Survivability, antimicrobial and anticancer effects, and cytotoxicity of Lactobacillus strains isolated from traditional Iranian cheese

This study aimed to explore the beneficial properties, antimicrobial, and potential anticancer effects of Lactobacillus bacteria isolated from traditional dairy products on oral cancer cell lines. Twenty-one Lactobacillus strains were obtained from Kermanshah traditional cheese in western Iran. Using the well-diffusion method, the antimicrobial activities of the bacterial extracts were assessed against several human pathogens, revealing significant inhibitory effects, particularly for strains C9 and C47. These strains demonstrated broad-spectrum activity against both gram-positive and gram-negative bacteria, with notable inhibition of Staphylococcus aureus and Klebsiella pneumoniae. Additionally, the MTT assay was used to evaluate the antiproliferative effects of these extracts against oral cancer cell lines (KB and OSCC) and normal fibroblast and HUVEC lines. The compounds extracted from strains C9 and C47 (predominantly proteins) effectively suppressed the survival and growth of KB and OSCC cancer cell lines in a dose- and duration-dependent manner without significant harm to normal cells. Acridine orange/ethidium bromide labeling and mRNA expression analysis confirmed apoptosis as the primary mechanism of cancer cell death. In summary, strains C9 (Limosilactobacillus fermentum KUMS-C9) and C47 (Lactiplantibacillus plantarum KUMS-C47) exhibited potent antimicrobial and anticancer activities, highlighting their potential as probiotic candidates for therapeutic applications.