Abstract
The Wnt signaling pathways play fundamental roles during both development and adult homeostasis. Aberrant activation of the canonical Wnt signal transduction pathway is involved in many diseases including cancer, and is especially implicated in the development and progression of colorectal cancer. Although extensively studied, new genes, mechanisms and regulatory modulators involved in Wnt signaling activation or silencing are still being discovered. Here we applied a genome-scale CRISPR-Cas9 knockout (KO) screen based on Wnt signaling induced cell survival to reveal new inhibitors of the oncogenic, canonical Wnt pathway. We have identified several potential Wnt signaling inhibitors and have characterized the effects of the initiation factor DExH-box protein 29 (DHX29) on the Wnt cascade. We show that KO of DHX29 activates the Wnt pathway leading to upregulation of the Wnt target gene cyclin-D1, while overexpression of DHX29 inhibits the pathway. Together, our data indicate that DHX29 may function as a new canonical Wnt signaling tumor suppressor and demonstrates that this screening approach can be used as a strategy for rapid identification of novel Wnt signaling modulators.
Highlights
The Wnt signal transduction pathways, which are essential for both embryonic development and adult homeostasis, regulate numerous fundamental cell functions, including proliferation, migration, apoptosis, stem cell renewal, and differentiation [1,2,3]
As Wnt signaling is frequently over-activated in different cancers especially colorectal cancer [5], we examined the levels of DExH-box protein 29 (DHX29) mRNA in early adenomas obtained from Familial Adenomatous Polyposis (FAP) patients
Our top candidates include genes previously shown to be associated with Wnt signaling, such as USP7 [12] and SETDB1 [31]
Summary
The Wnt signal transduction pathways, which are essential for both embryonic development and adult homeostasis, regulate numerous fundamental cell functions, including proliferation, migration, apoptosis, stem cell renewal, and differentiation [1,2,3]. The canonical Wnt/β-catenin pathway, to other signaling cascades, is initiated at the cell membrane and its primary output involves changes in gene transcriptional programs. These changes occur by regulating the expression levels, posttranslational modifications, and subcellular localization, of the Wnt signaling key effector-β-catenin [2, 6, 7]. At the core of this complex are the tumour suppressor adenomatous polyposis coli (APC), the scaffold protein axin, two kinases: glycogen synthase kinase-3 (GSK-3) and casein kinase 1 (CK1), and the E3-ubiquitin ligase β-TrCP [8] Mutations in these components may lead to uncontrolled activation of the pathway and the development of cancer [5]
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