Cyclophilin A Maintains Glioma-Initiating Cell Stemness by Regulating Wnt/β-catenin Signaling.

Purpose: Glioma-initiating cells (GIC) are glioma stem-like cells that contribute to glioblastoma (GBM) development, recurrence, and resistance to chemotherapy and radiotherapy. They have recently become the focus of novel treatment strategies. Cyclophilin A (CypA) is a cytosolic protein that belongs to the peptidyl-prolyl isomerase (PPIase) family and the major intracellular target of the immunosuppressive drug cyclosporin A (CsA). In this study, we investigate the functions of CypA and its mechanism of action in GICs' development. Experimental Design: We analyzed differences in CypA expression between primary tumors and neurospheres from the GDS database, both before and after GIC differentiation. A series of experiments was conducted to investigate the role of CypA in GIC stemness, self-renewal, proliferation, radiotherapy resistance, and mechanism. We then designed glutathione S-transferase (GST) pulldown and coimmunoprecipitation assays to detect signaling activity. Results: In this study, we demonstrated that CypA promotes GIC stemness, self-renewal, proliferation, and radiotherapy resistance. Mechanistically, we found that CypA binds beta-catenin and is recruited to Wnt target gene promoters. By increasing the interaction between b-catenin and TCF4, CypA enhances transcriptional activity. Conclusions: Our results demonstrate that CypA enhances GIC stemness, self-renewal, and radioresistance through Wnt/beta-catenin signaling. Due to its promotive effects on GICs, CypA is a potential target for future glioma therapy. (C) 2017 AACR.