Originally published In Press as doi:10.1074/mcp.M800596-MCP200 on July 28, 2009.
Molecular & Cellular Proteomics 8:2382-2395, 2009.
© 2009 by The American Society for Biochemistry and Molecular Biology, Inc.
Research
Identification of Tumor-associated Autoantigens for the Diagnosis of Colorectal Cancer in Serum Using High Density Protein Microarrays*,
Ingrid Babel , ,
Rodrigo Barderas , ,¶,
Ramón Díaz-Uriarte||,
Jorge Luis Martínez-Torrecuadrada**,
Marta Sánchez-Carbayo and
J. Ignacio Casal ,
From the Functional Proteomics Laboratory, Centro de Investigaciones Biológicas-Consejo Superior de Investigaciones Científicas, 28040 Madrid, Spain and
||Biostructural and Bioinformatics Program,
**Protein Technology Unit, and
 Tumor Markers Group, Centro Nacional de Investigaciones Oncológicas (CNIO), 28029 Madrid, Spain
There is a mounting evidence of the existence of autoantibodies associated to cancer progression. Antibodies are the target of choice for serum screening because of their stability and suitability for sensitive immunoassays. By using commercial protein microarrays containing 8000 human proteins, we examined 20 sera from colorectal cancer (CRC) patients and healthy subjects to identify autoantibody patterns and associated antigens. Forty-three proteins were differentially recognized by tumoral and reference sera (p value <0.04) in the protein microarrays. Five immunoreactive antigens, PIM1, MAPKAPK3, STK4, SRC, and FGFR4, showed the highest prevalence in cancer samples, whereas ACVR2B was more abundant in normal sera. Three of them, PIM1, MAPKAPK3, and ACVR2B, were used for further validation. A significant increase in the expression level of these antigens on CRC cell lines and colonic mucosa was confirmed by immunoblotting and immunohistochemistry on tissue microarrays. A diagnostic ELISA based on the combination of MAPKAPK3 and ACVR2B proteins yielded specificity and sensitivity values of 73.9 and 83.3% (area under the curve, 0.85), respectively, for CRC discrimination after using an independent sample set containing 94 sera representative of different stages of progression and control subjects. In summary, these studies confirmed the presence of specific autoantibodies for CRC and revealed new individual markers of disease (PIM1, MAPKAPK3, and ACVR2B) with the potential to diagnose CRC with higher specificity and sensitivity than previously reported serum biomarkers.
 To whom correspondence should be addressed:Functional Proteomics Laboratory, Centro de Investigaciones Biológicas (CIB-CSIC), Ramiro de Maeztu 9, 28040 Madrid, Spain. Tel.:34-91-8373112; Fax:34-91-5360432; E-mail:icasal{at}cib.csic.es.

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Copyright © 2009 by the American Society for Biochemistry and Molecular Biology.
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