Investigation of 3-aryl-pyrimido[5,4-e][1,2,4]triazine-5,7-diones as small molecule antagonists of β-catenin/TCF transcription

Abstract

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.

Gains from no real PAINS: Where ‘Fair Trial Strategy’ stands in the development of multi-target ligands

“…Compounds such as 3 and 5 could not be considered useful or progressable and should be excluded from screening libraries. Compound 5 should be redox active and is not unexpected considering its similarity to the isoalloxazine ring of flavins ( 6 and 7 ) 48 , 49 . …”

Synthesis and herbicidal activity of 3-substituted toxoflavin analogs

“…In this paper, we focused on the effect of the type of aromatic substituent on herbicidal activity. Here, the method for synthesizing toxoflavin analogs reported by Hollis Showalter et al and Mao et al 14,16) was modified. The imination of hydrazinouracil 2 with various aldehydes gave the corresponding hydrazones (3a-w, Scheme 1 and Supplemental Scheme S1).…”

“…Although the synthesis of toxoflavin and its analogs has been reported, [10][11][12][13][14][15][16] the structure-activity relationship (SAR) for their herbicidal activity is uncertain. Here, we found several herbicidally active toxoflavin analogs and identified their SARs.…”

Ubiquitin Proteasome System as Target for Tumor Therapy

“…The molecular action of proteasome inhibitors are mediated by different cellular mechanisms including, the control of cell cycle, regulation of pro-and antiapoptotic proteins, enhancement of cell sensitivity to ligand-induced apoptosis and autophagy associated pathways [16,64,65].…”