The dual role of calnexin on malignant progression and tumor microenvironment in glioma.

Glioma is the most common malignant brain tumor. Previous studies have reported that calnexin (CANX) is significantly up-regulated in a variety of malignant tumors, including glioma, but its biological function and mechanism in glioma is still unclear. In this study, differentially expressed proteins in 3 primary glioblastoma multiforme (GBM) tissues and 3 paracancer tissues were identified by liquid chromatography-tandem mass spectrometry-based proteomic and bioinformatic analysis. The biological function and molecular mechanism of CANX were studied in glioma cell lines (T98G and A172) by CCK-8 assay, matrigel invasion assay, wound healing assay, flow cytometry and so on. Bioinformatics methods were used to analyze the immune microenvironment of glioma patients in TCGA database, and single cell sequencing data of 8 cases of untreated primary GBM in GEO database were analyzed. Proteomic analysis found that CANX was significantly overexpressed in glioma tissues comparing with paracancer tissues. The data from TCGA validated this result and showed that CANX was associated with poor prognosis of patients. A series of experiments at the cellular level found that CANX overexpression significantly enhanced the proliferation, migration and invasion ability of GBM cells, whereas CANX silencing had opposite effects. Further research found this effect may be mediated through the activation of the PI3K/AKT/mTOR signaling. In addition, immune infiltration analysis found that CANX high-expression glioma tissues exhibited fewer CD8(+) T cells, natural killer cells and mast cells, along with significantly decreased tumor purity and significantly increased immune checkpoints expression. Single cell sequencing data analysis indicated that CANX was primarily expressed in astrocytes and dendritic cells. In conclusion, this study suggested that CANX may promote the malignant progression of glioma through PI3K/AKT/mTOR signaling pathway and play an important role in glioma immune escape. Therefore, CANX may be a valuable therapeutic target for glioma.