In the present study, we examined the role of let-7 in cancer cells and its connection to SNAI1. When cells from breast (MCF-7), pancreatic (PANC-1), and ovarian (OVCAR8, OVSAHO) cancer were treated with EMT-inducing agents (TGFB1 or EGF), increases in EMT factors including SNAI1, increases in stemness markers, and decreases in let-7 could be detected. This evidence concerns the gene TGFB1 and cancer.