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Originally published as JCO Early Release 10.1200/JCO.2005.02.4133 on December 5 2005 © 2006 American Society of Clinical Oncology. Evaluation of Two Phosphorylation Sites Improves the Prognostic Significance of Akt Activation in NonSmall-Cell Lung Cancer TumorsFrom the Cancer Therapeutics Branch; Laboratory of Population Genetics; Biometric Research Branch; and Laboratory of Pathology, National Cancer Institute, Bethesda, MD; Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY; Department of Pulmonary and Mediastinal Pathology, Armed Forces Institute of Pathology, Washington, DC Address reprint requests to Phillip A. Dennis, MD, Building 8, Room 5101, 8901 Wisconsin Ave, Bethesda, MD 20889; e-mail: pdennis{at}nih.gov PURPOSE: Akt is a serine/threonine kinase that has been implicated in lung tumorigenesis and lung cancer therapeutic resistance. Full activation of Akt requires two phosphorylation events, but only one site of phosphorylation (S473) has been evaluated thus far in clinical nonsmall-cell lung cancer (NSCLC) specimens, which has resulted in conflicting results regarding the prognostic significance of Akt activation in NSCLC. In this study, we sought to determine whether evaluation of Akt phosphorylation at T308 would improve prognostic accuracy. PATIENTS AND METHODS: Phosphospecific antibodies against T308 and S473 were validated and used in an immunohistochemical analysis of tissue microarray slides containing NSCLC specimens (n = 300) and surrounding lung tissue specimens (n = 100). RESULTS: Phosphorylation of either S473 or T308 was positive in most NSCSLC specimens, but was detected rarely in surrounding normal tissues. When Akt activation was defined by using both sites of phosphorylation, Akt activation was specific for NSCLC tumors versus surrounding tissue (73.4% v 0%; P < .05), was higher in adenocarcinoma than in squamous cell carcinoma (78.1% v 68.5%; P = .040), and was associated with shorter overall survival for all stages of disease (log-rank P = .041). In multivariate analyses, increased phosphorylation of T308 alone was a poor prognostic factor for stage I patients or for tumors < 5 cm (log-rank P = .011 and P = .015, respectively). CONCLUSION: These results suggest that monitoring phosphorylation of Akt at T308 improves the assessment of Akt activation, and show that Akt activation is a poor prognostic factor for all stages of NSCLC. Supported by the Intramural Research Program of the Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD. J.T. and J.F. contributed equally to this work. Terms in blue are defined in the glossary, found at the end of this article and online at www.jco.org. Authors' disclosures of potential conflicts of interest and author contributions are found at the end of this article. This article has been cited by other articles:
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Copyright © 2006 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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