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
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.
"Our study confirms the role of ANLN as a marker of poor prognosis, at the protein level, in an independent breast cancer cohort. PBK phosphorylates p38MAPK during mitosis, is considered a marker for cellular proliferation and is also implicated in DNA damaging sensing and repair [61,62]. PBK is associated with poorer prognosis in lung cancer , is up-regulated in IDC relative to DCIS at the transcriptomic level , and may be a promising molecular target for treatment of breast cancer . "
[Show abstract][Hide abstract] ABSTRACT: Background
Although omic-based discovery approaches can provide powerful tools for biomarker identification, several reservations have been raised regarding the clinical applicability of gene expression studies, such as their prohibitive cost. However, the limited availability of antibodies is a key barrier to the development of a lower cost alternative, namely a discrete collection of immunohistochemistry (IHC)-based biomarkers. The aim of this study was to use a systematic approach to generate and screen affinity-purified, mono-specific antibodies targeting progression-related biomarkers, with a view towards developing a clinically applicable IHC-based prognostic biomarker panel for breast cancer.
We examined both in-house and publicly available breast cancer DNA microarray datasets relating to invasion and metastasis, thus identifying a cohort of candidate progression-associated biomarkers. Of these, 18 antibodies were released for extended analysis. Validated antibodies were screened against a tissue microarray (TMA) constructed from a cohort of consecutive breast cancer cases (n = 512) to test the immunohistochemical surrogate signature.
Antibody screening revealed 3 candidate prognostic markers: the cell cycle regulator, Anillin (ANLN); the mitogen-activated protein kinase, PDZ-Binding Kinase (PBK); and the estrogen response gene, PDZ-Domain Containing 1 (PDZK1). Increased expression of ANLN and PBK was associated with poor prognosis, whilst increased expression of PDZK1 was associated with good prognosis. A 3-marker signature comprised of high PBK, high ANLN and low PDZK1 expression was associated with decreased recurrence-free survival (p < 0.001) and breast cancer-specific survival (BCSS) (p < 0.001). This novel signature was associated with high tumour grade (p < 0.001), positive nodal status (p = 0.029), ER-negativity (p = 0.006), Her2-positivity (p = 0.036) and high Ki67 status (p < 0.001). However, multivariate Cox regression demonstrated that the signature was not a significant predictor of BCSS (HR = 6.38; 95% CI = 0.79-51.26, p = 0.082).
We have developed a comprehensive biomarker pathway that extends from discovery through to validation on a TMA platform. This proof-of-concept study has resulted in the identification of a novel 3-protein prognostic panel. Additional biochemical markers, interrogated using this high-throughput platform, may further augment the prognostic accuracy of this panel to a point that may allow implementation into routine clinical practice.
BMC Cancer 04/2013; 13(1):175. DOI:10.1186/1471-2407-13-175 · 3.36 Impact Factor
"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). "
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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.
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