Hu F, Gartenhaus RB, Eichberg D, Liu Z, Fang HB, Rapoport AP.. PBK/TOPK interacts with the DBD domain of tumor suppressor p53 and modulates expression of transcriptional targets including p21. Oncogene 29: 5464-5474

Marlene and Stewart Greenebaum Cancer Center, University of Maryland, Baltimore, MD 21201, USA.
Oncogene (Impact Factor: 8.56). 10/2010; 29(40):5464-74. DOI: 10.1038/onc.2010.275
Source: PubMed

ABSTRACT PBK/TOPK (PDZ-binding kinase, T-LAK-cell-originated protein kinase) is a serine-threonine kinase that is overexpressed in a variety of tumor cells but its role in oncogenesis remains unclear. Here we show, by co-immunoprecipitation experiments and yeast two-hybrid analysis, that PBK/TOPK physically interacts with the tumor suppressor p53 through its DNA-binding (DBD) domain in HCT116 colorectal carcinoma cells that express wild-type p53. PBK also binds to p53 mutants carrying five common point mutations in the DBD domain. The PBK-p53 interaction appears to downmodulate p53 transactivation function as indicated by PBK/TOPK knockdown experiments, which show upregulated expression of the key p53 target gene and cyclin-dependent kinase inhibitor p21 in HCT116 cells, particularly after genotoxic damage from doxorubicin. Furthermore, stable PBK/TOPK knockdown cell lines (derived from HCT116 and MCF-7 cells) showed increased apoptosis, G(2)/M arrest and slower growth as compared to stable empty vector-transfected control cell lines. Gene microarray studies identified additional p53 target genes involved in apoptosis or cell cycling, which were differentially regulated by PBK knockdown. Together, these data suggest that increased levels of PBK/TOPK may contribute to tumor cell development and progression through suppression of p53 function and consequent reductions in the cell-cycle regulatory proteins such as p21. PBK/TOPK may therefore be a valid target for antineoplastic kinase inhibitors to sensitize tumor cells to chemotherapy-induced apoptosis and growth suppression.

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    • "To determine which domain of p53 is responsible for its interaction with angiogenin, we used 293T cell lysates transfected with vector alone, pEGFP-p53-WT (wild type) and deletion mutants of p53 with EGFP tags such as pEGFP-p53-mt1 (first activation domain AD1 deleted), pEGFP-p53-mt2 (both activation domains AD1 and AD2 deleted), pEGFP- p53-mt3 (both AD domains and the DNA binding domain [DBD] deleted), and pEGFP-p53- DBD (containing only the DBD domain) (Hu et al.,2010). Co-IP analysis demonstrated that the AD1 deletion mutant p53-mt1 interacts with angiogenin similar to p53-WT (Fig. 2D). "
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    ABSTRACT: Angiogenin, a 14-kDa multifunctional pro-angiogenic growth factor, is upregulated in several types of cancers. Anti-angiogenin monoclonal antibodies used as antagonists inhibited the establishment, progression and metastasis of human cancer cells in athymic mice (Olson et al., 1994). Silencing angiogenin and inhibition of angiogenin's nuclear translocation blocked cell survival and induced cell death in B-lymphoma and endothelial cells latently infected with Kaposi sarcoma-associated herpesvirus (Sadagopan et al., 2009), suggesting that actively proliferating cancer cells could be inducing angiogenin for inhibiting apoptotic pathways. However, the mechanism of cell survival and apoptosis regulation by angiogenin and their functional significance in cancer is not known. We demonstrate that angiogenin interacts with p53 and colocalizes in the nucleus. Silencing endogenous angiogenin induced p53 promoter activation and p53 target gene (p53, p21 and Bax) expression, downregulated anti-apoptotic Bcl-2 gene expression and increased p53-mediated cell death. In contrast, angiogenin expression blocked pro-apoptotic Bax and p21 expression, induced Bcl-2 and blocked cell death. Angiogenin also co-immunoprecipitated with p53 regulator protein Mdm2. Angiogenin expression resulted in the inhibition of p53 phosphorylation, increased p53-Mdm2 interaction, and consequently increased ubiquitination of p53. Taken together, these studies demonstrate that angiogenin promotes the inhibition of p53 function to mediate anti-apoptosis and cell survival. Our results reveal for the first time a novel p53 interacting function of angiogenin in anti-apoptosis and survival of cancer cells and suggest that targeting angiogenin could be an effective therapy for several cancers.Oncogene advance online publication, 23 January 2012; doi:10.1038/onc.2011.648.
    Oncogene 01/2012; 31(46). DOI:10.1038/onc.2011.648 · 8.56 Impact Factor
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    ABSTRACT: We integrated four gene expression profile data sets, namely two different pair-matched stage I lung adenocarcinoma data sets, secondary metastatic tumors vs benign tumors and lung tumor metastasizes to the brain, and we identified one kinase, T-LAK Cell-Originated Protein Kinase (TOPK), as a putative gene that promotes metastasis. To delineate the role of TOPK in lung cancer, we showed that overexpression of TOPK, but not a catalytically inactive form of TOPK, can enhance the migration and invasion of lung fibroblasts or cells with low TOPK expression. In addition, TOPK-induced cell migration was shown to be a PI3K/AKT-dependent event. TOPK concurrently promoted AKT phosphorylation at Ser(473) and decreased the phosphatase and tensin homolog (PTEN) levels, whereas TOPK knockdown had the reverse effects. LY294002, a PI3K inhibitor, did not inhibit the TOPK-induced decrease in PTEN, and co-expression of PTEN significantly reduced TOPK-induced AKT phosphorylation in a dose-dependent manner; these results indicate that the TOPK-mediated PTEN decrease has an upstream role in regulating PI3K/AKT-stimulated migration. Using immunohistochemical analysis of lung cancer tissue samples, we showed that a high TOPK expression level correlates strongly with reduced overall and disease-free survivals. Moreover, an inverse correlation between TOPK and PTEN expression was present and is consistent with the biochemical findings. Finally, a combination of high TOPK and low PTEN expression was inversely correlated with overall and disease-free survivals, independent of other pathologic staging factors. Our results suggest that TOPK is a potential therapeutic target in lung cancer that promotes cell migration by modulating a PI3K/PTEN/AKT-dependent signaling pathway; they also suggest that high TOPK expression, either alone or in combination with a low level of PTEN, may serve as a prognostic marker for lung cancer.
    Oncogene 09/2011; 31(19):2389-400. DOI:10.1038/onc.2011.419 · 8.56 Impact Factor
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    ABSTRACT: Tumor recurrence is the most common cause of disease failure after surgical resection in early-stage lung adenocarcinoma. Identification of clinically relevant prognostic markers could help to predict patients with high risk of disease recurrence. A meta-analysis of available lung adenocarcinoma microarray datasets revealed that T-LAK cell-originated protein kinase (TOPK), a serine/threonine protein kinase, is overexpressed in lung cancer. Using stable cell lines with overexpression or knockdown of TOPK, we have shown that TOPK can promote cell migration, invasion, and clonogenic activity in lung cancer cells, suggesting its crucial role in lung tumorigenesis. To evaluate the prognostic value of TOPK expression in resected stage I lung adenocarcinoma, a retrospective analysis of 203 patients diagnosed with pathological stage I lung adenocarcinoma was carried out to examine the expression of TOPK by immunohistochemistry (IHC). The prognostic significance of TOPK overexpression was examined. Overexpression of TOPK (IHC score >3) was detected in 67.0% of patients, and these patients were more frequently characterized with disease recurrence and angiolymphatic invasion. Using multivariate analysis, patient age (>65 years old; P = 0.002) and TOPK overexpression (IHC score >3; P < 0.001) significantly predicted a shortened overall survival. Moreover, TOPK overexpression (IHC score >3; P = 0.005) also significantly predicted a reduced time to recurrence in the patients. Our results indicate that overexpression of TOPK could predetermine the metastatic capability of tumors and could serve as a significant prognostic predictor of shortened overall survival and time to recurrence.
    Cancer Science 12/2011; 103(4):731-8. DOI:10.1111/j.1349-7006.2011.02197.x · 3.53 Impact Factor
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