In our study, we demonstrate that ccRCC cell lines with impaired function of pVHL to degrade HIFα express elevated levels of PD‐L1. In vitro analysis provided evidence that both reconstitution of pVHL and silencing of HIF2α, but not of HIF1α, lead to reduced PD‐L1 expression. The strong correlation of expression between the HIF2α‐specific HIF target Glut1 and PD‐L1 confirmed this finding in ccRCC cell lines and tissue. Soluble PD‐L1 levels remained constant in the sera of ccRCC patients regardless of the PD‐L1 expression status in their tumors. In conclusion, our data suggest PD‐L1 as HIF2α target, which is upregulated in pVHL deficient ccRCC. The combination of PD‐L1 targeting drugs with HIF inhibiting agents may be an additional option for the treatment of ccRCC.

Purpose: CD70, a member of the TNF ligand superfamily, has been shown frequently overexpressed in clear cell renal cell carcinoma (ccRCC). The mechanisms of CD70's upregulation and its role in ccRCC are unknown.Experimental Design: CD70 expression was immunohistochemically analyzed in 667 RCCs and RCC metastases. Von Hippel-Lindau gene (VHL) mutations, expression patterns of VHL protein (pVHL), hypoxia-inducible factor (HIF) a, and several HIF targets were studied in tissues and cell lines and correlated with CD70 overexpression. Gene promoter analysis was performed to confirm CD70 as HIF target gene. Consecutive tissue sections were immunostained to reveal the relation between CD70-expressing RCCs and tumor-infiltrating lymphocytes positive for the CD70 receptor (CD27). CD70-mediated release of soluble CD27 in RCC was assessed by coculture experiments and sera analysis of patients with RCC.

Mass spectrometry analysis of renal cancer cell lines recently suggested that the ProteinTyrosine Phosphatase Receptor Type J (PTPRJ), an important regulator of tyrosine kinase receptors, is tightly linked to the von-Hippel Lindau protein (pVHL). Therefore, we aimed to characterize the biological relevance of PTPRJ for clear cell renal cell carcinoma (ccRCC). In pVHL negative ccRCC cell lines both RNA and protein expression levels of PTPRJ were lower than those in the corresponding pVHL reconstituted cells. Quantitative RT-PCR and Western blot analysis of ccRCC with known VHL mutation status and normal matched tissues as well as RNA in situ hybridization on a Tissue Microarray (TMA) confirmed a decrease of PTPRJ expression in more than 80 % of ccRCCs, but in only 12 % of papillary RCCs. ccRCC patients with no or reduced PTPRJ mRNA expression had a less favourable outcome than those with a normal expression status (p = 0.05). Sequence analysis of 32 PTPRJ mRNA negative ccRCC samples showed five known polymorphisms, but no mutations implying other mechanisms leading to PTPRJ's down-regulation. Selective silencing of HIF-by siRNA and reporter gene assays demonstrated that pVHL inactivation reduces PTPRJ expression through a HIF-dependent mechanism, which is mainly driven by HIF-2 stabilization. Our results suggest PTPRJ as a member of a pVHL controlled pathway whose suppression by HIF is critical for ccRCC development. expression through a HIF-dependent mechanism, which is mainly driven by HIF-2 stabilization. Our results suggest PTPRJ as a member of a pVHL controlled pathway whose suppression by HIF is critical for ccRCC development.

CD70 upregulation by hypoxia-inducible factor and CD27 lymphocyte tumor infiltration are associated with worse survival in von Hippel-Lindau gene mutated clear cell renal cell carcinoma (ccRCC). CD70/CD27 interaction is accompanied by high soluble CD27 levels in the sera of ccRCC patients suggesting that soluble CD27 is a potential predictive tool for anti-CD70 therapy.

<p>Supplementary table S1: Antibodies used for Western blot analysis, immunohistochemistry and ChIP. Supplementary table S2: VHL and HIF1α mutation states in cell lines. Supplementary table S3: Primers used for ChIP analysis. Supplementary table S4: Correlations between tumor stage, grade and CD70 in ccRCC.</p>