Abstract NT-093: THE N6-METHYLATION OF ADENOSINE (M6A) IN FZD10 MRNA CONTRIBUTES TO RESISTANCE TO PARP INHIBITOR

Chemical modifications of RNAs have emerged as a new layer of epigenetic gene regulation. N6-methyladenosine (m6A) is the most abundant chemical modification of messenger RNA. The m6A modification affects RNA fate and functions such as RNA stability. Despite the high initial clinical response rates to PARP inhibitors in BRCA1/2-mutated epithelial ovarian cancers, PARP inhibitor (PARPi) resistance remains a major challenge. The role of m6A modification in PARPi resistance has not previously been explored. Here we show that m6A modification of FZD10 mRNA contributes to PARPi resistance by upregulating the Wnt/β-catenin pathway in BRCA-mutated EOC cells. Global m6A profile reveals a significant increase in m6A modification in FZD10 mRNA. This correlates with an increase in FZD10 mRNA stability and an upregulation of the Wnt/β-catenin pathway in PARPi resistant cells. FZD10 knockdown or inhibition of the Wnt/β-catenin sensitizes the resistant cells to PAPRi. Mechanistically, downregulation of m6A demethylases FTO and ALKBH5 is sufficient to increase FZD10 mRNA m6A modification and reduce PARPi sensitivity. Moreover, PAPRi and Wnt/β-catenin inhibitor showed synergistic suppression of growth of PAPRi resistant cancer both in vitro and in vivo in a xenograft ovarian cancer mouse model. Our results show that m6A contributes to PAPRi resistance in BRCA-deficient EOC cells by upregulating the Wnt/β-catenin pathway through stabilizing FZD10. They also suggest that inhibition of Wnt/β-catenin pathway represents a potential strategy to overcome PARPi resistance. Citation Format: Takeshi Fukumoto, Hengrui Zhu, Sergey Karakashev, Timothy Nacarelli, Nail Fatkhutdinov, Shuai Wu, Andrew V. Kossenkov, Louise Showe, Stephanie Jean, Lin Zhang, Rugang Zhang. THE N6-METHYLATION OF ADENOSINE (M6A) IN FZD10 MRNA CONTRIBUTES TO RESISTANCE TO PARP INHIBITOR [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr NT-093.