ZFP36 promotes ferroptosis and mitochondrial dysfunction and inhibits malignant progression in osteosarcoma by regulating the E2F1/ATF4 axis.

Zinc finger protein 36 (ZFP36) was found to be downregulated in osteosarcoma (OS) tumor tissues. We aimed to investigate the roles and mechanisms of ZFP36 in ferroptosis regulation during OS development. Two Gene Expression Omnibus (GEO) datasets showed that ZFP36 was a differentially expressed gene (DEG) in OS. Western blot and immunohistochemistry results showed that ZFP36 was downregulated in OS tumors and cell lines. ZFP36 overexpression plasmids and small interfering RNAs (siRNAs) were respectively transfected into OS cells. ZFP36 overexpression restrained proliferation, migration, and invasion in MG63 and U2OS cells, while ZFP36 knockdown displayed the opposite results. Moreover, ZFP36 overexpression increased the levels of intracellular Fe(2+), reactive oxygen species (ROS), and malondialdehyde (MDA), and decreased the levels of glutathione (GSH), glutathione peroxidase 4 (GPX4), and solute carrier family 7 member 11 (SLC7A11). ZFP36 overexpression disturbed mitochondrial membrane potential (MMP) and mitochondrial morphology in OS cells. However, ZFP36 knockdown had the opposite results. Mechanistic studies indicated that ZFP36 promoted E2F transcription factor 1 (E2F1) messenger RNA (mRNA) degradation by binding to the AU-rich elements (AREs) within E2F1 3' untranslated region (3'UTR) in OS cells. E2F1 overexpression abrogated the effects of ZFP36 overexpression on malignant progression, ferroptosis, and mitochondrial dysfunction in OS cells. Furthermore, E2F1 promoted the transcription activation of activating transcription factor 4 (ATF4) by binding to ATF4 promoter. E2F1 knockdown inhibited malignant progression, and promoted ferroptosis and mitochondrial dysfunction in OS cells, which was abrogated by ATF4 overexpression. Additionally, MG63 cells transfected with lentivirus ZFP36 overexpression vector (Lv-ZFP36) were injected into nude mice and tumor growth was monitored. ZFP36 overexpression significantly suppressed OS tumor growth under in vivo settings. In conclusion, ZFP36 overexpression promoted ferroptosis and mitochondrial dysfunction and inhibited malignant progression in OS by regulating the E2F1/ATF4 axis. We may provide the promising ZFP36 target for OS treatment.