In most colorectal cancers, Wnt/β-catenin signaling is activated by loss-of-function mutations in the () gene and plays a critical role in tumorigenesis. Tankyrases poly(ADP-ribosyl)ate and destabilize Axins, a negative regulator of β-catenin, and upregulate β-catenin signaling. Tankyrase inhibitors downregulate β-catenin and are expected to be promising therapeutics for colorectal cancer. However, colorectal cancer cells are not always sensitive to tankyrase inhibitors, and predictive biomarkers for the drug sensitivity remain elusive. Here we demonstrate that the short-form mutations predict the sensitivity of colorectal cancer cells to tankyrase inhibitors. By using well-established colorectal cancer cell lines, we found that tankyrase inhibitors downregulated β-catenin in the drug-sensitive, but not resistant, colorectal cancer cells. The drug-sensitive cells showed higher Tcf/LEF transcriptional activity than the resistant cells and possessed "short" truncated APCs lacking all seven β-catenin-binding 20-amino acid repeats (20-AARs). In contrast, the drug-resistant cells possessed "long" APC retaining two or more 20-AARs. Knockdown of the long APCs with two 20-AARs increased β-catenin, Tcf/LEF transcriptional activity and its target gene expression. Under these conditions, tankyrase inhibitors were able to downregulate β-catenin in the resistant cells. These results indicate that the long APCs are hypomorphic mutants, whereas they exert a dominant-negative effect on Axin-dependent β-catenin degradation caused by tankyrase inhibitors. Finally, we established 16 patient-derived colorectal cancer cells and confirmed that the tankyrase inhibitor-responsive cells harbor the short-form APC mutations. These observations exemplify the predictive importance of mutations, the most common genetic alteration in colorectal cancers, for molecular targeted therapeutics..

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.

The canonical WNT pathway plays an important role in cancer pathogenesis. Inhibition of poly­(ADP-ribose) polymerase catalytic activity of the tankyrases (TNKS/TNKS2) has been reported to reduce the Wnt/β-catenin signal by preventing poly ADP-ribosylation-dependent degradation of AXIN, a negative regulator of Wnt/β-catenin signaling. With the goal of investigating the effects of tankyrase and Wnt pathway inhibition on tumor growth, we set out to find small-molecule inhibitors of TNKS/TNKS2 with suitable drug-like properties. Starting from 1a, a high-throughput screening hit, the spiroindoline derivative 40c (RK-287107) was discovered as a potent TNKS/TNKS2 inhibitor with >7000-fold selectivity against the PARP1 enzyme, which inhibits WNT-responsive TCF reporter activity and proliferation of human colorectal cancer cell line COLO-320DM. RK-287107 also demonstrated dose-dependent tumor growth inhibition in a mouse xenograft model. These observations suggest that RK-287107 is a promising lead compound for the development of novel tankyrase inhibitors as anticancer agents.

Highlights d Intrinsic and break-induced chromatin dynamics show cellcycle dependence d Uls1 STUbL regulates local DSB dynamics through MRX and cohesin turnover d Chromatin expansion and ectopic movement are critical for DSB repair by HR d Loss of centromere tethering is not a major DNA damage response

Administration of antihistamines 2-4 weeks before the pollen season showed a greater inhibitory effect on nasal allergy symptoms in patients with seasonal allergic rhinitis. However, the mechanism of slow-onset effects of preseasonal treatment with antihistamines remains unclear. Here, we investigated the effect of preseasonal prophylactic treatment with antihistamines on nasal symptoms and the expression of histamine H₁ receptor (H1R) mRNA of the nasal mucosa in patients with cedar pollen pollinosis. During the peak pollen period, the expression of H1R mRNA in the nasal mucosa and the scores of sneezing and watery rhinorrhea in patients receiving preseasonal prophylactic treatment with antihistamines were significantly suppressed in comparison with those in the patients without treatment. Moreover, there was a significant correlation between the nasal symptoms and the expression of H1R mRNA in both patients with or without preseasonal prophylactic treatment. These findings suggest that preseasonal prophylactic treatment with antihistamines is more effective than on-seasonal administration to patients with pollinosis in reducing nasal symptoms during the peak pollen period by suppressing H1R gene expression in the nasal mucosa.