Abstract 3262: Single-cell spatial dynamics of the tumor-immune microenvironment of high-grade serous ovarian cancer during neoadjuvant chemotherapy

Abstract Neoadjuvant Platinum-based combination chemotherapy (NACT) is commonly offered to patients with high-grade serous ovarian cancer (HGSC) harboring unresectable disease in the primary setting. In order to develop effective immunotherapeutic and combinatorial treatment strategies for HGSC, a deeper knowledge on the effects of NACT on the spatial tumor-immune interactions is required. We performed genetic and single-cell spatial characterization of the tumor-immune microenvironment of 22 HGSC samples collected before and after NACT using Whole Genome Sequencing and tissue cyclic immunofluorescence (t-CycIF) highly-multiplexed imaging platform. We used image analysis and bioinformatics to analyze 30 antibodies in over 6 500 000 single-cells in the context of their spatial tissue architecture. The results were integrated with genomic features and clinical data. We identified four distinct tumor cell metaclusters, eight immune cell subtypes and six stromal cell subpopulations. Chemotherapy induced distinct phenotypic changes in the tumor and immune cells including glutamine metabolism, cell proliferation and antigen presentation. Using single-cell spatial analyses, we identified 18 unique tumor-immune-stromal communities, characterized by different tumor, stromal and immune cell proportions, as well as the tumor-stromal interface. Interestingly, we observed increased CD8+T-cell and decreased CD163+ macrophage infiltration specifically at the tumor-stroma interface induced by chemotherapy. Furthermore, NACT induced spatial CD8+T-cell and macrophage cell-cell interaction patterns specifically in the tumor-stromal interface. Further dissection of the functional properties of the spatial cell-cell interactions using spatial transcriptomics revealed distinct tumor-cell clonal dynamics and gene expression programs on the tumor-stroma interface during NACT. In conclusion, we identified distinct spatial features in the tumor-immune microenvironment indicating the tumor-stromal interface as the underpinning of spatial dynamics in HGSC during NACT. Using a spatial single-cell multi-omics approach has the potential to improve patient stratification and immunotherapeutic strategies in HGSC. Citation Format: Inga-Maria Pauliina Launonen, Angela Szabo, Fernando Perez, Julia Casado, Zoltan Maliga, Sampsa Hautaniemi, Jaana Oikkonen, Johanna Hynninen, Tuulia Vallius, Ajit Johnson Nirmal, Peter Sorger, Anna Vähärautio, Anniina Färkkilä. Single-cell spatial dynamics of the tumor-immune microenvironment of high-grade serous ovarian cancer during neoadjuvant chemotherapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3262.