Abstract A008: Intermittent fasting in combination with PD-inhibitor treatment as an innovative treatment strategy in a pre-clinical model of obesity-driven endometrial cancer

Abstract Objective: Endometrial cancer (EC) incidence and mortality continue to rise, with obesity a well-known driver of this disease. Obesity is associated with excess estrogen, hyperinsulinemia, activation of the Akt/mTOR pathway, chronic inflammation and a heightened capacity to harvest dietary energy, which all contribute to the development and progression of EC. Intermittent energy restriction (IER) is thought to have anti-tumorigenic benefits and has been shown to have synergistic effects with chemotherapy and hormonal therapy in various cancer types. IER may also promote anti-tumor immune responses by stimulating CD4+ and CD8+ cells, making this dietary strategy an innovative therapeutic partner with PD-1 inhibitors, which are commonly used in EC. Thus, we evaluated the anti-tumorigenic effects of a switch from high fat diet (HFD) to either IER or low-fat diet (LFD) with PD-1 inhibitor treatment in a mouse model of obesity-driven endometrioid EC. Methods: Lkb1fl/flp53fl/fl mice were fed either HFD or LFD starting at 4 weeks of age. At 12 weeks of age, the HFD-fed mice were randomized to three treatment groups: HFD, HFD-LFD switch or HFD-IER switch. The LFD-fed mice were maintained on LFD. At 16 weeks of age, all mice were injected with AdCre into the left uterine horn to induce EC development. At 26 weeks of age, mice were treated with placebo or a mouse PD-1 inhibitor (BioXCell) (10mg/kg, 2 times/wk, intraperitoneal) for 4 wks (N=8-10 mice per group). RNAseq was performed to determine differences in immune pathways between ECs of obese and lean mice. CD4+ and CD8+ T cells in tumors of obese and lean mice were evaluated by flow cytometry. Results: Obesity resulted in a 52% increase in tumor size, comparing obese versus lean mice (p0. 05). Expression of genes related to T-cell/B-cell receptors, NF-kappa B and TNF pathways were upregulated in the ECs of obese versus lean mice. PD-1 inhibitor therapy increased PD-1 expression on CD4+ and CD8+ T cells in both obese and lean ECs. In addition, PD-1 inhibitor treatment led to an increase in percentage of CD4+ T cells in obese and lean ECs but increased the percentage of CD8+ T cells in only lean ECs. At sacrifice and after PD-1 inhibitor treatment, mean body weights were significantly higher (p0. 05) in the HFD group (42g) than groups receiving LFD (29g), HFD-LFD switch (34g) or HFD-IER switch (23g). EC incidence was lowest in the HFD-IER group (~61%) and highest in the HFD group (~80%) ; rates were similar in the other diet groups (~75%). In placebo-treated groups, mean tumor weights were significantly lower in mice fed LFD (0. 45g), HFD-LFD switch (0. 41g) and HFD-IER switch (0. 29g) relative to continuous HFD-fed mice (0. 94g; p=0. 001-0. 05). PD-1 inhibitor treatment reduced EC size 24-68% across all diet groups (p=0. 05-0. 001) ; size reduction was greatest in the HFD-IER group (0. 18g) relative to mice receiving continuous HFD (0. 30g), HFD-LFD (0. 31g) or LFD (0. 31g). Conclusion: IER with PD-1 inhibitor treatment may be an innovative strategy in the management of EC, a highly obesity-driven cancer. Citation Format: Jennifer Haag, Olivia Lara, Chunxiao Zhou, Stephen D. Hursting, Victoria Bae-Jump. Intermittent fasting in combination with PD-inhibitor treatment as an innovative treatment strategy in a pre-clinical model of obesity-driven endometrial cancer abstract. In: Proceedings of the AACR Special Conference on Endometrial Cancer: Transforming Care through Science; 2023 Nov 16-18; Boston, Massachusetts. Philadelphia (PA): AACR; Clin Cancer Res 2024;30 (5Suppl): Abstract nr A008.