Abstract A080: CD8+T-cell interplay with myeloid cells as spatial determinant of chemotherapy response in the tumor microenvironment of metastatic high-grade serous ovarian cancer

Abstract Our goal was to characterize the effects of chemotherapy on the tumor microenvironment of high-grade serous ovarian cancer (HGSC) and suggest effective combination treatment strategies. We employed comprehensive multiomic spatial and single-cell profiling techniques, including tissue cyclic immunofluorescence t-CycIF, scRNA sequencing, and spatial transcriptomics (GeoMx) to characterize the tumor microenvironment of a total of 70 HGSC samples obtained from 41 patients from our prospective, observational trials (DECIDER, ONCOSYS-OVA). The longitudinal samples were collected before and after neoadjuvant chemotherapy (NACT), and they predominantly originated from intra-abdominal metastases. Utilizing cell type calls from whole slide t-CycIF high-dimensional marker expression data, we observed a significant increase in antigen presentation in IBA1+CD11c+ macrophages and CD11c+ myeloid cells interacting with CD4+ and interferon activated CD8+T-cells following NACT. These interactions formed spatial gradients within the tissues. To further investigate spatial heterogeneity, we identified recurring cellular neighborhoods using spatial clustering of cell types across all samples. These multicellular structures exhibited varying proportions of the 18 different cell types. Four out of five immune hotspot neighborhoods primarily comprised different myeloid cells. Interestingly, while the expression of the terminal exhaustion marker TIM3 did not differ in CD8+T-cells overall between the pre- and post-chemotherapy samples, TIM3 expression was specifically higher in CD8+T-cells in myeloid cell-rich neighborhoods from the post-chemotherapy samples, highlighting spatially restricted exhaustion patterns in HGSC. Notably, the most significant differences in overall cell type composition and cell-cell interaction patterns in samples collected before and after NACT were observed in the neighborhood corresponding to the tumor-stromal interface. CD8+T-cells exhibited higher-than-expected interactions with various myeloid cells, while their interactions with tumor cells were lower-than-expected, suggesting potential immune modulation following chemotherapy. Ligand-receptor analysis using paired site-matched scRNAseq data revealed upregulation of chemokines CXCL5 and CCL7 in macrophages after NACT, potentially induced by TNF from tumor cells. Spatial transcriptomics analysis provided further insights into the gene expression programs occurring between macrophages, CD8+T-cells, and tumor cells localized at the tumor-stromal interface. The prognostic power of the main findings were tested in bulk RNA-seq data from 33 patients treated with NACT. In conclusion, our findings indicate that the tumor microenvironment undergoes alterations following NACT, characterized by increased spatially coordinated interactions between CD8+T-cells and myeloid cells, particularly at the tumor-stromal interface. These insights contribute to a better understanding of the complex dynamics within the tumor microenvironment, facilitating the development of novel treatment strategies for HGSC. Citation Format: Inga-Maria P. Launonen, Erdogan P. Erkan, Iga Niemiec, Ada Junquera Mencía, Angela Szabo, Fernando Perez, Essi Kahelin, Sampsa Hautaniemi, Jaana Oikkonen, Johanna Hynninen, Anni Virtanen, Tuulia Vallius, Ajit J. Nirmal, Peter Sorger, Anna Vähärautio, Anniina Färkkilä. CD8+T-cell interplay with myeloid cells as spatial determinant of chemotherapy response in the tumor microenvironment of metastatic high-grade serous ovarian cancer 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 A080.