Enhancing Immunotherapy in Endometrial Cancer: Targeting PD-1 on γδ T Cells

Endometrial cancer (EC), the most prevalent gynecological malignancy, has shown a rising incidence and mortality in recent years. Standard treatments primarily involve surgery and/or chemotherapy. However, the identification of tumor escape mechanisms has prompted the development of novel therapeutic strategies, particularly immune checkpoint inhibitors targeting PD-1. In this context, we investigate the role of unconventional gamma delta (γδ) T cells, recognized for their favorable response in various human malignancies, although their role in EC remains unknown. Notably, a high frequency of Vδ1 T cells correlates with improved overall survival in EC patients. Flow cytometry analysis reveals that Vδ1 is the predominant γδ T cell subset infiltrating EC lesions in both early and advanced stages. Upon in vitro stimulation, these cells preserve their functional activity by producing key cytokines, such as IFN-γ and TNF. However, within the tumor microenvironment, they exhibit increased expression of PD-1, compared to their circulating blood-matched counterparts. Single-cell RNA-sequencing (scRNA-seq) analysis further confirms this upregulation in γδ T cells, exhibiting a progressive increase in PD-1 expression from peritumoral to tumor specimens, in contrast to healthy tissue. Crucially, despite PD-1 upregulation, tumor-infiltrating Vδ1 T cells retain their immune competence, which can be enhanced by PD-1 blockade. Indeed, their cytotoxic response against autologous tumor cell targets significantly increases upon treatment with a specific blocking anti-PD-1 monoclonal antibody compared to controls. Supporting the specific tumor-reactivity of Vδ1 T cells expressing PD-1, we also observed that PD-1+ γδ T cells within the tumor exhibit a more focused γδ repertoire compared with their PD-1 negative counterparts. Consistently, specific activation of Vδ1 T cells upon PD-1 blockade has been revealed by scRNA-seq analysis of EC patients undergoing anti-PD-1 therapy. Remarkably, the presence of Vδ1 T cells already before the treatment serves as a predictor of response to anti-PD-1 therapy. These findings underscore the potent antitumor role of Vδ1 T cells in EC and highlight their potential as therapeutic targets to enhance current immunotherapeutic strategies.