Pediococcus acidilactici isolated from traditional cheese as a potential probiotic with cytotoxic activity against doxorubicin-resistant MCF-7 cells.

The considerable flexibility of cancerous cells to escape from chemical and biological drugs makes it clear that much is to be done to control and eliminate such cells. Probiotic bacteria, in this regard, have shown promising performance. In this study, we isolated and characterized lactic acid bacteria from traditional cheese. Then we evaluated their activity against doxorubicin-resistant MCF-7 cells (MCF-7/DOX) through MTT assay, Annexin V/PI protocol, real-time PCR, and western blotting. Among the isolates, one strain with more than 97% similarity with Pediococcus acidilactici showed considerable probiotics properties. Low pH, high bile salts, and NaCl could not significantly affect this strain while it was susceptible to antibiotics. Also, it had a potent antibacterial activity. Besides, the cell-free supernatant of this strain (CFS) significantly reduced the viability of MCF-7 and MCF-7/DOX cancerous cells (to about 10% and 25%, respectively), while it was safe for normal cells. Also, we found that CFS could regulate the Bax/Bcl-2 at mRNA and protein levels to induce apoptosis in drug-resistant cells. We determined 75% early apoptosis, 10% late apoptosis, and 15% necrosis in the cells treated with the CFS. These findings can accelerate the development of probiotics as promising alternative treatments to overcome drug-resistant cancers.

Probiotic potential and anticancer properties of Pediococcus sp. isolated from traditional dairy products.

Herein, 18 lactic acid bacteria isolated from 30 samples of traditional dairy products were identified, and their probiotic potential was evaluated. According to the results, almost all strains showed the probiotic properties sufficiently, though M1 had better characterise. 16S rRNA gene sequencing revealed that this strain belongs to the Pediococcus sp. (<95 % similarity). This strain had substantial antipathogenic activity and did not show any worrying antibiotic resistance. Also, the strain was resistant to high concentrations of bile salt (1 %), NaCl (6.5 %), and low pH (2). Furthermore, it was revealed that cell-free supernatant (CFS), heat-killed cells and live cells derived from M1 significantly decreased the viability of MCF-7 cells so that the CFS resulted in 85 % cell death. Flow cytometry and western blot analysis determined that this compound induced apoptosis in the cancerous cells through increasing the BAX protein expression and decreasing the Bcl-2 protein expression.