Role of Fanconi anemia/BRCA pathway genes in hepatocellular carcinoma 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.