title: Riboregulator H19 induction of MDR1-associated drug resistance in human hepatocellular carcinoma cells.
abstract: Acquisition of drug resistance is one of the main obstacles encountered in cancer chemotherapy. Overexpression of multi-drug resistance 1 (MDR1) gene and its protein product P-glycoprotein, accompanied with a decrease in doxorubicin accumulation level, was observed in doxorubicin-resistant R-HepG2 cells, a subline derived by selection of human hepatocellular carcinoma HepG2 cells with doxorubicin. In addition, Northern-blot analysis revealed an eight fold upregulation of the imprinted H19 mRNA in R-HepG2 cells. H19 knockdown by transfection with antisense H19 oligonucleotides suppressed the MDR1/P-glycoprotein expression, increased the cellular doxorubicin accumulation level and sensitized doxorubicin toxicity in both HepG2 parent cells and R-HepG2 cells. Results from methylation-specific polymerase chain reaction analysis indicated that the MDR1 gene promoter was hypomethylated in R-HepG2 cells. Antisense H19 oligonucleotides transfection induced a marked increase in the percentage of MDR1 promoter methylation and decrease in MDR1 expression in R-HepG2 cells. Thus, the H19 gene is believed to induce P-glycoprotein expression and MDR1-associated drug resistance at least in liver cancer cells through regulation of MDR1 promoter methylation.
authors.affiliation: Department of Biochemistry, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China.
authors.forename: W P
authors.initials: WP
authors.lastname: Tsang
authors.forename: T T
authors.initials: TT
authors.lastname: Kwok
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics* / Q000378:metabolism; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology; D015152:Blotting, Northern; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D019175:DNA Methylation; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000494:pharmacology; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D016376:Oligonucleotides, Antisense / Q000235:genetics; D011401:Promoter Regions, Genetic; D062085:RNA, Long Noncoding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D022661:RNA, Untranslated / Q000235:genetics*; D014162:Transfection
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000903:Antibiotics, Antineoplastic; C094335:H19 long non-coding RNA; D016376:Oligonucleotides, Antisense; D062085:RNA, Long Noncoding; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D022661:RNA, Untranslated; D004317:Doxorubicin