Strain‐Specific Antiproliferative Activity of Lactobacillus Cell‐Free Supernatants in Gastric Cancer Cells and Modulation of Apoptosis‐Related Gene Expression

Nonpathogenic microorganisms confer various health benefits, including potential anticancer activity. Lactobacillus strains may influence tumor cell fate through immune modulation and microbial metabolites, with potential effects on apoptosis‐related signaling networks. In this study, the cytotoxic/antiproliferative activity of cell‐free supernatants (CFSs) from Lactobacillus fermentum PTCC 1744 and Lactobacillus casei PTCC 1608 was investigated in human gastric adenocarcinoma (AGS) cells. AGS cells were treated with graded concentrations of CFS for 24, 48, and 72 h, and cell viability/metabolic activity was assessed using the MTT assay. Based on the maximal cytotoxic effect, 12.5% CFS was selected for qRT‐PCR. At 72 h, qRT‐PCR was performed to evaluate the expression of apoptosis‐related genes ( BCL2 , PTEN , AKT1 , and BAX ), with GAPDH as the normalizer. Both CFSs induced a time‐dependent reduction in MTT signal; however, no linear concentration–response relationship was observed, and lower concentrations showed a stimulatory pattern. Gene expression analysis revealed strain‐specific transcriptional responses: L. casei CFS was associated with upregulation of BCL2 and downregulation of PTEN , AKT1 , and BAX , whereas L. fermentum CFS was associated with marked upregulation of PTEN and downregulation of BCL2 , AKT1 , and BAX . Collectively, these findings suggest strain‐specific cytotoxic/antiproliferative activity and differential modulation of apoptosis‐related gene expression in AGS cells, with L. fermentum showing a transcriptional profile more consistent with attenuation of PI3K/Akt–associated survival signaling under the tested conditions. Further studies using orthogonal assays are needed to confirm the mechanisms of cell death.