title: Karyotypic imbalances and differential gene expressions in the acquired doxorubicin resistance of hepatocellular carcinoma cells.
abstract: Administration of doxorubicin has been shown to prolong survival of patients with hepatocellular carcinoma (HCC). However, treatment regimen is often complicated by the emergence of drug resistance. The goal of our study is to enhance our understanding on the genetic changes that confer cellular chemoresistance to doxorubicin. To model this insensitive response, we established five doxorubicin-resistant (DOR) sublines through repeated exposure of escalating doses of doxorubicin to HCC cell lines (HKCI-2, -3, -4, -C1 and -C2). The DOR sublines developed displayed an average approximately 17-fold higher IC(50) value than their sensitive parental cell lines. The resistant phenotype displayed was investigated by the genome-wide analyses of comparative genomic hybridization (CGH) and complementary DNA microarray for the affected genomic anomalies and deregulated genes expressed, respectively. Over-representations of regional chr. 7q11-q21, 8q22-q23 and 10p13-pter were indicated in the DOR sublines from CGH analysis. Of particular interest was the finding of amplicon augmentations from regional or whole chromosome gains during the clonal expansion of resistant sublines. Most notably, recurring amplicon 7q11.2-q21 identified coincided with the location of the multi-drug-resistant gene, MDR1. The potential involvement of MDR1 was examined by quantitative reverse transcription-polymerase chain reaction RT-PCR (qRT-PCR), which indicated an upregulation in all DOR sublines (P=0.015). Consistent overexpression of the translated MDR1 gene, P-glycoprotein, in all five DOR sublines was further confirmed in Western blot analysis. Two distinct cluster dendrograms were achieved between the DOR sublines and their sensitive parental counterparts in expression profiling. Within the doxorubicin-resistant group, distinct features of candidate genes overexpressions including ABC transporting proteins, solute carriers and TOP2A were suggested. Further assessment of TOP2A messenger RNA levels by qRT-PCR confirmed array findings and pinpointed to a common up-regulation of TOP2A in DOR sublines. Our present study highlighted areas of genomic imbalances and candidate genes in the acquired doxorubicin-resistance behavior of HCC cells.
authors.affiliation: Department of Clinical Oncology, Sir YK Pao Centre for Cancer, The Chinese University of Hong Kong, Shatin, NT, Hong Kong SAR, China.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Pang
authors.forename: Ying
authors.initials: Y
authors.lastname: Hu
authors.forename: Kathy Y-Y
authors.initials: KY
authors.lastname: Chan
authors.forename: Paul B-S
authors.initials: PB
authors.lastname: Lai
authors.forename: Jeremy A
authors.initials: JA
authors.lastname: Squire
authors.forename: Pascale F
authors.initials: PF
authors.lastname: Macgregor
authors.forename: Ben
authors.initials: B
authors.lastname: Beheshti
authors.forename: Monique
authors.initials: M
authors.lastname: Albert
authors.forename: Thomas W-T
authors.initials: TW
authors.lastname: Leung
authors.forename: Nathalie
authors.initials: N
authors.lastname: Wong
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism; D000903:Antibiotics, Antineoplastic / Q000494:pharmacology*; D000951:Antigens, Neoplasm / Q000235:genetics / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D045744:Cell Line, Tumor; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism; D004273:DNA, Neoplasm / Q000032:analysis; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004317:Doxorubicin / Q000494:pharmacology*; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D018628:Gene Dosage; D020869:Gene Expression Profiling; D006801:Humans; D017403:In Situ Hybridization; D007621:Karyotyping; D008113:Liver Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D000075223:Poly-ADP-Ribose Binding Proteins; D012333:RNA, Messenger / Q000378:metabolism
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000903:Antibiotics, Antineoplastic; D000951:Antigens, Neoplasm; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D000075223:Poly-ADP-Ribose Binding Proteins; D012333:RNA, Messenger; D004317:Doxorubicin; D004250:DNA Topoisomerases, Type II; C000618811:TOP2A protein, human