Upstream stimulatory factor 2 inhibits erastin-induced ferroptosis in pancreatic cancer through transcriptional regulation of pyruvate kinase M2

Abstract

Ferroptosis is considered as a potential target in cancer treatment including chemotherapy and radiotherapy, however, its regulatory mechanism on pancreatic cancer (PC) is not fully understood. Herein, we explored the role of upstream stimulatory factor 2 (USF2) and pyruvate kinase M2 (PKM2) in ferroptosis in PC cells. USF2 and PKM2 were highly expressed in PC tissues and USF2 was positively correlated with PKM2. PC cell lines BxpC-3 and AsPC-1 were transfected with small interfering RNAs against USF2/PKM2 or USF2 overexpressing plasmids or co-transfected with small interfering RNAs against PKM2 and USF2 overexpressing plasmids. Twenty-four hours after cell transfection, ferroptotic cell death was induced by incubation with 20 μmol/l erastin for 24 h. Ferroptotic cell death was promoted by USF2 knockdown and inhibited by USF2 overexpression. USF2 knockdown increased lipid reactive oxygen species and malonaldehyde generation and decreased glutathione concentration and glutathione peroxidase 4 expressions, indicating the enhanced lipid peroxidation. USF2 knockdown also increased ferrous iron levels and ferritin heavy chain expressions and reduced solute carrier family 7 member 11 expressions. However, USF2 overexpression reversed these changes. Furthermore, dual-luciferase reporter assay, chromatin immunoprecipitation assay and DNA pull down assay validated that USF2 transcriptionally regulated PKM2 expression through binding to its promoter. Interestingly, PKM2 also negatively regulated ferroptosis and PKM2 knockdown markedly impaired the effects of USF2 on lipid peroxidation and ferroptotic cell death. This study demonstrated that USF2 negatively regulated ferroptosis in PC cells through transcriptional regulation of PKM2, providing new evidences for uncovering the regulatory mechanism of ferroptosis on PC.