Decreases in E-cadherin expression correlate with epithelial-mesenchymal transition, metastasis, and lower patient survival rates [10]. Four Snail1 complexes have been identified as mechanisms of E-cadherin repression. (1) Snail1 interacts with G9a, which concurrently recruits DNA methyltransferases (DNMTs) to the E-cadherin promoter. Snail1’s zinc fingers are thought to interact with the G9a ankyrin repeats, SET domain, or both. The complex has been shown to increase H3K9me2 and decrease H3K9 acetylation [56]. (2) The Snail1-Ajuba-PRMT5 complex promotes the methylation of H4R3. This, too, operates at the E-cadherin promoter [57]. The demethylation of H3K4 by Co-REST, CtBP, and HDAC complexes also

factors into the last two mechanisms [58]. (3) Snail1 works in conjunction with Sin3A and HDAC1/2 to deacetylate H3 and PF-01367338 purchase H4, which suppress E-cadherin [59]. (4) In perhaps the most elucidated case, the Snail1 SNAG domain interacts with the LSD1 AO domain to form a Snail1-LSD1-CoREST complex. Snail1 residues Pro2, Arg3, Ser4, Phe5, Arg8, and Lys9 have been shown to be particularly

crucial to this union, since mutants could not interact with LSD1. Likewise, LSD1 requires functional Asp375 IWR-1 and Glu379, Glu553, Glu555 and Glu556 to cooperate with Snail1. LSD1 inhibitors, histone H3, and SNAG peptides also hamper the activity of the complex. The formation of the Snail1-LSD1-CoREST complex results in the demethylation of H3K4me2 and consequential suppression of E-cadherin, while also increasing the stability of each of the components of the complex [60]. In a proposed second step to this mechanism, Snail1 recruits Suv39H1 to the E-cadherin promoter. Similar to prior cases, the Snail1 SNAG domain interacts with the Suv39H1 SET domain to suppress

E-cadherin. Knockdown of Suv39H1 restored E-cadherin expression by inhibiting H3K9me3 [61]. RKIP Raf kinase inhibitor protein (RKIP), a member of the phosphatidylethanolamine-binding protein (PEBP) group, suppresses metastasis by inhibiting the Raf-MEK-ERK and NF-κB pathways [62–65]. In prostate, breast, and colorectal HSP90 cancers, among others, RKIP expression is downregulated [64,66]. Furthermore, elevated RKIP expression is a positive prognostic indicator for survival [66,67]. Expression levels of RKIP correlate with those of E-cadherin, another Snail1 target, as they are both repressed by means of the E-boxes in their promoters [68]. PTEN Phosphatase and tensin homolog deleted in chromosome 10 (PTEN) dephosphorylates phosphoinositide-3,4,5-triphosphate (PIP3) and, thus, inhibits the PI3K pathway [69]. In this way, PTEN functions as a tumor suppressor. Snail1 binds to the PTEN promoter, which contains two E-boxes, and represses PTEN [70]. The specificity of this interaction is emphasized by the fact that neither Slug nor ZEB1 expression significantly BGB324 manufacturer alters PTEN levels [70].