Potential applications of lactic acid bacteria from Egyptian dairy products as novel antioxidant and anticancer agents.

Purpose: Several scientific studies have revealed the role of probiotic lactic acid bacteria and their metabolites, including antioxidant activity, which is required for reducing oxidative stress, and have implications for cancer treatment. This study evaluated the ability of isolates to exert antioxidative and in vitro anti-tumor effects against the HCT-116 colon cancer cell line, with fewer side effects compared to chemotherapy.

Methods: The in vitro antioxidative capacity of LAB isolates was quantified against DPPH free radicals. The cytotoxicity effects against the HCT-116 cells were analyzed using the MTT assay, microscopic fluorescence, flow cytometry, and qRT-PCR analysis of immunomodulatory cytokines and cancer-related gene expression.

Results: Seven LAB isolates exhibited potent antioxidant activity, scavenging 51.20 to 78.29% of DPPH free radicals. Lactobacillus delbrueckii subsp. bulgaricus (RE 254) demonstrated superior activity, with 78.29% scavenging and a ferric-reducing activity power of 38.04%. Conversely, Lactiplantibacillus plantarum (RE 298) showed 53.67% and 16.08% activity, respectively. At a concentration of 25 × 10³ CFU/ml, both strains induced pronounced cytotoxic effects on HCT-116 cells after 72 h (71.1% for RE 254 and 62.5% for RE 298). This cytotoxicity was mediated by apoptosis, driven by the upregulation of IL-2 and the concomitant downregulation of key genes, including BCL-2, PARK, TARC, LIF, IL-4, IL-6, CD1A, and CD1B.

Conclusion: The findings strongly suggest that RE 254 and RE 298 are compelling candidates for use as functional supplements and adjunctive therapeutics in colon cancer management. Their efficacy, demonstrated through multifaceted anti-tumor mechanisms, warrants further validation through in vivo studies to assess their clinical potential.