Transglutaminase 2 regulates ovarian cancer metastasis by modulating the immune microenvironment

Ovarian cancer is the most lethal gynecological malignancy. Deepening our knowledge of the interactions within the tumor microenvironment (TME) is important for discovering new targeted treatment strategies. Transglutaminase 2 (TG2) is a protein implicated in many biological and pathophysiological processes, including promoting tumor progression in ovarian cancer. Its role in disease progression has been studied in ovarian cancer cells; however, its role in the ovarian TME is less understood. Using the ID8 Trp53-/- Brca1-/- and KPCA.B syngeneic mouse models of ovarian cancer, we defined the contribution of TG2 in the TME to the metastatic process. Lack of TG2 in the TME prolonged survival in the ID8 Trp53-/- Brca1-/- metastatic model. Through extensive analysis of the immune composition in both the primary tumor and metastatic ascites in the ID8 Trp53-/- Brca1-/- model, we discovered that the lack of host TG2 resulted in decreased frequency of immunosuppressive tumor-associated macrophages, and increased frequency of T cells, NK cells, and B cells. RNA sequencing of the primary tumors with or without TG2 present in the TME, revealed an enrichment of pathways related to B cell activation and regulation, highlighting a crucial role for TG2 in modulating B cells to enhance survival in the ID8 Trp53-/- Brca1-/- model. Taken together, our findings highlight the importance of TG2 in the TME for ovarian cancer metastasis, potentially through the activation of humoral immunity. RNA-sequencing of primary tumors collected from ID8 Trp53-/- Brca1-/- tumor bearing WT and Tgm2-/- mice 6 weeks post implantation.