.
Differential expression of Rb2/p130 and p107 in normal human tissues and in primary lung cancer.
Clin Cancer Res. 1997; 3(10):1691-7 [PubMed] Related Publications
Two proteins, p107 and pRb2/p130, which are structurally and functionally similar to the product of the retinoblastoma gene (pRb), were cloned by taking advantage of their ability to bind transforming proteins of DNA tumor viruses through a particular region called the "pocket domain." Like pRb, both proteins play a fundamental role in growth control. Using immunocytochemical techniques, we examined a variety of normal human tissues for the expression of pRb2/p130 and p107. Both proteins were expressed ubiquitously, although a different tissue distribution and/or level of expression were found in various organs. Terminally differentiated cells, such as neurons and skeletal muscle, showed high expression levels for Rb2/p130, whereas p107 was expressed at higher levels in other cell types such as epithelia of the breast and prostate. We then examined the expression pattern of Rb2/p130 in 158 specimens of human lung cancer and found an inverse correlation between the histological grading of the tumors, the development of metastasis, and the level of expression of Rb2/p130.

Helin K, Holm K, Niebuhr A, et al.
Loss of the retinoblastoma protein-related p130 protein in small cell lung carcinoma.
Proc Natl Acad Sci U S A. 1997; 94(13):6933-8 [PubMed] Free Access to Full Article Related Publications
The retinoblastoma gene family consists of the tumor suppressor protein pRB and its two relatives p107 and p130. These proteins have been implicated in the regulation of cell cycle progression, in part, through inactivation of members of the E2F transcription factor family. Overexpression of pRB, p107, or p130 leads to growth arrest in the G1 phase of the cell cycle, and this arrest is abolished by complex formation with the adenovirus E1A, human papilloma virus E7, or simian virus 40 T oncoproteins. Inactivation of pRB by gross structural alterations or point mutations in the RB-1 gene has been described in a variety of human tumors, including retinoblastomas, osteosarcomas, and small cell lung carcinomas. Despite the structural and functional similarity between pRB, p107, and p130, alterations in the latter two proteins have not been identified in human tumors. We have screened a panel of 17 small cell lung carcinoma cell lines for the presence of functional p107 and p130 by evaluating their ability to form complexes with E1A in vitro. In the GLC2 small cell lung carcinoma cells no p130 protein was detected. The loss of the p130 protein is the result of a single point mutation within a splice acceptor sequence in the GLC2 genomic DNA. This mutation eliminates exon 2, leading to an in-frame stop codon, and no detectable protein is produced. These data are, to our knowledge, the first to describe the loss of p130 as a consequence of a genetic alteration, suggesting that not only pRB but also the other members of the family may contribute to tumorigenesis, providing a rationale for the observation that the DNA tumor viruses selectively target all the members of the retinoblastoma protein family.

Susini T, Baldi F, Howard CM, et al.
Expression of the retinoblastoma-related gene Rb2/p130 correlates with clinical outcome in endometrial cancer.
J Clin Oncol. 1998; 16(3):1085-93 [PubMed] Related Publications
PURPOSE: The retinoblastoma gene is the prototype of tumor-suppressor genes and has been shown to be involved in the pathogenesis and progression of several human malignancies. In this study, we determined the relation between the expression of a newly discovered retinoblastoma-related gene Rb2/p130 and outcome in patients with endometrial carcinoma.
PATIENTS AND METHODS: pRb2/p130 expression was determined immunohistochemically in specimens of endometrial carcinoma (stages I to IV) from 100 patients who underwent surgery as the first treatment. The pRb2/p130 status was analyzed in relation to the length of disease-free survival and disease-specific survival.
RESULTS: Decreased levels of pRb2/p130 in endometrial cancer cells was significantly associated with a decreased probability of remaining disease-free after treatment (P = .003) and with decreased probability of survival (P < .0001). In a multivariate analysis, pRb2/p130 status (P = .004), tumor stage (P = .009), and ploidy status (P = .02) were independent predictors of clinical outcome. The risk of dying of disease was increased substantially (risk ratio, 4.91; 95% confidence interval, 1.66 to 14.54) among patients with decreased levels of pRb2/p130 in tumor cells.
CONCLUSION: In patients with endometrial carcinoma who did not receive radiotherapy or chemotherapy before surgery, the presence of decreased levels of pRb2/p130 in tumor cells is associated with a significantly increased risk of recurrence and death of disease, independent of tumor stage and ploidy status.

Massaro-Giordano M, Baldi G, De Luca A, et al.
Differential expression of the retinoblastoma gene family members in choroidal melanoma: prognostic significance.
Clin Cancer Res. 1999; 5(6):1455-8 [PubMed] Related Publications
We evaluated 55 samples of choroidal melanoma managed by enucleation. Knowing that the immunohistochemical expression of the retinoblastoma gene family members Rb/p105, p107, and pRb2/p130 was inversely correlated with the degree of malignancy in at least some histological types, we investigated the expression of these three proteins in choroidal melanoma. We focused on the relationship between patient survival and the immunohistochemical detection of the retinoblastoma proteins. No correlation with clinical outcome was found for Rb/p105 and p107. However, we found pRb2/p130 to be an independent prognostic factor correlating positively or directly with patient survival times and indirectly or inversely with the degree of malignancy. Demonstration of the prognostic value of the immunohistochemical expression of pRb2/p130 is of significance, even if additional studies are required to confirm these data and to compare the prognostic value of pRb2/p130 immunodetection to that of other recently proposed markers, such as p53.

Claudio PP, Howard CM, Fu Y, et al.
Mutations in the retinoblastoma-related gene RB2/p130 in primary nasopharyngeal carcinoma.
Cancer Res. 2000; 60(1):8-12 [PubMed] Related Publications
Nasopharyngeal carcinoma (NPC) is an endemic cancer in southern China and northern Africa, and its pathogenesis is not yet well defined at the molecular level. Although the involvement of p53 and of the retinoblastoma gene (RB/p105) in NPC has been well studied, there is paucity of mutational data regarding the retinoblastoma-related gene RB2/p130 in primary tumors and particularly in NPC. We have shown previously that RB2/p130 could be rearranged in a nasopharyngeal cell line. In the present study, we screened by single-strand conformation polymorphism and sequence analysis the retinoblastoma-related gene RB2/p130 for mutations within exons 19-22. Mutations in the RB2/p130 gene were detected in 3 of 10 primary human NPCs from Northern Africa (30%). These findings, along with previous data showing that genetic replacement of RB2/p130 restores a normal growth pathway in the nasopharyngeal cell line Hone-1, strengthen the hypothesis that genetic changes of RB2/p130 may be involved in the development and/or progression of nasopharyngeal cancer and suggest that RB2/p130 could be considered a tumor suppressor gene and may be a candidate for novel gene therapeutic approaches for NPC.

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