Abstract PD12-05: PD12-05 Adipocyte directed vaccination to reduce the risk of breast cancer

Abstract Background: Obesity is an important risk factor for breast cancer and women with metabolic syndrome may be at the highest risk. Infiltration of CD8 T-cells into fat is an early event in obesity. Type I cytokines secreted by CD8 T-cells upregulate costimulatory molecules on enlarged adipocytes. The adipocytes, now antigen presenting cells, further stimulate Type I T-cell activation. The resulting T-cells compete for glucose and fatty acids which leads to metabolic dysfunction in both the adipose tissue and the T-cells themselves. The T-cells are not able to maintain tumor immune surveillance and secretion of adipokines promotes malignant transformation. Immunologic memory prevents inflammation from resolving even if an individual becomes normal weight. Strategies to increase Type II (anti-inflammatory) T-cells in inflamed adipose could have clinical benefit. Methods: We developed a method of CD4 epitope identification that includes functional screening for Th1 or Th2 epitopes. We use a multi-algorithm approach to ensure responsiveness across diverse HLA alleles. We identified Th2 selective epitopes associated with high IL-10 secretion for 6 adipocyte associated antigens that become overexpressed in inflamed adipocytes (IGF-IR, HIF-1a, DUSP1, FABP4, PAI-1 and ATGL). The epitopes were highly homologous between mouse and man (median 100% (range-82-100%). When the epitopes were used to immunize mice, all antigens generated a significant IL-10 response compared to control (p< 0.05). We questioned whether our “adipocyte directed” vaccine (ADVac) could prevent the development of breast cancer in obese mice. Results: First, C57BL/6 mice were fed a high fat high sucrose (HFHS) diet or normal chow. When mice became obese, vaccination with ADVac or adjuvant alone (Alum) was initiated. Four weeks after the final vaccine, visceral adipose tissue showed significantly fewer CD8 T-cells in the obese mice immunized with ADVac as compared to the control, p=0.0011. The decrease in CD8 T-cells was specific for adipose tissue as no change was observed in matched spleen. There was a significant increase in T-regulatory cells in the adipose tissue of mice immunized with ADVac as compared to control, p=0.031. Two weeks after the final vaccine, a glucose tolerance test (GTT) and insulin tolerance (ITT) showed blood glucose concentrations were significantly lower at all time points for the ADVac-immunized obese mice as compared to the control obese mice (p< 0.01 for all). TgMMTV-neu develop aggressive breast cancer when made obese. Ten-week old TgMMTV-neu mice were fed a HFHS diet for 4 weeks, then randomized into 2 cohorts when obese, one cohort receiving the adjuvant only (Alum) and one receiving ADVac. Mice were sacrificed at 31 weeks of age when all controls had developed tumor. ITT showed the glucose levels in the blood were significantly lower in the ADVac group as compared to control (p< 0.0001). Fewer CD8 T-cells were observed in mammary adipose tissue of AdVac immunized mice compared to control (p=0.001). There was significantly less leptin detected in the serum of ADVac vaccinated mice compared to Alum immunized, p=0.024. The median age of tumor development was 25 weeks in controls and 29 weeks in the immunized group (p=0.009). Sixty percent (9/15) of the vaccinated mice were tumor free at study termination, whereas 100% of the control mice had developed tumor. Conclusions: ADVac represents the first vaccine to lower breast cancer risk in obesity. Vaccination corrected metabolic dysfunction as evidenced by reversal of diabetes and prevented breast cancer in the majority of obese ADVac immunized mice. Further studies are ongoing evaluating the systemic distribution of ADVac specific T-cells and the safety of the approach. Citation Format: Mary Disis, Lauren Corulli, Erin R. Rodmaker, Denise Cecil. PD12-05 Adipocyte directed vaccination to reduce the risk of breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD12-05.