Abstract: Objective To investigate the expression of minichromosome maintenance proteins 5 (MCM5) in breast cancer and its  biological functions. Methods The expression of MCM5 in breast cancer and para⁃cancerous tissues, along with its prognostic correlation, were analyzed by GEO database. Cancer tissue and para⁃cancerous tissue samples of breast cancer patients treated in Guangxi Medical University Cancer Hospital from 2021 to 2023 were collected. Breast cancer cells MDA⁃MB⁃231, MDA⁃MB⁃468 and MCF⁃7 and normal breast epithelial cells MCF⁃10A were cultured in vitro. The expression of MCM5 in tissues and cells were assessed by immunohistochemistry (IHC), RT⁃qPCR and Western blot. To investigate the effects of MCM5 on breast cancer cell proliferation, migration, invasion and apoptosis, lentivirus⁃mediated MCM5 knockdown cells were evaluated by EdU assay, colony formation, wound healing assay, Transwell invasion assay and flow cytometry. Results Analysis of the GSE42568 dataset revealed that MCM5 expression was significantly higher in breast cancer tissues compared to normal tissues (P<0.001). Furthermore, high MCM5 expression was significantly associated with poorer disease⁃free survival and overall survival (all P<0.05). IHC results demonstrated that the positive expression rate of MCM5 in breast cancer tissues  was significantly higher than that in para⁃cancer tissues (53.13% vs 16.76%, P<0.0001). RT⁃qPCR and Western blot analysis revealed that both the mRNA and protein expression levels of MCM5 were higher in breast cancer cells than in normal breast cells (all P<0.05). Functional assays revealed that MCM5 knockdown significantly inhibited breast cancer cell proliferation, migration and invasion, while increasing cell apoptosis (all P<0.05). Conclusions MCM5 is highly expressed in breast cancer and is strongly associated with poor patient prognosis. MCM5 knockdown significantly inhibited the proliferation and migration of breast cancer cells and promoting apoptosis. MCM5 may serve as a novel and potential therapeutic target for breast cancer treatment.

Key words:  Breast cancer, MCM5 gene, Cell proliferation, Cell migration, Cell invasion, Cell apoptosis