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

Lactic acid bacteria isolated from kimchi include beneficial microorganisms with diverse health-promoting properties. Among these, <i>Lactiplantibacillus plantarum</i> has attracted attention owing to its potential anticancer effects. In this study, we investigated the anticancer activity and underlying mechanisms of <i>L. plantarum</i> WB4404 and <i>L. plantarum</i> WB4503, isolated from kimchi, in HT-29 human colorectal cancer cells <i>in vitro</i>. 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 <i>L. plantarum</i> WB4404 and <i>L. plantarum</i> WB4503 induce intrinsic apoptosis in HT-29 human colorectal cancer cells <i>in vitro</i> and suggest their potential as probiotic candidates for functional food applications.