title: Antibody-based profiling of the phosphoinositide 3-kinase pathway in clinical prostate cancer.
abstract: OBJECTIVE
  As kinase inhibitors transition from the laboratory to patients, it is imperative to develop biomarkers that can be used in the clinic. The primary objectives are to identify patients most likely to benefit from molecularly targeted therapies and to document modulation of the drug target. Constitutive activation of the phosphoinositide 3-kinase (PI3K) pathway and its downstream effectors, as a result of PTEN loss or by other mechanisms, occurs in a high proportion of prostate cancers, making it an ideal template for the design of clinical trials involving PI3K pathway inhibitors. Prostate cancers also present unique organ-specific challenges, in that tumors are heterogeneous and diagnostic tissue is extremely limited.
  
  
  METHODS
  Working within these limitations, we have developed a set of immunohistochemical assays that define activation of the PI3K pathway in clinical samples.
  
  
  CONCLUSIONS
  Using both univariate and multivariate analyses, we show that loss of PTEN is highly correlated with the activation of AKT, and this, in turn, is associated with the phosphorylation of S6, one of its main effectors. These three antibodies are potentially able to define a molecular signature of PTEN loss and/or AKT pathway activation in prostate cancer.
authors.affiliation: Department of Pathology and Laboratory Medicine, David Geffen School of Medicine, University of California-Los Angeles, Los Angeles, California 90095, USA.
authors.forename: George V
authors.initials: GV
authors.lastname: Thomas
authors.forename: Steve
authors.initials: S
authors.lastname: Horvath
authors.forename: Bradley L
authors.initials: BL
authors.lastname: Smith
authors.forename: Katherine
authors.initials: K
authors.lastname: Crosby
authors.forename: Lori A
authors.initials: LA
authors.lastname: Lebel
authors.forename: Matthew
authors.initials: M
authors.lastname: Schrage
authors.forename: Jonathan
authors.initials: J
authors.lastname: Said
authors.forename: Jean
authors.initials: J
authors.lastname: De Kernion
authors.forename: Robert E
authors.initials: RE
authors.lastname: Reiter
authors.forename: Charles L
authors.initials: CL
authors.lastname: Sawyers
mesh_terms: D000911:Antibodies, Monoclonal; D015536:Down-Regulation; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D011467:Prostate / Q000201:enzymology / Q000276:immunology / Q000473:pathology; D011471:Prostatic Neoplasms / Q000201:enzymology* / Q000276:immunology / Q000473:pathology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism; D015398:Signal Transduction; D025521:Tumor Suppressor Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D051059:PTEN Phosphohydrolase; D019869:Phosphatidylinositol 3-Kinases; D010744:Phosphoric Monoester Hydrolases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D019893:Ribosomal Protein S6 Kinases; D025521:Tumor Suppressor Proteins; C494918:AKT1 protein, human; C494929:PTEN protein, human