5P Physiologically relevant treatment models to investigate epigenetic mechanisms driving platinum resistance in ovarian high grade serous carcinoma

Abstract

The prognosis for patients with platinum-resistant ovarian High Grade Serous Carcinoma (HGSC) remains poor. BriTROC-1 data indicate that genomic alterations alone cannot explain acquired platinum resistance. We investigate epigenetic changes that may drive platinum resistance in HGSC. Using in an in vitro two-dimensional model, we recreated multiple cycles of chemotherapy. We utilised both established cell lines and primary cultures derived from HGSC ascites. Following cell characterisation (p53, PAX8 IHC), carboplatin sensitivity was assessed (sulforhodamine B assay). Cells were then pulsed with four cycles of carboplatin (50μM for 6 hours) with a week of recovery between each cycle. Methylation (Illumina 850k array), transcriptomic (RNAseq) and chromatin accessibility (ATACseq) assays were performed. Cells were also imaged using Stochastic Optical Reconstruction Microscopy. Firstly, we focused on RNAseq analysis to evaluate genes (and related biological processes) that are consistently enriched following carboplatin cycles and the unique genes that are conversely enriched at cycle level. We attempted to identify uniformly up-/down-regulated pathways across the different cultures. These data were compared with the same results obtained from the OvCar4, an established HGSC cell line and IVR01, an in-vivo resistant OvCar4 derivative. The ATACseq and methylation analyses are still ongoing, aiming to identify possible concordant changes in the chromatin accessibility and the methylation patterns that will allow us to clarify the changes observed in transcriptomic. The preliminary data obtained from the RNAseq analysis show that the highest number of enriched genes seems to occur after the first Carboplatin cycle, with a lower number of progressively enriched genes across all other ones. No constant biological processes were identified for the moment, across the different primary cell cultures. Further comparisons will be certainly needed. Understanding the epigenetic landscape of HGSC using physiologically relevant models will allow us to identify possible therapeutic targets that could eventually prevent platinum resistance.