Abstract 1536: Unsaturated fatty acids promote cell cycle progression and proliferation of platinum resistant ovarian cancer cells

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. Here, we determined 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 = 2.881mM) vs Pt-R (IC50 = 6.831 mM) and PEO1 (IC50 = 4.901 mM) vs PEO4 (IC50 = 8.285 mM). 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, cell cycle, and cell death analysis. Quantitative RT-PCR measured expression of key FAs transporters in Pt-S and Pt-R cells. Immunohistochemistry (IHC) assessed expression of FABP4 in primary and recurrent human tumors. The FABP inhibitor BMS-309403 was used to pharmacologically inhibit the FA transporters in vitro and in vivo. Results: Pt-R cells rely more on unsaturated FAs than Pt-S cells, upregulating transporters for increased FA uptake. Cell viability assays showed Pt-R cells were less viable under serum depletion, with oleic acid (OA, unsaturated) promoting proliferation of both OC cell lines. OA rescued Pt-R cells significantly more than Pt-S cells: 268.4% vs 91.6% for OVCAR-5 and 38.1% vs 12.1% for PEO4 vs PEO1. OA also reduced apoptosis, as shown by Annexin V assays, and decreased Caspase-3 and -8 cleavage. RNA-Seq analysis linked OA-induced proliferation to upregulation of cell cycle-related pathways, including G2/M checkpoints, driven by E2F1. OA increased S- and G2/M phase populations (e.g., 6.95% to 11.6%; p<0.05), while E2F1 inhibition reduced OA-induced proliferation. Pt-R cells also expressed higher levels of transported proteins FABP4 and CD36. Inhibiting FABPs reduced Pt IC50 values (e.g., from 11.893 μM to 5.0415 μM in OVCAR5) and blocked ovarian cancer progression in vivo. IHC showed FABP4 overexpression in metastatic and recurrent tumors (n=21 paired tumors, p<0.05). Conclusion: Pt-R OC cells are more dependent on unsaturated FAs compared to Pt-S cells and upregulate key transporters to allow increased uptake of FAs. Inhibiting intracellular FA transport reduces OC progression in vivo. OA supports proliferation of Pt-R cells by rescuing them from apoptosis and by promoting cell cycle progression from G1 to S- and G2/M phases. Citation Format: Ana Maria Isac, Andres Valdivia, Guangyuan Zhao, Yinu Wang, Jian-Jun Wei, Sandra Orsulic, 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 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1536.