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      Aurora Kinase A expression is associated with lung cancer histological-subtypes and with tumor de-differentiation

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          Abstract

          Background

          Aurora kinase A ( AURKA) is a member of serine/threonine kinase family. Several kinases belonging to this family are activated in the G2/M phase of the cell cycle being involved in mitotic chromosomal segregation. AURKA overexpression is significantly associated with neoplastic transformation in several tumors and deregulated Aurora Kinases expression leads to chromosome instability, thus contributing to cancer progression. The purpose of the present study was to investigate the expression of AURKA in non small cell lung cancer (NSCLC) specimens and to correlate its mRNA or protein expression with patients' clinico-pathological features.

          Materials and methods

          Quantitative real-time PCR and immunohistochemistry analysis on matched cancer and corresponding normal tissues from surgically resected non-small cell lung cancers (NSCLC) have been performed aiming to explore the expression levels of AURKA gene.

          Results

          AURKA expression was significantly up-modulated in tumor samples compared to matched lung tissue (p < 0.01, mean log2(FC) = 1.5). Moreover, AURKA was principally up-modulated in moderately and poorly differentiated lung cancers (p < 0.01), as well as in squamous and adenocarcinomas compared to the non-invasive bronchioloalveolar histotype (p = 0.029). No correlation with survival was observed.

          Conclusion

          These results indicate that in NSCLC AURKA over-expression is restricted to specific subtypes and poorly differentiated tumors.

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          Most cited references12

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          Aurora-A overexpression reveals tetraploidization as a major route to centrosome amplification in p53-/- cells.

          Aberrations in centrosome numbers have long been implicated in aneuploidy and tumorigenesis, but their origins are unknown. Here we have examined how overexpression of Aurora-A kinase causes centrosome amplification in cultured cells. We show that excess Aurora-A does not deregulate centrosome duplication but gives rise to extra centrosomes through defects in cell division and consequent tetraploidization. Over expression of other mitotic kinases (Polo-like kinase 1 and Aurora-B) also causes multinucleation and concomitant increases in centrosome numbers. Absence of a p53 checkpoint exacerbates this phenotype, providing a plausible explanation for the centrosome amplification typical of p53-/- cells. We propose that errors during cell division, combined with the inability to detect the resulting hyperploidy, constitute a major cause for numerical centrosome aberrations in tumors.
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            Aurora-A abrogation of p53 DNA binding and transactivation activity by phosphorylation of serine 215.

            The tumor suppressor p53 is important in the decision to either arrest cell cycle progression or induce apoptosis in response to a variety of stimuli. p53 posttranslational modifications and association with other proteins have been implicated in the regulation of its stability and transactivation activity. Here we show that p53 is phosphorylated by the mitotic kinase Aurora-A at serine 215. Unlike most identified phosphorylation sites of p53 that positively associate with p53 function (Brooks, C. L., and Gu, W. (2003) Curr. Opin. Cell Biol. 15, 164-171), the phosphorylation of p53 by Aurora-A at Ser-215 abrogates p53 DNA binding and transactivation activity. Downstream target genes of p53, such as p21Cip/WAF1 and PTEN, were inhibited by Aurora-A in a Ser-215 phosphorylation-dependent manner (i.e. phosphomimic p53-S215D lost and non-phosphorylatable p53-S215A retained normal p53 function). As a result, Aurora-A overrides the apoptosis and cell cycle arrest induced by cisplatin and gamma-irradiation, respectively. However, the effect of Aurora-A on p53 DNA binding and transactivation activity was not affected by phosphorylation of Ser-315, a recently identified Aurora-A phosphorylation site of p53 (Katayama, H., Sasai, K., Kawai, H., Yuan, Z. M., Bondaruk, J., Suzuki, F., Fujii, S., Arlinghaus, R. B., Czerniak, B. A., and Sen, S. (2004) Nat. Genet. 36, 55-62). Our data indicate that phosphorylation of p53 at Ser-215 by Aurora-A is a major mechanism to inactivate p53 and can provide a molecular insight for Aurora-A function.
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              Amplification/overexpression of a mitotic kinase gene in human bladder cancer.

              The mitotic kinase-encoding gene STK15/BTAK/ AuroraA is associated with aneuploidy and transformation when overexpressed in mammalian cells. STK15 overexpression activates an unknown oncogenic pathway that involves centrosome amplification and results in missegregation of chromosomes. Because clinical prognosis and tumor aneuploidy are tightly linked in human bladder cancer, we examined whether increased STK15 copy number and protein levels are linked to aneuploidy in bladder cancers. STK15 protein was visualized by immunohistochemistry in 205 formalin-fixed, paraffin-embedded human bladder tumors. STK15 gene copy number was evaluated in 61 tumors by Southern blot hybridization and in 21 of these 61 tumors by fluorescence in situ hybridization (FISH). Copy numbers of chromosomes 3, 17, 20, and 21 were evaluated by FISH with chromosome-specific probes. STK15 expression levels were related to histologic grade, stage, and DNA ploidy of the tumors and to the patients' follow-up data. The chi-square test for association was used to analyze the relationship between STK15 expression and pathologic features. All statistical tests were two-sided. Tumors with low levels of STK15 amplification (3-4 copies) showed minimal deviation in their chromosome copy number and diploid or near-diploid total nuclear DNA content. Tumors with higher levels of STK15 amplification (>4 copies) had a major increase of chromosome copy number and of their total nuclear DNA content, i.e., exhibited pronounced aneuploidy. Elevated expression of STK15 was strongly associated with parameters of clinical aggressiveness including high histologic grade (P<.001), invasion (P<.001), increased rate of metastasis (P<.001), and decreased metastasis-free (P<.001) and overall (P<.001) survival of patients with bladder cancer. STK15 gene amplification and associated increased expression of the mitotic kinase it encodes are associated with aneuploidy and aggressive clinical behavior in human bladder cancer.
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                Author and article information

                Journal
                J Transl Med
                Journal of Translational Medicine
                BioMed Central
                1479-5876
                2011
                30 June 2011
                : 9
                : 100
                Affiliations
                [1 ]Department of Clinical and Biological Sciences, University of Turin, Turin, Italy
                Article
                1479-5876-9-100
                10.1186/1479-5876-9-100
                3148570
                21718475
                41ecdee0-e7b6-47b3-b08f-bb028c853431
                Copyright ©2011 Lo Iacono et al; licensee BioMed Central Ltd.

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 7 October 2010
                : 30 June 2011
                Categories
                Research

                Medicine
                Medicine

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