Background : Probiotics are defined as different microorganisms that may have positive effects on preventing or treatment of special pathologic conditions. Lactobacillus casei and L. paracasei as probiotics could induce the apoptosis in human cancer cells in vitro. Chronic myeloid leukemia is categorized as a blood cells cancer and the most common type of leukemia. The expression of mutant p53 protein increases resistance against apoptosis in cancer lines. So the aim of this study was to evaluate the effect of L. casei and L. paracasei cell wall and cytoplasmic fractions on the expression of mutant p53 protein in K562 cancer line by ELISA.

Materials and Methods: First, L. casei and L. paracasei was cultured and disrupted by sonication and finally cell wall separated from cytoplasmic extraction by centrifugation, then prepared different concentrations of cell wall and cytoplasmic fraction. Finally, p53 protein levels were measured by ELISA, in cells treated with the cell wall and cytoplasmic fraction.

Results: ELISA result showed that cell wall and cytoplasmic fraction statistically (P˂0.05) reduced the levels of mutant p53 protein compared to the control.

Conclusion: It’s concluded that there is a relationship between reduced expression of p53 protein and induction of apoptosis in cells with mutant p53 gene. It could provide a way for cancer treatment in a smart manner.