LRP6 expression promotes cancer cell proliferation and tumorigenesis by altering beta-catenin subcellular distribution

Harvard University, Cambridge, Massachusetts, United States
Oncogene (Impact Factor: 8.56). 01/2005; 23(56):9129-35. DOI: 10.1038/sj.onc.1208123
Source: PubMed

ABSTRACT The Wnt signaling pathway plays key roles in both embryogenesis and tumorigenesis. The low-density lipoprotein (LDL) receptor-related protein-6 (LRP6), a novel member of the expanding LDL receptor family, functions as an indispensable co-receptor for the Wnt signaling pathway. Although the role of LRP6 in embryonic development is now well established, its role in tumorigenesis is unclear. We report that LRP6 is readily expressed at the transcript level in several human cancer cell lines and human malignant tissues. Furthermore, using a retroviral gene transfer system, we find that stable expression of LRP6 in human fibrosarcoma HT1080 cells alters subcellular beta-catenin distribution such that the cytosolic beta-catenin level is significantly increased. This is accompanied by a significant increase in Wnt/beta-catenin signaling and cell proliferation. Finally, we demonstrate that LRP6 expression promotes tumorigenesis in vivo. These results thus indicate that LRP6 may function as a potential oncogenic protein by modulating Wnt/beta-catenin signaling.

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    ABSTRACT: Background The deregulation of microRNAs has been reported to play a pivotal role in hepatocellular carcinoma (HCC). MiR-126-3p has been reported to be associated with poor prognosis in HCC. However the underlying mechanism of miR-126-3p in HCC remains unclear.Methods The expression levels of miR-126-3p in HCC tissues and cells were detected by RT-PCR. Transwell assay and capillary tube formation assay were applied to assess the metastasis and angiogenesis in vitro. Nude mice subcutaneous tumor model was used to perform in vivo study. Dual- luciferase reporter assay was conducted to confirm the direct binding of miR-126-3p and target genes. The changes of biomarker protein levels were examined by western blot and Immunohistochemistry.ResultsWe observed that the miR-126-3p expression levels in HCC tissues and cells were significantly down-regulated. Through gain- and loss- of function studies, we showed that miR-126-3p dramatically inhibited HCC cells from migrating and invading extracellular matrix gel and suppressed capillary tube formation of endothelial cells in vitro. Furthermore, overexpression of miR-126-3p significantly reduced the volume of tumor and microvessel density in vivo. LRP6 and PIK3R2 were identified as targets of miR-126-3p. Silencing LRP6 and PIK3R2 had similar effects of miR-126-3p restoration on metastasis and angiogenesis individually in HCC cells. Furthermore, the miR-126-3p level was inversely correlated with LRP6 and PIK3R2 in HCC tissues. In addition, the rescue experiments indicated that the metastasis and angiogenesis functions of miR-126-3p were mediated by LRP6 and PIK3R2.Conclusion Our results demonstrates that deregulation of miR-126-3p contributes to metastasis and angiogenesis in HCC. The restoration of miR-126-3p expression may be a promising strategy for HCC therapy.
    Journal of Translational Medicine 09/2014; 12(1):259. DOI:10.1186/s12967-014-0259-1 · 3.99 Impact Factor
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    ABSTRACT: Triple-negative breast cancer (TNBC) is difficult to treat because there is no targeted therapy available. Clinical studies have demonstrated that S-phase kinase-associated protein 2 (Skp2) and low-density lipoprotein receptor-related protein 6 (LRP6) are highly expressed in TNBC. Therefore, therapeutic strategies designed to downregulate LRP6 or Skp2 may play an important clinical role in the treatment of TNBC. However, the regulatory effects of many drugs on Skp2 and LRP6 expression are currently unknown. In the present study, combined treatment with chrysin and 1,2,3,4,6-penta-O-galloyl-β-D-glucose (5GG) synergistically induced apoptosis and cell cycle arrest and inhibited cell proliferation and colony formation in AU565 and MDA-MB-231 human breast cancer cells. Furthermore, the combination of chrysin and 5GG suppressed tumor growth in nude mice with xenografted MDA-MB-231 cells by downregulating the phospho-LRP6 (pLRP6) and Skp2 proteins. Overall, our findings suggested that the combination of chrysin and 5GG has a potential therapeutic value in treating breast cancer, particularly for TNBC associated with Skp2/LRP6 overexpression, and hence warrants further investigation. © 2014 Wiley Periodicals, Inc.
    Molecular Carcinogenesis 10/2014; DOI:10.1002/mc.22234 · 4.77 Impact Factor
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    ABSTRACT: Wnt/beta-catenin signaling pathway plays important roles in human cancer progression. Better understanding the mechanism underlying regulation of Wnt/beta-catenin signaling pathway might provide novel therapeutic targets for cancer treatment. miR-610 expression levels in hepatocellular carcinoma (HCC) cell lines, HCC tissues and 76 archived HCC specimens were determined using real-time PCR. Cell viability was measured by 3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide (MTT) assay. The level of DNA synthesis was determined by BrdU incorporation assay. Flow cytometry analysis was used to analyze cell cycle progression. The cells proliferation and tumorigenesis were determined by colony formation and anchorage-independent growth assays in vitro, and by xenograft tumors in vivo. Luciferase assay and micro-ribonucleoprotein complex immunoprecipitation assay were used to confirm the association of the targeted mRNAs with miR-610. miR-610 was downregulated in human HCC cells and tissues, and correlated with HCC progression and patient survival. Inhibition of miR-610 promoted, but overexpression of miR-610 reduced, HCC cell proliferation and tumorigenicity both in vitro and in vivo. Furthermore, we found that inhibiting miR-610 activated, but overexpressing miR-610 decreased, the Wnt/beta-catenin activity through directly suppressing lipoprotein receptor-related protein 6 (LRP6) and transducin beta-like protein 1 (TBL1X). The in vitro analysis was consistent with the inverse correlation detected between miR-610 levels with expression of LRP6 and TBL1X in a cohort of human HCC samples. Our results indicate that miR-610 downregulation plays essential roles in HCC progression and reduced miR-610 is correlated with Wnt/beta-catenin signaling pathway.
    Molecular Cancer 12/2014; 13(1):261. DOI:10.1186/1476-4598-13-261 · 5.40 Impact Factor


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