Association of resistance to antiangiogenic therapy with an immunosuppressive tumor microenvironment in metastatic renal cell carcinoma.

419 Background: Renal cell carcinoma (RCC) is an immunogenic and proangiogenic cancer, and anti-angiogenic therapy is the current mainstay of treatment. RCC patients develop innate or adaptive resistance to anti-angiogenic therapy. There is a need to identify biomarkers which predict therapeutic resistance and guide combination therapy. Methods: Tissue microarrays with triplicate cores for each case were generated from 33 unaffected kidneys, 41 untreated primary RCC, and 42 bevacizumab and 39 sunitinib pretreated primary RCC from patients with metastatic RCC. Immunohistochemistry was used to visualize immune cell infiltration. Staining quantitation was performed using a Vectra multispectral system. Statistical analysis was performed using unpaired Student´s t-test. Results: We assessed the interaction between anti-angiogenic therapy and tumor immune microenvironment, and determined their impact on clinical outcome. Here we found that anti-angiogenic therapy treated RCC primary tumors demonstrated increase...