Abstract 5782: The dynamic immune behavior of primary and metastatic tumors of ovarian cancer

Background: Despite advances in cancer diagnosis and therapy, high-grade serous ovarian cancer (HGSC) is often diagnosed when spread to multiple intraperitoneal areas; it is prone to metastasize to adipose-rich tissues such as the omentum. To gain a deeper understanding of the molecular determinants of the HGSC milieu, we carried out a single-cell analysis of primary and metastatic tumors of HGSC. Thus, our aim is to identify molecular mechanisms that lead to immunosuppressive mechanisms of HGSC in primary and metastatic tumors of HGSC. Methods: Fresh HGSC surgical samples from 19 patients were collected right after surgery, dissociated, and then frozen. For single-cells analysis, cells were sorted by a viability dye and CD45+/- populations followed by Single cell 10 × 3’v3 protocol (10X Genomics) and sequenced using the NovaSeq6000 S2 sequencer. Cell Ranger toolkit v3.1.0 (10x Genomics) was applied for data processing, followed by further downstream analysis using multiple packages from R Package Seurat. Results: To elucidate the cellular heterogeneity of HGSC, we analyzed 100,480 cells, including epithelial, lymphoid, and myeloid populations; these were identified and represented across all patients. We explored the epithelial compartment further, including a total of 21,144 cells. Given the importance of metastatic lesions for the treatment and outcome of patients with HGSC, we examined expression programs among primary and omentum tumors as well treated and untreated tumors. The major differences between primary and omental metastatic tumors included enrichment of EMT pathways and angiogenesis, as well as a decrease in the IFNα and IFNγ response in the omentum. IFNα and IFNγ response pathways were also upregulated in primary treated (P-NACT) tumors, when compared with primary untreated (P-UT) tumors. To explore the immune compartment, we clustered the immune cells across patients in 28 sub-clusters, including 19 sub-clusters of T-cells and Natural Killer cells. Altogether, the immune infiltration on P-UT indicated an immune infiltrate environment and the composition of P-UT was highly enriched in lymphoid cells with a late stage of differentiation. This finding was also demonstrated by the analysis of T cell trajectories, with a clear definition that CD8 and CD4 cells from P-UT tumors are in a late/final and exhausted stage of differentiation, while post-NACT tumors (independent of tissue type) are in early stages (naïve/central memory). The measurement of a dysfunctional score showed that P-UT tumors have the highest scores, indicating a potential increase in tumor reactivity in P-UT tumors. Conclusions: Collectively, these data indicate that HGSC primary and omentum tumors are very distinct niches for immune cells, with primary being much more dysfunctional than omentum tissue, which could indicate that the application of immunotherapies would have different impacts in variable niches of HGSC. Citation Format: Elaine Stur, Fuduan Peng, Pang-ning Teng, Emine Bayraktar, Min Hu, Sara Corvigno, David J. Brown, Sanghoon Lee, Kathleen N. Moore, Nicholas W. Bateman, Kathleen M. Darcy, George L. Maxwell, Thomas Conrads, Nicole Fleming, Nicholas Navin, Linghua Wang, Anil K. Sood. The dynamic immune behavior of primary and metastatic tumors of ovarian cancer. [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 5782.