Tribbles 2 mediates cisplatin sensitivity and DNA damage response in epithelial ovarian cancer

Abstract

Aim was to identify methylated genes with functional involvement in cisplatin-resistance development of epithelial ovarian cancer (EOC). Genome-wide analyses of hypermethylated CpG-islands in resistant cell lines in combination with qRT-PCR analyses were used to identify epigenetically silenced genes. EOC-type-II tumors were analyzed for gene methylation and expression and TCGA data were interrogated in-silico. Experiments revealed 37 commonly hypermethylated genes in resistant cells of which Tribbles 2 (TRIB2) showed the most pronounced down-regulation on mRNA level and was characterized further. TRIB2 showed a reactivation after 5'-Aza-Cytidine treatment in resistant cells but a cisplatin-dependent, prominent up-regulation on mRNA level in sensitive cells, only. Re-expression in resistant A2780 cells increased the sensitivity to cisplatin and other DNA-damaging agents, but not taxanes. Contrary, knockdown of TRIB2 increased resistance to cisplatin in sensitive cells. TRIB2 was involved in the induction of a cisplatin-dependent cell cycle arrest and apoptosis by influencing p21 and survivin expression. An increased Pt-DNA-adduct formation in TRIB2 re-expressing cells did not translate in higher levels of dsDNA damage (yH2AX-foci). Thus, TRIB2 is potentially involved in the signal transduction from nucleotide excision repair of intrastrand cross links. Importantly, patient stratification of two homogenous cohorts of EOC-type-II patients from Jena (n=38) and the TCGA (n=149) by TRIB2 mRNA expression consistently revealed a significantly decreased PFS for patients with low TRIB2 levels (log-rank p<0.05). Tumors from resistant patients expressed the lowest levels of TRIB2. Down-regulation of TRIB2 contributes to platin-resistance and TRIB2 expression should be validated as prognostic and predictive marker for EOC. This article is protected by copyright. All rights reserved.

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