FOXO1 and cancer: Recently, we obtained evidence that another thiazole antibiotic, thiostrepton, which structurally differs from Siomycin A by only 2 residues (Fig. 1A) possesses anti-cancer [30] and anti-FoxM1 properties [29] similar to Siomycin A. To evaluate the effects of thiostrepton on FoxM1 transcriptional activity and also to study how the thiazole antibiotics affect the transcriptional activity of other members of the Forkhead family, we developed the C3-Luc2.3-FoxO1 cell line.