Mechanism of ORC1 Regulating Cancer Stemness and Cisplatin Resistance in Non‐Small Cell Lung Cancer

ABSTRACT This study aimed to investigate the role and molecular mechanisms of origin recognition complex 1 (ORC1) in Cisplatin resistance and tumor stemness in non‐small cell lung cancer (NSCLC), and to evaluate its potential as a target for reversing chemotherapy resistance. ORC1 expression and its clinical significance in NSCLC were analyzed using TCGA and GTEx databases. ORC1‐knockdown NSCLC cell lines and Cisplatin‐resistant A549 DDP cells were established. Colony formation, Transwell, tumor sphere formation, and flow cytometry assays were performed to assess proliferation, invasion, stemness, and drug resistance phenotypes. A subcutaneous xenograft model in nude mice was used to evaluate the in vivo antitumor efficacy of lentivirus‐mediated ORC1 knockdown combined with Cisplatin. Protein expression levels of stemness markers (LGR5, NANOG, CD44), the resistance‐associated protein P‐gp, and EMT‐related proteins were detected by Western blotting. ORC1 was significantly overexpressed in NSCLC tissues and resistant cells, and its expression positively correlated with poor prognosis and tumor stemness markers. ORC1 knockdown markedly inhibited proliferation, invasion, EMT, and sphere‐forming capacity, and downregulated stemness‐associated proteins. In A549 DDP cells, ORC1 knockdown reduced the Cisplatin IC 50 , restored chemosensitivity, downregulated MDR1/P‐gp, and enhanced Cisplatin‐induced apoptosis. In vivo, ORC1 knockdown combined with Cisplatin significantly suppressed resistant tumor growth, reduced the proportion of CD133 + CD44 + cancer stem cells, and promoted apoptosis. ORC1 mediated Cisplatin resistance in NSCLC by regulating tumor stemness and EMT. Targeted silencing of ORC1 effectively reversed resistance both in vitro and in vivo, representing a potential molecular target for overcoming Cisplatin resistance in NSCLC.