Natural killer cells display unique, non-cytotoxic profiles in human endometrial cancer

Abstract

Abstract Endometrial cancer (EC) responds variably to immune checkpoint blockade, warranting study of the tumor microenvironment (TME). Natural killer (NK) cells are cytotoxic innate lymphocytes that can directly kill tumor cells, yet their diversity, locations, and functions in the EC TME are unknown. CITE-seq analysis of fresh EC tumor samples revealed multiple NK cell populations in the TME, with distinct patterns of surface activating and inhibitory receptor expression and less cytolytic granule expression by tumor-derived conventional NK (cNK) and tissue-resident NK (trNK) cells compared to autologous blood cNK. Ex vivo flow cytometry revealed significantly lower expression of cytolytic granules by TME-derived NK cell subsets (granzyme B MFI: blood cNK 1.5e5 +/- 5.4e4, tumor cNK 7.9e4 +/- 2.9e4 p<0.05, tumor trNK 3.7e4 +/- 1.4e4 p<0.05, n=10; perforin MFI: blood cNK 1.3e4 +/- 3.1e3, tumor cNK 1.0e4 +/- 3.2e3 p=0.19, tumor trNK 3.5e3 +/-1.3e3 p<0.01, n=8). To identify NK cell subsets within the TME, we performed immunohistochemistry using CD3, CD56, granzyme B, and CD103 to demarcate cNK and trNK, respectively. We observed granzyme B+ cells primarily in the stroma (78.6 +/- 3.7% Stroma, 21.4 +/- 3.7% Glands, n=10, p<0.05) and CD103+ cells primarily among tumor cells (15.6 +/- 4.5% Stroma, 84.3 +/- 0.64% Glands, n=10, p=0.07). These data suggest that both cNK and trNK cell cytotoxicity is suppressed in the EC TME and ongoing work seeks to elucidate the mechanisms.