Prohibitin2 knockdown decreases glioma malignant phenotypes and radio-resistance by inhibiting mitophagy.

Purpose: Prohibitin2 (PHB2), located in inner mitochondrial membrane (IMM), is an important receptor to induce mitophagy. PHB2 was identified as a cancer-promoting factor in most cancers. However, the function of PHB2 in glioma cells remains unclear. This study delved into the impact of PHB2 knockdown on the phenotype, radiosensitivity and mitophagy of glioma cells.

Methods: PHB2 expression and its clinical relevance in glioma were investigated by western blot, quantitative reverse transcription polymerase chain reaction (qRT-PCR) and TCGA databases. The malignant phenotypes of glioma cells were analyzed in vitro using cell proliferation, cell cycle, wound healing and transwell assay. The radiosensitivity of glioma cells was detected by colony forming assay. The potential mechanism by which PHB2 regulated mitophagy was investigated by coimmunoprecipitation assay.

Results: The expression of PHB2 was significantly upregulated in glioma cells and closely correlated with the malignant degree of glioma. The knockdown of PHB2 inhibited the proliferation, migration and invasion activities of glioma cells. Furthermore, PHB2 knockdown enhanced the radiosensitivity of normoxic and hypoxic glioma cells and suppressed the ionizing radiation-induced mitophagy in glioma cells. Cyanide 3-chlorophenylhydrazone (CCCP), a mitophagy agonist, could reverse the phenotypes and radiosensitivity changes elicited by PHB2 knockdown. Additionally, PHB2 regulated the expression of PGAM5 and PINK1 by directly binding to PARL.

Conclusions: Our findings revealed that PHB2 knockdown decreased glioma malignant phenotypes and radio-resistance by inhibiting mitophagy PARL-PGAM5-PINK1-Parkin pathway. PHB2 is a promising candidate target for the development of new therapeutic strategy to enhance the efficacy of radiotherapy for glioma.