staphylococcus epidermidis modulates emt-related gene expression and viability in mda-mb-231 breast cancer cells

Background and objectives: breast tissue microbiota differs between healthy and cancerous tissues, with some bacteria influencing tumor progression. staphylococcus epidermidis, a common skin commensal found in breast tumors, may play a role in epithelial-mesenchymal transition (emt), a key step in metastasis. this study evaluated the effects of s. epidermidis culture and cell-free supernatant (cfs) on mda-mb-231 breast cancer cell survival and expression of emt-related genes snail1, fibronectin 1 (fn1), and n-cadherin (cdh2).materials and methods: different concentrations of s. epidermidis cultures and their cfs were applied to mda-mb-231 cells. cytotoxic effects were assessed by mtt assay at 2, 4, and 24 hours post-treatment. real-time pcr analyzed gene expression after 24 hours of exposure to non-toxic concentrations (moi 50 and 100 for cultures; 14% for cfs).results: low concentrations did not affect viability, while higher doses (moi 100 and 14% cfs) reduced viability by up to 60% and 90%, respectively, at 24 hours. moi 50 did not significantly alter gene expression. at moi 100, snail1 and fn1 were significantly upregulated, but cdh2 was unchanged. treatment with 5% and 7% cfs significantly increased all three emt gene expressions, indicating emt induction.conclusion: s. epidermidis affects emt gene expression and cell viability, indicating potential involvement in breast cancer progression.