title: Multiplex profiling of tumor-associated proteolytic activity in serum of colorectal cancer patients.
abstract: OBJECTIVE
  The monitoring of tumor-associated protease activity in blood specimens has recently been proposed as new diagnostic tool in cancer research. In this paper, we describe the screening of a peptide library for identification of reporter peptides (RPs) that are selectively cleaved in serum specimens from colorectal cancer patients and investigate the benefits of RP multiplexing.
  
  
  METHODS
  A library of 144 RPs was constructed that contained amino acid sequences of abundant plasma proteins. Proteolytic cleavage of RPs was monitored with MS. Five RPs that were selectively cleaved in serum specimens from tumor patients were selected for further validation in serum specimens of colorectal tumor patients (n = 30) and nonmalignant controls (n = 60).
  
  
  RESULTS
  RP spiking and subsequent quantification of proteolytic fragments with LC-MS showed good reproducibility with CVs always below 26%. The linear discriminant analysis and PCA revealed that a combination of RPs for diagnostic classification is superior to single markers. Classification accuracy reached 88% (79/90) when all five markers were combined.
  
  
  CONCLUSIONS
  Functional protease profiling with RPs might improve the laboratory-based diagnosis, monitoring and prognosis of malignant disease, and has to be evaluated thoroughly in future studies.
authors.affiliation: Institute for Clinical Chemistry, Medical Faculty Mannheim of the University of Heidelberg, University Hospital Mannheim, Mannheim, Germany.
authors.forename: Diego
authors.initials: D
authors.lastname: Yepes
authors.forename: Victor
authors.initials: V
authors.lastname: Costina
authors.forename: Lothar R
authors.initials: LR
authors.lastname: Pilz
authors.forename: Ralf
authors.initials: R
authors.lastname: Hofheinz
authors.forename: Michael
authors.initials: M
authors.lastname: Neumaier
authors.forename: Peter
authors.initials: P
authors.lastname: Findeisen
mesh_terms: D000368:Aged; D015179:Colorectal Neoplasms / Q000097:blood* / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D019151:Peptide Library; D059748:Proteolysis; D040901:Proteomics / Q000379:methods*; D015203:Reproducibility of Results
chemical_list: D019151:Peptide Library
keywords: Colorectal cancer; Multiparametric analysis; Protease profiling; Reporter peptides/Serum