Parasporin-4, a novel apoptosis inducer of breast cancer cells produced by Bacillus thuringiensis.

Background: Parasporin (PS) proteins have cytocidal activity preferential for various human malignant cells. The purpose of this investigation was to see if the PS separated from B. thuringiensis strain E8 isolate had any particular cytotoxicity against breast cancer.

Methods And Results: The extracted spores-crystal proteins were solubilized and digested with proteinase K. Cytotoxicity effects were analysed by MTT assay. Caspases activities were measured using ELISA. SDS-PAGE analysis was performed for determination of molecular weight of Cry protein. Identification of extracted proteins function was evaluated by MALDI-TOF MS analysis. Breast cancer cells line (MCF-7) was highly susceptible to 1 mg/mL PS and showed apoptosis characteristics, but it has no effects on the normal cells (HEK293). Apoptosis evaluation showed that caspases 1, 3, 9 and BAX were remarkably up-regulated in cancer cells, indicating the intrinsic pathway activation in these cells. PS Size was determined using SDS-PAGE in E8 isolate as 34 kDa and a 25 kDa digested peptide was identified as PS4. The function of PS4 was reported as an ABC-transporter by spectrometry.

Conclusion: The data of the present study show that PS4 is a selective cytotoxic protein against breast cancer and a molecule with a lot of potentials for next researches.