CAAP1 (Caspase Activity and Apoptosis Inhibitor 1) functions as an anti-apoptotic protein that negatively regulates apoptosis through multiple mechanisms 1. Beyond its canonical role in suppressing apoptosis, CAAP1 has emerged as a critical component of SOS splicing, a spliceosome-independent RNA processing system that excises DNA transposons from host mRNAs 23. In this pathway, CAAP1 bridges the RNA ligase RTCB and the transposon-binding protein AKAP17A, enabling mRNA fragment ligation after transposon excision 2. CAAP1 phosphorylation regulates its involvement in splicing mechanisms and apoptosis pathways, with phosphoregulation implicated in cancer progression 1. Clinically, CAAP1 expression inversely correlates with platinum resistance in ovarian cancer, with elevated CAAP1 enhancing cisplatin sensitivity via mRNA splicing mechanisms 4. In gastric cancer, CAAP1 operates within regulatory axes (MKL1/miR-5100/CAAP1 and LINC01087/miR-135a-5p/CAAP1) controlling apoptosis and autophagy 56. CAAP1 is incorporated into prognostic signatures for ovarian cancer patient stratification and treatment response prediction 7. Additionally, CAAP1 provides neuroprotection against hypoxic-ischemic brain injury 8.