THOC1 is a core component of the THO complex, a conserved mRNA biogenesis and export factor that physically links transcriptional elongation with RNA processing. THOC1 associates with elongating RNA polymerase II and facilitates cotranscriptional loading of RNA splicing and export factors onto nascent transcripts 1. This coupling mechanism is essential for efficient gene expression in metazoans with intron-containing genes. THOC1 plays significant roles in cancer pathogenesis. Expression levels are altered across multiple tumor types, with upregulation in ovarian and lung cancers correlating with aberrant cell proliferation 2. In triple-negative breast cancer, THOC1 promotes cancer stem cell characteristics and metastasis through regulation of stemness-related gene export, and its downregulation by andrographolide suppresses tumor growth 3. In glioblastoma, THOC1 complexes with SIN3A to regulate R-loop accumulation at telomeres; THOC1 knockdown increases R-loops and telomeric dysfunction, reducing GBM viability and enhancing survival 4. Notably, THOC1 loss-of-function serves as a therapeutic target in T-cell acute lymphoblastic leukemia, achieved through RBM39-targeting drugs that induce THOC1 mis-splicing and protein depletion 5. Additionally, combination gene therapy targeting both THOC1 and p53 pathways overcomes p53-resistance in pancreatic adenocarcinoma 6. THOC1 alterations also associate with telomere-related autoimmunity in systemic sclerosis 7.