Abstract
Objective
To investigate the influence of MEK5/ERK5 pathway on mitophagy in osteosarcoma (OS), as well as the involved molecular mechanisms.
Methods
The overlapped genes of mitophagy-related genes from MSigDB database and DEGs between metastatic and primary OS groups from GSE32981 were identified. GSVA of mitophagy-related pathways between the metastatic and primary groups were analyzed. The relationships between Nur77 and mitophagy-related pathways, prognosis were investigated. Western blotting was utilized to assess protein levels of MEK5, ERK5, p-ERK5, Nur77, PINK1, and Parkin. Cellular behaviors and mitochondrial potential were evaluated via CCK-8, Transwell assay and JC-1 staining.
Results
Total 4 overlapped genes were obtained as mitophagy-related DEGs, including GABARAPL1, HIF1A, PINK1, RB1CC1. The activity scores of 3 mitophagy-related pathways exhibited significant differences between metastatic and primary groups. Importantly, Nur77 was significantly negatively correlated with a mitophagy-related pathway (GOBP MITOPHAGY: R = -0.48, P = 0.02). The Nur77 expression in metastatic group was remarkedly higher than that in the primary group (P < 0.001). Patients with high Nur77 expression had poor prognosis, with AUC values all above 0.615 in predicting 1, 3, and 5 years survival. In addition, MEK5/ERK5 pathway is activated in OS, and MEK5/ERK pathway promotes Nur77 expression, tumorigenesis and mitochondrial function in U2OS cells. Cytosporone B implement significantly increased the tumorigenesis of U2OS cells in sh-MEK5 group, and inhibited the weaken in mitochondrial membrane potential caused by MEK5 downregulation, and reversed the protein levels of mitophagy markers PINK1 and Parkin in sh-MEK5 group.
Conclusion
MEK5-ERK5 pathway mediates mitophagy by regulating Nur77 to promote tumorigenesis of OS cells. These findings offered promising therapeutic targets for OS.