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MP21-01 SINGLE CELL TRANSCRIPTIONAL PROFILING OF IMMUNE POPULATIONS WITHIN RENAL CELL CARCINOMA TUMOR MICROENVIRONMENT

INTRODUCTION AND OBJECTIVES: Recent development of drugs that block the programmed death-1 and cytotoxic T-lymphocyte antigen-4 interaction within the tumor microenvironment has led to improvements in clinical outcomes in patients with renal cell carcinoma (RCC). However, only a minority of patients achieve a complete response. We performed single cell gene expression analysis on nephrectomy specimens to define immune cell phenotypes within the tumor microenvironment and identify additional relevant therapeutic targets. METHODS: 25,000 sorted immune cells from three clear cell RCC and matched normal kidney tissue were isolated into single cell droplet suspension. The transcriptional profile of individual immune cells was obtained via high throughput chromium 10x single-cell RNA sequencing technology. Cells were clustered by multiple iterations of the iterClust algorithm and top differentially expressed genes were identified in each cluster. RESULTS: To generate a transcriptional map of the immune cell states in the RCC tumor microenvironment, we constructed an atlas comprising 25,000 CD45+ cells. Similar frequencies of myeloid and lymphoid subpopulations were observed between tumor and adjacent normal tissue. A specific population of monocytes expressing complement factors C1QA, C1QB, and C1QC as well as apolipoprotein E was identified in the tumor microenvironment that was not present in matched adjacent normal tissue. CONCLUSIONS: A better understanding of the immune phenotypes in RCC microenvironment can potentially help elucidate the immunologic mechanisms promoting and opposing tumorigenesis. We observed a C1Q-high monocyte subpopulation only present in tumor microenvironment, suggesting that activation of the complement system may play a role in RCC tumorigenesis. Figure. No caption available. Figure. No caption available. Source of Funding: NIH R38 Grant, ASCO Young Investigator Award, Columbia MSTP