Research IndicatorsGraph generated 15 March 2017 using data from PubMed using criteria.
Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic. Tag cloud generated 15 March, 2017 using data from PubMed, MeSH and CancerIndex
Specific Cancers (6)
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).
OMIM, Johns Hopkin University
Referenced article focusing on the relationship between phenotype and genotype.
International Cancer Genome Consortium.
Summary of gene and mutations by cancer type from ICGC
Cancer Genome Anatomy Project, NCI
COSMIC, Sanger Institute
Somatic mutation information and related details
GEO Profiles, NCBI
Search the gene expression profiles from curated DataSets in the Gene Expression Omnibus (GEO) repository.
Latest Publications: MAD1L1 (cancer-related)
Li D, Meng Q, Zhang H, et al.Mitotic arrest deficient-like 1 is correlated with poor prognosis in small-cell lung cancer after surgical resection.
Tumour Biol. 2016; 37(4):4393-8 [PubMed
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Mitotic arrest deficient-like 1 (MAD1L1) whose dysfunction is associated with chromosomal instability plays a pathogenic role in a few human cancers. However, the status of MAD1L1 expression in small-cell lung cancer (SCLC) remains unknown. Immunohistochemistry was used to determine the expression of MAD1L1 protein in 32 lymph node metastasis (LN-M) tissues and 88 primary SCLCs compared with 32 adjacent noncancerous tissues. The associations of MAD1L1 protein expression with the clinicopathologic features and clinical outcomes in patients with SCLC were analyzed. The ratio of MAD1L1 positive expression was higher in primary SCLC tissues (39.8 %) and LN-M tissues (46.9 %) compared with adjacent noncancerous tissues (9.4 %). MAD1L1 positive expression was associated with tumor-node-metastasis (TNM) stage (P = 0.003), International Association for the Study of Lung Cancer (IASLC) stage (P = 0.004), tumor size (P = 0.015), lymph node metastasis (P = 0.014), and recurrence (P < 0.001). Multivariate analysis suggested that MAD1L1 positive expression was an independent factor for overall survival (hazard ratio (HR) 2.002; 95 % confidence interval (CI) 1.065-3.763; P = 0.031) and recurrence-free survival (HR 2.263; 95 % CI 1.197-4.276; P = 0.012). To sum up, MAD1L1 positive expression may be associated with tumour progression and metastasis in SCLCs and may thus serve as a new biomarker for prognosis in these patients.
The spindle assembly checkpoint (SAC) has been established as an important mechanism of driving aneuploidy, which occurs at a high frequency in the colorectal tumorigenesis. Two important components of SAC are MAD1L1 and MAD2L1, which function together in an interactive manner to initiate the checkpoint signal. We hypothesize that genetic variants in the binding domains of MAD1L1 and MAD2L1 may modulate protein structures and eventually contribute to CRC susceptibility. A case-control study including 710 CRC cases and 735 controls was performed to examine MAD1L1 Arg558His and MAD2L1 Leu84Met's conferring susceptibility to CRC. Cytokinesis-block micronucleus cytome assays were applied to assess the effect of two functional variants on chromosomal instability (CIN). Significant associations with CRC risk were observed for MAD1L1 Arg558His (OR = 1.38,95% CI: 1.09-1.75) and MAD2L1 Leu84Met in a dominant model (OR = 1.48,95% CI: 1.09-2.01). Moreover, significant multiplicative gene-smoking interactions were found in MAD1L1 Arg558His (P = 0.019) and MAD2L184 Leu/Met (P = 0.016) to enhance CRC risk. Additionally, the frequencies of lymphocytic micro-nucleated binucleated cells for MAD1L1 Arg558His polymorphism were significantly different in the exposed group (P = 0.013), but not in the control group. The study emphasized that MAD1L1 Arg558His and MAD2L1 Leu84Met can significantly interact with smoking to enhance CRC risk, and the genetic effects of MAD1L1Arg558His on CIN need to be further clarified in follow-up studies.
Feng J, Chen X, Wang Y, et al.Myricetin inhibits proliferation and induces apoptosis and cell cycle arrest in gastric cancer cells.
Mol Cell Biochem. 2015; 408(1-2):163-70 [PubMed
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Myricetin is a flavonoid that is abundant in fruits and vegetables and has protective effects against cancer and diabetes. However, the mechanism of action of myricetin against gastric cancer (GC) is not fully understood. We researched myricetin on the proliferation, apoptosis, and cell cycle in GC HGC-27 and SGC7901 cells, to explore the underlying mechanism of action. Cell Counting Kit (CCK)-8 assay, Western blotting, cell cycle analysis, and apoptosis assay were used to evaluate the effects of myricetin on cell proliferation, apoptosis, and the cell cycle. To analyze the binding properties of ribosomal S6 kinase 2 (RSK2) with myricetin, surface plasmon resonance (SPR) analysis was performed. CCK8 assay showed that myricetin inhibited GC cell proliferation. Flow cytometry analysis showed that myricetin induces apoptosis and cell cycle arrest in GC cells. Western blotting indicated that myricetin influenced apoptosis and cell cycle arrest of GC cells by regulating related proteins. SPR analysis showed strong binding affinity of RSK2 and myricetin. Myricetin bound to RSK2, leading to increased expression of Mad1, and contributed to inhibition of HGC-27 and SGC7901 cell proliferation. Our results suggest the therapeutic potential of myricetin in GC.
Dasgupta P, Sengupta SBRole of diallyl disulfide-mediated cleavage of c-Myc and Sp-1 in the regulation of telomerase activity in human lymphoma cell line U937.
Nutrition. 2015 Jul-Aug; 31(7-8):1031-7 [PubMed
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OBJECTIVE: Garlic (Allium sativum) has been considered a wonder herb for years with a reputation of disease prevention. Telomerase, a ribonucleoprotein enzyme responsible for telomere integrity, is strongly up-regulated in different types of cancers. The aim of this study was to reveal the role of diallyl disulfide (DADS), an organosulfur component of garlic, on telomerase activity in human lymphoma with an emphasis on key transcription factors c-Myc and Sp-1.
METHODS: Human lymphoma cell line U937 was used as model cell line. Telomerase activity was measured by telomerase repeat amplification protocol assay, levels of related proteins and mRNAs were measured by Western blot and reverse transcriptase polymerase chain reaction, respectively. Moreover, in vitro binding assay was performed using radiolabeled double-stranded DNA having specific sequences to detect involvement of transcription factors in DADS-dependent modulation of telomerase activity.
RESULTS: The present study demonstrated DADS-mediated decrease in telomerase activity in U937 cells with concomitant transcriptional down-regulation of human telomerase reverse transcriptase (hTERT) that is caused by reduced binding of c-Myc and Sp-1 to their respective binding sites on hTERT promoter. Lowering of DNA-binding activity of c-Myc and Sp-1 due to DADS treatment is caused by the deactivation of these transcription factors due to cleavage. Additionally, Mad1-the repressor protein of hTERT expression-is also overexpressed in DADS-treated U937 cells.
CONCLUSIONS: These findings strongly suggest that DADS down-regulate telomerase activity through c-Myc-, Sp-1-, and Mad1-dependent transcriptional down-regulation of hTERT.
Karsli-Ceppioglu S, Ngollo M, Adjakly M, et al.Genome-wide DNA methylation modified by soy phytoestrogens: role for epigenetic therapeutics in prostate cancer?
OMICS. 2015; 19(4):209-19 [PubMed
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In prostate cancer, DNA methylation is significantly associated with tumor initiation, progression, and metastasis. Previous studies have suggested that soy phytoestrogens might regulate DNA methylation at individual candidate gene loci and that they play a crucial role as potential therapeutic agents for prostate cancer. The purpose of our study was to examine the modulation effects of phytoestrogens on a genome-wide scale in regards to DNA methylation in prostate cancer. Prostate cancer cell lines DU-145 and LNCaP were treated with 40 μM of genistein and 110 μM of daidzein. DNMT inhibitor 5-azacytidine (2 μM) and the methylating agent budesonide (2 μM) were used to compare their demethylation/methylation effects with phytoestrogens. The regulatory effects of phytoestrogens on DNA methylation were analyzed by using a methyl-DNA immunoprecipitation method coupled with Human DNA Methylation Microarrays (MeDIP-chip). We observed that the methylation profiles of 58 genes were altered by genistein and daidzein treatments in DU-145 and LNCaP prostate cancer cells. In addition, the methylation frequencies of the MAD1L1, TRAF7, KDM4B, and hTERT genes were remarkably modified by genistein treatment. Our results suggest that the modulation effects of phytoestrogens on DNA methylation essentially lead to inhibition of cell growth and induction of apoptosis. Genome-wide methylation profiling reported here suggests that epigenetic regulation mechanisms and, by extension, epigenetics-driven novel therapeutic candidates warrant further consideration in future "omics" studies of prostate cancer.
Malignant testicular germ cell tumors (TGCT) are the most frequent cancers in Caucasian males (20-40 years) with an 70% increasing incidence the last 20 years, probably due to combined action of (epi)genetic and (micro)environmental factors. It is expected that TGCT have carcinoma in situ(CIS) as their common precursor, originating from an embryonic germ cell blocked in its maturation process. The overall cure rate of TGCT is more than 90%, however, men surviving TGCT can present long-term side effects of systemic cancer treatment. In contrast, men diagnosed and treated for CIS only continue to live without these long-term side effects. Therefore, early detection of CIS has great health benefits, which will require an informative screening method. This review described the etiology and early pathogenesis of TGCT, as well as the possibilities of early detection and future potential of screening men at risk for TGCT. For screening, a well-defined risk profile based on both genetic and environmental risk factors is needed. Since 2009, several genome wide association studies (GWAS) have been published, reporting on single-nucleotide polymorphisms (SNPs) with significant associations in or near the genes KITLG, SPRY4, BAK1, DMRT1, TERT, ATF7IP, HPGDS, MAD1L1, RFWD3, TEX14, and PPM1E, likely to be related to TGCT development. Prenatal, perinatal, and postnatal environmental factors also influence the onset of CIS. A noninvasive early detection method for CIS would be highly beneficial in a clinical setting, for which specific miRNA detection in semen seems to be very promising. Further research is needed to develop a well-defined TGCT risk profile, based on gene-environment interactions, combined with noninvasive detection method for CIS.
BACKGROUND: Androgen Receptor (AR) is an essential transcription factor for the development of secondary sex characteristics, spermatogenesis and carcinogenesis. Recently AR has been implicated in the development and progression of breast and prostate cancers. Although some of the functions of the AR are known but the mechanistic details of these divergent processes are still not clear. Therefore understanding the regulatory mechanisms of the functioning of the AR in ER-/AR+ breast cancer will provide many novel targets for the purpose of therapeutic intervention.
METHODS/RESULTS: Using bioinformatics tools, we have identified 75 AR targets having prominent roles in cell cycle, apoptosis and metabolism. Herein, we validated 10 genes as AR targets by studying the regulation of these genes in MDA-MB-453 cell line on stimulation by androgens like 5α-dihydrotestosterone (DHT), using RT-qPCR and ChIP assay. It was observed that all the identified genes involved in cell cycle except MAD1L1 were found to be up regulated whereas expression of apoptosis related genes was decreased in response to DHT treatment. We performed an exhaustive, rigid-body docking between individual ARE and DNA binding domain (DBD) of the AR protein and it was found that novel residues K567, K588, K591 and R592 are involved in the process of DNA binding. To verify these specific DNA-protein interactions electrostatic energy term calculations for each residue was determined using the linearized Poisson-Boltzmann equation. Our experimental data showed that treatment of breast cancer cells with DHT promotes cell proliferation and decreases apoptosis. It was observed that bicalutamide treatment was able to reverse the effect of DHT.
CONCLUSION: Taken together, our results provide new insights into the mechanism by which AR promotes breast cancer progression. Moreover our work proposes to use bicalutamide along with taxanes as novel therapy for the treatment of TNBCs, which are positive for downstream AR signalling.
Aberrant regulation of microRNA expression in pancreatic cancers has been shown to play an important role in its inherent poor prognosis and malignant potential. MicroRNAs have also been shown to inhibit translation of genes by targeting the 3'-untranslated region (3-UTR) of mRNAs resulting in the inhibition of translation and often destruction of the mRNA. In the present study we investigated the role of the microRNA miR-202 in the apoptotic pathways of pancreatic cancer cells. The adamantyl-related molecule, 3-Cl-AHPC down-regulated expression of miR-202 and miR-578 resulting in the increased expression of mRNA and protein expression of their target genes, Max dimerization protein 1 (Mxd1/Mad1) and the Sin3A associated protein 18 (SAP18). Overexpression of pre-miR-202 led to diminished levels of Mxd1 and blocked the 3-Cl-AHPC-mediated increase in Mxd1 mRNA expression. The addition of the microRNA inhibitor 2'-O-methylated miR-202 enhanced the 3-Cl-AHPC-mediated increase of Mxd1 mRNA levels as well as 3-CI-AHPC-mediated apoptosis. We found increased Mxd1 bound to the Sin3A repressor protein complex through its increased binding with HDAC-2 and subsequently enhanced transcriptional repression in cells as evidenced by increased HDAC activity. Mxd1 also repressed human telomerase reverse transcriptase (hTERT) mRNA expression through its increased binding to the hTERT promoter site and resulted in decreased telomerase activity in cells. Our results demonstrate that down regulation of miR-202 increased the expression of its target Mxd1, followed by Mxd1 recruitment to the Sin3A repressor complex and through its dimerization with Max, and increased repression of Myc-Max target proteins.
Avram S, Milac A, Mernea M, et al.Structure-biological function relationship extended to mitotic arrest-deficient 2-like protein Mad2 native and mutants-new opportunity for genetic disorder control.
Int J Mol Sci. 2014; 15(11):21381-400 [PubMed
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Overexpression of mitotic arrest-deficient proteins Mad1 and Mad2, two components of spindle assembly checkpoint, is a risk factor for chromosomal instability (CIN) and a trigger of many genetic disorders. Mad2 transition from inactive open (O-Mad2) to active closed (C-Mad2) conformations or Mad2 binding to specific partners (cell-division cycle protein 20 (Cdc20) or Mad1) were targets of previous pharmacogenomics studies. Here, Mad2 binding to Cdc20 and the interconversion rate from open to closed Mad2 were predicted and the molecular features with a critical contribution to these processes were determined by extending the quantitative structure-activity relationship (QSAR) method to large-size proteins such as Mad2. QSAR models were built based on available published data on 23 Mad2 mutants inducing CIN-related functional changes. The most relevant descriptors identified for predicting Mad2 native and mutants action mechanism and their involvement in genetic disorders are the steric (van der Waals area and solvent accessible area and their subdivided) and energetic van der Waals energy descriptors. The reliability of our QSAR models is indicated by significant values of statistical coefficients: Cross-validated correlation q2 (0.53-0.65) and fitted correlation r2 (0.82-0.90). Moreover, based on established QSAR equations, we rationally design and analyze nine de novo Mad2 mutants as possible promoters of CIN.
Zang W, Wang T, Wang Y, et al.Myricetin exerts anti-proliferative, anti-invasive, and pro-apoptotic effects on esophageal carcinoma EC9706 and KYSE30 cells via RSK2.
Tumour Biol. 2014; 35(12):12583-92 [PubMed
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Myricetin, a common dietary flavonoid, is widely distributed in fruits and vegetables and is used as a health food supplement based on its anti-tumor properties. However, the effect and mechanisms of myricetin in esophageal carcinoma are not fully understood. Here, we demonstrated the effect of myricetin on the proliferation, apoptosis, and invasion of the esophageal carcinoma cell lines EC9706 and KYSE30 and explored the underlying mechanism and target protein(s) of myricetin. CCK-8 assay, transwell invasion assay, wound-healing assay, cell cycle analysis, and apoptosis assay were used to evaluate the effects of myricetin on cell proliferation, invasion, and apoptosis. Nude mouse tumor xenograft model was built to understand the interaction between myricetin and NTD RSK2. Pull-down assay was used to verify molecular mechanism. Myricetin inhibited proliferation and invasion and induced apoptosis of EC9706 and KYSE30 cells. Moreover, myricetin was shown to bind RSK2 through the NH2-terminal kinase domain. Finally, myricetin inhibited EC9706 and KYSE30 cell proliferation through Mad1 and induced cell apoptosis via Bad. Myricetin inhibits the proliferation and invasion and induces apoptosis in EC9706 and KYSE30 cells via RSK2. Myricetin exerts anti-proliferative, anti-invasive, and pro-apoptotic effects on esophageal carcinoma EC9706 and KYSE30 cells via RSK2. Our results provide novel insight into myricetin as a potential agent for the prevention and treatment of esophageal carcinoma.
The RZZ (Rod, ZW10, and Zwilch) complex and Mad1 proteins tightly associate with kinetochores to generate the spindle checkpoint signal, but they are released when a kinetochore forms mature microtubule attachments. Here we demonstrate that the centromere protein CENP-I is required to generate a stable association of RZZ and Mad1 with kinetochores. CENP-I also inhibits their removal by dynein stripping. This regulation of Mad1 and RZZ dissociation functions independently of Aurora B, which regulates their association. We show that the microtubule status of each kinetochore independently dictates the recruitment of Aurora B kinase, kinase activity on a kinetochore substrate, and loading of spindle checkpoint proteins. This dynamic regulation of Mad1 association by Aurora B is only uncovered when CENP-I is depleted, consistent with our finding that CENP-I inhibits the dissociation of Mad1. We conclude that the dual activities of Aurora B and CENP-I generate a molecular switch that maintains a robust spindle checkpoint signal at prometaphase kinetochores until they attain mature attachments to microtubules.
MIR137, transcribed as the microRNA miR-137, is one of the leading candidate schizophrenia susceptibility genes to arise from large genome-wide association studies (GWAS) of the disorder. Recent data suggest that miR-137 modulates the expression of other schizophrenia susceptibility genes. Although bioinformatic resources are available with which to predict genes regulated by individual microRNA, there has been a lack of empirical data on genome-wide gene expression changes following miR-137 manipulation. We have therefore performed a genome-wide assessment of transcriptional changes in a human neural progenitor cell line after miR-137 over-expression and inhibition in order to elucidate molecular pathways by which genetic perturbation of miR-137 could promote susceptibility to schizophrenia. Bioinformatically-predicted miR-137 targets showed a small but highly significant down-regulation following miR-137 over-expression. Genes that were significantly down-regulated in association with miR-137 over-expression were enriched for involvement in neuronal differentiation. Differentially expressed genes that were confirmed by qPCR included others at genome-wide significant risk loci for schizophrenia (MAD1L1 and DPYD) and BDNF. These data point to molecular pathways through which genetic variation at the MIR137 locus could confer risk for schizophrenia.
Sze KM, Chu GK, Mak QH, et al.Proline-rich acidic protein 1 (PRAP1) is a novel interacting partner of MAD1 and has a suppressive role in mitotic checkpoint signalling in hepatocellular carcinoma.
J Pathol. 2014; 233(1):51-60 [PubMed
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Loss of mitotic checkpoint of cells contributes to chromosomal instability and leads to carcinogenesis. Mitotic arrest deficient 1 (MAD1) is a key component in mitotic checkpoint signalling. In this study, we identified a novel MAD1 interacting partner, proline-rich acidic protein 1 (PRAP1), using yeast-two hybrid screening, and investigated its role in mitotic checkpoint signalling in hepatocellular carcinoma (HCC). We demonstrated the physical interaction of PRAP1 with MAD1 and of PRAP1 with MAD1 isoform MAD1β, using a co-immunoprecipitation assay. Moreover, stable expression of PRAP1 in mitotic checkpoint-competent HCC cells, BEL-7402 and SMMC-7721, induced impairment of the mitotic checkpoint (p < 0.01), formation of chromosome bridges (p < 0.01) and aberrant chromosome numbers (p < 0.001). Interestingly, ectopic expression PRAP1 in HCC cells led to significant under-expression of MAD1. In human HCC tumours, 40.4% (23/57) of HCCs showed under-expression of PRAP1 protein as compared with their corresponding non-tumorous livers; up-regulation of MAD1 protein was significantly associated with down-regulation of PRAP1 (p = 0.030). Our data revealed that PRAP1 is a protein interacting partner of MAD1 and that PRAP1 is able to down-regulate MAD1 and suppress mitotic checkpoint signalling in HCC.
Sun Q, Zhang X, Liu T, et al.Increased expression of mitotic arrest deficient-like 1 (MAD1L1) is associated with poor prognosis and insensitive to Taxol treatment in breast cancer.
Breast Cancer Res Treat. 2013; 140(2):323-30 [PubMed
] Related Publications
Aneuploidy is a characteristic of human cancers, and recent studies have suggested that defects of mitotic checkpoints play a role in carcinogenesis. Mitotic Arrest Deficient-Like 1 (MAD1L1), whose altered expression is associated with chromosomal instability, is a checkpoint gene. We examined MAD1L1 protein expression from 461 breast cancer tissues and patients' normal breast tissues by tissue microarray to study the correlation between the MAD1L1 expression and the clinicopathological features. MAD1L1 protein expression was significantly increased in the nuclei of cancer cells (28.4 %) compared with that in normal mammary cells (2.2 %), and was correlated with Her-2 status, cancer subtypes, p53 status, and age. High level of MAD1L1 expression in nuclei was associated with worse OS (p = 0.018). Furthermore, patients with high level of MAD1L1 expression (in nuclei) and undergone Taxol chemotherapy treatment have shorter overall survival than ones without Taxol treatment in this study (p = 0.026). In conclusion, our data demonstrated a significant correlation between nuclear expression of MAD1L1 protein and adverse prognosis in breast cancer. MAD1L1 might be used as a prognostic biomarker for breast cancer and expression of MAD1L1 in nuclei is also a predict biomarker of contraindication to pacilitaxel treatment in breast cancer.
We conducted a meta-analysis to identify new susceptibility loci for testicular germ cell tumor (TGCT). In the discovery phase, we analyzed 931 affected individuals and 1,975 controls from 3 genome-wide association studies (GWAS). We conducted replication in 6 independent sample sets comprising 3,211 affected individuals and 7,591 controls. In the combined analysis, risk of TGCT was significantly associated with markers at four previously unreported loci: 4q22.2 in HPGDS (per-allele odds ratio (OR) = 1.19, 95% confidence interval (CI) = 1.12-1.26; P = 1.11 × 10(-8)), 7p22.3 in MAD1L1 (OR = 1.21, 95% CI = 1.14-1.29; P = 5.59 × 10(-9)), 16q22.3 in RFWD3 (OR = 1.26, 95% CI = 1.18-1.34; P = 5.15 × 10(-12)) and 17q22 (rs9905704: OR = 1.27, 95% CI = 1.18-1.33; P = 4.32 × 10(-13) and rs7221274: OR = 1.20, 95% CI = 1.12-1.28; P = 4.04 × 10(-9)), a locus that includes TEX14, RAD51C and PPM1E. These new TGCT susceptibility loci contain biologically plausible genes encoding proteins important for male germ cell development, chromosomal segregation and the DNA damage response.
Androgen-stimulated growth of the molecular apocrine breast cancer subtype is mediated by an androgen receptor (AR)-regulated transcriptional program. However, the molecular details of this AR-centered regulatory network and the roles of other transcription factors that cooperate with AR in the network remain elusive. Here we report a positive feed-forward loop that enhances breast cancer growth involving AR, AR coregulators, and downstream target genes. In the absence of an androgen signal, TCF7L2 interacts with FOXA1 at AR-binding sites and represses the basal expression of AR target genes, including MYC. Direct AR regulation of MYC cooperates with AR-mediated activation of HER2/HER3 signaling. HER2/HER3 signaling increases the transcriptional activity of MYC through phosphorylation of MAD1, leading to increased levels of MYC/MAX heterodimers. MYC in turn reinforces the transcriptional activation of androgen-responsive genes. These results reveal a novel regulatory network in molecular apocrine breast cancers regulated by androgen and AR in which MYC plays a central role as both a key target and a cooperating transcription factor to drive oncogenic growth.
Cho K, Shin HW, Kim YI, et al.Mad1 mediates hypoxia-induced doxorubicin resistance in colon cancer cells by inhibiting mitochondrial function.
Free Radic Biol Med. 2013; 60:201-10 [PubMed
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Cancer cells acquire resistance to chemotherapy under hypoxia, which is mainly driven by the transcription factor HIF (hypoxia-inducible factor). Yet, it is uncertain which molecules mediate such resistance. While profiling gene expression in colon cancer cells, we found that Mad1 (MAX dimerization protein 1) is substantially induced during hypoxia. The hypoxic induction of Mad1 was confirmed by RT-PCR and Western blotting. The Mad1 expression was attenuated by HIF-1α small interfering (si) RNAs, but less so by HIF-2α siRNAs. Moreover, luciferase reporter and chromatin immunoprecipitation analyses revealed that HIF-1 transactivates the MAD1 gene by directly targeting a putative hypoxia-response element in the MAD1 promoter. We next investigated if Mad1 is responsible for the hypoxia-induced drug resistance. We treated colon cancer cells with doxorubicin and found that the cells under hypoxia survived more than those under normoxia. The doxorubicin resistance was not induced in Mad1-knocked-down cells even under hypoxia. Mad1 knockdown reactivated the caspase-9/caspase-3/PARP apoptotic pathway under hypoxia. Moreover, doxorubicin-induced production of reactive oxygen species was significantly reduced under hypoxia, which was reversed by Mad1 knockdown. During hypoxia, mitochondria became bigger in size and less active in respiration, both of which were attenuated by Mad1 knockdown. These data indicate that hypoxia-induced Mad1 lowers doxorubicin-stimulated generation of reactive oxygen species through mitochondrial inhibition and subsequently contributes to tumor resistance to doxorubicin. Therefore, Mad1 could be a potential target for sensitizing cancer cells to redox-cycling drugs such as doxorubicin.
Reuss DE, Mucha J, Hagenlocher C, et al.Sensitivity of malignant peripheral nerve sheath tumor cells to TRAIL is augmented by loss of NF1 through modulation of MYC/MAD and is potentiated by curcumin through induction of ROS.
PLoS One. 2013; 8(2):e57152 [PubMed
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Malignant peripheral nerve sheath tumor (MPNST) is a rare aggressive form of sarcoma often associated with the tumor syndrome neurofibromatosis type 1 (NF1). We investigated the effects of tumor necrosis factor-related apoptosis inducing ligand (TRAIL) on NF1 associated MPNST and determinants of TRAIL sensitivity. MPNST cell lines with complete neurofibromin deficiency were sensitive to apoptotic cell death induced by TRAIL whereas MPNST cells with retained neurofibromin expression or normal human Schwann cells were resistant. Increased sensitivity to TRAIL was associated with overexpression of death receptors, especially DR5. Re-expression of the GAP related domain of neurofibromin (NF1-GRD) suppressed DR5 expression and decreased sensitivity to TRAIL. We show that death receptor expression and TRAIL sensitivity critically depend on c-MYC and that c-MYC amounts are increased by MEK/ERK and PI3K/AKT signalling pathways which are suppressed by neurofibromin. Furthermore PI3K/AKT signalling strongly suppresses the MYC-antagonist MAD1 which significantly contributes to TRAIL sensitivity. Re-expression of the NF1-GRD decreased c-MYC and increased MAD1 amounts suggesting that neurofibromin influences TRAIL sensitivity at least in part by modulating the MYC/MAX/MAD network. The phytochemical curcumin further increased the sensitivity of neurofibromin deficient MPNST cells to TRAIL. This was presumably mediated by ROS, as it correlated with increased ROS production, was blocked by N-acetylcysteine and mimicked by exogenous ROS.
Sandhu SK, Volinia S, Costinean S, et al.miR-155 targets histone deacetylase 4 (HDAC4) and impairs transcriptional activity of B-cell lymphoma 6 (BCL6) in the Eμ-miR-155 transgenic mouse model.
Proc Natl Acad Sci U S A. 2012; 109(49):20047-52 [PubMed
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Multiple studies have established that microRNAs (miRNAs) are involved in the initiation and progression of cancer. Notably, miR-155 is one of the most overexpressed miRNAs in several solid and hematological malignancies. Ectopic miR-155 expression in mice B cells (Eμ-miR-155 transgenic mice) has been shown to induce pre-B-cell proliferation followed by high-grade lymphoma/leukemia. Loss of miR-155 in mice resulted in impaired immunity due to defective T-cell-mediated immune response. Here we provide a mechanistic insight into miR-155-induced leukemogenesis in the Eμ-miR-155 mouse model through genome-wide transcriptome analysis of naïve B cells and target studies. We found that a key transcriptional repressor and proto-oncogene, Bcl6 is significantly down-regulated in Eμ-miR-155 mice. The reduction of Bcl6 subsequently leads to de-repression of some of the known Bcl6 targets like inhibitor of differentiation (Id2), interleukin-6 (IL6), cMyc, Cyclin D1, and Mip1α/ccl3, all of which promote cell survival and proliferation. We show that Bcl6 is indirectly regulated by miR-155 through Mxd1/Mad1 up-regulation. Interestingly, we found that miR-155 directly targets HDAC4, a corepressor partner of BCL6. Furthermore, ectopic expression of HDAC4 in human-activated B-cell-type diffuse large B-cell lymphoma (DLBCL) cells results in reduced miR-155-induced proliferation, clonogenic potential, and increased apoptosis. Meta-analysis of the diffuse large B-cell lymphoma patient microarray data showed that miR-155 expression is inversely correlated with Bcl6 and Hdac4. Hence this study provides a better understanding of how miR-155 causes disruption of the BCL6 transcriptional machinery that leads to up-regulation of the survival and proliferation genes in miR-155-induced leukemias.
Identification of gene expression changes that improve prediction of survival time across all glioma grades would be clinically useful. Four Affymetrix GeneChip datasets from the literature, containing data from 771 glioma samples representing all WHO grades and eight normal brain samples, were used in an ANOVA model to screen for transcript changes that correlated with grade. Observations were confirmed and extended using qPCR assays on RNA derived from 38 additional glioma samples and eight normal samples for which survival data were available. RNA levels of eight major mitotic spindle assembly checkpoint (SAC) genes (BUB1, BUB1B, BUB3, CENPE, MAD1L1, MAD2L1, CDC20, TTK) significantly correlated with glioma grade and six also significantly correlated with survival time. In particular, the level of BUB1B expression was highly correlated with survival time (p<0.0001), and significantly outperformed all other measured parameters, including two standards; WHO grade and MIB-1 (Ki-67) labeling index. Measurement of the expression levels of a small set of SAC genes may complement histological grade and other clinical parameters for predicting survival time.
Velpula KK, Dasari VR, Tsung AJ, et al.Transcriptional repression of Mad-Max complex by human umbilical cord blood stem cells downregulates extracellular signal-regulated kinase in glioblastoma.
Stem Cells Dev. 2012; 21(10):1779-93 [PubMed
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Previously, we have shown that human umbilical cord blood stem cell (hUCBSC) treatment downregulate cyclin D1 in glioma cells. To study the cell cycle progression and investigate the upstream molecules regulating cyclin D1 expression, we analyzed the involvement of extracellular signal-regulated kinase (ERK) and its functionality after treatment with hUCBSC. We observed downregulation of pERK after hUCBSC treatment at both transcriptional and translational levels. Increased translocation of ERK from cytoplasm to the nucleus was observed in glioma cells, whereas hUCBSC cocultures with glioma cells showed suppressed nuclear translocation. This finding suggests that hUCBSC regulates ERK by suppressing its phosphorylation at phospho-Thr(202)/Tyr(204) retarding pERK nuclear translocation. ERK promoter analysis has shown c-Myc binding sites, indicative of possible transcriptional interactions that regulate cyclin D1 and ERK expression levels. Treatment of U251 and 5310 glioma cells with U0126, a MEK/ERK inhibitor receded pERK and c-Myc levels. In another experiment, U251 and 5310 cells treated with 10074-G5, c-Myc/Max inhibitor displayed reduction in pERK and c-Myc levels suggestive of a positive feedback loop between ERK/c-Myc/Max molecules. In the present study, we show that glioma cells exhibit abundant c-Myc expression and increased c-Myc/Max activity. In contrast, the glioma cells cocultured with hUCBSC demonstrated high Mad1 expression that competitively binds to Max to repress the c-Myc/Max mediated gene transcription. Our studies thus elucidate the potential role of hUCBSC in controlling glioma cell cycle progression and invasion by limiting Max binding to c-Myc, thus regulating the expression of glioma cell cycle and invasion associated molecules such as ERK, integrins via increased levels of Mad1 expression.
Epigallocatechin-3-gallate (EGCG), a major component of green tea polyphenols (GTP), has been reported to downregulate telomerase activity in breast cancer cells thereby increasing cellular apoptosis and inhibiting cellular proliferation. However, the major concerns with GTPs are their bioavailability and stability under physiologic conditions. In the present study, we show that treatments with EGCG and a novel prodrug of EGCG (pro-EGCG or pEGCG) dose- and time-dependently inhibited the proliferation of human breast cancer MCF-7 and MDA-MB-231 cells but not normal control MCF10A cells. Furthermore, both EGCG and pro-EGCG inhibited the transcription of hTERT (human telomerase reverse transcriptase), the catalytic subunit of telomerase, through epigenetic mechanisms in estrogen receptor (ER)-positive MCF-7 and ER-negative MDA-MB-231 cells. The downregulation of hTERT expression was found to be because of hTERT promoter hypomethylation and histone deacetylations, mediated at least partially through inhibition of DNA methyltransferase and histone acetyltransferase activities, respectively. In addition, we also observed that EGCG and pEGCG can remodel chromatin structures of the hTERT promoter by decreasing the level of acetyl-H3, acetyl-H3K9, and acetyl-H4 to the hTERT promoter. EGCG and pEGCG induced chromatin alterations that facilitated the binding of many hTERT repressors such as MAD1 and E2F-1 to the hTERT regulatory region. Depletion of E2F-1 and MAD1 by using siRNA reversed the pEGCG downregulated hTERT expression and associated cellular apoptosis differently in ER-positive and ER-negative breast cancer cells. Collectively, our data provide new insights into breast cancer prevention through epigenetic modulation of telomerase by using pro-EGCG, a more stable form of EGCG, as a novel chemopreventive compound.
Bosco N, Pelliccia F, Rocchi ACharacterization of FRA7B, a human common fragile site mapped at the 7p chromosome terminal region.
Cancer Genet Cytogenet. 2010; 202(1):47-52 [PubMed
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Common fragile sites (CFS) are specific regions of the mammalian chromosomes that are particularly prone to gaps and breaks. They are a cause of genome instability, and the location of many CFS correlates with breakpoints of aberrations recurrent in some cancers. The molecular characterization of some CFS has not clarified the causes of their fragility. In this work, by using fluorescence in situ hybridization analysis with BAC and PAC clones, we determined the DNA sequence of the CFS FRA7B. The FRA7B sequence was then analyzed to identify coding sequences and some structural features possibly involved in fragility. FRA7B spans about 12.2 megabases, and is therefore one of the largest CFS analyzed. It maps at the 7p21.3-22.3 chromosome bands, therefore at the interface of G- and R-band regions that are probably difficult to replicate. A 90-kilobase long sequence that presents very high flexibility values was identified at the very beginning of the more fragile CFS region. Three large genes (THSD7A, SDK1, and MAD1L1) and two miRNA genes (MIRN589 and MIRN339) map in the fragile region. The chromosome band 7p22 is a recurrent breakpoint in chromosome abnormalities in different types of neoplasm. FRA7B is the first characterized CFS located in a chromosome terminal region.
Huynh KM, Soh JW, Dash R, et al.FOXM1 expression mediates growth suppression during terminal differentiation of HO-1 human metastatic melanoma cells.
J Cell Physiol. 2011; 226(1):194-204 [PubMed
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Induction of terminal differentiation represents a potentially less toxic cancer therapy. Treatment of HO-1 human metastatic melanoma cells with IFN-β plus mezerein (MEZ) promotes terminal differentiation with an irreversible loss of growth potential. During this process, the transcription factor FOXM1 is down-regulated potentially inhibiting transactivation of target genes including those involved in G(2)/M progression and cell proliferation. We investigated the mechanism of FOXM1 down-regulation and its physiological role in terminal differentiation. Genetic and pharmacological studies revealed that FOXM1 down-regulation was primarily caused by MEZ activation of PKCα and co-treatment with IFN-β plus MEZ augmented the effect of PKCα. Promoter analysis with a mutated E-box on the FOXM1 promoter, and in vitro and in vivo binding assays confirm a direct role of c-Myc on FOXM1 expression. Reduction of c-Myc and overexpression of Mad1 by IFN-β plus MEZ treatment should cause potent and persistent reduction of FOXM1 expression during terminal differentiation. Overexpression of FOXM1 restored expression of cell cycle-associated genes and increased the proportion of cells in the S phase. Our experiments support a model for terminal differentiation in which FOXM1 down-regulation via activation of PKCα followed by suppression of c-Myc expression, are causal events in promoting growth inhibition during terminal differentiation.
BACKGROUND: Sulforaphane (SFN), an isothiocyanate found in cruciferous vegetables, is a common dietary component that has histone deacetylase inhibition activity and exciting potential in cancer prevention. The mechanisms by which SFN imparts its chemopreventive properties are of considerable interest and little is known of its preventive potential for breast cancer.
PRINCIPAL FINDINGS: We found that SFN significantly inhibits the viability and proliferation of breast cancer cells in vitro while it has negligible effects on normal breast cells. Inhibition of telomerase has received considerable attention because of its high expression in cancer cells and extremely low level of expression in normal cells. SFN treatment dose- and time-dependently inhibited human telomerase reverse transcriptase (hTERT), the catalytic regulatory subunit of telomerase, in both MCF-7 and MDA-MB-231 human breast cancer cells. DNA methyltransferases (DNMTs), especially DNMT1 and DNMT3a, were also decreased in SFN-treated breast cancer cells suggesting that SFN may repress hTERT by impacting epigenetic pathways. Down-regulation of DNMTs in response to SFN induced site-specific CpG demethylation occurring primarily in the first exon of the hTERT gene thereby facilitating CTCF binding associated with hTERT repression. Chromatin immunoprecipitation (ChIP) analysis of the hTERT promoter revealed that SFN increased the level of active chromatin markers acetyl-H3, acetyl-H3K9 and acetyl-H4, whereas the trimethyl-H3K9 and trimethyl-H3K27 inactive chromatin markers were decreased in a dose-dependent manner. SFN-induced hyperacetylation facilitated the binding of many hTERT repressor proteins such as MAD1 and CTCF to the hTERT regulatory region. Depletion of CTCF using siRNA reduced the SFN-induced down-regulation of hTERT mRNA transcription in these breast cancer cells. In addition, down-regulation of hTERT expression facilitated the induction of cellular apoptosis in human breast cancer cells.
SIGNIFICANCE: Collectively, our results provide novel insights into SFN-mediated epigenetic down-regulation of telomerase in breast cancer prevention and may open new avenues for approaches to SFN-mediated cancer prevention.
Wang HB, Wang XW, Zhou G, et al.PinX1 inhibits telomerase activity in gastric cancer cells through Mad1/c-Myc pathway.
J Gastrointest Surg. 2010; 14(8):1227-34 [PubMed
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INTRODUCTION: The aim of this study was to investigate the role of Mad1/c-Myc in telomerase regulation in gastric cancer cells in order to gain insight into telomerase activity and to evaluate PinX1 as a putative inhibitor of gastric cancer.
METHODS: PinX1 and PinX1siRNA eukaryotic expression vectors were constructed by recombinant technology and transfected into gastric carcinoma cells using Lipofectamine 2000. Telomerase activity was measured by the telomeric repeat amplification protocol. Apoptosis of gastric cancer cells was analyzed by flow cytometry and transmission electron microscopy. Reverse transcription-polymerase chain reaction and Western blotting were used to assess the expression levels of PinX1 and Mad1/c-Myc.
RESULTS: We found that PinX1-negative gastric cancer cells showed significantly higher telomerase activity than did the PinX1-postive cells. PinX1-transfection reduced telomerase activity in PinX1-negative gastric cancer cells and exhibited an upregulation of Mad1 and downregulation of c-Myc expression. Pinx1 RNAi treatment led to downregulation of Mad1 and upregulation of c-Myc.
CONCLUSION: Suppression of telomerase activity mediated by PinX1 is involved in the Mad1/c-Myc pathway.
Guo Y, Zhang X, Yang M, et al.Functional evaluation of missense variations in the human MAD1L1 and MAD2L1 genes and their impact on susceptibility to lung cancer.
J Med Genet. 2010; 47(9):616-22 [PubMed
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BACKGROUND: Human MAD1 mitotic arrest deficient-like 1 (MAD1L1) and MAD2 mitotic arrest deficient-like 1 (MAD2L1) are two interactive proteins playing important roles in maintaining spindle checkpoint function. This study examined the functional relevance of missense coding single nucleotide polymorphisms (SNPs) in MAD1L1 and MAD2L1 and their association with susceptibility to lung cancer.
METHODS: SNPs in the MAD2L1 coding region were discovered by sequencing and impact of MAD1L1 and MAD2L1 variants on spindle checkpoint function was examined by flow cytometry and mitotic index assay. The associations of MAD1L1 and MAD2L1 variants with lung cancer were analysed in a case-control cohort of 1000 patients and 1000 controls. ORs and 95% CIs were estimated by logistic regression.
RESULTS: A novel C-to-A SNP at codon 84 of MAD2L1 (Leu84Met substitution) was discovered. Cells expressing MAD2L1-84Met and MAD1L1-558His had impaired spindle checkpoint function, with a lower 4N-DNA content and mitotic index when treated with nocodazole. Case-control analysis showed that the MAD2L1 Leu84Met SNP was associated with increased risk of lung cancer in an allele dose dependent manner, with the ORs being 2.55 (95% CI 1.95 to 3.33) for the Leu/Met and 2.68 (95% CI 2.05 to 3.48) for the Met/Met genotype compared with the Leu/Leu genotype. The MAD1L1 558 His/His genotype was also associated with 1.4-fold elevated lung cancer risk compared with the Arg/Arg genotype.
CONCLUSION: These results suggest that genetic variants in MAD1L1 and MAD2L1 confer susceptibility to lung cancer, which might result from reduced spindle checkpoint function due to attenuated function of MAD1L1 and/or MAD2L1.
Azouz A, Wu YL, Hillion J, et al.Epigenetic plasticity of hTERT gene promoter determines retinoid capacity to repress telomerase in maturation-resistant acute promyelocytic leukemia cells.
Leukemia. 2010; 24(3):613-22 [PubMed
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The expression of hTERT gene, encoding the catalytic subunit of telomerase, is a feature of most cancer cells. Changes in the chromatin environment of its promoter and binding of transcriptional factors have been reported in differentiating cells when its transcription is repressed. However, it is not clear whether these changes are directly involved in this repression or only linked to differentiation. In a maturation-resistant acute promyelocytic leukemia (APL) cell line (NB4-LR1), we have previously identified a new pathway of retinoid-induced hTERT repression independent of differentiation. Using a variant of this cell line (NB4-LR1(SFD)), which resists to this repression, we show that although distinct patterns of histone modifications and transcription factor binding at the proximal domain of hTERT gene promoter could concur to modulate its expression, this region is not sufficient to the on/off switch of hTERT by retinoids. DNA methylation analysis of the hTERT promoter led to the identification of two distinct functional domains, a proximal one, fully unmethylated in both cell lines, and a distal one, significantly methylated in NB4-LR1(SFD) cells, whose methylation was further re-enforced by retinoid treatment. Interestingly, we showed that the binding to this distal domain of a known hTERT repressor, WT1, was defective only in NB4-LR1(SFD) cells. We propose that epigenetic modifications targeting this distal region could modulate the binding of hTERT repressors and account either for hTERT reactivation and resistance to retinoid-induced hTERT downregulation.
Ju W, Yoo BC, Kim IJ, et al.Identification of genes with differential expression in chemoresistant epithelial ovarian cancer using high-density oligonucleotide microarrays.
Oncol Res. 2009; 18(2-3):47-56 [PubMed
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A major obstacle in treatment of epithelial ovarian cancer is chemoresistance. The aim of this study was to determine whether distinct gene expression profiles are associated with chemoresistance in epithelial ovarian carcinoma. We performed global gene expression analysis in 13 primary epithelial ovarian cancer tissues including 5 primary chemosensitive tumors and 8 primary chemoresistant tumors using Affymetrix HGU133A microarray. The gene expression patterns of chemosensitive tumors were compared with those of chemoresistant tumors using fold change. Validity of microarray results was examined by semiquantitative RT-PCR. We identified over 320 genes differentially expressed in chemoresistant epithelial ovarian cancer (> or = twofold). Upregulated genes in chemoresistant tumors included cell cycle regulating genes (TOP2A, BCAT1, CDCA8, CCNA2, CENPE), and genes with previously known mechanisms in tumorigenesis (S100A9, APOA1, RNF125, IFI16). Downregulated genes in chemoresistant tumors included genes related to cell adhesion (MUC5B, CITED2), transcription regulating genes (FOXD1, MAD1L1, PAX2), genes involving signal transduction (SOSTDC1, SNX1, SFRP1, FOXA2, PLK2), and stress protein gene (TP53AP1). These data show that gene expression profiling can discriminate primary chemoresistant from primary chemosensitive ovarian cancers. This type of molecular profiling could provide a basis for additional functional studies.
Toaldo C, Pizzimenti S, Cerbone A, et al.PPARgamma ligands inhibit telomerase activity and hTERT expression through modulation of the Myc/Mad/Max network in colon cancer cells.
J Cell Mol Med. 2010; 14(6A):1347-57 [PubMed
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In human cells the length of telomeres depends on telomerase activity. This activity and the expression of the catalytic subunit of human telomerase reverse transcriptase (hTERT) is strongly up-regulated in most human cancers. hTERT expression is regulated by different transcription factors, such as c-Myc, Mad1 and Sp1. In this study, we demonstrated that 15d-PG J2 and rosiglitazone (an endogenous and synthetic peroxisome proliferators activated receptor gamma (PPARgamma) ligand, respectively) inhibited hTERT expression and telomerase activity in CaCo-2 colon cancer cells. Moreover, both ligands inhibited c-Myc protein expression and its E-box DNA binding activity. Additionally, Mad1 protein expression and its E-box DNA binding activity were strongly increased by 15d-PG J2 and, to a lesser extent, by rosiglitazone. Sp1 transcription factor expression and its GC-box DNA binding activity were not affected by both PPARgamma ligands. Results obtained by transient transfection of CaCo-2 cells with pmaxFP-Green-PRL plasmid constructs containing the functional hTERT core promoter (including one E-box and five GC-boxes) and its E-box deleted sequences, cloned upstream of the green fluorescent protein reporter gene, demonstrated that 15d-PG J2, and with minor effectiveness, rosiglitazone, strongly reduced hTERT core promoter activity. E-boxes for Myc/Mad/Max binding showed a higher activity than GC-boxes for Sp1. By using GW9662, an antagonist of PPARgamma, we demonstrated that the effects of 15d-PG J2 are completely PPARgamma independent, whereas the effects of rosiglitazone on hTERT expression seem to be partially PPARgamma independent. The regulation of hTERT expression by 15d-PG J2 and rosiglitazone, through the modulation of the Myc/Max/Mad1 network, may represent a new mechanism of action of these substances in inhibiting cell proliferation.