GOLPH3 promotes glioma progression via facilitating JAK2-STAT3 pathway activation.

INTRODUCTION: Our recent work reported that GOLPH3 promotes glioma progression via inhibiting endocytosis and degradation of EGFR. The current study aimed to explore the potential regulating mechanism of GOLPH3 on JAK2-STAT3 signaling, a downstream effector of EGFR, in glioma progression. METHODS: The expression of JAK2, STAT3 and GOLPH3 in glioma tissues was detected by western blotting, tissue microarray and immunohistochemistry. The U251 and U87 cells with GOLPH3 down-regulation or over-expression were generated by lentivirus system. The effects of GOLPH3 on the activity of JAK2 and STAT3 were detected by western blotting and reverse transcription polymerase chain reaction. Co-immunoprecipitation was used to detect the association of GOLPH3 with JAK2 and STAT3. Cell proliferation was detected by CCK8 and EdU assay. RESULTS: The level of JAK2, STAT3 and GOLPH3 were significantly up-regulated and exhibited pairwise correlation in human glioma tissues. The level of p-JAK2 and p-STAT3, as well as the mRNA and protein levels of cyclin D1 and c-myc, two target genes of STAT3, decreased after GOLPH3 down-regulation, while they increased after GOLPH3 over-expression both in U251 and U87 cells. Interestingly, GOLPH3, JAK2 and STAT3 existed in the same protein complex and GOLPH3 affected the interaction of JAK2 and STAT3. Importantly, down-regulation of STAT3 partially abolished cell proliferation induced by GOLPH3 over-expression. CONCLUSIONS: GOLPH3 may act as a scaffold protein to regulate JAK2-STAT3 interaction and then its activation, which therefore mediates the effect of GOLPH3 on cell proliferation.

PAK1 Inhibition Suppresses the Proliferation, Migration and Invasion of Glioma Cells.

BACKGROUND: p21-activated kinase 1 (PAK1) is abnormally expressed in glioma, but its roles and mechanisms in glioma remain unclear. This study aims to explore the effects of PAK1 inhibition on the proliferation, migration and invasion of glioma cells. METHODS: Cell Counting Kit-8 (CCK-8), 5-ethynyl-20-deoxyuridine (EdU) incorporation and colony formation assays were performed to evaluate the effects of PAK1 inhibition on the proliferation of glioma cells. The cell cycle distribution and apoptosis rate of glioma cells were explored by flow cytometry. Wound healing and Transwell assays were performed to investigate the effects of PAK1 inhibition on glioma cell migration and invasion. The orthotopic xenograft glioma model was used to probe the effect of PAK1 silencing on glioma tumor formation. RESULTS: PAK1 inhibition arrested cells at the G1 phase and induced apoptosis of glioma cells. Moreover, the knockdown of PAK1 decreased the protein expression levels of MDM2, p38, p-p38, cyclin D1, CDK4, Bcl-2, MMP2, MMP9, and cofilin but increased the protein levels of p53, Bax, p21 and cleaved caspase-3. A xenograft glioma model confirmed that the silencing of PAK1 repressed the formation of tumors induced by U87 cell transplantation. CONCLUSION: This study showed that PAK1 inhibition impedes the proliferation, migration, and invasion of glioma cells.