Characteristics and immunological changes of tumor-infiltrating lymphocytes during neoadjuvant chemo-immunotherapy in epithelial ovarian cancer (251)

Abstract

<b>Objectives:</b> Epithelial ovarian cancer (EOC) is an aggressive gynecologic malignancy with a poor prognosis. Even after standard-care treatment, most patients eventually relapse and thus show a low survival rate. It is well known that tumor-infiltrating lymphocytes (TILs) are associated with survival outcomes in EOC. However, characteristics and dynamic changes of TILs during treatment courses have not been well investigated in EOC. In this study, we examined the characteristics of TILs from ovarian cancer patients and their dynamic changes during neoadjuvant chemotherapy (NACT) or neoadjuvant chemoimmunotherapy (NACI). <b>Methods:</b> We isolated peripheral blood mononuclear cells (PBMCs) and TILs from treatment-naïve (<i>n</i>=18) or post-NACT treated (<i>n</i>=22) or post-NACI treated EOC patients (<i>n</i>=8). NACT was paclitaxel plus carboplatin, and NACI was NACT with durvalumab plus tremelimumab. Immunologic characteristics and functions of CD8, CD4, and regulatory T (Treg) cells in each group were compared using flow cytometry. <b>Results:</b> The percentages of CD8 TILs of post-NACT and post-NACI were increased, but conventional CD4 and Foxp3⁺ Treg were decreased after NACT and NACI. Therefore, CD8/Treg cells ratio was increased in post-NACT and post-NACI. When we examined the memory differentiation status of CD8 and CD4 TILs, there was no significant difference among treatment-naïve, post-NACT, and post-NACI. The percentages of central memory and effector memory were not significantly different. In addition, comparing expressions of immune checkpoints, including PD-1, CTLA-4, and TIGIT on TILs, there was no significant difference among them. However, 4-1BB⁺ and Ki-67⁺ cells in CD8 and Treg cells were significantly decreased after NACT or NACI. It meant that tumor-reactive proliferating CD8 TILs and Treg cells were decreased after NACT. Next, we examined expressions of TCF-1 and TOX in PD-1+CD8 TIL in post-NACT or post-NACI to investigate changes of exhaustion status, and it was revealed that TCF-1⁺ cells were increased and TOX⁺ cells were decreased after NACT or NACI. However, cytokine production capacity (IFN-γ and TNF-α) of CD8 TILs was not different. In the case of Treg cells, suppressive CD45RA-Foxp3^high Treg cells and CCR8⁺ Treg cells were significantly decreased after NACT or NACI. In addition, comparing post-NACT with post-NACI, CCR8⁺ Treg cells were more significantly decreased in post-NACI. <b>Conclusions:</b> The current study investigated immunologic changes after NACT and NACI in ovarian TILs. According to a decrease in tumor burden during chemotherapy, the immunologic tumor-microenvironment changed to favor antitumor immunity. Furthermore, Treg cells with more suppressive properties (CCR8⁺ or 4-1BB⁺ Treg cells) were more decreased after NACI. Further studies are ongoing on the effect of NACI on Treg cells and their clinical significance in EOC.