Targeting cTRIP12 counteracts ferroptosis resistance and augments sensitivity to immunotherapy in pancreatic cancer

Current therapeutic strategies for pancreatic ductal adenocarcinoma (PDAC) have limited efficacy in increasing patient survival rates, largely due to ferroptosis resistance and immunosuppression. The aim of this study is to identify molecular mechanisms associated with ferroptosis resistance and immunosuppression in PDAC tumour cells. Circular RNA sequencing (circRNA-seq) was performed on clinical samples to identify potential circRNAs that mediate ferroptosis resistance. C11-BODIPY staining, FerroOrange staining, the glutathione ratio, malondialdehyde quantification, and transmission electron microscopy were employed to assess ferroptosis. RNA pulldown, mass spectrometry, RNA immunoprecipitation, and coimmunoprecipitation assays were conducted to investigate the molecular mechanisms involved. A HuNSG mouse xenograft tumour model was utilized to validate therapeutic agents. A circRNA derived from TRIP12 (cTRIP12) was identified in PDAC samples resistant to ferroptosis. cTRIP12 knockdown increased the sensitivity of PDAC cells to ferroptosis and immunotherapy. Subsequent mechanistic studies revealed that cTRIP12 specifically binds to the O-linked N-acetylglucosamine transferase (OGT) protein and increases intracellular O-GlcNAcylation levels, leading to increased protein levels of ferritin heavy chain (FTH) and PD-L1 in tumour cells. Notably, high cTRIP12 expression suppressed ferroptosis sensitivity and increased immune resistance in PDAC cells by functioning as a protein scaffold through its interaction with OGT and protein kinase R-like endoplasmic reticulum kinase (PERK). cTRIP12 inhibition induced ferroptosis in PDAC cells by reducing FTH and PD-L1 expression and synergistically increased the immunotherapy efficacy. In vivo animal experiments confirmed that the triple therapy consisting of GSK2656157, erastin, and anti-CTLA-4 effectively suppressed the progression of PDAC in tumours with high cTRIP12 expression. We elucidated the molecular mechanisms underlying the simultaneous occurrence of ferroptosis resistance and immune suppression in PDAC patients. Our study provides a novel therapeutic strategy that could promote ferroptosis in tumour cells and increase immunotherapy efficacy.