TMOD3 accelerated resistance to immunotherapy in KRAS-mutated pancreatic cancer through promoting autophagy-dependent degradation of ASCL4

The high prevalence of KRAS mutations in pancreatic cancer (PC) is widely acknowledged and results in the resistance of targeted ferroptosis therapy and immunotherapy. Herein, via a CRISPR/Cas9 library screen, the effects of ferroptosis agonists were increased in KRAS-mutant PC cells upon knockout of tropomodulin 3 (TMOD3), while these effects were not observed in KRAS-wild-type cells. Increased levels of TMOD3 were found in PC tissues, particularly in those with KRAS mutations. The increase in TMOD3 expression was facilitated by KRAS via the ETS transcription factor ELK1. Liquid chromatography–mass spectrometry (LC/MS) showed that TMOD3 increased acyl-CoA synthetase long chain family member 4 (ACSL4) protein expression and fatty acid metabolism. Mechanistically, TMOD3 promoted F-actin polymerization, thereby facilitating the fusion of autophagosomes with lysosomes, increasing the degradation of the ACSL4 protein, and augmenting the ferroptosis-inducing effects of RSL3. These effects of TMOD3 were counteracted by the administration of cytochalasin, the removal of the α2 domain of TMOD3, or the introduction of a mutation at S71. Cangrelor, an FDA-approved drug, can target TMOD3. In a mouse model, the suppression of TMOD3 using cangrelor or gene silencing technology resulted in increased infiltration of CD8+ T cells into tumor tissues with KRAS mutations and exhibited a synergistic effect with the PD-1 antibody. In conclusion, TMOD3 was found to inhibit ferroptosis and induced the resistance to PD-1 antibody by facilitating the fusion of autophagosomes and lysosomes through the promotion of F-actin polymerization in KRAS-mutant PC. TMOD3 was identified as a novel target for PC therapy.