Neoadjuvant chemotherapy modulates the immune microenvironment in metastases of tubo-ovarian high-grade serous carcinoma

Abstract

Purpose: The purpose of this study was to assess the effect of neoadjuvant chemotherapy (NACT) on immune activation in stage IIIC/IV tubo-ovarian high-grade serous carcinoma (HGSC), and its relationship to treatment response. Experimental Design: We obtained pre- and posttreatment omental biopsies and blood samples from a total of 54 patients undergoing platinum-based NACT and 6 patients undergoing primary debulking surgery. We measured T-cell density and phenotype, immune activation, and markers of cancer-related inflammation using IHC, flow cytometry, electrochemiluminescence assays, and RNA sequencing and related our findings to the histopathologic treatment response. Results: There was evidence of T-cell activation in omental biopsies after NACT: CD4+ T cells showed enhanced IFNγ production and antitumor Th1 gene signatures were increased. T-cell activation was more pronounced with good response to NACT. The CD8+ T-cell and CD45RO+ memory cell density in the tumor microenvironment was unchanged after NACT but biopsies showing a good therapeutic response had significantly fewer FoxP3+ T regulatory (Treg) cells. This finding was supported by a reduction in a Treg cell gene signature in post-versus pre-NACT samples that was more pronounced in good responders. Plasma levels of proinflammatory cytokines decreased in all patients after NACT. However, a high proportion of T cells in biopsies expressed immune checkpoint molecules PD-1 and CTLA4, and PD-L1 levels were significantly increased after NACT. Conclusions: NACT may enhance host immune response but this effect is tempered by high/increased levels of PD-1, CTLA4, and PD-L1. Sequential chemoimmunotherapy may improve disease control in advanced HGSC.