Immune cell phenotyping of clear cell renal cell carcinoma.

Abstract

511 Background: Clear cell renal cell carcinoma (ccRCC) tumors develop mechanisms that impair function and/or prevent entry of the host infiltrating immune cells (immune exclusion) within the tumor microenvironment. The goal of immunotherapy is to overcome this immune resistance. We aim to characterize the T−cell populations in a cohort of largely untreated high risk patients with ccRCC. Methods: We prospectively collected ccRCC tumor and adjacent normal kidney (NK) from patients undergoing surgical resection at our institution from 6/2015-8/2016. Immune cell phenotyping was performed by immune cell staining of single cell suspensions. Analysis of immune cell populations were determined by CD45+ staining and corresponding proportions of different T−cell populations (CD3+, CD4+, CD4+Treg, and CD8+ T cells). Staining for CD4+Treg was not available for two patients. Student t−test was utilized to compare the immune populations between tumor and adjacent NK tissue. Analysis was also conducted by stratifying patients who presented with localized versus metastatic disease. Results: A total of 31 tumor and adjacent NK were analyzed. Median tumor pathological size was 8.5cm (2.9cm−18cm), 27(87%) had pT3a−pT3b and 13(42%) presented with metastatic disease. Overall 84% of tumors had higher immune infiltrate with an average ratio of four-fold increase compared to adjacent NK as determined by CD45+ cells. Intriguingly, the other 16% presented with metastatic (4) or rapidly metastatic disease (1). Orthogonal validation with inferred immune populations using RNAseq data from the The Cancer Genome Atlas (TCGA) demonstrated similar aggressive behavior in tumors with lower immune infiltrate compared to NK. Comparison of immune cell populations of tumor and NK tissue is shown in table 1. No specific T-cell subtype was associated with specific clinical outcomes in this cohort. Conclusions: Our data shows a general trend of immune infiltration in ccRCC when compared to adjacent NK with a diversity of T-cell subsets and possible evidence of immune exclusion. Further genomic characterization of these tumors is currently underway. [Table: see text]