Akt2 and nucleophosmin/B23 function as an oncogenic unit in human lung cancer cells
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.
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ABSTRACT: Dysregulation of nucleophosmin 1 (NPM1) has been found in numerous solid and hematological malignancies. Our previous meta-analysis of colorectal cancer (CRC) high throughput gene expression profiling studies identified it as a consistently reported up-regulated gene in the malignant state. Our aims were to compare NPM1 expression in normal colon, adenoma and CRC, to correlate their expressions with clinico-pathological parameters, and to assess the biological role of aberrant NPM1 expression in CRC cells. NPM1 transcript levels were studied in human CRC cell lines, whereas a tissue microarray of 57 normal human colon, 40 adenoma and 185 CRC samples was used to analyze NPM1 protein expression by immunohistochemistry. CRC cell lines were subjected to transient siRNA-mediated knockdown to study NPM1's roles on cell viability and senescence. NPM1 transcript levels were 7-11 folds higher in three different human CRC cell lines compared to normal colon cells. NPM1 protein expression was found to be progressively and significantly upregulated in CRC compared to adenomas, and in adenomas compared to normal mucosa. Reducing NPM1 expression by siRNA had caused a significant decrease in cell viability, a concomitant increase in cellular senescence, and cell cycle arrest. Cellular senescence induced under conditions of forced NPM1 suppression could be prevented by knocking down p53. The differential expression of NPM1 along the normal colon-adenoma-carcinoma progression, and its involvement resisting p53 related senescent growth arrest in CRC cell lines implicate its role in supporting CRC tumorigenesis. © 2013 Wiley Periodicals, Inc.International Journal of Cancer 10/2013; 133(7). DOI:10.1002/ijc.28180 · 5.01 Impact Factor
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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.03/2012; 1:e4. DOI:10.1038/oncsis.2012.4
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ABSTRACT: Drug resistance and recurrence are the major obstacles to bladder cancer chemotherapy. Our laboratory had reported that nucleophosmin1 was one of the differentially expressed proteins between bladder cancer cell lines PUMC-91 and PUMC-91/1.0ADM based on 2D-PAGE proteomics approaches. In this study, we want to explore the relationship among nucleophosmin1, drug resistance, and recurrence of bladder cancer, using normal bladder epithelia cell line SV-HUC-1, bladder cancer cell lines PUMC-91, PUMC-91 against gradient doses of adriamycin (0.3, 0.6, and 1.0 μg/ml), and bladder cancer tissue samples. The bladder cancer tissue samples were divided into two groups according to the interval of recurrence (<6 months and >2 years). The differences were detected by Western blotting and immunohistochemistry. The protein of nucleophosmin1 was differentially expressed with each other in SV-HUC-1, PUMC-91, PUMC-91/0.3ADM, and PUMC-91/1.0ADM (p < 0.05). Nucleophosmin1 was less expressed in later recurring (>2 years) bladder cancer tissue samples compared with samples that recurred <6 months (p = 0.035). The expression of nucleophosmin1 was independently associated with gradient drug resistance and recurrent frequency of bladder cancer. Nucleophosmin1 was a key regulator in either a drug-resistant bladder cancer or bladder cancer recurrence model. It may be possible to think nucleophosmin1 can provide more helpful information for clinical drug treatment of bladder cancer patients and frequently recurred ones.Clinical and Experimental Medicine 06/2014; DOI:10.1007/s10238-014-0288-3 · 2.82 Impact Factor