Abstract 2815: Sulindac reverses an immunosuppressive tumor microenvironment associated with obesity-driven metastatic mammary tumors in mice

Abstract

Abstract Obesity is an established risk factor for several breast cancer (BC) subtypes. Obese BC patients also show poorer response to therapy, increased metastases, and increased mortality. While high levels of inflammation are thought to be a driver for BC metastasis, it is unknown how chronic exposure to low levels of obesity-associated inflammation contributes to BC progression and metastasis. We previously showed that treatment with the non-steroidal anti-inflammatory drug (NSAID) Sulindac (140 ppm mixed into control [10% kcal/fat] or diet induced obesity [DIO, 60% kcal/fat] diets) offset both the pro-growth and pro-metastatic effects of obesity on BC using three different mouse models of metastatic BC - basal-like E0771, and claudin-low metM-Wnt-lung and metM-Wnt-liver. To characterize the effect of Sulindac treatment on the tumor microenvironment, we conducted microarray analysis on E0771 tumors from mice in all four diet groups (Control, Control+Sulindac, DIO, and DIO+Sulindac). Ingenuity Pathway Analysis revealed significant Sulindac-induced differences (q<0.01) in several pathways relating to immune function. Specifically, Th1/Th2 pathways, CD28 signaling, and markers of dendritic cell maturation were significantly downregulated in DIO tumors compared to all other diet groups. Similarly, immune burden calculation using CIBERSORT showed lower levels of CD4+ T memory cells (p<0.05) and higher levels of resting dendritic cells (p<0.001) in DIO tumors compared to all other diet groups. To further explore Sulindac-associated effects on immune and cancer cell gene expression, we performed single-cell RNA-seq on E0771 tumors. Preliminary analyses showed marked differences in gene expression between DIO and DIO+Sulindac tumor cells. Of the top 25 significant (q<0.01) genes upregulated in DIO vs DIO+Sulindac tumor cells, 15 have been previously shown to be drivers of breast cancer progression or metastasis, with only 2 showing tumor suppressive functions. Similarly, 13 of the top 25 genes upregulated in DIO+Sulindac compared to DIO tumor cells have previously shown to have tumor suppressive functions, while only 2 are pro-tumorigenic. Immune analyses showed fewer immune cells in DIO tumors as well as increased pro-tumorigenic or immunosuppressive gene expression in DIO immune cells, while DIO+Sulindac immune cells showed increased markers of immune activation. Finally, T cell receptor (TCR) analysis showed greater TCR diversity in DIO+Sulindac T cells compared to DIO. Taken together, these preclinical findings indicate that obesity-driven mammary tumor progression and metastatic burden are associated with an immunosuppressive tumor microenvironment that is largely reversed by Sulindac treatment. This suggests treatment with NSAIDs like Sulindac should be further assessed as a possible strategy for improving outcomes in obese breast cancer patients. Citation Format: Shannon B. McDonell, Alyssa J. Cozzo, Lydia K. Eisenbeis, Andrew J. Dannenberg, Stephen D. Hursting. Sulindac reverses an immunosuppressive tumor microenvironment associated with obesity-driven metastatic mammary tumors in mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2815.