The Wnt/β-catenin signaling pathway is an evolutionary conserved pathway, which has important functions in vertebrate early development, axis formation, cellular proliferation and morphogenesis. Additionally, Wnt/β-catenin signaling pathway is one of the most important intracellular pathways that controls cancer progression. To date most of the identified targets of this pathway are shown to harbor tumorigenic properties. We previously showed that Mannosyl glycoprotein acetylglucosaminyl-transferase (MGAT1) enzyme is among the Wnt/β-catenin signaling putative target genes in hepatocellular carcinoma cell lines (Huh7).
MGAT1 protein levels were determined by Western Blotting from Huh7 cell lines in which Wnt/β-catenin pathway was activated by means of different approaches such as LiCl treatment and mutant β-catenin overexpression. Luciferase reporter assay was used to analyze the promoter activity of MGAT1. The mRNA levels of MGAT1 were determined by quantitative real-time PCR from Huh7 cells that were treated with either Wnt agonist or GSK-3β inhibitor. Wound healing and XTT cell proliferation assays were performed in order to determine the proliferation and migration capacities of MGAT1 overexpressing stable Huh7 cells. Finally, xenograft experiments were carried out to measure the tumor formation capacities in vivo.
In this study we showed that the activation of Wnt/β-catenin pathway culminates in the upregulation of MGAT1 enzyme both at transcriptional and post-transcriptional levels. We also showed that overexpression of the β-catenin gene (CTNNB1) increased the promoter activity of MGAT1. We applied a set of complementary approaches to elucidate the functional importance of MGAT1 as a vital target of Wnt/β-catenin signaling in Huh7 cells. Our analyses related to cell proliferation and migration assays showed that in comparison to the control cells, MGAT1 expressing Huh7 cells have greater proliferative and invasive capabilities. Furthermore, the stable overexpression of MGAT1 gene in Huh7 cell lines lead to a significant increase in tumor growth rate in Severe Combined Immunodeficient (SCID) mice.
Taken together, we showed for the first time that MGAT is a novel Wnt/β-catenin pathway target that has important implications for tumorigenesis.
Cadigan KM, Nusse R. Wnt signaling: a common theme in animal development. Genes Dev. 1997;11:24–32. CrossRef
Polakis P. Wnt signaling and cancer. Genes Dev. 2000;14:1837–51. PubMed
Paul S, Dey A. Wnt signaling and cancer development: therapeutic implication. Neoplasma. 2008;55:165–76. PubMed
Polakis P. Wnt signaling in cancer. Cold Spring Harb Perspect Biol. 2012;4:1–14. CrossRef
Kavak E, Najafov A, Ozturk N, Seker T, Cavusoglu K, Aslan T, Duru AD, Saygili T, Hoxhaj G, Hiz MC, Unal DO, Birgül-Iyison N, Ozturk M, Koman A. Analysis of the Wnt/B-catenin/TCF4 pathway using SAGE, genome-wide microarray and promoter analysis: identification of BRI3 and HSF2 as novel targets. Cell Signal. 2010;22:1523–35. CrossRefPubMed
Stambolic V, Ruel L, Woodgett JR. Lithium inhibits glycogen synthase kinase-3 activity and mimics wingless signalling in intact cells. Curr Biol. 1996:1664–8.
- MGAT1 is a novel transcriptional target of Wnt/β-catenin signaling pathway
Necla Birgül Iyison
- BioMed Central
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