Probiotic Lactiplantibacillus plantarum WB4404 and WB4503 from Kimchi Induce Apoptosis in Human Colorectal Cancer Cells In Vitro

Lactic acid bacteria isolated from kimchi include beneficial microorganisms with diverse health-promoting properties. Among these, Lactiplantibacillus plantarum has attracted attention owing to its potential anticancer effects. In this study, we investigated the anticancer activity and underlying mechanisms of L. plantarum WB4404 and L. plantarum WB4503, isolated from kimchi, in HT-29 human colorectal cancer cells in vitro. Both strains significantly inhibited HT-29 cell proliferation and activated apoptotic pathways. Flow cytometry analysis confirmed apoptosis, and DAPI staining revealed DNA fragmentation. The expression of apoptosis-related proteins, such as caspase-3, caspase-9, and the Bax/Bcl-2 ratio, was significantly altered, indicating activation of the intrinsic cell death pathway. Furthermore, crude exopolysaccharide reduced HT-29 cell viability, suggesting that bacterial metabolites may contribute to the overall anticancer effect rather than acting as independent determinants. These findings highlight that L. plantarum WB4404 and L. plantarum WB4503 induce intrinsic apoptosis in HT-29 human colorectal cancer cells in vitro and suggest their potential as probiotic candidates for functional food applications.