Small molecule–mediated disruption of Wnt-dependent signaling in tissue regeneration and cancer

Abstract

SUMMARYThe pervasive influence of secreted Wnt signaling proteins in tissue homeostasis and tumorigenesis has galvanized efforts to identify small molecules that target Wnt-mediated cellular responses. By screening a diverse synthetic chemical library, we have discovered two novel classes of small molecules that disrupt Wnt pathway responses - whereas one class inhibits the activity of Porcupine (Porcn), a membrane-bound acyltransferase that is essential to the production of Wnt proteins, the other abrogates destruction of Axin proteins, suppressors of Wnt/β-catenin pathway activity. With these small molecules we establish a chemical genetic approach for studying Wnt pathway responses and stem cell function in adult tissue. We achieve transient, reversible suppression of Wnt/β-catenin pathway response in vivo, and establish a mechanism-based approach to target cancerous cell growth. The signal transduction mechanisms shown here to be chemically tractable additionally contribute to Wnt-independent signal transduction pathways and thus could be broadly exploited for chemical genetics and therapeutic goals.

Kremen1 and Dickkopf1 control cell survival in a Wnt-independent manner

“…18 To determine whether it promotes survival in a Wnt-dependent manner, we applied endo-IWR1, a chemical inhibitor of Wnt canonical signaling, 25 on ablated embryos. Unlike Dkk1 treatment, endo-IWR1 failed to recue apoptosis (Figure 1), indicating that Dkk1 anti-apoptotic function is Wnt and cumulative distributions showing the number of TUNEL + cells per section counted in ablated embryos untreated (35 sections from five animals), Dkk1-treated (25 sections from three animals at 0.2 μg/ml, 36 sections from four animals at 0.5 μg/ml and 34 sections from four animals at 1 μg/ml) or Endo-IWR1-treated (27 sections from three animals at 10 μM); *Po0.01 using Student's t-test and Po0.003 using Kolmogorov-Smirnov test, **Po0.003 using Student's t-test and Po0.001 using Kolmogorov-Smirnov test, NS: nonsignificant Kremen1 is a dependence receptor for Dickkopf1 F Causeret et al independent, and thus suggesting the possibility of a novel signaling pathway downstream Dkk1.…”

“…We found the protein most efficient when used shortly after resuspension and therefore used only recently prepared aliquots. The Axin2 stabilizer Endo-IWR1 (Tocris, Minneapolis, MN, USA) was used at concentrations ranging from 2 to 10 μM to inhibit Wnt signaling, 25 the GSK-3β inhibitor 1-Azakenpaullone (SigmaAldrich, St. Louis, MO, USA) was used at concentrations ranging from 0.5 to 2 μM to activate Wnt signaling. 30 Staining.…”

Canonical and noncanonical Wnt signaling in neural stem/progenitor cells

“…It is therefore not surprising that so much effort has gone into the development of new drugs based on our knowledge of Wnt signaling to treat disease. Among the commercially available drugs that have been developed to manipulate Wnt signaling are IWP-2 and Wnt-C59, potent porcupine inhibitors that block Wnt secretion [13,14], IWR-1 and XAV939, which are tankyrase inhibitors that stabilize Axin and thereby inhibiting canonical Wnt signaling [13,15], CHIR99021 (CHIR), a GSK-3 inhibitor that activates Wnt signaling [16], and iCRT-14, which inhibits the β-catenin/TCF complex [17]. These inhibitors, as well as several others not mentioned here, have been important for driving progress of research in this field, and the development of possible therapies for Wnt-related diseases.…”

Targeting Wnts at the Source—New Mechanisms, New Biomarkers, New Drugs

“…9-12). Screens for downstream inhibitors have provided an important insight that b-catenin stability can be regulated by tankyrasemediated degradation of AXIN (11,13). Tankyrase inhibitors increase AXIN abundance and therefore increase b-catenin degradation.…”