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Abstract Objective: High-fat diets have been associated with cancer progression. Yet, studies indicate that the effects can differ based on the type of fat involved, such as saturated versus unsaturated fatty acids. Uncovering the role of fatty acids may help guide nutrition and provide dietary therapy for cancer patients. In this study, we investigated the effect of common long-chain fatty acids, stearic acid (SA) and oleic acid (OA), on ovarian cancer (OC). Methods: We evaluated the cytotoxicity of SA and the effects of OA using IC50, a 72-hour proliferation assay, flow cytometry, and western blot. The concentration of fatty acids within the tumor was measured using liquid chromatography-mass spectrometry (LC/MS). CAY10566 was used to inhibit SCD1, the enzyme that converts SA to OA. In vivo, tumor growth was analyzed in human OC cell lines and patient-derived xenografts (PDX) using a mouse model fed with a normal diet (ND), an SA-rich diet, or an OA-rich diet combined with CAY10566. The SA-rich diet, which we specially created, had a stearic acid concentration of 33%. Results: SA displayed prominent cytotoxicity compared to other fatty acids. SA dose-dependently increased unfolded protein response (UPR) marker expression. Adding 1μM CAY10566 increased intracellular SA, decreased OA, and reduced IC50 to 20μM (p0. 05). CAY10566 significantly enhanced the cytotoxicity of SA, but the addition of exogenous OA canceled the increase in cell toxicity and UPR marker expression induced by SA (p0. 05). In vivo, tumor growth of OC cell lines and PDXs was significantly suppressed in the SA-rich with CAY10566 group compared to the ND group (p0. 05), while this suppression was nullified in the OA-rich with CAY10566 group. As confirmed by LC/MS, the stearic acid concentration significantly increased in the SA-rich group. Immunohistochemistry demonstrated that CHOP, gH2AX, and caspase-3 expression significantly increased in the SA-rich with CAY10566 group and dramatically decreased in the OA-rich with CAY10566 group (p0. 01). Conclusion: An ectopic supply of SA inhibits OC growth via UPR, while OA counteracts this effect. Creating a Stearate-rich/Oleate-limited environment through diet might affect tumor growth in vivo. Dietary content may greatly contribute to altering function in cancer. Citation Format: Jumpei Ogura, Koji Yamanoi, Mana Taki, Ryusuke Murakami, Ken Yamaguchi, Junzo Hamanishi, Masaki Mandai. Elucidating the influence of long-chain fatty acids on ovarian cancer progression abstract. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84 (5 Suppl₂): Abstract nr B107.
Ogura et al. (Mon,) studied this question.