Research IndicatorsGraph generated 31 August 2019 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 31 August, 2019 using data from PubMed, MeSH and CancerIndex
Specific Cancers (5)
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: FLNC (cancer-related)
Qian L, Xu F, Wang X, et al.LncRNA expression profile of ΔNp63α in cervical squamous cancers and its suppressive effects on LIF expression.
Cytokine. 2017; 96:114-122 [PubMed
] Related Publications
We aim to determine the lncRNA targets of ΔNp63α in cervical cancer and molecular programs in cancerous differentiation. Different profiles of the lncRNAs were assayed and validated in overexpressing p63 SiHa cells (SiHa/ΔNp63α) and the control cell lines (SiHa/pCon). ENST00000422259, ENST00000447565 (Lnc-LIF-AS) and ENST00000469965, together with their related antisense mRNA DPYD (dihydropyrimidine dehydrogenase, a pyrimidine catabolic pathway gene), LIF (leukemia inhibitor factor) and FLNC (filamin C) were all notably differentially expressed in both ΔNp63α overexpression cells and knockdown cells. Here, we illustrated that ΔNp63α can inhibit the levels of LIF mRNA by direct transcription regulation and decrease LIF mRNA stability by suppressing the expression of Lnc-LIF-AS. An inverse interaction of LIF and ΔNp63α expression was as well validated in clinical samples of cervical cancer, and high level of LIF in cervical cancers was related with poor patient survival. The decrease of ΔNp63α also attenuated the differentiation of cervical cancerous cells. Suggesting that ΔNp63α may be form a complex network in regulation cervical cancerous differentiation.
Li W, Liu J, Zou D, et al.Exploration of bladder cancer molecular mechanisms based on miRNA-mRNA regulatory network.
Oncol Rep. 2017; 37(3):1461-1468 [PubMed
] Related Publications
To explore the complex molecular mechanisms of bladder cancer, mRNA and miRNA expression profiles were combined for systematic analyses. A total of 18 common differentially expressed genes (DEGs) were identified from two mRNA expression datasets which consisted of 206 tumor and 74 normal tissues. Then, survival analysis based on the SurvExpress database showed that the common DEGs were able to significantly differentiate low- and high-risk groups in 4 public bladder cancer datasets (p<0.01). Notably, the tumor and normal samples were able to be almost clearly classified into 4 groups based on these identified common DEGs. In addition, 6 out of the 18 common DEGs, including ALDH1A1 and SRPX, are regulated by 6 reported miRNAs based on regulatory network analyses. Expression levels of the 6 DEGs were validated in 10 bladder cancer samples using RT-PCR, and the expression values were concordant with the microarray results. Collectively, our analyses indicated that various biological processes are involved in the development and progression of bladder cancer. Firstly, cell cycle checkpoints and DNA repair networks of cancer stem-like cells were regulated by high expression of ALDH1A1, and hence promoted tumor self-renewal or metastasis. Then, activation of HspB6 induced the angiogenesis process which provides necessary nutrition and oxygen for tumor cells. Moreover, downregulation of the expression of tumor-suppressor genes SRPX and FLNC further promoted apoptosis and metastasis. The identification of potential biological processes and genes can be helpful for the understanding of bladder cancer molecular mechanisms.
Tanabe K, Shinsato Y, Furukawa T, et al.Filamin C promotes lymphatic invasion and lymphatic metastasis and increases cell motility by regulating Rho GTPase in esophageal squamous cell carcinoma.
Oncotarget. 2017; 8(4):6353-6363 [PubMed
] Free Access to Full Article Related Publications
To establish treatments to improve the prognosis of cancer patients, it is necessary to find new targets to control metastasis. We found that expression of FilaminC (FLNC), a member of the actin binding and cross-linking filamin protein family is correlated with lymphatic invasion and lymphatic metastasis in esophageal squamous cell carcinoma (ESCC) by increasing cell motility through activation of Rho GTPase.Immunohistochemistry analysis showed that FLNC expression in ESCC is associated with lymphatic invasion, metastasis, and prognosis. FLNC knockdown in esophageal cancer cell lines decreased cell migration in wound healing and transwell migration assays, and invasion in transwell migration assays. Furthermore, FLNC knockdown reduced the amount of activated Rac-1 (GTP-Rac1) and activated Cdc42 (GTP-Cdc42). Our results suggest that FLNC expression is a useful biomarker of ESCC metastatic tendency and that inhibiting FLNC function may be useful to control the metastasis of ESCC.
E-cadherin (CDH1) is a glycoprotein that mediates adhesion between epithelial cells and also suppresses cancer invasion. Mutation or deletion of the CDH1 gene has been reported in 30-60% cases of invasive lobular carcinoma (ILC). However, little is known about genomic differences between ILC with and without a CDH1 alteration. Therefore, we analyzed whole genome sequencing data of 169 ILC cases from The Cancer Genome Atlas (TCGA) to address this deficiency. Our study shows that CDH1 gene was altered in 59.2% (100/169) of ILC. No significant difference was identified between CDH1-altered and -unaltered ILC cases for any of the examined demographic, clinical or pathologic characteristics, including histologic grade, tumor stage, lymph node metastases, or ER/PR/HER2 states. Seven recurrent mutations (PTEN, MUC16, ERBB2, FAT4, PCDHGA2, HERC1 and FLNC) and four chromosomal changes with recurrent copy number variation (CNV) (11q13, 17q12-21, 8p11 and 8q11) were found in ILC, which correlated with a positive or negative CDH1 alteration status, respectively. The prevalence of the most common breast cancer driver abnormalities including TP53 and PIK3CA mutations and MYC and ERBB2 amplifications showed no difference between the two groups. However, CDH1-altered ILC with an ERBB2 mutation shows a significantly worse prognosis compared to its counterparts without such a mutation. Our study suggests that CDH1-altered ILC patients with ERBB2 mutations may represent an actionable group of patients who could benefit from targeted breast cancer therapy.
Giant cell tumor of bone (GCT) is the most commonly reported non-malignant bone tumor in Hong Kong. This kind of tumor usually affects people aged 20-40 years. Also, it is well known for recurrence locally, especially when the tumor cannot be removed completely. Filamins are actin-binding proteins which contain three family members, filamin A, B and C. They are the products of three different genes, FLNA, FLNB and FLNC, which can generate various transcript variants in different cell types. In this study, we focused on the effects of FLNBv2 and FLNBv4 toward GCT cells. The only difference between FLNBv2 and FLNBv4 is that FLNBv4 does not contain hinge 1 region. We found that the relative abundance of FLNBv4 varies among different GCT cell lines while the expression level of FLNBv4 in normal osteoblasts was only marginally detectable. In the functional aspect, overexpression of FLNBv4 led to upregulation of RANKL, OCN, OPG and RUNX2, which are closely related to GCT cell survival and differentiation. Moreover, FLNBv4 can have a negative effect on cell viability of GCT cells when compare with FLNBv2. In conclusion, splicing variants of FLNB are differentially expressed in GCT cells and may play a role in the proliferation and differentiation of tumor cells.
Li H, Lei B, Xiang W, et al.Differences in Protein Expression between the U251 and U87 Cell Lines.
Turk Neurosurg. 2017; 27(6):894-903 [PubMed
] Related Publications
AIM: The U251 and U87 cell lines are commonly used as experimental models of glioblastoma. However, these cells exhibit significant differences in their proliferation, invasion, and migration. The aim of the present study was to compare the protein expression profiles of the U251 and U87 cell lines in order to provide a molecular basis for the observed phenotypic differences.
MATERIAL AND METHODS: Isobaric tags for relative and absolute quantitation (iTRAQ) and gene ontology (GO) analyses were performed to detect differentially expressed proteins and to predict protein functions, respectively.
RESULTS: Two hundred and forty-four proteins were highly expressed, while 263 proteins exhibited lower levels of expression, in the U251 cells compared to the U87 cells. In particular, higher expression levels of the proteins, C10orf58, FLNC, PDLIM1, TPM4, and lower expression levels of MYH10, PSIP1, SYNM, SLC9A3R2, BCAM, were verified by qPCR in the U251 cell line versus the U87 cell line. When a GO analysis was applied to the iTRAQ results, the proteins that were highly expressed in the U251 cells were found to differ in their molecular functions, biological processes, cellular distribution, and cellular pathways associated with them compared with the highly expressed proteins detected in the U87 cells.
CONCLUSION: Differentially expressed proteins between the U251 and U87 cell lines are associated with regulation of nicotinamide nucleotide metabolism, RNA splicing, glycolysis, and purine metabolism pathways. Further studies on these pathways may identify whether these various pathways account for the observed phenotype differences between the U87 and U251 GBM cell lines.
Hepatocellular carcinoma (HCC) caused by hepatitis B virus (HBV) infection is one of the most life-threatening human cancers in China. However, the pathogenesis of HCC development is still unclear. Here, we systemically analyzed liver tissues from different stages of HCC patients through 8-plex Isobaric Tags for Relative and Absolute Quantitation (iTRAQ) approach. A total of 4,620 proteins were identified and 3,781 proteins were quantified. When T1, T2 and T3 tumor tissues were compared with T1 non-tumor cells, 330, 365 and 387 differentially expressed proteins were identified respectively. IPA (Ingenuity Pathway Analysis) analysis revealed that these differentially expressed proteins were involved in endothelial cancer, cell spreading, cell adhesion and cell movement of tumor cell lines pathway and so on. Further study showed that the filamin C (FLNC) protein was significantly overexpressed with the development of HCC, which might play an important role in HCC invasion and metastasis. These results were also confirmed with western blot (WB). The mRNA levels were significantly increased in 50 pairs of tumor and adjacent non-tumor tissues from TCGA database. The higher expression of FLNC in HCC might be a common phenomenon, thereby shedding new light on molecular mechanism and biomarker for the diagnosis purpose of HCC development.
BACKGROUND: Aberrant promoter methylation has been considered as a potential molecular marker for gastric cancer (GC). However, the role of methylation of FLNC, THBS1, and UCHL1 in the development and progression of GC has not been explored.
METHODS: The promoter methylation status of UCHL1, FLNC, THBS1, and DLEC1 was assessed by quantitative methylation-specific PCR (QMSP) in the serum of 82 GC patients, 46 chronic atrophic gastritis (CAG) subjects, and 40 healthy controls.
RESULTS: All four genes had significantly higher methylation levels in GC patients than in CAG and control subjects. However, only UCHL1 methylation was significantly correlated with the tumor stage and lymph node metastasis. While THBS1 methylation was altered in an age-dependent manner, FLNC methylation was correlated with differentiation and Helicobacter pylori infection. DLEC1 methylation was only associated with tumor size. Moreover, methylated UCHL1 with or without THBS1 in the serum was found to be significantly associated with a poor prognosis.
CONCLUSION: The promoter methylation degree of FLNC, THBS1, UCHL1, and DLEC1 in serum could tell the existence of GC and only UCHL1 in the serum was also associated with poor prognosis of GC.
Aakula A, Kohonen P, Leivonen SK, et al.Systematic Identification of MicroRNAs That Impact on Proliferation of Prostate Cancer Cells and Display Changed Expression in Tumor Tissue.
Eur Urol. 2016; 69(6):1120-8 [PubMed
] Related Publications
BACKGROUND: Systematic approaches to functionally identify key players in microRNA (miRNA)-target networks regulating prostate cancer (PCa) proliferation are still missing.
OBJECTIVE: To comprehensively map miRNA regulation of genes relevant for PCa proliferation through phenotypic screening and tumor expression data.
DESIGN, SETTING, AND PARTICIPANTS: Gain-of-function screening with 1129 miRNA molecules was performed in five PCa cell lines, measuring proliferation, viability, and apoptosis. These results were integrated with changes in miRNA expression from two cohorts of human PCa (188 tumors in total). For resulting miRNAs, the predicted targets were collected and analyzed for patterns with gene set enrichment analysis, and for their association with biochemical recurrence free survival.
OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS: Rank product statistical analysis was used to evaluate miRNA effects in phenotypic screening and for expression differences in the prostate tumor cohorts. Expression data were analyzed using the significance analysis of microarrays (SAM) method and the patient material was subjected to Kaplan-Meier statistics.
RESULTS AND LIMITATIONS: Functional screening identified 25 miRNAs increasing and 48 miRNAs decreasing cell viability. Data integration resulted in 14 miRNAs, with aberrant expression and effect on proliferation. These miRNAs are predicted to regulate >3700 genes, of which 28 were found up-regulated and 127 down-regulated in PCa compared with benign tissue. Seven genes, FLNC, MSRB3, PARVA, PCDH7, PRNP, RAB34, and SORBS1, showed an inverse association to their predicted miRNA, and were identified to significantly correlate with biochemical recurrence free survival in PCa patients.
CONCLUSIONS: A systematic in vitro screening approach combined with in vivo expression and gene set enrichment analysis provide unbiased means for revealing novel miRNA-target links, possibly driving the oncogenic processes in PCa.
PATIENT SUMMARY: This study identified novel regulatory molecules, which impact on PCa proliferation and are aberrantly expressed in clinical tumors. Thus, our study reveals regulatory nodes with potential for therapy.
Singh TD, Gupta S, Shrivastav BR, Tiwari PKEpigenetic profiling of gallbladder cancer and gall stone diseases: Evaluation of role of tumour associated genes.
Gene. 2016; 576(2 Pt 2):743-52 [PubMed
] Related Publications
BACKGROUND: As on today, the global mortality rate of gallbladder cancer is still very high. Both genetic and epigenetic alterations play pivotal roles in the development of cancer. We selected seven tumour associated genes, implicated in other cancers, to assess their methylation status in gallbladder cancer and gallstone diseases.
AIM OF STUDY: To study the promoter methylation of certain tumour associated genes in the molecular pathogenesis of gallbladder cancer and gall stone diseases.
MATERIALS AND METHODS: Methylation specific PCR for seven tumour associated genes, viz., MASPIN, 14-3-3 sigma gene, THBS1, FLNC, HLTF, COX-2 and SOCS1, was performed in 50 gallbladder cancer (GBC), 30 gall stone diseases (GSD) and their respective adjacent control tissues. Semi-quantitative PCR and immunohistochemistry was carried out to check the expression level. Student's t-test was carried out to compare the differences in the methylation and expression patterns between cases and control tissues.
RESULTS: We observed methylation of CpG islands in seven of the studied markers, but, the frequency of methylation was found varying among different samples. Of them, 14-33 sigma showed methylation in 45 GBC (90%; p=0.0001) and 25 GSD (86.66%; p=0.001), MASPIN in 35 GBC (70%; p=0.0008) and 18 GSD (51.43%; p=0.040), FLNC in 16 GBC (32%; p=0.0044) and 9 GSD (25.71%; p=ns), THBS1 in 26 GBC (52%; p=0.0009) and 10 GSD (28.57%; p=0.0505), HLTF in 8 GBC (16%; p=ns) and 2 GSD (5.71%; p=ns), COX2 in 10 GBC (20%; p=ns) and 6 GSD (17.14%; p=ns) and SOCS-1 in 3 GBC samples only (6%; p=ns), but not in GSD. Semi-quantitative PCR revealed down regulation in MASPIN, 14-3-3 sigma, THBS1, HLTF, COX2 and SOCS1 in advanced gallbladder cases. Immunohistochemistry further confirmed the down-regulation of SOCS1 in GBC.
CONCLUSION: The present study infers that accumulation of epigenetic alterations increases poor prognosis of GBC patients. Out of seven genes, MASPIN and THBS1 play key epigenetic role in GBC, but not in GSD. The reason for downregulation of SOCS1 only in GBC, and unaltered expression of 14-3-3 sigma protein in all the GBC and GSD tissue samples is not clear. Further investigation on the expression pattern of these genes in GBC cell lines may elucidate their likely functional role in in association with gallbladder cancer.
BACKGROUND: Glioma is the most common primary malignant central nervous system tumor in adult, and is usually not curable due to its invasive nature. Establishment of serum biomarkers for glioma would be beneficial both for early diagnosis and adequate therapeutic intervention. Filamins are an actin cross-linker and filamin C (FLNC), normally restricted in muscle tissues, offers many signaling molecules an essential communication fields. Recently, filamins have been considered important for tumorigenesis in cancers.
METHODS: We searched for novel glioma-associated antigens by serological identification of antigens utilizing recombinant cDNA expression cloning (SEREX), and found FLNC as a candidate protein. Tissue expressions of FLNC (both in normal and tumor tissues) were examined by immunohistochemistry and quantitative RT-PCR analyses. Serum anti-FLNC autoantibody level was measured by ELISA in normal volunteers and in the patients with various grade gliomas.
RESULTS: FLNC was expressed in glioma tissues and its level got higher as tumor grade advanced. Anti-FLNC autoantibody was also detected in the serum of glioma patients, but its levels were inversely correlated with the tissue expression. Serum anti-FLNC autoantibody level was significantly higher in low-grade glioma patients than in high-grade glioma patients or in normal volunteers, which was confirmed in an independent validation set of patients' sera. The autoantibody levels in the patients with meningioma or cerebral infarction were at the same level of normal volunteers, and they were significantly lower than that of low-grade gliomas. Total IgG and anti-glutatione S-transferase (GST) antibody level were not altered among the patient groups, which suggest that the autoantibody response was specific for FLNC.
CONCLUSIONS: The present results suggest that serum anti-FLNC autoantibody can be a potential serum biomarker for early diagnosis of low-grade gliomas while it needs a large-scale clinical study.
Yadav DS, Chattopadhyay I, Verma A, et al.A pilot study evaluating genetic alterations that drive tobacco- and betel quid-associated oral cancer in Northeast India.
Tumour Biol. 2014; 35(9):9317-30 [PubMed
] Related Publications
The susceptibility of an individual to oral cancer is mediated by genetic factors and carcinogen-exposure behaviors such as betel quid chewing, tobacco use, and alcohol consumption. This pilot study was aimed to identify the genetic alteration in 100 bp upstream and downstream flanking regions in addition to the exonic regions of 169 cancer-associated genes by using Next Generation sequencing with aim to elucidate the molecular pathogenesis of tobacco- and betel quid-associated oral cancer of Northeast India. To understand the role of chemical compounds present in tobacco and betel quid associated with the progression of oral cancer, single nucleotide polymorphisms (SNPs) and insertion and deletion (Indels) found in this study were analyzed for their association with chemical compounds found in tobacco and betel quid using Comparative Toxogenomic Database. Genes (AR, BRCA1, IL8, and TP53) with novel SNP were found to be associated with arecoline which is the major component of areca nut. Genes (BARD1, BRCA2, CCND2, IGF1R, MSH6, and RASSF1) with novel deletion and genes (APC, BRMS1, CDK2AP1, CDKN2B, GAS1, IGF1R, and RB1) with novel insertion were found to be associated with aflatoxin B1 which is produced by fermented areca nut. Genes (ADH6, APC, AR, BARD1, BRMS1, CDKN1A, E2F1, FGFR4, FLNC, HRAS, IGF1R, IL12B, IL8, NBL1, STAT5B, and TP53) with novel SNP were found to be associated with aflatoxin B1. Genes (ATM, BRCA1, CDKN1A, EGFR, IL8, and TP53) with novel SNP were found to be associated with tobacco specific nitrosamines.
Biomarkers are important for early detection of cancer, prognosis, response prediction, and detection of residual or relapsing disease. Special attention has been given to diagnostic markers for prostate cancer since it is thought that early detection and surgery might reduce prostate cancer-specific mortality. The use of prostate-specific antigen, PSA (KLK3), has been debated on the base of cohort studies that show that its use in preventive screenings only marginally influences mortality from prostate cancer. Many groups have identified alternative or additional markers, among which PCA3, in order to detect early prostate cancer through screening, to distinguish potentially lethal from indolent prostate cancers, and to guide the treatment decision. The large number of markers proposed has led us to the present study in which we analyze these indicators for their diagnostic and prognostic potential using publicly available genomic data. We identified 380 markers from literature analysis on 20,000 articles on prostate cancer markers. The most interesting ones appeared to be claudin 3 (CLDN3) and alpha-methysacyl-CoA racemase highly expressed in prostate cancer and filamin C (FLNC) and keratin 5 with highest expression in normal prostate tissue. None of the markers proposed can compete with PSA for tissue specificity. The indicators proposed generally show a great variability of expression in normal and tumor tissue or are expressed at similar levels in other tissues. Those proposed as prognostic markers distinguish cases with marginally different risk of progression and appear to have a clinically limited use. We used data sets sampling 152 prostate tissues, data sets with 281 prostate cancers analyzed by microarray analysis and a study of integrated genomics on 218 cases to develop a multigene score. A multivariate model that combines several indicators increases the discrimination power but does not add impressively to the information obtained from Gleason scoring. This analysis of 10 years of marker research suggests that diagnostic and prognostic testing is more difficult in prostate cancer than in other neoplasms and that we must continue to search for better candidates.
The pathogenesis of splenic marginal zone lymphoma (SMZL) remains largely unknown. Recent high-throughput sequencing studies have identified recurrent mutations in key pathways, most notably NOTCH2 mutations in >25% of patients. These studies are based on small, heterogeneous discovery cohorts, and therefore only captured a fraction of the lesions present in the SMZL genome. To identify further novel pathogenic mutations within related biochemical pathways, we applied whole exome sequencing (WES) and copy number (CN) analysis to a biologically and clinically homogeneous cohort of seven SMZL patients with 7q abnormalities and IGHV1-2*04 gene usage. We identified 173 somatic non-silent variants, affecting 160 distinct genes. In additional to providing independent validation of the presence of mutation in several previously reported genes (NOTCH2, TNFAIP3, MAP3K14, MLL2 and SPEN), our study defined eight additional recurrently mutated genes in SMZL; these genes are CREBBP, CBFA2T3, AMOTL1, FAT4, FBXO11, PLA2G4D, TRRAP and USH2A. By integrating our WES and CN data we identified three mutated putative candidate genes targeted by 7q deletions (CUL1, EZH2 and FLNC), with FLNC positioned within the well-characterized 7q minimally deleted region. Taken together, this work expands the reported directory of recurrently mutated cancer genes in this disease, thereby expanding our understanding of SMZL pathogenesis. Ultimately, this work will help to establish a stratified approach to care including the possibility of targeted therapy.
Gastric cancer is one of the most common malignancies and remains the second leading cause of cancer-related death worldwide. Over 70% of new cases and deaths occur in developing countries. In the early years of the molecular biology revolution, cancer research mainly focuses on genetic alterations, including gastric cancer. Epigenetic mechanisms are essential for normal development and maintenance of tissue-specific gene expression patterns in mammals. Disruption of epigenetic processes can lead to altered gene function and malignant cellular transformation. Recent advancements in the rapidly evolving field of cancer epigenetics have shown extensive reprogramming of every component of the epigenetic machinery in cancer, including DNA methylation, histone modifications, nucleosome positioning, noncoding RNAs, and microRNAs. Aberrant DNA methylation in the promoter regions of gene, which leads to inactivation of tumor suppressor and other cancer-related genes in cancer cells, is the most well-defined epigenetic hallmark in gastric cancer. The advantages of gene methylation as a target for detection and diagnosis of cancer in biopsy specimens and non-invasive body fluids such as serum and gastric washes have led to many studies of application in gastric cancer. This review focuses on the most common and important phenomenon of epigenetics, DNA methylation, in gastric cancer and illustrates the impact epigenetics has had on this field.
Yoshida T, Kato J, Maekita T, et al.Altered mucosal DNA methylation in parallel with highly active Helicobacter pylori-related gastritis.
Gastric Cancer. 2013; 16(4):488-97 [PubMed
] Related Publications
BACKGROUND: Chronic inflammation triggered by Helicobacter pylori causes altered DNA methylation in stomach mucosae, which is deeply involved in gastric carcinogenesis. This study aimed to elucidate the correlation between altered mucosal DNA methylation levels and activity of H. pylori-related gastritis, because inflammatory activity shows particular correlations with the development of diffuse-type cancer.
METHODS: Methylation levels in stomach mucosae of 78 healthy volunteers were determined by real-time methylation-specific PCR or bisulfite pyrosequencing. Examined loci were the promoter CpG islands of six genes (FLNc, HAND1, THBD, p41ARC, HRASLS, and LOX) and the CpG sites of non-coding repetitive elements (Alu and Satα) that are reportedly altered by H. pylori infection. Activity of H. pylori-related gastritis was evaluated using two serum markers: H. pylori antibody titer and pepsinogen II.
RESULTS: Methylation levels of the six CpG islands were consistently increased, and those of the two repetitive elements were consistently decreased in a stepwise manner with the activity of gastric inflammation as represented by serum marker levels. Each serum marker level was well correlated with the overall DNA methylation status of stomach mucosa, and these two serologic markers were additive in the detection of the mucosa with severely altered DNA methylation.
CONCLUSIONS: Alteration in mucosal DNA methylation level was closely correlated with activity of H. pylori-related gastritis as evaluated by serum markers. The observed correlation between altered DNA methylation levels and activity of H. pylori-related gastritis appears to be one of the relevant molecular mechanisms underlying the development of diffuse-type cancer.
Mahapatra S, Klee EW, Young CY, et al.Global methylation profiling for risk prediction of prostate cancer.
Clin Cancer Res. 2012; 18(10):2882-95 [PubMed
] Related Publications
PURPOSE: The aim of this study was to investigate the promoter hypermethylation as diagnostic markers to detect malignant prostate cells and as prognostic markers to predict the clinical recurrence of prostate cancer.
EXPERIMENTAL DESIGN: DNA was isolated from prostate cancer and normal adjacent tissues. After bisulfite conversion, methylation of 14,495 genes was evaluated using the Methylation27 microarrays in 238 prostate tissues. We analyzed methylation profiles in four different groups: (i) tumor (n = 198) versus matched normal tissues (n = 40), (ii) recurrence (n = 123) versus nonrecurrence (n = 75), (iii) clinical recurrence (n = 80) versus biochemical recurrence (n = 43), and (iv) systemic recurrence (n = 36) versus local recurrence (n = 44). Group 1, 2, 3, and 4 genes signifying biomarkers for diagnosis, prediction of recurrence, clinical recurrence, and systemic progression were determined. Univariate and multivariate analyses were conducted to predict risk of recurrence. We validated the methylation of genes in 20 independent tissues representing each group by pyrosequencing.
RESULTS: Microarray analysis revealed significant methylation of genes in four different groups of prostate cancer tissues. The sensitivity and specificity of methylation for 25 genes from 1, 2, and 4 groups and 7 from group 3 were shown. Validation of genes by pyrosequencing from group 1 (GSTP1, HIF3A, HAAO, and RARβ), group 2 (CRIP1, FLNC, RASGRF2, RUNX3, and HS3ST2), group 3 (PHLDA3, RASGRF2, and TNFRSF10D), and group 4 (BCL11B, POU3F3, and RASGRF2) confirmed the microarray results.
CONCLUSIONS: Our study provides a global assessment of DNA methylation in prostate cancer and identifies the significance of genes as diagnostic and progression biomarkers of prostate cancer.
Zeller C, Dai W, Steele NL, et al.Candidate DNA methylation drivers of acquired cisplatin resistance in ovarian cancer identified by methylome and expression profiling.
Oncogene. 2012; 31(42):4567-76 [PubMed
] Related Publications
Multiple DNA methylation changes in the cancer methylome are associated with the acquisition of drug resistance; however it remains uncertain how many represent critical DNA methylation drivers of chemoresistance. Using isogenic, cisplatin-sensitive/resistant ovarian cancer cell lines and inducing resensitizaton with demethylating agents, we aimed to identify consistent methylation and expression changes associated with chemoresistance. Using genome-wide DNA methylation profiling across 27 578 CpG sites, we identified loci at 4092 genes becoming hypermethylated in chemoresistant A2780/cp70 compared with the parental-sensitive A2780 cell line. Hypermethylation at gene promoter regions is often associated with transcriptional silencing; however, expression of only 245 of these hypermethylated genes becomes downregulated in A2780/cp70 as measured by microarray expression profiling. Treatment of A2780/cp70 with the demethylating agent 2-deoxy-5'-azacytidine induces resensitization to cisplatin and re-expression of 41 of the downregulated genes. A total of 13/41 genes were consistently hypermethylated in further independent cisplatin-resistant A2780 cell derivatives. CpG sites at 9 of the 13 genes (ARHGDIB, ARMCX2, COL1A, FLNA, FLNC, MEST, MLH1, NTS and PSMB9) acquired methylation in ovarian tumours at relapse following chemotherapy or chemoresistant cell lines derived at the time of patient relapse. Furthermore, 5/13 genes (ARMCX2, COL1A1, MDK, MEST and MLH1) acquired methylation in drug-resistant ovarian cancer-sustaining (side population) cells. MLH1 has a direct role in conferring cisplatin sensitivity when reintroduced into cells in vitro. This combined genomics approach has identified further potential key drivers of chemoresistance whose expression is silenced by DNA methylation that should be further evaluated as clinical biomarkers of drug resistance.
Filamin-A, also called actin binding protein 280 (ABP-280), cross-links the actin filaments into dynamic orthogonal network to serve as scaffolds in multiple signaling pathways. It has been reported that filamin-A interacts with DNA damage response proteins BRCA1 and BRCA2. Defects of filamin-A impair the repair of DNA double strand breaks (DSBs), resulting in sensitization of cells to ionizing radiation. In this study, we sought to test the hypothesis that filamin-A can be used as a target for cancer chemotherapy and as a biomarker to predict cancer response to therapeutic DNA damage. We found that reduction of filamin-A sensitizes cancer cells to chemotherapy reagents bleomycin and cisplatin, delays the repair of not only DSBs but also single strand breaks (SSBs) and interstrand crosslinks (ICLs), and increases chromosome breaks after the drug treatment. By treating a panel of human melanoma cell lines with variable filamin-A expression, we observed a correlation between expression level of filamin-A protein and drug IC(50). We further inhibited the expression of filamin-A in melanoma cells, and found that this confers an increased sensitivity to bleomycin and cisplatin treatment in a mouse xenograft tumor model. These results suggest that filamin-A plays a role in repair of a variety of DNA damage, that lack of filamin-A is a prognostic marker for a better outcome after DNA damage based treatment, and filamin-A can be inhibited to sensitize filamin-A positive cancer cells to therapeutic DNA damage. Thus filamin-A can be used as a biomarker and a target for DNA damage based cancer therapy.
PURPOSE: The importance of genetic and epigenetic alterations maybe in their aggregate role in altering core pathways in tumorigenesis.
EXPERIMENTAL DESIGN: Merging genome-wide genomic and epigenomic alterations, we identify key genes and pathways altered in colorectal cancers (CRC). DNA methylation analysis was tested for predicting survival in CRC patients using Cox proportional hazard model.
RESULTS: We identified 29 low frequency-mutated genes that are also inactivated by epigenetic mechanisms in CRC. Pathway analysis showed the extracellular matrix (ECM) remodeling pathway is silenced in CRC. Six ECM pathway genes were tested for their prognostic potential in large CRC cohorts (n = 777). DNA methylation of IGFBP3 and EVL predicted for poor survival (IGFBP3: HR = 2.58, 95% CI: 1.37-4.87, P = 0.004; EVL: HR = 2.48, 95% CI: 1.07-5.74, P = 0.034) and simultaneous methylation of multiple genes predicted significantly worse survival (HR = 8.61, 95% CI: 2.16-34.36, P < 0.001 for methylation of IGFBP3, EVL, CD109, and FLNC). DNA methylation of IGFBP3 and EVL was validated as a prognostic marker in an independent contemporary-matched cohort (IGFBP3 HR = 2.06, 95% CI: 1.04-4.09, P = 0.038; EVL HR = 2.23, 95% CI: 1.00-5.0, P = 0.05) and EVL DNA methylation remained significant in a secondary historical validation cohort (HR = 1.41, 95% CI: 1.05-1.89, P = 0.022). Moreover, DNA methylation of selected ECM genes helps to stratify the high-risk stage 2 colon cancers patients who would benefit from adjuvant chemotherapy (HR: 5.85, 95% CI: 2.03-16.83, P = 0.001 for simultaneous methylation of IGFBP3, EVL, and CD109).
CONCLUSIONS: CRC that have silenced genes in ECM pathway components show worse survival suggesting that our finding provides novel prognostic biomarkers for CRC and reflects the high importance of integrative analyses linking genetic and epigenetic abnormalities with pathway disruption in cancer.
Kim JH, Jung EJ, Lee HS, et al.Comparative analysis of DNA methylation between primary and metastatic gastric carcinoma.
Oncol Rep. 2009; 21(5):1251-9 [PubMed
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Metastasis is a multi-step process involving many biomolecular changes and DNA methylation is one such molecular change. Although differences in DNA methylation have been reported in matched primary and metastatic mammary carcinoma, no such differences have been reported in gastric carcinoma. Accordingly, to investigate whether DNA methylation profiles in metastatic gastric carcinoma differ from those of their primary counterparts, we investigated the DNA methylation of eleven genes, ADAM23, CDH1, FHIT, FLNC, GSTP1, ITGA4, LOX, RUNX3, THBS1, TIMP3, and UCHL1 in 74 matched human primary gastric carcinomas, lymph node metastases, non-neoplastic gastric mucosal, and uninvolved lymph node tissues by utilizing methylation-specific PCR. Seven of these genes (ADAM23, FLNC, ITGA4, LOX, RUNX3, TIMP3, and UCHL1) showed cancer-specific methylation, and three (CDH1, FHIT, and THBS1) showed cancer-unrelated methylation. GSTP1 was rarely methylated in any tissue type. Of the seven genes that showed cancer-specific methylation, FLNC was more frequently methylated in metastatic gastric carcinomas than in their primary counterparts (p=0.004). In addition, the average number of methylated genes in metastatic tumors was greater than that in primary tumors (p=0.004). The high-methylation group (cases with three or more genes methylated in primary tumors) was found to contain more women (p=0.031) and diffuse type tumors by Lauren classification (p=0.022). DNA methylation profiles were not found to affect prognosis. We suggest that promoter methylation of FLNC may be involved in the lymph node metastasis of gastric carcinoma and that the DNA methylation statuses of metastatic tumors should be considered in node-positive gastric carcinoma.
To identify the relevant CpG sites as molecular markers, for the diagnosis and to distinguish the indolent and aggressive prostate tumors, we have determined the methylation status of 8 genes, including FLNC, EFS, ECRG4, RARB2, PITX2, GSTP1, PDLIM4, and KCNMA1 in 32 nonrecurrent, 32 recurrent primary prostate tumors, and 32 benign prostate tissues using EpiTYPER technology. Specific CpG site hypermethylation of RARB2 and GSTP1 CpG sites were useful for diagnosis of prostate cancer. Furthermore, CpG site hypermethylation of genes FLNC, EFS, ECRG4, PITX2, PDLIM4, and KCNMA1 were associated with prediction of biochemical, local, and systemic recurrence of prostate cancer.
Nakajima T, Maekita T, Oda I, et al.Higher methylation levels in gastric mucosae significantly correlate with higher risk of gastric cancers.
Cancer Epidemiol Biomarkers Prev. 2006; 15(11):2317-21 [PubMed
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BACKGROUND: Helicobacter pylori infection potently induces methylation of CpG islands in gastric mucosae, which is considered to decrease to a certain level after active H. pylori infection discontinues. Noncancerous gastric mucosae of H. pylori-negative cases with a gastric cancer had higher methylation levels than those of H. pylori-negative healthy individuals. Here, using cases with multiple gastric cancers, we analyzed whether the higher methylation levels correlated with the higher risk of gastric cancers.
METHODS: Twenty-six healthy volunteers (HV), 30 cases with a single well-differentiated gastric cancer (S cases), and 32 cases with multiple well-differentiated gastric cancers (M cases) were recruited. H. pylori infection status was analyzed by the culture method. Methylation levels were quantified by real-time methylation-specific PCR of seven CpG islands.
RESULTS: In H. pylori-negative individuals, significant increasing trends were present in the order of HV, S cases, and M cases for FLNc and HAND1 methylation levels (P < 0.01, Spearman's rank-order test). Furthermore, the FLNc methylation level of M cases was significantly higher than that of S cases (P < 0.01, t test). Even adjusted by the extent of gastric atrophy, the FLNc methylation level retained a significant increasing trend (P = 0.03). In contrast, methylation levels in H. pylori-positive individuals were increased to various degrees in all the three groups.
CONCLUSIONS: In H. pylori-negative individuals, methylation levels in gastric mucosae significantly increased in cases with a single gastric cancer and more in cases with multiple gastric cancers. Quantitative analysis of methylation levels is a promising risk marker for gastric cancers.
Chang MS, Uozaki H, Chong JM, et al.CpG island methylation status in gastric carcinoma with and without infection of Epstein-Barr virus.
Clin Cancer Res. 2006; 12(10):2995-3002 [PubMed
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PURPOSE: EBV-associated gastric carcinoma shows global CpG island methylation of the promoter region of various cancer-related genes. To further clarify the significance of CpG island methylator phenotype (CIMP) status in gastric carcinoma, we investigated methylation profile and clinicopathologic features including overall survival in four subgroups defined by EBV infection and CIMP status: EBV-associated gastric carcinoma and EBV-negative/CIMP-high (H), EBV-intermediate (I), and EBV-negative (N) gastric carcinoma.
EXPERIMENTAL DESIGN: Methylation-specific PCR was applied to 106 gastric carcinoma cases. CIMP-N, CIMP-I, and CIMP-H status was determined by the number (0, 1-3, and 4-5, respectively) of methylated marker genes (LOX, HRASLS, FLNc, HAND1, and TM), that were newly identified as highly methylated in gastric cancer cell lines. The methylation status of 10 other cancer-related genes (p14, p15, p16, p73, TIMP-3, E-cadherin, DAPK, GSTP1, hMLH1, and MGMT) was also evaluated.
RESULTS: Nearly all (14 of 15) of EBV-associated gastric carcinoma exhibited CIMP-H, constituting a homogenous group (14%). EBV-negative gastric carcinoma consisted of CIMP-H (24%), CIMP-I (38%), and CIMP-N (24%). EBV-associated gastric carcinoma showed significantly higher frequencies of methylation of cancer-related genes (mean number +/- SD = 6.9 +/- 1.5) even if compared with EBV-negative/CIMP-H gastric carcinoma (3.5 +/- 1.8). Among EBV-negative gastric carcinoma subgroups, CIMP-H gastric carcinoma showed comparatively higher frequency of methylation than CIMP-I or CIMP-N, especially of p16 and hMLH1. CIMP-N gastric carcinoma predominantly consisted of advanced carcinoma with significantly higher frequency of lymph node metastasis. The prognosis of the patients of CIMP-N was significantly worse compared with other groups overall by univariate analysis (P = 0.0313).
CONCLUSION: The methylation profile of five representative genes is useful to stratify gastric carcinomas into biologically different subgroups. EBV-associated gastric carcinoma showed global CpG island methylation, comprising a pathogenetically distinct subgroup in CIMP-H gastric carcinoma.
Oue N, Mitani Y, Motoshita J, et al.Accumulation of DNA methylation is associated with tumor stage in gastric cancer.
Cancer. 2006; 106(6):1250-9 [PubMed
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BACKGROUND: The authors purpose in this study was to clarify the difference in terms of clinicopathologic features between gastric cancer (GC) with high numbers of DNA methylated genes and CpG island methylator phenotype (CIMP)-positive GC as originally defined.
METHODS: We analyzed DNA methylation of 12 tumor-related genes (hMLH1, MGMT, p16(INK4a), CDH1, RAR-beta, HLTF, RIZ1, TM, FLNc, LOX, HRASLS, HAND1) in 75 samples of GC from 75 patients, 25 samples of corresponding nonneoplastic mucosa from 25 patients, and 10 samples of normal gastric mucosa from 10 healthy young individuals by methylation-specific polymerase chain reaction (PCR) and bisulfite PCR. We also investigated CIMP status by examining the methylation of five MINT loci and p53 mutation status by PCR single-strand conformation polymorphism. We measured levels of expression of mRNAs for these 12 genes by quantitative reverse transcription PCR in 50 GC specimens.
RESULTS: The average number of methylated genes per tumor was 4.83. DNA methylation of each gene was correlated with low expression of the respective mRNA. High methylation (GC with 5 or more methylated genes) was detected in 39 (52.0%) of 75 GCs. Twenty-nine (37.8%) of 75 GCs were CIMP-positive. DNA methylation of each of the 12 genes was observed more frequently in the high-methylation group than in the low-methylation group. Methylation of 6 specific genes occurred more frequently in CIMP-positive GC than in CIMP-negative GC. Methylation of the remaining 6 genes was not correlated with CIMP-status. High methylation was found more frequently in Stage III/IV GC (26 of 40 cases, 65.0%) than in Stage I/II GC (13 of 35 cases, 37.1%, P = 0.029).CONCLUSIONS.These findings indicate that GCs with higher numbers of methylated genes have more distinct DNA methylation profiles than the originally defined CIMP-positive GCs. DNA methylation of tumor-related genes accumulates in conjunction with tumor progression.
Imura M, Yamashita S, Cai LY, et al.Methylation and expression analysis of 15 genes and three normally-methylated genes in 13 Ovarian cancer cell lines.
Cancer Lett. 2006; 241(2):213-20 [PubMed
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Aberrant methylation of CpG islands (CGIs) in promoter regions of tumor-suppressor genes causes their silencing, and aberrant demethylation of normally methylated CGIs in promoter regions causes aberrant expression of cancer-testis antigens. Here, we comprehensively analyzed aberrant methylation of 15 genes and demethylation of three normally methylated genes in 13 ovarian cancer cell lines. RASSF1A was most frequently methylated (complete methylation in 7 and partial methylation in 4 cell lines), followed by ESR1 (5 and 2, respectively), FLNC (4 and 4), HAND1 (4 and 2), LOX (3 and 2), HRASLS (3 and 2), MGMT (3 and 0), CDKN2A (3 and 0), THBD (2 and 1), hMLH1 (2 and 0), CDH1 (1 and 1) and GSTP1 (1 and 0). hTERC and TIMP3 were only partially methylated in 7 and 2 cell lines, respectively. BRCA1 was not methylated at all. Aberrant demethylation of MAGE-A3, -B2 and -A1 was detected in 8, 4 and 3 cell lines, respectively. Gene expression was consistently absent in cell lines without unmethylated DNA molecules. Aberrant methylation was frequently observed in MCAS, RMUG-L (mucinous cell carcinomas), RTSG (poorly-differentiated carcinoma) and TYK-nu (undifferentiated carcinoma) while infrequent in HTOA, JHOS-2, and OV-90 (serous cell carcinomas). Aberrant demethylation was frequently observed in OV-90, OVK-18, and ES-2 cell lines. It was shown that aberrant methylation and demethylation were frequently observed in ovarian cancer cell lines, and these data will provide a basis for further epigenetic analysis in ovarian cancers.
Kaneda A, Kaminishi M, Sugimura T, Ushijima TDecreased expression of the seven ARP2/3 complex genes in human gastric cancers.
Cancer Lett. 2004; 212(2):203-10 [PubMed
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The Arp2/3 complex and filamins play important roles in organization of actin cytoskeleton, and thus in cellular morphology and locomotion. We recently identified decreased expression of a gene for one of seven subunits of the Arp2/3 complex, the p41-Arc gene, and silencing of a filamin gene, the FLNc gene, in human gastric cancers. In this study, gene expressions of the seven subunits of the Arp2/3 complex, including p41-Arc, and their methylation statuses were analyzed in human gastric cancers. Quantitative real-time RT-PCR analysis of 32 primary gastric cancer samples and eight gastric cancer cell lines revealed that expressions of all the seven genes were significantly decreased. All the 32 primary cancer samples showed decreased expression of at least one subunit, and 25 samples showed decreased expressions of four or more of the seven subunits. Methylation-specific PCR analysis showed that none of the CpG islands in the 5' regions of the six genes other than p41-Arc were methylated in primary gastric cancers or cell lines. The consistent decrease of the Arp2/3 complex genes and its important role in actin organization suggested that the decrease could be involved in cancer phenotypes, such as dysplastic morphology.
Kaneda A, Kaminishi M, Yanagihara K, et al.Identification of silencing of nine genes in human gastric cancers.
Cancer Res. 2002; 62(22):6645-50 [PubMed
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Aberrant methylations in human gastric cancers were searched for by a genome scanning technique, methylation-sensitive representational difference analysis. Nine CpG islands (CGIs) in the 5' regions of nine genes, LOX, HRASLS, bA305P22.2.3, FLNc (gamma-filamin/ABPL), HAND1, a homologue of RIKEN 2210016F16, FLJ32130, PGAR (HFARP/ANGPTL4/ARP4), and thrombomodulin, were found to be methylated in two gastric cancer cell lines, MKN28 and MKN74, but unmethylated in the normal sample. Their expressions were lost in the two cell lines, and the causal roles of the methylations in gene silencing were shown by treatment with 5-aza-2'-deoxycytidine. In 41 primary gastric cancers, methylations of these CGIs in association with reduced expressions were observed at high incidences (29-41%) for five genes, including LOX and HRASLS, which have been reported to have tumor-suppressive activities. The other four genes were methylated at low incidences (0-7%). By analysis of the numbers of aberrant methylations in individual cancers, a subset of cancers with high prevalence of aberrant methylations was identified, and all of the 11 cancers in the subset were diffuse type. To analyze the possible involvement of decreased fidelity of maintenance methylation in this subset of cancers, aberrant hypomethylations of three normally methylated CGIs were examined. Cancers with high prevalence of hypomethylations of normally methylated CGIs, however, constituted a different subset. It is expected that these nine genes may include important genes in gastric cancer development and would be useful to identify a distinct subset of gastric cancers.
Prat AG, Cunningham CC, Jackson GR, et al.Actin filament organization is required for proper cAMP-dependent activation of CFTR.
Am J Physiol. 1999; 277(6):C1160-9 [PubMed
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Previous studies have indicated a role of the actin cytoskeleton in the regulation of the cystic fibrosis transmembrane conductance regulator (CFTR) ion channel. However, the exact molecular nature of this regulation is still largely unknown. In this report human epithelial CFTR was expressed in human melanoma cells genetically devoid of the filamin homologue actin-cross-linking protein ABP-280 [ABP(-)]. cAMP stimulation of ABP(-) cells or cells genetically rescued with ABP-280 cDNA [ABP(+)] was without effect on whole cell Cl(-) currents. In ABP(-) cells expressing CFTR, cAMP was also without effect on Cl(-) conductance. In contrast, cAMP induced a 10-fold increase in the diphenylamine-2-carboxylate (DPC)-sensitive whole cell Cl(-) currents of ABP(+)/CFTR(+) cells. Further, in cells expressing both CFTR and a truncated form of ABP-280 unable to cross-link actin filaments, cAMP was also without effect on CFTR activation. Dialysis of ABP-280 or filamin through the patch pipette, however, resulted in a DPC-inhibitable increase in the whole cell currents of ABP(-)/CFTR(+) cells. At the single-channel level, protein kinase A plus ATP activated single Cl(-) channels only in excised patches from ABP(+)/CFTR(+) cells. Furthermore, filamin alone also induced Cl(-) channel activity in excised patches of ABP(-)/CFTR(+) cells. The present data indicate that an organized actin cytoskeleton is required for cAMP-dependent activation of CFTR.
Tantravahi R, Dudek H, Patel G, Reddy EPMurine myeloid leukemic cells with disrupted myb loci show splicing anomalies that account for heterogeneous sizes in myb proteins.
Oncogene. 1996; 13(6):1187-96 [PubMed
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The ABPL tumor cell lines represent a group of myeloid cell lines which contain an altered myb locus due to viral insertional mutagenesis within the third exon of c-myb. Immunoprecipitation analysis of the proteins produced in three ABPL lines revealed an interesting anomaly. Despite the invariant position of the virus integration event, the three ABPL tumor cell lines we examined (ABPL-1, ABPL-2 and ABPL-4) produced three different sized proteins. In this report, we examined the molecular basis for this protein size heterogeneity. Molecular cloning and sequence analysis of the cDNAs derived from the myb transcripts show that ABPL-1 tumor produces a tripartate mRNA containing sequences derived from the viral gag and env genes fused to the myb coding region. This results in the synthesis of a 74 kd protein. In the ABPL-2 tumor line, a gag-myb fusion protein is produced which is of 68 kd. In ABPL-4 cell line a gag-myb fusion protein is produced which contains an internal deletion of coding sequences derived from exons 13 and 14. This deletion results in the synthesis of a 59 kd protein in ABPL-4 tumor cell line. These observations were further confirmed by RNase protection assays which demonstrate the presence of aberrantly spliced mRNAs in ABPL-1 and ABPL-4 tumor cells but not in cells containing an undisrupted c-myb locus. In vitro translation and immuno-precipitation analysis of the cRNAs derived from the ABPL-1, ABPL-2 and ABPL-4 cDNAs show the synthesis of protein products that were identical to Myb proteins produced by these tumors in vivo. These results suggest that integration of Mo-MuLV within the c-myb locus not only results in deletions of the 5' end of the transcript but splicing aberrations within the encoded mRNA, which results in the synthesis of a heterogeneous array of proteins, not seen in normal hematopoietic cells.