DACT2 is a functional tumor suppressor through inhibiting Wnt/β-catenin pathway and associated with poor survival in colon cancer

Abstract

Dapper homolog (DACT) 2 is one of the Dact gene family members, which are important modulators of Wnt signaling pathway. We aim to clarify its epigenetic inactivation, biological function and clinical implication in colon cancer. DACT2 was silenced in five out of eight colon cancer cell lines, but robustly expressed in normal colon tissues. The loss of DACT2 expression was regulated by promoter hypermethylation. Restoring DACT2 expression in colon cancer cell lines suppressed tumor cell growth by inducing cell apoptosis and inhibiting cell proliferation both in vitro and in vivo. Moreover, DACT2 overexpression effectively reduced lung metastasis of colon cancer cells in nude mice. These effects by DACT2 were attributed to inhibition of Wnt/β-catenin signaling. Reexpression of DACT2 significantly suppressed the transcriptional activity of both wild-type β-catenin and degradation-resistant form mutant β-catenin (S33Y). DACT2 could actively shuttle into and out of nuclei, with its predominant steady-state localization in the cytoplasm dependent on its nuclear export signal. Co-immunoprecipitation results indicated that DACT2 strongly associated β-catenin as well as lymphoid enhancer-binding factor 1 (LEF1) and directly disrupted the formation of the β-catenin-LEF1 complex in the nucleus. Whereas in the cytoplasm, DACT2 restored junctional localization of E-cadherin-β-catenin complexes and prevented β-catenin nuclear translocation through direct interaction with β-catenin. DACT2 methylation was detected in 43.3% (29/67) of colon cancer tissues, but none in normal controls. Multivariate analysis revealed that patients with DACT2 methylation had a significant decrease in overall survival (P = 0.006). Kaplan-Meier survival curves showed that DACT2 methylation was significantly associated with shortened survival in stage I-III colon cancer patients. In conclusion, DACT2 acts as a functional tumor suppressor in colon cancer through inhibiting Wnt/β-catenin signaling. Its methylation at early stages of colon carcinogenesis is an independent prognostic factor.

Delamination of neural crest cells requires transient and reversible Wnt inhibition mediated by DACT1/2

“…7C,D). Interestingly, β-catenin has been shown to interact directly with the three murine DACT paralogues (Kivimäe et al, 2011;Wang et al, 2015) and our data showed that a GFPtagged version of Dact2 (Dact2-GFP) and β-catenin colocalised in spherical intranuclear punctuate structures resembling nuclear bodies (Fig. 7C,D).…”

“…More recent data showed that these scaffold proteins can form complexes with β-catenin (Cheyette et al, 2002;Gao et al, 2008;Kivimäe et al, 2011;Wang et al, 2015), which is a key mediator of the Wnt signalling pathway (Clevers and Nusse, 2012). Although we do not rule out a contribution of DACT in non-canonical Wnt signalling, as previously shown in Xenopus embryos (Park et al, 2006;Wen et al, 2010;Kivimäe et al, 2011), our results show a strong and conserved inhibitory role played by DACT proteins in the canonical Wnt pathway.…”

“…Dact2 belongs to a small family of intracellular scaffold proteins (Dact1-Dact4; Schubert et al, 2014), which are nucleocytoplasmic proteins that were initially identified in Xenopus as dishevelled (Dsh)-interacting proteins that regulate Wnt activity by promoting degradation of Dsh (Cheyette et al, 2002;Gloy et al, 2002;Zhang et al, 2006). DACT proteins can also form complexes with β-catenin (Gao et al, 2008;Kivimäe et al, 2011;Wang et al, 2015), a key element in the canonical Wnt pathway (Clevers and Nusse, 2012). All vertebrates express at least one member of the DACT family in NC progenitors (Alvares et al, 2009;Hikasa and Sokol, 2004;Schubert et al, 2014), suggesting that they fulfil a conserved role in NC development.…”

Resetting the epigenetic balance of Polycomb and COMPASS function at enhancers for cancer therapy

“…Interestingly, many of the down-regulated genes in both MLL3 and BAP1 knockout cells are known tumor suppressors, such as RBMS 3 35 , ITM2A 36 , GRHL2 37 , TCEA3 38 , DSC3 39 , FRZB 40 , and DACT2 41 (Fig 4f and Supplementary Fig. 6b, c).…”

Methylation of DACT2 contributes to the progression of breast cancer through activating WNT signaling pathway

“…In addition to deletion, epigenetic modifications of DACT genes were also reported. For instance, DACT1 and DACT2 were reported to be methylated in hepatocellular carcinoma, oral squamous, gastric cancer, nasopharyngeal carcinoma, thyroid cancer, colon cancer and lung cancer (10,(26)(27)(28)(29)(30)(31). In addition, DACT3 was identified to have histone modifications in colorectal cancer (25,26,32).…”