Sana Ferroudj1,2,3, Gokhan Yildiz1,4, Mourad Bouras1,5, Evin Iscan3, Umut Ekin3, Mehmet Ozturk1,3. 1. CRI INSERM/UJF U823, Grenoble, France. 2. Biochemistry Department, Faculty of Natural and Life Sciences, University of Sétif, Algeria. 3. Izmir International Biomedicine and Genome Institute, Dokuz Eylul University, İzmir, Turkey. 4. Department of Medical Biology, Faculty of Medicine, Erzincan University, Erzincan, Turkey. 5. Biochemistry and Molecular Biology Department of Pharmacy, School of Medicine, University of Batna, Algeria.
Abstract
AIM: To investigate the expression of DNA repair genes and the impact of the breast cancer 1, early onset (BRCA1) protein on chemoresistance of hepatocellular carcinoma (HCC). METHODS: Microarray gene expression datasets were analyzed using the gene set enrichment analysis method. BRCA1 protein was tested by Western blotting. Response of HCC cells to interstrand cross-links was investigated by cell viability assay following exposure to mitomycin C, cisplatin, and melphalan. Effects of BRCA1 ectopic expression were studied in HepG2 cells with BRCA1-expression plasmids. Effects of BRCA1 downregulation were studied in SNU449 cells with BRCA1-specific siRNAs. Response of transfected SNU449 cells to mitomycin C was analyzed by cell viability tests and cell cycle analysis using flow cytometry. RESULTS: Expression of Fanconi anemia and double-stranded DNA break repair genes was significantly upregulated in HCC tumors. This upregulation displayed a gradual amplification during tumor progression. BRCA1 and BRCA2 genes were among consistently upregulated genes. Epithelial-like HCC cells had low BRCA1 expression and low chemoresistance, whereas mesenchymal-like HCC cells had high BRCA1 expression and increased chemoresistance. Ectopic expression of BRCA1 increased the chemoresistance of epithelial-like HepG2 cells. Conversely, BRCA1 knockdown chemosensitized mesenchymal-like SNU449 cells. Chemosensitization of SNU449 cells was due to cell cycle arrest at 4N stage. CONCLUSION: Increased expression of Fanconi anemia and double-stranded DNA repair genes such as BRCA1 is a novel mechanism of HCC chemoresistance. However, functional inactivation of BRCA1 expression is sufficient to reverse such chemoresistance.
AIM: To investigate the expression of DNA repair genes and the impact of the breast cancer 1, early onset (BRCA1) protein on chemoresistance of hepatocellular carcinoma (HCC). METHODS: Microarray gene expression datasets were analyzed using the gene set enrichment analysis method. BRCA1 protein was tested by Western blotting. Response of HCC cells to interstrand cross-links was investigated by cell viability assay following exposure to mitomycin C, cisplatin, and melphalan. Effects of BRCA1 ectopic expression were studied in HepG2 cells with BRCA1-expression plasmids. Effects of BRCA1 downregulation were studied in SNU449 cells with BRCA1-specific siRNAs. Response of transfected SNU449 cells to mitomycin C was analyzed by cell viability tests and cell cycle analysis using flow cytometry. RESULTS: Expression of Fanconi anemia and double-stranded DNA break repair genes was significantly upregulated in HCC tumors. This upregulation displayed a gradual amplification during tumor progression. BRCA1 and BRCA2 genes were among consistently upregulated genes. Epithelial-like HCC cells had low BRCA1 expression and low chemoresistance, whereas mesenchymal-like HCC cells had high BRCA1 expression and increased chemoresistance. Ectopic expression of BRCA1 increased the chemoresistance of epithelial-like HepG2 cells. Conversely, BRCA1 knockdown chemosensitized mesenchymal-like SNU449 cells. Chemosensitization of SNU449 cells was due to cell cycle arrest at 4N stage. CONCLUSION: Increased expression of Fanconi anemia and double-stranded DNA repair genes such as BRCA1 is a novel mechanism of HCC chemoresistance. However, functional inactivation of BRCA1 expression is sufficient to reverse such chemoresistance.
Authors: Jingjing Jiao; Weibo Niu; Ying Wang; Keith Baggerly; Yuanqing Ye; Xifeng Wu; Dewitt Davenport; Jose Luis Almeda; Monica M Betancourt-Garcia; R Armour Forse; Heather L Stevenson; Gordon P Watt; Joseph B McCormick; Susan P Fisher-Hoch; Laura Beretta Journal: Cancer Prev Res (Phila) Date: 2017-10-31