PAFAH1B1 stabilization, through PUM2-mediated competitive binding with miRNAs on its’ 3’-UTR, takes active actions on ferroptosis to overcome the radioresistance to 125I radioactive particles of pancreatic ductal adenocarcinoma

Abstract

Pancreatic cancer is one of the most fatal malignancies with the lowest 5-year survival worldwide. Radioresistance remains the major challenge for pancreatic cancer treatment. The aim of this study is to unravel the mechanism underlying PAFAH1B1-regulated radiosensitivity in pancreatic ductal adenocarcinoma (PDAC). Immunohistochemistry (IHC), western blot or qRT-PCR were employed to detect the expression of PAFAH1B1, PUM2 and other molecules. Two radiation-resistant (RR) PDAC cell lines and a xenograft mouse model were established. CCK-8, colony formation assays and flow cytometry analysis were used to assess cell proliferation and apoptosis in PDAC cells, respectively. Ferroptosis was evaluated using commercial kits and BODIPY 581/591 C11 staining. The association between PUM2 and PAFAH1B1 3’UTR, as well as between miR-421/miR-301a-3p and PAFAH1B1 3’UTR, were detected by luciferase and RNA immunoprecipitation (RIP) assays. PAFAH1B1 was downregulated in PDAC, and it was associated with unfavorable prognosis and radiotherapy response of PDAC patients. PAFAH1B1 overexpression enhanced the radiosensitivity to 125I particle in BxPC-3-RR, PANC-1-RR cells and PANC-1-RR xenograft tumors. Overexpression of PAFAH1B1 potentiated radiation-impaired cell viability and proliferation via triggering ferroptosis in PDAC cells. Mechanistically, PUM2 increased PAFAH1B1 expression via competitively binding to PAFAH1B1 3’UTR with miR-421 and miR-301a-3p. Moreover, PUM2 promoted radiation-induced ferroptosis in a PAFAH1B1-dependent manner. PUM2/PAFAH1B1 axis decreased the radioresistance to 125I radioactive particles in PDAC via triggering ferroptosis. Downregulated PAFAH1B1 was associated with poor prognosis and radioresistance in PDAC. Reinforced PAFAH1B1 enhanced the radiosensitivity to 125I particle in PDAC cells and xenograft tumors. PAFAH1B1 decreased radioresistance by fostering radiation-induced ferroptosis. PUM2 upregulated PAFAH1B1 expression via competitively binding to PAFAH1B1 3’UTR with miR-421 and miR-301a-3p. PUM2 enhanced radiation-induced ferroptosis in a PAFAH1B1-dependent manner.