ERCC1 is the non-catalytic subunit of the ERCC1-XPF nuclease complex, a critical DNA repair enzyme 1. The ERCC1-XPF complex performs specialized endonuclease activities, cleaving DNA at junctions between double-stranded and single-stranded regions, particularly when single-strands are oriented 5' to 3' away from the junction 1. ERCC1 functions primarily in nucleotide excision repair (NER) for repairing platinum-induced DNA adducts and distorting lesions 2, and additionally contributes to interstrand crosslink repair, double-strand break repair pathways, and telomere regulation 1. ERCC1 expression levels significantly influence chemotherapy sensitivity; low ERCC1 expression correlates with prolonged survival in cisplatin/gemcitabine-treated lung cancer patients 2. Alternative splicing of ERCC1 exon 8 regulates ERCC1-XPF complex formation and cisplatin resistance in lung adenocarcinoma 3. Genetic polymorphisms in ERCC1 (rs11615, rs3212986, rs2298881) associate with chemotherapy response and clinical outcomes in osteosarcoma and gastric cancer, with specific genotypes predicting improved treatment response 4, 5. Complete ERCC1 deletion is embryonic lethal 1, while mutations cause rare inherited disorders including cerebro-oculo-facio-skeletal syndrome and xeroderma pigmentosum 1.