Cytotoxic Effects of Cytoplasmic Extracts from Traditional Yogurt-derived Lactobacillus Strains on HT-۲۹ Human Colorectal Cancer Cells

Introduction: Traditional yogurt is a rich source of probiotic Lactobacillus species with potential anticancer properties. This study aimed to isolate Lactobacillus strains from traditional yogurt and evaluate the cytotoxic effects of their cytoplasmic extracts on human colorectal cancer cells (HT-۲۹). Methods: This in vitro study was conducted between ۲۰۲۳ and ۲۰۲۴. A total of ۲۱ yogurt samples from various regions near Isfahan were processed via serial dilution and cultured on MRS agar anaerobically. Based on the results, ۸ Lactobacillus isolates were identified through biochemical characterization and ۱۶S rRNA sequencing. Three representative strains, including L. casei (MGB۰۴۷۰), L. casei (LcA), and L. fermentum (AGR۱۴۸۷), were selected for cytotoxicity evaluation. Cytoplasmic extracts were obtained following cell lysis via freeze–thaw cycles and sonication. HT-۲۹ cells were treated with extracts (۰.۵-۲ mg/mL) for ۲۴ hours, and cell viability was measured using the MTT assay. Data were analyzed using one-way ANOVA and Tukey’s post hoc test. Results: All extracts exhibited a dose-dependent reduction in HT-۲۹ cell viability (P < ۰.۰۰۱). At ۲ mg/mL, viability decreased by over ۷۰%. Additionally, L. fermentum (AGR۱۴۸۷) demonstrated the most potent inhibitory effect, with IC۵۰ values ranging from ۱.۲ to ۱.۴ mg/mL. Phylogenetic analysis confirmed the genetic identity of the isolates. Conclusion: Cytoplasmic extracts from Lactobacillus strains isolated from traditional yogurt significantly inhibited colorectal cancer cell viability in a dose-dependent manner. These results suggest that native probiotic strains, especially L. fermentum (AGR۱۴۸۷), hold promise as potential adjunctive agents in anticancer therapy. Further molecular and preclinical investigations are warranted to elucidate their mechanisms and therapeutic potential.