Golgi phosphoprotein 3 sensitizes the tumour suppression effect of gefitinib on gliomas

We previously reported that Golgi phosphoprotein 3 (GOLPH3) promotes glioma progression by inhibiting EGFR endocytosis and degradation, leading to EGFR accumulation and PI3K-AKT pathway over-activation. In the current study, we examine whether GOLPH3 affects the response of glioma cells to gefitinib, an EGFR selective inhibitor.

The expression of GOLPH3 and EGFR in glioma cells was detected by immunofluorescence and immunoblotting. The cell viability or growth in vitro was determined by CCK-8, EdU incorporation and clonogenic assays. The primary glioma cells were cultured by trypsin and mechanical digestion. The transwell invasion assay was used to examine the primary glioma cell motility. Intracranial glioma model in nude mice were established to explore the sensitivity of gefitinib to GOLPH3 high cancer cells in vivo.

Both the immortalized and primary glioma cells with GOLPH3 over-expression hold higher EGFR protein levels on the cell membrane and exhibited higher sensitivity to gefitinib. In addition, primary glioma cells with higher GOLPH3 level exhibited stronger proliferation behaviour. Importantly, GOLPH3 enhanced the anti-tumour effect of gefitinib in vivo. Consistently, after gefitinib treatment, tumours derived from GOLPH3 over-expression cells exhibited lower Ki67-positive and higher cleaved caspase-3-positive cells than control tumours.

Our results demonstrate that GOLPH3 increases the sensitivity of glioma cells to gefitinib. Our study provides foundation for further exploring whether GOLPH3 high gliomas will be more sensitive to anti-EGFR therapy in clinic and give ideas for developing new possible treatments for individual glioma patients.