Investigation of aberrant DNA methylation in association with cisplatin-resistant hepatoblastoma.

Abstract

258 Background: Cisplatin (CDDP) is a key-drug of mainstream treatment for hepatoblastoma (HB), but 22.3% of HB patients have resistance to CDDP, and their prognoses are poor. We investigated methylation status of HB patients and identified CDDP resistant candidate genes in HB. Methods: First, we performed a genome-wide methylation array analysis of 11 resected HB tumors. These cases included six cases of RECIST (Response Evaluation Criteria In Solid Tumors) CR or PR (S group) and five cases of SD or PD (R group). We analyzed methylation status of these patients, comparing with clinical course, and selected significant differentially methylated genes. Next, We made CDDP-resistant HepG2 cells by repeated CDDP treatments for a year, then compared expression levels between the CDDP-resistant cells and original cells, using cDNA microarray analysis. We selected CDDP resistant candidate genes from these data. Results: In methylation array analysis data, unsupervised hierarchical clustering analysis showed that methylation profiles were separable into 2 groups in accord with clinical S group and R group. In principal component analysis, the S group also showed a different methylation pattern to the R group. We compared survival rates using Kaplan-Meier method, and results showed that the R group had poorer prognosis significantly. The R group showed 336 hypermethylated genes and 106 hypomethylated genes around the transcriptional start site compared with S group significantly. And in cDNA microarray analysis, 1271 genes were downregulated and 1571 genes were upregulated significantly in CDDP-resistant cells. From among these genes, we selected 15 suppressor and 8 promoter candidate genes that could be related to CDDP-resistance. Conclusions: We identified methylation status associated with CDDP resistance and poor prognosis, and 23 candidates genes in HB. Further refining might lead us to find out the pathogenesis of chemoresistance or new target of therapies and biomarkers in HB.