Cd73 Expression In Primary And Metastatic Renal Cell Carcinoma (Rcc).

643Background: Agents targeting the PD-1 pathway have improved outcomes in RCC. CD73 may be an additional mechanism which tumors can exploit for immune evasion. It is regulated by hypoxia inducible factor (HIF) and converts AMP to adenosine. The resulting increase in extracellular adenosine can inhibit T-cell effector function. We evaluated CD73 expression in primary and metastatic tumor samples in patients with RCC. Methods: A commercial TMA (US Biomax) consisting of 31 primary clear cell RCC samples (2 with sarcomatoid features) with 8 matched and 1 unmatched metastases was used to assess CD73 expression. A genitourinary pathologist (OH) confirmed pathology and grade. Immunohistochemistry (IHC) was performed using a monoclonal anti-CD73 antibody (Cell Signaling; D7F9A). A combined score (CS: % of cells positive x intensity) was employed to quantify CD73 expression. Expression levels between matched primary and metastatic tissue was compared using Wilcoxon signed-rank test. Correlation of CD73 expression...