Objectives: Obesity is associated with increased risk of and mortality from endometrial cancer (EC). Previous studies have shown that omega-3 polyunsaturated fatty acid (PUFA) supplementation may counteract the detrimental effects of obesity-driven cancers, but this has not been thoroughly investigated in EC. We aimed to assess the effect of omega-3 PUFAs on cell proliferation and tumor growth in endometroid EC cell lines and an LKB1fl/flp53fl/fl mouse model of endometroid EC.

Methods: The human endometrioid EC cell lines ECC-1 and KLE were exposed to varying concentrations of the omega-3 PUFA, docosahexaenoic acid (DHA). Cell proliferation was assessed by MTT assay. Apoptosis was assessed by Annexin V-FITC assay. Reactive oxygen species (ROS) were measured using the dichloro-dihydro-fluorescein diacetate (DCFH-DA) assay. Western immunoblotting was performed to determine the effects of DHA on the anti-apoptotic proteins BCL-2 and MCL-1 and the cellular stress proteins PERK, Bip, and PDI. LKB1fl/flp53fl/fl mice were fed either a low fat diet (10% of calories from fat, lean) or high fat diet (60% of calories from fat, obese). Following EC onset, the mice were treated with placebo or DHA (15mg/kg weekly for 4 weeks, IP). Immunohistochemistry (IHC) was performed on tumors in the treated and untreated mice to assess for proliferation and apoptosis. Global, unbiased metabolomics was used to identify the metabolic effects of DHA in the endometrial tumors.

Results: DHA inhibited cell proliferation in a dose-dependent manner in both cell lines (ECC-1 IC50 of 60µM; KLE IC50 of 35µM). DHA increased the expression of annexin V (p<0.05) as well as decreased BCL-2 and MCL-1 expression. Treatment with DHA significantly increased ROS production and induced PERK, Bip, and PDI expression in both cell lines. Treatment of mice in the obese cohort demonstrated an 81% reduction in tumor weight while the lean group demonstrated a 64% reduction in tumor weight (p<0.05). There was no change in mouse weight with DHA treatment; average mouse weight in the obese cohort was 40g compared to 26g in the lean group. IHC showed decreased Ki67 expression and increased BCL-XL expression in both groups with DHA treatment. Metabolomic profiling revealed that total monacyl-, diacyl- and triacyl-glycerols were increased with DHA treatment in both obese and lean mice, suggesting that lipids were being diverted from membrane biosynthesis to energy storage. Differences were found in DHA’s effect when comparing obese and lean mice, including (1) decreases in lipid biosynthesis and amino acid metabolism in only obese mice, and (2) increases in fatty acid desaturase activity in only lean mice.

Conclusions: DHA robustly inhibits EC proliferation and tumor growth in vitro and in vivo. This suggests that omega-3 PUFA supplementation may be a promising dietary strategy for EC prevention and treatment.

Citation Format: Jillian A. O'Donnell, Lindsey K. Buckingham, Stuart R. Pierce, Lindsay West, Yiajie Yin, Wenchuan Sun, Ziwei Fang, Douglas P. Lee, Chunxiao Zhou, Victoria L. Bae-Jump. Docosahexaenoic acid demonstrates anti-tumorigenic effects in endometrial cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference: Endometrial Cancer: New Biology Driving Research and Treatment; 2020 Nov 9-10. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(3_Suppl):Abstract nr PO031.