RK‐287107, a potent and specific tankyrase inhibitor, blocks colorectal cancer cell growth in a preclinical model

Abstract

Aberrant activation of Wnt/β‐catenin signaling causes tumorigenesis and promotes the proliferation of colorectal cancer cells. Porcupine inhibitors, which block secretion of Wnt ligands, may have only limited clinical impact for the treatment of colorectal cancer, because most colorectal cancer is caused by loss‐of‐function mutations of the tumor suppressor adenomatous polyposis coli (APC) downstream of Wnt ligands. Tankyrase poly(ADP‐ribosyl)ates (PARylates) Axin, a negative regulator of β‐catenin. This post‐translational modification causes ubiquitin‐dependent degradation of Axin, resulting in β‐catenin accumulation. Tankyrase inhibitors downregulate β‐catenin and suppress the growth of APC‐mutated colorectal cancer cells. Herein, we report a novel tankyrase‐specific inhibitor RK‐287107, which inhibits tankyrase‐1 and ‐2 four‐ and eight‐fold more potently, respectively, than G007‐LK, a tankyrase inhibitor that has been previously reported as effective in mouse xenograft models. RK‐287107 causes Axin2 accumulation and downregulates β‐catenin, T‐cell factor/lymphoid enhancer factor reporter activity and the target gene expression in colorectal cancer cells harboring the shortly truncated APC mutations. Consistently, RK‐287107 inhibits the growth of APC‐mutated (β‐catenin‐dependent) colorectal cancer COLO‐320DM and SW403 cells but not the APC‐wild (β‐catenin‐independent) colorectal cancer RKO cells. Intraperitoneal or oral administration of RK‐287107 suppresses COLO‐320DM tumor growth in NOD‐SCID mice. Rates of tumor growth inhibition showed good correlation with the behavior of pharmacodynamic biomarkers, such as Axin2 accumulation and MYC downregulation. These observations indicate that RK‐287107 exerts a proof‐of‐concept antitumor effect, and thus may have potential for tankyrase‐directed molecular cancer therapy.

Wnt signaling in cancer: therapeutic targeting of Wnt signaling beyond β-catenin and the destruction complex

“…Tankyrase interacts with and degrades AXIN via ubiquitin-mediated proteasomal degradation [90][91][92] . Tankyrase inhibitors have been developed 90,[93][94][95] . Indeed, Tankyrase inhibitors have been shown to negatively regulate Wnt signaling in APC-mutated cancer cells 93-95 . (i) Tankyrase inhibitors Tankyrase inhibitors downregulate β-catenin stabilization.…”

“…(c) β-Catenin fold induction is essential for the activation of β-catenin target genes [119][120][121] . (d) Increased AXIN1 by Tankyrase inhibitor suppresses cell proliferation of cancer cells where Wnt/β-catenin signaling is genetically hyperactive 43,90,93,95,122 . (e) Mutations in RNF43 and ZNRF3 E3 ligases that degrade Wnt receptors contribute to tumor development 111,115 .…”

ALDH1A3‐mTOR axis as a therapeutic target for anticancer drug‐tolerant persister cells in gastric cancer

“…Cells were lysed in TNE lysis buffer consisting of 150 mmol/L NaCl, 0.5% Nonidet P‐40, 60 mmol/L Tris and 1 mmol/L EDTA, supplemented with 1× protease inhibitor cocktail (Nacalai Tesque) and PhosSTOP phosphatase inhibitor cocktail (Roche). Western blot analysis was performed as described previously . Primary antibodies used in this study were as follows: mouse anti–ALDH1A3 (0.5 μg/mL, GT926; GeneTex), rabbit anti–phospho‐p70S6 kinase (p70S6K, phosphorylated at T389) (1:1000, #9234; Cell Signaling Technology), rabbit anti–p70S6K (1:1000, #9202; Cell Signaling Technology), rabbit anti–phospho‐4E‐BP1 (phosphorylated at S65) (1:1000, #2855; Cell Signaling Technology), rabbit anti–4E‐BP1 (1:1000, #9644; Cell Signaling Technology) and mouse anti–GAPDH (0.02 μg/mL, 10R‐G109a; Fitzgerald).…”

“…Western blot analysis was performed as described previously. 23 Primary antibodies used in this study were as follows: mouse anti-ALDH1A3 (0.5 μg/ mL, GT926; GeneTex), rabbit anti-phospho-p70S6 kinase (p70S6K, phosphorylated at T389) (1:1000, #9234; Cell Signaling Technology), rabbit anti-p70S6K (1:1000, #9202; Cell Signaling Technology), rabbit anti-phospho-4E-BP1 (phosphorylated at S65) (1:1000, #2855;…”

3D imaging of colorectal cancer organoids identifies responses to Tankyrase inhibitors

“…The inhibition of Wnt signalling has been validated as a means of blocking tumour growth in many cancer models [6,7]. Small molecule inhibitors of TNKS1 and TNKS2 have been shown to reduce Wnt signalling in intestinal cancer cell lines and have been suggested to prevent tumour growth due to their ability to stabilise AXIN1 and AXIN2 levels and as a result, to inhibit β-catenin mediated transcription [5,[8][9][10][11][12][13][14][15][16]. However, the progression of TNKSi into clinical trials has been restricted due to significant issues of intestinal toxicity within in vivo models, emphasising the important role of Wnt signalling in adult tissue homeostasis [17] [18].…”