title: Identification of hypermethylated genes associated with cisplatin resistance in human cancers.
abstract: Cisplatin is among the most widely used cytotoxic anticancer agents in solid tumors; however, the development of secondary resistance remains a major obstacle to clinical efficacy. Treatment-related DNA hypermethylation may play a role in creating drug-resistant phenotypes by inactivating genes that are required for cytotoxicity. We applied a pharmacologic unmasking approach to detect hypermethylated genes whose inactivation contributes to cisplatin resistance. Using three pairs of isogeneic, cisplatin-sensitive, and cisplatin-resistant cell lines derived from two parental cell lines (KB-3-1 and SCC25), we identified several hundred genes that were downregulated in each resistant cell line and reactivated by the DNA methyltransferase inhibitor 5-aza-2'-deoxycytidine. Among them, 30 genes were common to two or more cell lines and/or reported to be downregulated in previous studies. Bisulfite sequencing confirmed that 14 genes were hypermethylated in resistant cell lines but not in the sensitive parental cell lines. Six of 14 genes (SAT, C8orf4, LAMB3, TUBB, G0S2, and MCAM) were cisplatin inducible in sensitive but not in resistant cell lines. Small interfering RNA knockdown of two genes, SAT and S100P, increased cell viability with cisplatin treatment in sensitive parental cell lines. S100P knockdown significantly decreased the S-phase fraction of parental sensitive cell lines and slowed cell proliferation, which was associated with decreased sensitivity to cisplatin. Based on these findings, we conclude that DNA methylation is a frequent event in cells that are chronically exposed to cisplatin and that methylation-induced gene silencing may play a role in the development of resistance to cytotoxic chemotherapeutic agents.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Head and Neck Cancer Research Division, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA.
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Chang
authors.forename: Constance L
authors.initials: CL
authors.lastname: Monitto
authors.forename: Semra
authors.initials: S
authors.lastname: Demokan
authors.forename: Myoung Sook
authors.initials: MS
authors.lastname: Kim
authors.forename: Steven S
authors.initials: SS
authors.lastname: Chang
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Zhong
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Califano
authors.forename: David
authors.initials: D
authors.lastname: Sidransky
mesh_terms: D000465:Algorithms; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000235:genetics; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy* / Q000235:genetics*; D002453:Cell Cycle / Q000235:genetics; D048708:Cell Growth Processes / Q000235:genetics; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology*; D019175:DNA Methylation; D000077209:Decitabine; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D055785:Gene Knockdown Techniques; D020868:Gene Silencing; D006801:Humans; D007624:KB Cells; D009363:Neoplasm Proteins / Q000235:genetics; D011401:Promoter Regions, Genetic; D034741:RNA, Small Interfering / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014158:Transcription, Genetic / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D002135:Calcium-Binding Proteins; D009363:Neoplasm Proteins; D034741:RNA, Small Interfering; C103003:S100P protein, human; D000077209:Decitabine; D001374:Azacitidine; D002945:Cisplatin