Celastrol Elicits Antitumor Effects through Inducing Immunogenic Cell Death and Downregulating PD-L1 in ccRCC

Targeting immunogenic cell death (ICD) is considered a promising therapeutic strategy for cancer. However, the commonly identified ICD inducers promote the expression of programmed cell death ligand 1 (PD-L1) in tumor cells, thus aiding them to evade the recognition and killing by the immune system. Therefore, the finding of novel ICD inducers to avoid enhanced PD-L1 expression is of vital significance for cancer therapy. Celastrol (CeT), a triterpene isolated from Tripterygium wilfordii Hook. F induces various forms of cell death to exert anti-cancer effects, which may make celastrol an attractive candidate as an inducer of ICD.

In the present study, bioinformatics analysis was combined with experimental validation to explore the underlying mechanism by which CeT induces ICD and regulates PD-L1 expression in clear cell renal cell carcinoma (ccRCC).

The results showed that EGFR, IKBKB, PRKCQ and MAPK1 were the crucial targets for CeT-induced ICD, and only MAPK1 was an independent prognostic factor for the overall survival (OS) of ccRCC patients. In addition, CeT triggered autophagy and up-regulated the expressions of HMGB1 and CRT to induce ICD in 786-O cells in vitro. Importantly, CeT can down-regulate PD-L1 expression through activating autophagy. At the molecular level, CeT suppressed PD-L1 via the inhibition of MAPK1 expression. Immunologically, the core target of celastrol, MAPK1, was tightly correlated with CD8+ T cells and CD4+ T cells in ccRCC.

These findings indicate that CeT not only induces ICD but also suppresses PD-L1 by down-regulating MAPK1 expression, which will provide an attractive strategy for ccRCC immunotherapy.