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ABSTRACT
           Background and objective: Considering the toxic side effects of chemotherapy in treatment of cancer, anticancer drugs of natural origin including probiotic Lactobacillus strains have recently attracted a lot of attention.
Methods: After culturing chronic myeloid leukemia cell line K562 in 96-well plates, effects of different concentrations of culture supernatant from Lactobacillus casei on differentiation of the cells were investigated after 48 and 72 hours under an inverted microscope. Number of live cells and percentage of viable cells were determined by trypan blue exclusion test of cell viability. Cytotoxicity was assessed by MTT assay. Data analysis was performed by SPSS (version) 22 using one-way analysis of variance and Tukey's test at significance level of 0.05.
          Results: Secondary metabolites from the probiotic bacteria L. casei induced cellular differentiation, exerted anti-cancer effects and inhibited growth in K562 cells. Apoptotic cell death was confirmed by MTT and DNA fragmentation assays in a way that increasing the dilution from 1.2 to 1.32 significantly increased the viability of cells (P=0.001). In addition, increasing the dilution significantly increased the number of live cells in the first 48 hours (P=0.001).
        Conclusion: Culture supernatant of L. casei reduces the number of live cells, and induces apoptosis and monocytic differentiation in K562 cells in a dose- and time-dependent manner. Therefore, combined chemotherapy and differentiation therapy using such supernatants could be useful for treatment of cancer.
        Keywords: Cell differentiation, K562 cell line, Probiotic, Lactobacillus casei.

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Background: Discovering new cytotoxic compounds has received significant attention due to the rise in drug resistance and the adverse effects associated with chemotherapy drugs. In this study, the cytoplasmic extract of Lactobacillus casei was used to produce iron oxide nanoparticles (Fe₂o₃ NPs), and the cytotoxic effects of NPs were investigated on MCF-7 and human embryonic kidney 293 (HEK-293) cells.
Methods: The cytoplasmic extract of L. casei was mixed with 10³M iron sulfate solution and incubated for 3 weeks at 37 °C and 5% CO₂. The coprecipitation method was used to synthesize chemical Fe₂o₃ NPs. The synthesis of NPs was studied by electron microscopy and X-ray diffraction (XRD) analysis, and the cytotoxic effects were evaluated with dilutions (10, 100, and 1000 µg/mL) on MCF-7 and HEK cells.
Results: X-ray diffraction analysis and scanning electron microscopy presented the mean of NPs synthesized by the green method to be about 15 nm and their shape to be spherical, as well as the average of chemically synthesized NPs to be about 20 nm with cubic structure. Chemical and green synthesized NPs only at a concentration of 1000 µg/mL were able to significantly reduce the survival rate of normal HEK-293 cells; chemically synthesized NPs decreased MCF-7 cell survival only at 1000 µg/mL and green synthesis at 100 µg/mL and 1000 µg/mL.
Conclusion: Generating Fe₂o₃ NPs is biologically safe using the green synthesis method and the cytoplasmic extract of L. casei, which may be a suitable candidate for the treatment of cancer cells.