SNX4 promotes glioblastoma progression through the TGFβ1/Smad signaling pathway and represents a potential therapeutic target

Abstract

Glioblastoma multiforme (GBM) is a highly malignant primary brain tumor that still lacks highly specific and clinically effective molecular targets for GBM treatment. Sorting Nexin 4 (SNX4) is an important regulatory molecule involved in intracellular membrane trafficking, protein sorting, and receptor recycling on the cell membrane. However, the roles and mechanism of action of SNX4 in GBM remain unclear. RT-qPCR and Western blotting methods were used to measure the expression levels of SNX4 in GBM cell lines and glioma tissue samples from GBM patients. The prognostic role of SNX4 in glioma patients was analyzed by bioinformatic analysis. The roles and underlying mechanism of action of SNX4 in the cell proliferation, cell apoptosis, cell cycle progression, cell migration, and cell invasion of GBM cell lines whose SNX4 gene was silenced or the regulatory pathway of SNX4 was pharmacologically inhibited were examined by the corresponding assays. The role of SNX4 in GBM growth was measured in subcutaneous and intracranial orthotopic tumor models in nude mice. Candidate SNX4-binding small-molecule compounds were discovered by virtual drug screening of a library of small molecule compounds and cell-based drug activity screening. SNX4 was overexpressed in GBM cell lines and glioma tissue samples from GBM patients measured by RT-qPCR and Western blotting and its high expression was associated with poor prognosis in patients with glioma. SNX4 promoted GBM progression by activating the TGFβ1/Smad signaling pathway in in vitro cell-based assays. Nevertheless, the precise molecular mechanism linking SNX4 to TGFβ receptor trafficking remains to be elucidated. SNX4 also promoted glioma growth in subcutaneous and intracranial orthotopic GBM tumor models in nude mice. Two candidate SNX4-binding small-molecule compounds, G149 and G431, were identified through virtual screening and validated by cell-based assay. Both compounds suppressed GBM growth and were associated with reduced SNX4 expression and inhibition of the TGFβ1/Smad signaling pathway in vitro and in vivo. Our findings suggest that SNX4 functions as an important regulator of GBM progression, may serve as a potential prognostic biomarker for glioma patients, and may represent a potential therapeutic target.