Biochem/physiol Actions
The key mediator of Wnt signaling is the transcriptional co-activator b-catenin. In the cytoplasm, b-catenin is tightly bound to a complex that includes Axin and GSK-3b. Stimulation causes b-catenin stabilization, translocation to the nucleus and association with TCF4 to initiate transcription of responsive genes, referred to as Catenin Responsive Transcription (CRT). Virtually all Wnt-associated cancers are the result of misregulated CRT. Three inhibitors of CRT (iCRT) were identified in a screen that employed RNAi based knockdown of Axin, which stimulates CRT without affecting upstream mechanisms such as GSK activity, transduction by disheveled / frizzled, etc. These compounds are potent inhibitors of CRT reporter genes, as well as endogenous gene targets. The compounds also disrupt b-catenin-TCF4 interaction in a dose dependent manner, and cause G0/G1 arrest in colon tumor lines.