Inactivation of GSK-3β through phosphorylation renders it unable to phosphorylate Snail, which remains in the nucleus where it acts as a transcriptional repressor of the E-cadherin gene, CDH1. Although this is a biological process of critical importance during development [13], it is hijacked by cancer cells to enable them to metastasize and invade tissues. This evidence concerns the gene SNAI1 and cancer.