title: Different involvement of promoter methylation in the expression of organic cation/carnitine transporter 2 (OCTN2) in cancer cell lines.
abstract: Organic cation/carnitine transporter 2 (OCTN2) is responsible for the cellular uptake of the antineoplastic agent, oxaliplatin. Epigenetic modification is a possible mechanism of altered drug-transporter expression in cancers, leading to altered efficacy of chemotherapeutic drugs. However, the mechanisms governing OCTN2 regulation are not completely understood. In this study, the low levels of OCTN2 in HepG2 and LS174T cells were elevated by the demethylating reagent, decitabine (DCA). To further reveal the epigenetic mechanism of down-regulation of OCTN2, we found that Region-1 within the OCTN2 promoter (spanning -354 to +85) was a determinant of OCTN2 expression in a luciferase reporter assay. Moreover, methylation-specific PCR (MSP) and bisulfite genomic sequencing showed that the degree of individual methylated CpG sites within this region was inversely correlated with the levels of OCTN2 in different cancer cells. Application of DCA to HepG2 and LS174T cells reversed the hypermethylation status of the OCTN2 promoter and increased OCTN2 expression, enhancing cellular uptake of oxaliplatin. Thus, we identified that promoter methylation is responsible for epigenetic down-regulation of OCTN2 in HepG2 and LS174T cells. Given the essential role of OCTN2 in cancer cell uptake of chemotherapeutics, and thus treatment efficacy, pretreatment with a demethylating reagent is a possible strategy for optimizing pharmacotherapies against cancers.
authors.affiliation: Institute of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, Xiangya School of Medicine, Central South University, Changsha, Hunan, China.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Qu
authors.forename: Jian
authors.initials: J
authors.lastname: Qu
authors.forename: Min
authors.initials: M
authors.lastname: Zhan
authors.forename: Lan-Xiang
authors.initials: LX
authors.lastname: Wu
authors.forename: Yi-Wen
authors.initials: YW
authors.lastname: Zhang
authors.forename: Xiao-Ya
authors.initials: XY
authors.lastname: Lou
authors.forename: Li-Juan
authors.initials: LJ
authors.lastname: Fu
authors.forename: Hong-Hao
authors.initials: HH
authors.lastname: Zhou
mesh_terms: D000818:Animals; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D001483:Base Sequence; D019556:COS Cells; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002522:Chlorocebus aethiops; D018899:CpG Islands; D019175:DNA Methylation / Q000235:genetics*; D000077209:Decitabine; D015972:Gene Expression Regulation, Neoplastic; D017930:Genes, Reporter; D015894:Genome, Human / Q000235:genetics; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000235:genetics*; D027701:Organic Cation Transport Proteins / Q000235:genetics* / Q000378:metabolism; D009944:Organoplatinum Compounds / Q000494:pharmacology; D000077150:Oxaliplatin; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D000074058:Solute Carrier Family 22 Member 5; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D027701:Organic Cation Transport Proteins; D009944:Organoplatinum Compounds; D012333:RNA, Messenger; C492020:SLC22A5 protein, human; D000074058:Solute Carrier Family 22 Member 5; D000077150:Oxaliplatin; D000077209:Decitabine; D008156:Luciferases; D001374:Azacitidine