Siomycin A is a thiopeptide antibiotic that selectively inhibits Forkhead box M1 (FOXM1) without affecting other Forkhead box family members, exhibiting anti-tumor properties and promoting apoptosis.

cell viability in a dose-dependent and a time-dependent association in K562, MCF7 and MiaPaCa-2 cells markedly reduced by Siomycin A (0-10 μM; 24-72 hours; K562, MCF7 and MiaPaCa-2 cells). Among the three cell lines(IC50 of the human leukemia K562 cells is the lowest at 6.25 μM at 24 h), while that for the human pancreatic cancer MiaPaCa-2 cells is 6.38 μM. However, the IC50 of the human pancreatic cancer MiaPaCa-2 cells at 48 and 72 h are the lowest of the three cell lines, which are 0.76 and 0.54 μM, respectively[1]. Siomycin A (0-10 μM; MiaPaCa-2 cells) treatment has potent proapoptotic effect in MiaPaCa-2 cells[1]. Siomycin A (0-10 μM; 24 hours; MiaPaCa-2 cells) treatment significantly reduces the expression levels of MMP-2, MMP-9 and α-tubulin protein in the MiaPaCa-2 cells[1].

In vivo mouse model,Siomycin A (1 μM; subcutaneous injection; for 4 weeks; male Balb/c nude mice) pretreatment decreases tumour growth [2].