Abstract 443: Unsaturated fatty acids promote cell cycle progression and proliferation of platinum resistant ovarian cancer cells

Abstract Introduction: Ovarian cancer (OC) depends on fat as fuel for metastasis and growth. We have previously demonstrated that cisplatin resistant (Pt-R) OC cells uptake higher amounts of fatty acids (FAs) compared to sensitive (Pt-S) cells- a process which facilitates cancer cell survival under cisplatin-induced oxidative stress. Here we aimed to determine which class of FAs promotes the Pt-R phenotype and to identify the mechanism through which FAs support cancer survival. Materials and methods: We used two isogenic OC cell lines pairs, sensitive and resistant to cisplatin: OVCAR5 Pt-S (IC50 = 2.881μM) vs Pt-R (IC50 = 6.831 μM) and PEO1 (IC50 = 4.901 μM) vs PEO4 (IC50 = 8.285 μM). Cells were cultured under low serum conditions, supplemented with 50 µM oleic (OA) or 50 µM palmitic acid (PA), and used for viability assays, RNA-Seq, and cell cycle analysis. Quantitative RT-PCR measured expression of key FAs transporters in Pt-S and Pt-R cells. Results: A viability assay showed that Pt-R cells were less viable under serum depletion compared to Pt-S OC cells. OA (unsaturated), but not PA (saturated), promoted proliferation of both OC cell lines, and rescued Pt-R vs Pt-S cells; 268.4% vs 91.6% for OVCAR-5 and 38.1% for PEO4 vs 12.1% for PEO1, suggesting that Pt-R cells depend more on unsaturated FAs compared to Pt-S cells. Quantification of key FAs transporters demonstrated that Pt-R cell expressed higher levels of FABP4, FABP5 and CD36 compared to Pt-S cells. Treatment with an FABP inhibitor reduced the Pt IC50 in Pt-R cells (from 11.893 μM to 5.0415 μM in OVCAR5 and from 8.285 μM to 6.968 μM in PEO4). RNA-Seq analysis analysed transcriptomic changes induced by 24 hour treatment with OA in OVCAR5 cells. There were 923 differentially expressed protein-coding genes, with 300 upregulated and 623 downregulated transcripts (FDR<0.05). Pathway analysis revealed cell cycle related pathways like: cell cycle mitotic, cell cycle checkpoints, G2/M checkpoints among the top 10 most significantly upregulated pathways and E2F1 was identified as the main effector. Cell cycle analysis confirmed that OA induced increased percentages of cells in S- and G2/M phases - from 6.95% to 11.6% (p<0.05), and 13.6 to 17.6% (P<0.05), respectively. Treatment with an E2F1 inhibitor significantly reduced the OA-induced cell proliferation. Conclusion: Pt-R OC cells are dependent on unsaturated FAs compared to Pt-S cells and upregulate key transporters to allow increased uptake of FAs. OA supports proliferation of Pt-R cells and cell cycle progression from G1 to S- and G2/M phases. Ongoing experiments focus on key mechanisms activated by unsaturated FAs in Pt-R cells. Citation Format: Ana Maria Isac, Guangyuan Zhao, Horacio Cardenas, Daniela Matei. Unsaturated fatty acids promote cell cycle progression and proliferation of platinum resistant ovarian cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 443.