The Significance of Insulin Receptor Expression to Predict the Resistance to VEGFR-TKIs and Induce PD-L1 Expression in Advanced Clear Cell Renal Cell Carcinoma.

592 Background: Previously we have identified the prognostic gene set of ccRCC patients, where insulin receptor (INSR) expression was decreased in the patients with poor outcome (Proc Natl Acad Sci U S A., 2001). We examined the clinical significance of decreased INSR expression and sought to elucidate the underlying mechanisms. Methods: The INSR expression was immunohistochemically examined in the nephrectomy specimens of RCC patients (n = 33) who then received axitinib. We established patient derived Xenograft model (PDX) of ccRCC and examined the INSR expression in the axitinib resistant PDX tumors by Western blotting. As the INSR is expressed in the vascular endothelial cells, we co-cultured the RCC cell lines with the human renal glomerular endothelial cells (HGEC) treated with si-RNA of INSR (si-INSR) and the microarray experiment was conducted. Results: In RCC patients with axitinib, those with low INSR expression had poor outcome (median PFS 19.5 vs 2.3 months, p < 0.001; median OS 34.2 vs 5.6 months, p = 0.001). The INSR expression was the significantly independent predictor of PFS (p = 0.006). In the axitinib-resistant PDX tumors, the expression of INSR was decreased. In the co-culture experiments, the microarray experiments revealed that the decreased INSR expression in the HGECs may be involved with the important signaling pathway including interferon response in Caki-1 cells. Interferon- β was highly expressed in HGECs with si-INSR. The decreased INSR expression and the increased interferon-β expression in HGEC were confirmed when axitinib was administered. The Caki-1 cells that was co-cultured with HGECs treated with si-INSR demonstrated high expression of PD-L1. The PD-L1 expression was increased in a concentration-dependent manner of recombinant interferon-β and increased phosphorylation of STAT1 and STAT3 were observed. Conclusions: In conclusion, the decreased INSR expression could be a biomarker to predict the resistance to VEGFR-TKIs. The decreased INSR expression was correlated with the increased interferon-β expression in HGECs, which leads to the induction of PD-L1 through increased phosphorylation of STAT1 and STAT3.