Abstract B061: Multiparametric single-cell characterization of the immune tumor microenvironment in ovarian carcinomas

Abstract Tubo-ovarian high-grade serous carcinoma (HGSC) has an overall 5-year survival rate of ~50%. Standard-of-care treatment is surgical debulking followed by platinum-based chemotherapy. Initially, most women respond, but eventually, most (~80%) will relapse within 5 years. Nevertheless, for women with tumors for whom upfront debulking surgery is not possible, neoadjuvant chemotherapy (NACT) with interval debulking surgery followed by chemotherapy is an alternative. Cancer immunotherapy, an alternative treatment modality, drives an anti-tumor immune response. Immunotherapy approaches targeting a patient’s T cells have shown remarkable success for a variety of malignancies. Unfortunately, HGSC is largely unresponsive. In a previous study, we applied mass cytometry to newly diagnosed HGSC tumors to characterize intra-tumoral T and natural killer (NK) cells. We identified intra-tumoral decidual-like (dl) -NK cells that were positively correlated with tumor cell and transitioning epithelial-mesenchymal cell abundance. Decidual NK cells comprise 70% of lymphocytes during the first trimester of pregnancy and have a critical immune tolerant role in preventing a mother-to-be from rejecting her hemi-allogenic fetus. dl-NK cells, like their decidual counterparts, are distinguished from other NK cell phenotypes by the expression of the tetraspanin CD9. In vitro data demonstrated that CD9 endowed NK cells with immune-suppressive functions (attenuated cytotoxicity and reduced anti-tumor cytokine production). This study also revealed that in four out of ten patient-matched HGSC samples pre- and post-NACT, chemotherapy induced a more immune-suppressive immune tumor microenvironment (iTME). These data led to our hypothesis that the spatial architecture of the HGSC iTME, specifically encompassing cellular neighborhoods (CNs) comprising dl-NK and T cells, will predict response to platinum-based chemotherapy. Thus, we have applied CO-Detection by indEXing (CODEX), a highly-multiplex single-cell proteomic imaging technology, to comprehensively characterize the iTME of HGSC tumors. By measuring ~60 markers per tissue section at a resolution of 400 nm, CODEX generates proteomic co-expression information to deeply phenotype individual cells while preserving their spatial coordinates and relationships within the HGSC iTME. We have developed and validated a CODEX antibody panel targeting tumor, stroma and immune cells, NK cells receptors and ligands, and proteins specific for decidual NK cells, for formalin-fixed paraffin-embedded tissues. We developed and validated a panel comprised of 57 CODEX antibodies to image the iTME of 14 HGSC tumors, 7 matched before- and after-NACT. Our continuing data analyses will identify the spatial features of cellular neighborhoods enriched for dl-NK and T-cells to gain insight into their role in disease progression and treatment outcomes. In conclusion, we used CODEX, a highly multiplex single-cell imaging platform to deeply characterize the cellular architecture of the iTME in HGSC tumors before and after NACT. Citation Format: Antonio Delgado-Gonzalez, Kenyi Donoso, Maximilian Haist, Veronica D Gonzalez, Ying-Wen Huang, Brooke E. Howitt, Garry P. Nolan, Katherine Fuh, Wendy J. Fantl. Multiparametric single-cell characterization of the immune tumor microenvironment in ovarian carcinomas abstract. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84 (5 Suppl₂): Abstract nr B061.