Preclinical Development Of Combination Therapy Targeting The Dominant Cytokine Interleukin-1 Beta For Renal Cell Carcinoma.

e14237 Background: Targeting myeloid-derived suppressor cells (MDSCs), key mediators of intrinsic and adaptive immune resistance, remains a significant challenge in kidney cancer immunotherapy. One potential driver of MDSC mediated tumor immunosuppression is the cytokine interleukin-1 beta (IL-1β). Although large cancer prevention studies show that targeting IL1 decreases cancer risk, the exact mechanism of anti-IL-1 mediated anti-tumor efficacy is not yet defined. To understand the immunogenic effects of IL-1β blockade and effects on MDSCs, we used the RENCA model of RCC. Methods: We inoculated BALB/c mice with 1x106 RENCA cells. On Day +10 we treated mice (n = 8/group) with vehicle, αPD1, αIL1β, cabozantinib, combination αPD1/αIL1β, or cabozantinib/αIL1β. We harvested day +18 tumors to quantify tumor size and immune cells by flow cytometry. We then isolated immune cells for differential gene expression profiling by RNAseq. Results: Treatment with αIL1β significantly decreased tumor size compared to vehicle or αPD1 monotherapy. Combining αPD1/αIL1β or cabozantinib/αIL1β potentiated the anti-tumor effects of αPD1 or cabozantinib monotherapy respectively. Anti-IL1β therapy decreased polymorphonuclear (PMN)-MDSC infiltration (αIL1β: 0.76% +/- 0.21 vs. vehicle: 1.89% +/- 0.37, P = 0.014). Relative to PD1 monotherapy, combining αPD1 and αIL1β decreased PMN-MDSCs (αPD1: 2.14% +/- 0.56 vs αPD1/αIL1β: 0.91% +/- 0.15, P = 0.033) and increased M1-like tumor associated macrophages (TAM) (αPD1: 0.798% +/- 0.21 vs. αPD1/αIL1β: 12.04% +/- 2.9, P = 0.0008). Gene expression profiling from sorted immune cells from αIL1β treated tumors revealed multiple differentially regulated cytokines including interleukin-6, IFN-γ, and IL-10. Conclusions: Blockade of IL-1β depletes intratumoral PMN-MDSCs and increases M1-like TAM with minimal effects observed on the T cell compartment. Treatment with cabozantinib or αPD1 in combination with αIL1β led to sustained control of tumor growth. IL-1β represents a promising target for kidney cancer immunotherapy. Based on the preclinical data, a clinical trial of neoadjuvant αPD1 and αIL1β therapy is planned for patients with high risk RCC.