High IDO-1 Expression in Tumor Endothelial Cells is Associated with Response to Immunotherapy in Metastatic Renal Cell Carcinoma

Nivolumab belongs to the standard therapy in the second-line setting of metastatic renal cell carcinoma (mRCC). Although deep and long-lasting responses are seen in some patients, the majority of patients will further progress. PD-L1 as predictive biomarker is still under critical evaluation. Thus, more accurate biomarkers are clearly warranted. Here, we investigated for the first time the predictive role of IDO-1, a negative immune-regulatory molecule, on clear cell RCC tissues of 15 patients undergoing nivolumab therapy. IDO-1 and other immune inhibitory molecules (PD-L1, PD-L2, FOXP3) as well as immune cell subsets (CD3, CD4, CD8) were measured on formalin-fixed, paraffin-embedded sections of RCC specimens by immunohistochemistry. IDO-1 was predominantly expressed in tumor endothelial cells, and was totally absent from tumor cells itself. IDO-1 overexpression (>10%) could be detected more frequently in responders (100%, n=6/6) compared to non-responders (33.3%, n=3/9; p=0.028), resulting in a better progression-free survival during immunotherapy (IDO-1 ≤10% vs. >10%, median: 3.5 vs. NE months, p=0.01 by log-rank test). In addition, IDO-1 was positively correlated with CD8+T cell expression (rs=0.691, p=0.006). PD-L1 expression on tumor cells was negative in 13 (86.7%) of 15 patients, irrespective of therapeutic response (responders vs. non-responders: 83.3% vs. 88.9%). No differences were noticed in the PD-L1 expression on tumor-infiltrating immune cells (PD-L1<1% in 66.7% of both responders and non-responders). In contrast to PD-L1, these results suggest that IDO-1 may be a more promising predictive biomarker for response to immune-based cancer therapy in mRCC. This article is protected by copyright. All rights reserved.

Cancer science. 2018 Mar 02 [Epub ahead of print]

Andreas Seeber, Gerald Klinglmair, Josef Fritz, Fabian Steinkohl, Kai-Christian Zimmer, Friedrich Aigner, Wolfgang Horninger, Günther Gastl, Bettina Zelger, Andrea Brunner, Renate Pichler

Department of Internal Medicine V Hematology and Oncology, Medical University of Innsbruck., Department of Urology, Medical University of Innsbruck., Department of Medical Statistics, Informatics and Health Economics., Department of Radiology, Medical University of Innsbruck., Department of Pathology Division of General Pathology, Medical University of Innsbruck, A-6020, Innsbruck, Austria.