ACIN1 (apoptotic chr14 condensation inducer 1) is a multifunctional protein with roles in RNA splicing and apoptosis regulation. As an auxiliary component of the exon junction complex (EJC), ACIN1 contributes RNA-binding activity to ASAP complexes that regulate intron excision and mRNA metabolism 1. ACIN1 specifically modulates alternative splicing of apoptotic genes, particularly inhibiting formation of proapoptotic Bcl-X(S) isoforms 2. Upon caspase-3 activation, ACIN1 directly induces apoptotic chr14 condensation 3. Clinically, ACIN1 dysregulation associates with multiple malignancies. ACIN1::NUTM1 fusion represents a recurrent cryptic rearrangement in non-KMT2A-rearranged infant acute lymphoblastic leukemia, characterized by upregulation of HOXA9 and HOXA10, yet showing excellent prognosis with high chemotherapy sensitivity 45. ACIN1 expression is significantly upregulated in hepatocellular carcinoma, potentially regulated by miR-674-5p-mediated mechanisms 6. In cervical cancer, METTL3-mediated enhancement of ACIN1 mRNA stability through IGF2BP3 promotes tumor progression 2. Elevated platelet ACIN1 mRNA levels show potential diagnostic value in lung cancer 1. ACIN1 also emerges as a hub gene in bicalutamide-resistant prostate cancer, connected to RNA splicing pathways 7.