EGR1 Promotes Erastin-induced Ferroptosis Through Activating Nrf2-HMOX1 Signaling Pathway in Breast Cancer Cells.

Purpose: Early growth response 1 (EGR1) is a crucial transcription factor composed of zinc finger structures, inhibitory and activating regulatory regions. We identified the biological effect and molecular mechanisms of EGR1 in breast cancer (BC). Methods: We used qRT-PCR, western blot and immunohistochemistry to examine the expression of EGR1 in BC samples. CCK-8 and colony assay were performed to reveal the effect of EGR1 on the proliferation of BC cells. LDH release assay, MCB assay, MDA assay, C-AM assay and TMRE assay were performed to measure the levels of LDH release, GSH, MDA, LIP and mitochondrial membrane potential. The regulation of EGR1 on the expression of Nrf2 and HMOX1 was investigated through Western blot. Xenograft models were conducted to determine the impact of EGR1 overexpression on BC in vivo. Results: The expression of EGR1 was downregulated in BC tissues compared with the normal tissues, and lower expression of EGR1 associated with poorer clinical outcome in BC patients. Through in vitro experiments, we found that EGR1 downregulation facilitated the proliferation of BC cells, and overexpression of EGR1 inhibited the proliferation of BC cells. In addition, EGR1 knockdown alleviated erastin-induced ferroptosis and overexpression of EGR1 facilitated erastin-induced ferroptosis in BC cells. Moreover, overexpression of EGR1 facilitated the anti-tumor effect caused by erastin in vivo. Mechanistically, the phosphorylation levels of Nrf2 and the expression of HMOX1 were reduced due to the downregulation of EGR1, and increased due to the upregulation of EGR1. Additionally, the finding that EGR1 facilitated erastin-induced ferroptosis was alleviated by the inhibition of Nrf2-HMOX1. Conclusion: The expression of EGR1 is downregulated in BC, which is correlated with poor prognosis of BC patients. EGR1 suppresses the proliferation of BC cells and facilitates erastin-induced ferroptosis by activating Nrf2-HMOX1 signaling pathway in BC cells.