Abstract 2350: Vaccination enhances anti-tumor immunity in ovarian cancer following repolarization of the tumor microenvironment with CCR2 blockade

Abstract

Abstract Introduction: Ovarian cancer (OC) expresses the tumor associated antigen mesothelin and contains a relative abundance of T-cells. However, ovarian cancer is also infiltrated by immunosuppressive tumor associated macrophages (TAM) that dominate the tumor microenvironment (TME). The CCL2/CCR2 chemokine axis is co-opted by various human malignancies to facilitate the recruitment of bone marrow (BM) derived inflammatory monocytes (IM) to the TME where they become immunosuppressive TAMs. Herein, we explore the rationale for combination of a CCR2 inhibitor (CCR2i) with a mesothelin peptide vaccine. Methods: Monocyte counts were obtained from preoperative CBCs under IRB approval. Mice were vaccinated with a dual eight-mer peptide (50 nM/vaccination) on days 0 and 7 with an irradiated peptide pulsed dendritic cell boost on day 14. Mice were challenged with 4 million syngeneic OC cells (ID8) on day 15. CCR2 inhibitor (Tocris) and CCR2 KO mice were used. Results: Preoperative monocyte counts of human ovarian cancer patients were stratified into low (>1 SD below mean), mid (within 1 SD of mean), and high (>1 SD above the mean) groups. Patients with a high monocyte count (n = 15) had a significantly decreased median survival of 1.2 years compared to 4.8 years in the low monocyte group (n = 15). The mid group (n = 69) had a median survival of 3.5 years (p 0.001). The hazard ratio between the low and high groups was 0.24 (0.05-0.39). Flow cytometry of peripheral blood from these patients demonstrated that the majority of these monocytes were CCR2+ inflammatory monocytes. Human OC overexpresses CCL2 compared to normal ovarian tissue and analysis of the TME from resected human OC patients revealed an abundance of CCR2+ TAM, which greatly outnumbered tumor infiltrating lymphocytes (TIL). In a murine ID8 tumor model, which recapitulates features of human OC, CCR2i prevented IM egress from the bone marrow with a resultant decrease in TAM at the primary tumor site. Furthermore, there was an increase in TIL infiltrate following CCR2 blockade. Addition of vaccine to CCR2i caused an improvement of effector to suppressor ratio and prolonged survival compared to vaccine (p = 0.02) or CCR2i alone (p = 0.02) and control (p<0.0001). Conclusion: Thus far vaccination has not provided durable patient responses in OC. Therapies targeting the immunosuppressive TME are an attractive treatment modality to enhance vaccination and facilitate anti-tumor immunity in OC. Citation Format: Darren Cullinan, Pratibha Binder, Timothy Nywening, Ivy Wilkinson-Ryan, Brian Belt, Peter Goedegebuure, David Linehan, Matthew Powell, William Hawkins. Vaccination enhances anti-tumor immunity in ovarian cancer following repolarization of the tumor microenvironment with CCR2 blockade. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2350.