Over-expression Of Endogenous PD-L1 Is Regulated By Notch1 In Clear Cell Renal Cell Carcinoma

Objectives: High expression of programmed death ligand 1 (PD-L1) has been well-demonstrated that correlates with poor prognosis of clear cell renal cell carcinoma(ccRCC) and its antibodies are undergoing several clinical trials. However, mechanisms and functions of the endogenous expression of PD-L1 on ccRCC remain unclear. Notch signaling pathway plays a key role in contributing to tumorigenesis of ccRCC, but the relationship between Notch 1 and PD-L1 is also unknown.Therefore, this study aims to explore whether there is a relationship between Notchl and PD-L1 as we hypothesize and the functions of endogenous expression of PD-L1 on ccRCC.Materials and methods: The expression of Notchl and PD-L1 were validated at thirty-seven paired ccRCC and adjacent non-neoplastic renal tissues, HKC, 786-0 and 769-P cell lines on both mRNA and protein levels. Knockdown of Notchl and/or PD-L1 expression in cell lines were achieved by transfecting their specific short interfering RNAs,and plasmid containing the ORF clone of Notchl was used for forced over-expression assay. Cell proliferation, migration and invasion were detected by MTS assay, flow cytometric analyses and Transwell assay respectively and the statistical analyses were used properly.Results: Concurrently Over-expressed Notch1 and PD-L1 were showed in 86.5%(thirty-two) ccRCC specimens compared with adjacent normal renal tissues and ccRCC cell lines, 21.6% (eight) were down-regulated concurrently and 8.1% (3) showed changing inconsistently. Knockdown or forced over-expression of Notchl could restrain the PD-L1 expression on both mRNA and protein levels in vitro. Although knockdown of PD-L1 had no effect on Notch11 expression, it significantly restrained the cell proliferation, migration and invasion of ccRCC cell lines in vitro, which could be augmented by combining knockdown of Notchl.Conclusion: Our work provides the first evidence that Notchl is strongly associated with endogenous PD-L1 expression in ccRCC and may influence the response to ccRCC anti-PD-L1 immunotherapy.