Identification of the role of TRPM8 in glioblastoma and its effect on proliferation, apoptosis and invasion of the U251 human glioblastoma cell line.

Abstract

Glioblastoma multiforme (GBM) is the most commonly occurring brain cancer, and is characterized by its poor patient outcomes. The present study examined the mRNA expression levels of the transient receptor potential melastatin (TRPM) family in various types of cancer using the ONCOMINE database, along with their corresponding expression profiles in an array of cancer cell lines based on the Cancer Cell Line Encyclopedia (CCLE) datasets. Kaplan‑Meier plotter survival analysis via the Chinese Glioma Genome Atlas (CGGA) database was also used to evaluate the prognostic value of transient receptor potential melastatin 8 (TRPM8). For the activity test on the TRPM8 channel, patch‑clamp recordings and Ca2+ measurements by fluorescence imaging of Fluo‑4am were performed. Short hairpin RNA (shRNA) targeting TRPM8 was designed, synthesized and then transfected into the U251 cells via Lipofectamine 2000. The expression of extracellular singnal‑regulated kinase (ERK), cyclin D1 and Bcl‑2 were detected by performing western blotting and immunofluorescence. The apoptosis, proliferation and invasion of glioma cells were detected by using flow cytometry, and CCK‑8 and Transwell invasion assays. In the present study, TRPM8 was distinctively upregulated in GBM cell lines. TRPM8 is functional and has the characteristic of outward rectification, which was verified via electrophysiology and Ca2+ fluorescence imaging in U251 cells. The western blot and immunofluorescence results revealed that the expression of ERK, cyclin D1 and Bcl‑2 were decreased in the shRNA interference group. The CCK‑8 assay demonstrated that the proliferation ability of U251 cells in the U251/TRPM8 group was higher than that in the U251 group and U251/Con group (P<0.05). The result of the Transwell invasion assay indicated that the invasion of human glioblastoma U251 cells was positively correlated with the expression level of TRPM8. Collectively, the results of the present study indicated that Ca2+‑permeable TRPM8 nonselective cation channels contribute to survival, proliferation, apoptosis, and local tumor invasion of glioblastoma. Therefore, TRPM8 is a promising biomarker for aggressiveness of GBM, and a potential target in future anti‑glioblastoma therapies.