Exopolysaccharide from Marine Bacillus velezensis MHM3 Induces Apoptosis of Human Breast Cancer MCF-7 Cells through a Mitochondrial Pathway

Objective: The production of new natural pharmaceutical agents that increase the efficiency of chemotherapy without affecting the normal cells is the goal of all researchers. Therefore, the present study expects to evaluate the antioxidant and anticancer studies against MCF-7 cell lines of EPS produced by novel Egyptian marine bacterial strain. Methods: Marine bacterium was isolated, purified and identified by 16S rRNA gene amplification and sequence analyses. MHMEPS (the produced EPS) was analyzed by Fourier Transform Infra-red (FTIR), monosugars identification by HPLC, molecular weight estimation and sulfur content were determined. While, in-vitro antioxidants characters was determined using various methods and anticancer studies against MCF-7 cell lines. Results: Bacillus velezensis MHM3 produced 5.8 g/L of MHMEPS. The chemical analysis of MHMEPS showed 24% uronic acid and 18.19% sulfate and monosugars glucuronic acid, glucose, fructose and rhamnose with molar ratio of 4.00: 2.00: 1.00: 0.13, correspondingly, with an overall weight average molecular weight Mw of 1.145×104 g/mol and the number average of molecular weights Mn of 5.155 ×103 g/mol. The FTIR analysis and periodate oxidation indicate the existence of β-(1–4) linkage acidic polysaccharide. MHMEPS showed antioxidant scavenging activity against DPPH•, H2O2 and Metal chelating activity, respectively. So, reducing power method give high activity at 500 μg/ml. MHMEPS hinder the proliferation of MCF-7 cells at 5-80 μg/ml compared to the control group. Moreover, induced apoptosis was associated with activation of caspase-3. Also increased cytochrome C levels significantly in a dose-dependent manner compared with the control. The Caspase-3 activity was raised in MHMEPS treated MCF-7 cells compared with the control (p<0.05) in a dose-dependent manner. Therefore, the result of DNA fragmentation was confirmed by DNA ladder assay. We presume that MHMEPS has high potential at its low concentration, as a novel restorative agent for the treatment of MCF-7 cells, with no cytotoxicity against normal cells.