Abstract 165: PVRL2 upregulation by tumor-associated macrophages confers a regulatory phenotype and is associated with poor prognosis in high-grade serous ovarian cancer

Abstract

Abstract Advanced or recurrent high-grade serous ovarian cancer (HGSOC) are associated with poor prognosis. While HGSOC is moderately immunogenic, anti-PD-1/L1 therapy has fared poorly in trials. PVRL2 (Nectin2) is both a cell-adhesion molecule as well as a ligand for PVRIG, a novel co-inhibitory receptor. While PVRL2 is constitutively expressed by epithelial/tumor cells, it can also be upregulated by macrophages. Whether macrophage-expressed PVRL2 functions exclusively as an immunoregulatory ligand in HGSOC is not known. CD45+ tumor infiltrate from 6 treatment-naïve and 3 neoadjuvant chemotherapy-treated patients with HGSOC was evaluated by CITE-seq. Multiplex immunofluorescence (mIF) of PanCK, CD68 and PVRL2 was performed on 28 FFPE sections. In vivo, we monitored survival of wild-type and PVRL2−/− mice as well as corresponding bone marrow chimeras orthotopically implanted with ID8-Vegf-Defb29 ovarian tumors. CITE-seq was run on CD45+ cells sorted from wild-type vs PVRL2−/− tumors and ascites. In tumor-bearing mice, macrophages, CD8 or NK cells were depleted and differences in survival assessed. In vitro, M1 and M2 macrophages were differentiated from steady-state bone marrow progenitors and myeloid gene profiles were analyzed. CITE-seq of patient-derived immune cells revealed that PVRL2 expression was restricted to macrophage clusters. Macrophages with low PVRL2 expression showed M1 polarity and abundant expression of inflammatory cytokines and chemokines. Overall macrophage counts and PVRL2 expression were lower in post-chemotherapy cases. In mIF, PVRL2 staining was observed on CD68-positive cells as well as tumor cells. In addition, PVRL2-expressing macrophages accumulated in tumor areas, especially in residual tumor areas after chemotherapy. PVRL2−/− mice and PVRL2 bone marrow chimeras had significantly improved survival compared to their respective control cohorts. Macrophage depletion significantly shortened the prognosis of PVRL2−/− mice compared to wild-type mice. In contrast, depletion of CD8 T cells or NK cells had no effect on survival of wild-type and PVRL2−/− mice. M1 macrophages from PVRL2−/− mice expressed higher levels of inflammatory cytokines and chemokines compared to their wild-type counterparts. Furthermore, CITE-seq showed that tumor-infiltrating macrophages in PVRL2−/− mice exhibited M1 polarization compared to those from wild-type tumors. However, the inflammatory phenotype appeared to be linked more with the tumor-infiltrating macrophages than with ascites macrophages. In conclusion, our research suggests that PVRL2 upregulation by tumor-infiltrating macrophages polarizes towards a pro-tumor phenotype and affects prognosis of HGSOC. PVRL2-deficient macrophages exert their antitumor effects via inflammatory tumor killing and not via antigen-presentation to effector T cells. Citation Format: Kosuke Murakami, Hirofumi Ando, Michele Doucet, Dacheng Ding, William Huang, Sudipto Ganguly. PVRL2 upregulation by tumor-associated macrophages confers a regulatory phenotype and is associated with poor prognosis in high-grade serous ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 165.