The Discovery and Characterization of K-756, a Novel Wnt/β-Catenin Pathway Inhibitor Targeting Tankyrase

Abstract

The Wnt/b-catenin pathway is a well-known oncogenic pathway. Its suppression has long been considered as an important challenge in treating cancer patients. Among colon cancer patients in particular, most patients carry an adenomatous polyposis coli (APC) mutation that leads to an aberration of Wnt/b-catenin pathway. To discover the small molecule inhibitors of the Wnt/b-catenin pathway, we conducted highthroughput screening in APC-mutant colon cancer DLD-1 cells using a transcriptional reporter assay, which identified a selective Wnt/b-catenin pathway inhibitor, K-756. K-756 stabilizes Axin and reduces active b-catenin, and inhibits the genes downstream of endogenous Wnt/b-catenin. We subsequently identified that K-756 is a tankyrase (TNKS) inhibitor. TNKS, which belongs to the PARP family, poly-ADP ribosylates Axin and promotes Axin degradation via the proteasome pathway. K-756 binds to the induced pocket of TNKS and inhibits its enzyme activity. Moreover, PARP family enzyme assays showed that K-756 is a selective TNKS inhibitor. K-756 inhibited the cell growth of APC-mutant colorectal cancer COLO 320DM and SW403 cells by inhibiting the Wnt/b-catenin pathway. An in vivo study showed that the oral administration of K-756 inhibited the Wnt/b-catenin pathway in colon cancer xenografts in mice. To further explore the therapeutic potential of K-756, we also evaluated the effects of K-756 in non-small cell lung cancer cells. Although a single treatment of K-756 did not induce antiproliferative activity, when K-756 was combined with an EGFR inhibitor (gefitinib), it showed a strong synergistic effect. Therefore, K-756, a novel selective TNKS inhibitor, could be a leading compound in the development of anticancer agents. Mol Cancer Ther; 15(7); 1525-34. Ó2016 AACR.

Crosstalk between signaling pathways and DNA damage response

“…Therefore, it is possible to enhance the efficiency of DNA damage therapy by suppressing Wnt/β-catenin signaling components in such cases. In keeping with this notion, iCRT14 and K-756, two inhibitors of Wnt/β-catenin signaling, were reported to promote colorectal cancer radio-sensitivity by targeting TCF/β-catenin and Axin (Jun et al 2016;Okada-Iwasaki et al 2016). Moreover, rapamycin analogs and AKT inhibitors are used to inhibit mTOR and PI3K/AKT signaling activity, which increased radiation sensitivity of human breast cancer and non-small cell lung cancer cell lines (Holler et al 2016).…”

Discovery of chemical probes that suppress Wnt/β‐catenin signaling through high‐throughput screening

“…An additional phenotype‐based assay using zebrafish fin corroborated the inhibitory effect of Wnt activity by IWR and XAV939. Other TNKS inhibitors such as JW74, WIKI4, and K‐756 have also been found by cell‐based HTS.…”

Regulation of Wnt/β‐catenin signalling by tankyrase‐dependent poly(ADP‐ribosyl)ation and scaffolding

“…All low MW TNKSi developed to date are mimetics of β‐nicotinamide adenine dinucleotide (NAD + ) or its adenosine or nicotinamide portions. The first potent toolbox TNKSi, XAV939 (Huang et al, ), IWR‐1 and IWR‐2 (Chen et al, ; Gunaydin et al, ), were discovered in phenotypic screens designed to identify antagonists of the Wnt/β‐catenin pathway, as were the inhibitors JW74 (Waaler et al, ), JW55 (Waaler et al, ), WIKI4 (James et al, ) and K‐756 (Okada‐Iwasaki et al, ). Numerous additional inhibitors were established through diverse approaches (see Zhan et al, ), including screening for compounds that rescue tankyrase‐induced lethality of yeast cells (Yashiroda et al, ) or induce a mitotic spindle defect (Johannes et al, ), fragment screening (Larsson et al, ; de Vicente et al, ), proteomics (Thomson et al, ), in silico screening or substructure searching, followed by compound optimization (Bregman et al, ; Elliott et al, ), screening of a DNA‐encoded library (Samain et al, ) and extensive structure–activity relationship studies, assisted by the structural analysis of tankyrase/PARP:inhibitor complexes (Hua et al, ; Shultz et al, ; Voronkov et al, ; Narwal et al, ; Liscio et al, ; Qiu et al, ; Haikarainen et al, ; Kumpan et al, ; Nkizinkiko et al, ; Paine et al, ; Haikarainen et al, ; Thomson et al, ).…”