Probiotic intervention in colorectal cancer: the cytotoxic and apoptotic potential of Lactobacillus cell-free supernatants

Abstract

Background/aim Failures in the treatment of colorectal cancer (CRC) have increased scientific interest in the potential of the bioactive compounds contained in cell-free supernatants (CFSs) obtained from probiotic bacteria for cancer treatment. The aim in this study was to investigate the effects of CFSs obtained from Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus) and Lactobacillus paracasei subsp. paracasei (L. paracasei) on colorectal cancer cell lines (HT-29 and Caco-2) and a healthy colon epithelial cell line (CCD841 CoN). Materials and methods Cytotoxic effects on the cell lines were determined by MTT assay. In line with the IC50 values obtained, morphological changes were examined by fluorescent cell staining and cell cycle analyses were performed. In addition, the expression levels of the apoptosis-related genes Bax, Cas 9, Cas 8, Cas 3, and Bcl-2 in CFS-treated cells were measured using the qRT-PCR method. Results The MTT assay revealed that CFSs exerted a significant cytotoxic effect on cancer cells. Assessments with AO/PI fluorescent staining confirmed the increase in the number of apoptotic cells. Cell cycle analyses showed a tendency for accumulation in the G0/G1 phase and a decrease in the S phase. Furthermore, in cells treated with inactive CFS, proapoptotic genes (Bax, Cas 9, Cas 8, and Cas 3) were significantly increased, while antiapoptotic Bcl-2 gene expression decreased. Conclusion This study demonstrates that both live and inactivated Lactobacillus CFSs can exert targeted anticancer effects in Caco-2 and HT-29 cells. These results indicate that CFSs may be a potential biotherapeutic option for cancer treatment in the future.