DDX39B Predicts Poor Survival and Associated with Clinical Benefit of Anti-PD-L1 Therapy in ccRCC.

Background Immune checkpoint inhibitors (ICI) have been shown to improve overall survival (OS) in clear cell renal cell carcinoma (ccRCC) patients. However, less than half of the ccRCC patients have objective response to ICI. Objective We aim to assess the role of DDX39B in predicting ccRCC patients' OS and ICI therapy response. Methods DDX39B was detected by immunohistochemistry in a tissue microarray of 305 ccRCC patients. DDX39B and its relationship with the prognosis of ccRCC were also evaluated in TCGA set and a RECA-EU set. The expression of DDX39B and patients survival was also analysed in two datasets of ccRCC patients treated with ICI. Results Overexpression of DDX39B predicted poor OS of ccRCC patients in SYSU set, TCGA set, and a RECA-EU set. DDX39B expression was significantly positive with the expression of PD-L1 and other immunomodulators., DDX39B negatively correlated with cytotoxic T-lymphocyte and HDAC10 exon 3 inclusion in ccRCC. DDX39B knockdown decreased the expression of PD-L1 and increased the expression of HDAC10 exon 3 in renal cancer ACHN cells. Patients of ccRCC with lower levels of HDAC10 exon 3 inclusion have higher TNM stage, higher Fuhrman grade and poor OS. There was a tendency that patients with DDX39B high expression had longer OS and PFS than patients with DDX39B low expression in ccRCC patients treated with ICI. Conclusion DDX39B gene is highly expressed in ccRCC and is closely related to patients' OS. DDX39B might increase PD-L1 expression via the enhancement of HDAC10 exon 3 skipping, thereby promoting the ICI therapy response.