Research On The Anti-tumor Mechanism Of Surfactin In Vitro

Bacillus natto TK-1was used to produce a kind of lipopeptide called surfactin, which was considered as a safe and high-performance biosurfactant. It had been reported that surfactin had potent effects on antisepsis, antitumor, antivirus and thrombolysis. However, the effects on antitumor and antivirus remained to be complete elucidated. Our previous study had discovered that surfactin could induce apoptotic cell death in human breast cancer MCF-7cell line via mitochondrial pathway. Mitochondria permeability transition pore (MPTP) served as "vital center" of a cellula, which played an essential role in apoptosis. In this paper, the mechanisms of MPTP opening within surfactin-induced apoptosis in MCF-7mammary tumor cells had been investigated. Besides, ERK/MAPK pathway involves in the growth and proliferation of tumor cells which induced by surfactin had also been discussed.MCF-7cells were treated with surfactin in vitro in order to determine the effects of surfactin on tumor cells proliferation and apoptotic process. The results of cell proliferation test showed that surfactin had a dramatic suppressive effect on MFC-7cells growth in concentration-dependent and time-dependent manners. The IC50after24h treatment was40.2μg/mL, while IC50after48h treatment was32.3μg/mL. Histological assays such as HE stain, AO/EB stain and Hoechst33342/PI stain illustrated typical apoptosis in cell structure of MCF-7cells after surfactin treatment.Laser scanning confocal microscope (LSCM) was used to detected that surfactin evoked mitochondrial ROS generation and increased cytoplasmic Ca2+concentration in MCF-7cells, which could be inhibited by NAC (a inhibitor of ROS) and BAPTA-AM (a intracellular Ca2+chelant), respectively. It indicated that the increasing of Ca2+concentration regulated by ROS. Meanwhile, elevation of ROS led to the MPTP opening, which could be inhibited by CsA (a inhibitor of MPTP). The opening of MPTP accompanied with the collapse of mitochondrial membrane potential (△Ψm), which could be inhibited by NAC, BAPTA-AM and CsA. The results of western blotting showed a down-regulation of mitochondrial cyt c. whereas the cytoplasmic cyt c was up-regulated after the opening of MPTP, following an up-regulation of caspase-9. On the other hand, the expression of p-ERK was down-regulated, whereafter the expression of Bcl-2was decreased. Altogether, surfactin could induce apoptosis in MCF-7cells, which was associated with mitochondrial pathway and the opening of MPTP. And ERK/MAPK pathway involved the inhibition of proliferation in MCF-7cells which induced by surfactin.