Cyclin O promotes lung cancer progression and cetuximab resistance via cell cycle regulation and CDK13 interaction

Background: Cyclin O (CCNO) is a novel cyclin family protein containing a cyclin-like domain, which plays a role in cell cycle regulation. Recent research suggests that inhibition of CCNO leads to cell apoptosis in gastric cancer, cervical squamous cell carcinoma, and post-operative lung cancer. Methods: The protein expression and signal transduction were detected by Western blot (WB) and immunohistochemistry (IHC). Overexpression or lacking CCNO stable cell lines were transfected with lentiviruses and selected with puromycin. The tumor behaviors of lung adenocarcinoma (LUAD) cells were assessed: cell proliferation by 5-Ethynyl-2 '-deoxyuridine (EdU) staining and Cell Counting Kit-8 (CCK8) assay, cell cycle and by flow cytometry analysis, and migration and invasion using wound healing and Transwell system. Co-immunoprecipitation was used to detect protein-protein interactions. Xenograft models for evaluating tumor growth and anti-tumor drug efficacy. Results: A higher expression of CCNO was observed in LUAD cancer tissues and predicted the overall survival of LUAD patients. Moreover, CCNO expression was negatively correlated with cancer cell proliferation, migration, and invasion. Co-immunoprecipitation and western blot indicated that CCNO interacted with CDK13 to promote cancer cell proliferation signaling activation. Furthermore, CCNO promoted tumor cell growth and cetuximab resistance in vivo, and a CDK13 inhibitor effectively inhibited the oncological effect of CCNO. Conclusions: The current study suggests that CCNO may be a driver in the development of LUAD and that its function is related to CDK13 interaction that promotes proliferation signaling activation.