Figure 1: Schematic representation of the PI3K, MEK, Notch and TGFβ pathway with their inhibitors. TGF-β binds to and activates heterotetrameric TGF-β receptors, and leads to activation of Smad2 and Smad3. The phosphorylated Smad2/Smad3 complex interacts with Smad4 to form a heteromeric complex that translocates to the nucleus and regulates the transcription of a diverse array of genes. Both MEK-ERK signaling and PI3K signaling are activated by RTK. Notch is cleaved by γ-secretase and releases Notch intracellular domain (NICD). The NICD translocates to the nucleus, interacts with the CSL, and then converts CSL from a transcriptional repressor to an activator.