Bacillus subtilis supernatant improves the efficacy of radiation therapy in rat intestinal epithelial cells by upregulation of bax and caspase-3 genes.

Background: Colorectal Cancer (CC) is among the most prevalent cancers in elderly persons. Radiotherapy is usually prescribed as CC develops, however, radiation beams indiscriminately affect normal cells. Previous studies nominated that probiotics and their metabolites can be used to minimize the side effects of radiotherapy. Hereby, the aim of this study was to investigate the probable correlation between cell-free supernatant of Bacillus subtilis and radiation response in normal and cancerous cell lines.

Methods And Results: IEC-18 and SW-48 cells were treated with different concentrations of B. subtilis supernatant. To evaluate the effect of probiotic treatments under radiation and the normal situation, the cytotoxicity of the treatments was measured using the MTT method. The cell cycle status was analyzed by flow cytometry. The expression levels of Bax, Bcl-2, and Caspase 3 genes were also determined by real-time (RT) PCR. B. subtilis supernatant increased the viability of normal cells under radiation treatment, although this effect was not significant. 40% v/v of this mixture could amplify the lethal effect of radiation and decreased the viability of cancer cells. SW-48 cells that received 40% v/v of the supernatant had a significantly higher rate of apoptosis. Probiotic supernatant effectively induced the expression of proapoptotic Bax and Caspase 3 genes.

Conclusion: Presented results confirmed that the supernatant of B. subtilis can be supposed as a clue to improve the efficacy of radiation therapy in CC patients as it increased the sensitivity of cancerous cells and protected normal epithelial cells from detrimental effects of radiation.