Abstract 2810: Intracellular tumor microbiota promotes metastasis and drives an immunosuppressive phenotype in ovarian cancer

Abstract Background: The tumor microenvironment has immense potential to change a patient’s prognosis and therapeutic response. One of the emerging components of interest in the tumor microenvironment is the presence of intracellular microbes. Numerous studies have focused on colon and pancreatic cancer because of their proximity to the commensals in the gut. The female reproductive system is another site in our body where the rich vaginal microbiome has the potential to affect nearby organs and impact diseases. However, there is still little investigation done to understand the impact of microbes on Ovarian Cancer (OC). Objective: To understand the role of the microbiome in OC metastasis, to develop new therapies to target the tumor microbiome Methods: We used a co-culture study, the parameters of which were optimized to study the infection of microbes in different cell lines. Using a wide array proteome profiler, we looked for cytokines and chemokines to understand changes in signaling post-infection. Protein levels in the conditioned media using ELISA. Changes in actin, paxillin, and LC3B (autophagy marker) were monitored using immunofluorescence microscopy and western blots. Migration was studied by using transwell assay and spheroid cultures. Results: We have identified two species of bacteria preferentially enriched in human ovarian tumors based on recent findings in the literature. We have demonstrated that these microbes are better at infecting OC cells in vitro over non-specific bacteria, can reside intracellularly, and are metabolically active. Upon infection, this intracellular uptake drives the release of pro-inflammatory cytokines and chemokine signaling by cancer and normal ovarian surface cells. We have also observed increased autophagy, changes in the actin cytoskeleton and reduced Paxillin foci on cancer cells infected with OC-associated microbes. This has led to increased migration in them; however, inactivated microbes did not change their migratory behavior. The infection also caused individual tumor cells to form more numerous and larger colonies when seeded into soft agar, suggesting an effect on cancer cell migration. Furthermore, we have shown that these microbes also elicit a more robust reaction in immune cells like Dendritic cells and macrophages, causing them to secrete chemokines like CCL 2, 3, 4, 5, which also cause the cancer cells to migrate and have the potential to recruit neutrophils to drive the tumor microenvironment towards an immunosuppressive phenotype. Conclusion: Most ovarian cancer patients are diagnosed at Stage III/IV, where cancer has metastasized, and is unresponsive to immunotherapy as the cancer is considered “cold”. Through functional studies, we were able to gain insights into the role of the microbiome, which is associated with the clinical outcomes of OC, hoping to potentiate the existing therapies by probing the tumor microbiome. Citation Format: Ashutosh Kumar, Neelkanth Manoj Bardhan, Angela M. Belcher. Intracellular tumor microbiota promotes metastasis and drives an immunosuppressive phenotype in 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 (6Suppl): Abstract nr 2810.