Effects and mechanism of siomycin A on the growth and apoptosis of MiaPaCa-2 cancer cells.

Siomycin A is a type of thiopeptide antibiotic that is isolated from the fermentation products of an endophytic actinomycin, which is derived from the medicinal plant . The present study investigated whether siomycin A has antitumor effects on a variety of cell lines. A Cell Counting Kit-8 assay was performed to detect the effects of siomycin A on cell viability; morphological changes in the MiaPaCa-2 cell line were analyzed using an inverted phase contrast microscope. A Transwell migration assay was applied to detect cell migration ability. The cytoskeleton was observed by laser confocal microscopy, and apoptosis was detected using flow cytometry. A western blot assay was used to detect the expression of matrix metalloproteinase (MMP)-2, MMP-9 and α-tubulin. The results revealed that siomycin A inhibited the proliferation of human tumor cell lines of different origins. As the concentration of siomycin A increased, the cell density decreased gradually and cells exhibited a morphological change from spindle to spherical shape. Furthermore, 24 h after administration, the cell migration ability was inhibited. The cytoskeleton complexity and morphological changes were increased after administration of siomycin A. The percentage of apoptotic cells was significantly increased and the expression levels of MMP-2, MMP-9 and α-tubulin were downregulated by siomycin A. Therefore, siomycin A was determined to effectively inhibit the proliferative ability of a variety of human tumor cell lines. Siomycin A was also determined to affect the cytoskeleton of tumor cells by downregulating the expression of α-tubulin protein.