Akt2 and nucleophosmin/B23 function as an oncogenic unit in human lung cancer cells

Department of Molecular Cell Biology, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon 440-746, Korea
Experimental Cell Research (Impact Factor: 3.25). 12/2010; 317(7):966-75. DOI: 10.1016/j.yexcr.2010.12.013
Source: PubMed

ABSTRACT The signaling network of protein kinase B(PKB)/Akt has been implicated in survival of lung cancer cells. However, understanding the relative contribution of the different isoform of Akt network is nontrival. Here, we report that Akt2 is highly expressed in human lung adenocarcinoma cell line A549 cells. Suppression of Akt2 expression in A549 cells results in notable inhibition of cell poliferation, soft agar growth, and invasion, accompanying by a decrease of nucleophosmin/B23 protein. Overexpression of Akt1 restores cancerous growth of A549 cells in B23-knockdown (KD) cells while Akt2 overexpression did not restore proliferating potential in cells with downregulated B23, thus suggesting Akt2 requires B23 to drive proliferation of lung cancer cell. Loss of functional Akt2 and B23 has similar defects on cell proliferation, apoptotic resistance and cell cycle regulation, while loss of Akt1 has less defects on cell proliferation, survival and cell cycle progression in A549 cells. Moreover, overexpression of B23 rescues the proliferative block induced as a consequence of loss of Akt2. Thus our data suggest that Akt2/B23 functions as an oncogenic unit to drive tumorigenesis of A549 lung cancer cells.

10 Reads
  • Source
    • "The MTT and BrdU incorporation assay results showed that cells with NPM1 knockdown exhibited decreased cell proliferation (Figures 2B and 3C) and decreased PCNA expression (Figure 3D). This finding indicated that NPM1 function was inhibited in HCT116 cells, consistent with previous reports [30-32]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: We aimed to examine the expression level of Nucleophosmin (NPM1) protein in colon cancer tissues and to investigate the potential role of NPM1 in the regulation of cell migration and invasiveness. Immunohistochemical assay was performed to examine the expression pattern of NPM1 in 31 groups of colonic carcinoma samples, including colon tumors, adjacent normal tissues, and matched metastatic lymph nodes from the same patients. Small interfering RNA technique and exogenous expression of wild type NPM1 methods were used to further verify the function of NPM1. High-expression of NPM1 correlates with lymph node metastasis (P = 0.0003) and poor survival rate of human colon cancer patients (P = 0.017). SiRNA-mediated reduction of NPM1 was also shown to inhibit the migration and invasiveness of metastatic colon cancer HCT116 cell line. In addition, the exogenous expression of NPM1 in HT29 cells, a NPM1 low expression and low invasive colon cancer cell line, enhanced cell migration and invasiveness along with increased cell proliferation. The current study uncovered the critical role of NPM1 in the regulation of colon cancer cells migration and invasion, and NPM1 may serve as a potential marker for the prognosis of colon cancer patients.
    Journal of Biomedical Science 05/2012; 19(1):53. DOI:10.1186/1423-0127-19-53 · 2.76 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Nucleophosmin (NPM) is a nucleolar phosphoprotein that is involved in many cellular processes and has both oncogenic and growth suppressing activities. NPM is localized primarily in nucleoli but shuttles between the nucleus and the cytoplasm, and sustained cytoplasmic distribution contributes to its tumor promoting activities. Plakoglobin (PG, γ-catenin) is a homolog of β-catenin with dual adhesive and signaling functions. These proteins interact with cadherins and mediate adhesion, while their signaling activities are regulated by association with various intracellular partners. Despite these similarities, β-catenin has a well-defined oncogenic activity, whereas PG acts as a tumor/metastasis suppressor through unknown mechanisms. Comparison of the proteomic profiles of carcinoma cell lines with low- or no PG expression with their PG-expressing transfectants has identified NPM as being upregulated upon PG expression. Here, we examined NPM subcellular distribution and in vitro tumorigenesis/metastasis in the highly invasive and very low PG expressing MDA-MB-231 (MDA-231) breast cancer cells and their transfectants expressing increased PG (MDA-231-PG) or NPM shRNA (MDA-231-NPM-KD) or both (MDA-231-NPM-KD+PG). Increased PG expression increased the levels of nucleolar NPM and coimmunoprecipitation studies showed that NPM interacts with PG. PG expression or NPM knockdown decreased the growth rate of MDA-231 cells substantially and this reduction was decreased further in MDA-231-NPM-KD+PG cells. In in vitro tumorigenesis/metastasis assays, MDA-231-PG cells showed substantially lower and MDA-231-NPM-KD cells substantially higher invasiveness relative to the MDA-231 parental cells, and the co-expression of PG and NPM shRNA led to even further reduction of the invasiveness of MDA-231-PG cells. Furthermore, examination of the levels and localization of PG and NPM in primary biopsies of metastatic infiltrating ductal carcinomas revealed coordinated expression of PG and NPM. Together, the data suggest that PG may regulate NPM subcellular distribution, which may potentially change the function of the NPM protein from oncogenic to tumor suppression.
    Oncogenesis 03/2012; 1(3):e4. DOI:10.1038/oncsis.2012.4 · 3.95 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of the study was to investigate the expression levels of 'NPM'/nucleophosmin/B23 and human epidermal growth factor receptor 2 (Her-2)/neu in gastric cancer (GC) and corresponding non-malignant tissues, correlation with their clinicopathological parameters and the relationship of nucleophosmin/B23 and Her-2/neu in the occurrence and development of GC. A total of 131 postoperative patients were examined for nucleophosmin/B23 expression by immuno-histochemistry and for Her-2/neu expression by fluorescence in situ hybridization with the median follow-up period of 38 months. The positive expression rates of nucleophosmin (NPM) in neoplastic tissues and adjacent gastric mucosa were 65.6% and 52.7%, respectively. Nucleophosmin/B23 levels were linked to more advanced tumor stages, poor prognosis, and likelihood of recurrence (p < 0.05). The Cox multivariate analysis indicated that the nucleophosmin/B23 expression was an independent indicator for tumor recurrence (p = 0.011). Of the total GC specimens 12.21% were positive for Her-2/neu, but whose expression was of no correlation with patients' survival. Patients who were positive for Her-2/neu also had high NPM expression levels (p = 0.0303). The results suggest that nucleophosmin/B23 is a favorable prognostic indicator for GC. But Her-2/neu has no relationship with the prognosis of GC. The combined clinical significance of nucleophosmin/B23 and Her-2/neu remains to be further investigated.
    Apmis 03/2013; 121(7). DOI:10.1111/apm.12043 · 2.04 Impact Factor
Show more