1907P - Low NK cell abundance correlates with high expression of PD-1 in CD8+ T cells

Abstract

BackgroundRenal cell carcinoma (RCC) is considered an immunogenic cancer with a high frequency of indel mutations, immuno-oncological (IO) sensitivity, and infiltration of T cells. Because natural killer (NK) cells are a lesser known population compared to their T cell counterparts, we aimed to investigate the intratumoral phenotype of the cells to assess the overall immune landscape of RCC. MethodsThe tumor, matching peripheral blood (PB) and healthy kidney tissue samples were obtained from 40 RCC patients that underwent radical nephrectomy and were phenotyped using multi-parameter flow cytometry and a comprehensive immunostaining panel containing 56 fundamental markers to cancer immunology. ResultsUsing hierarchical clustering and correlation analysis, we discovered that our cohort clustered into two distinct subgroups defined by the abundance of NK cells from the intratumoral lymphocyte population, defined as NKhigh (n=17; mean 24.3%) and NKlow (n=18; mean 7.5%). Consequently, an increased abundance of NK cells correlated with a lower expression of PD-1, particularly in the CD8+ T cells (r=-0.5722, p=0.0003), but not with LAG-3. Contrastingly, clinical parameters such as tumor grade, gender and age did not differ between the two NK subgroups. However, patients with high NK cell abundance significantly had more often necrosis present in the tumors (p=0.04). We also independently phenotyped two regions of the same tumor sample (n=10) to compare the periphery and core lymphocytes. Surprisingly, both spatially different regions displayed similar quantities of immune cell populations and immunophenotypic markers. Overall, the tumor immune landscape in RCC resulted in a proportion of tumors carrying a higher abundance of NK cells than their T cell-rich corresponding PB and healthy tissue samples, which supports our findings that a proportion of tumors accumulate NK cells. ConclusionsOur study has led to the discovery of two distinct RCC tumoral NK cell subgroups, NKhigh and NKlow. Next, we aim to further explore the transcriptional differences of the two subgroups with ongoing bulk RNA sequencing (RNAseq). Furthermore, prospective single-cell RNA sequencing (sc-RNAseq) will be carried out to investigate the immunological heterogeneities in higher resolution. Legal entity responsible for the studyThe authors. FundingUniversity of Helsinki, Hematology Research Unit Helsinki. DisclosureAll authors have declared no conflicts of interest.