Investigation of 3-aryl-pyrimido[5,4-e][1,2,4]triazine-5,7-diones as small molecule antagonists of β-catenin/TCF transcription.
Nearly all colorectal cancers (CRCs) and varied subsets of other cancers have somatic mutations leading to β-catenin stabilization and increased β-catenin/TCF transcriptional activity. Inhibition of stabilized β-catenin in CRC cell lines arrests their growth and highlights the potential of this mechanism for novel cancer therapeutics. We have pursued efforts to develop small molecules that inhibit β-catenin/TCF transcriptional activity. We used xanthothricin, a known β-catenin/TCF antagonist of microbial origin, as a lead compound to synthesize related analogues with drug-like features such as low molecular weight and good metabolic stability. We studied a panel of six candidate Wnt/β-catenin/Tcf-regulated genes and found that two of them (Axin2, Lgr5) were reproducibly activated (9-10 fold) in rat intestinal epithelial cells (IEC-6) following β-catenin stabilization by Wnt-3a ligand treatment. Two previously reported β-catenin/TCF antagonists (calphostin C, xanthothricin) and XAV939 (tankyrase antagonist) inhibited Wnt-activated genes in a dose-dependent fashion. We found that four of our compounds also potently inhibited Wnt-mediated activation in the panel of target genes. We investigated the mechanism of action for one of these (8c) and demonstrated these novel small molecules inhibit β-catenin transcriptional activity by degrading β-catenin via a proteasome-dependent, but GSK3β-, APC-, AXIN2- and βTrCP-independent, pathway. The data indicate the compounds act at the level of β-catenin to inhibit Wnt/β-catenin/TCF function and highlight a robust strategy for assessing the activity of β-catenin/TCF antagonists.
Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109, USA.
Jörg
J
Zeller
Anjanette J
AJ
Turbiak
Ian A
IA
Powelson
Surin
S
Lee
Duxin
D
Sun
H D Hollis
HD
Showalter
Eric R
ER
Fearon
D000818:Animals; D002460:Cell Line; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D054852:Small Molecule Libraries / Q000737:chemistry* / Q000494:pharmacology*; D051820:TCF Transcription Factors / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015533:Transcriptional Activation / Q000187:drug effects*; D014227:Triazines / Q000737:chemistry* / Q000494:pharmacology*; D060449:Wnt Signaling Pathway / Q000187:drug effects; D051176:beta Catenin / Q000037:antagonists & inhibitors* / Q000378:metabolism
D054852:Small Molecule Libraries; D051820:TCF Transcription Factors; D014227:Triazines; D051176:beta Catenin; C093444:1,2,4-triazine
Small molecule antagonists; T-cell factor (TCF); Wnt signaling; β-Catenin