Quantitative proteomic analysis by iTRAQ(R) for the identification of candidate biomarkers in ovarian cancer serum.
BACKGROUND
Ovarian cancer is the most lethal gynecologic malignancy, with the majority of cases diagnosed at an advanced stage when treatments are less successful. Novel serum protein markers are needed to detect ovarian cancer in its earliest stage; when detected early, survival rates are over 90%. The identification of new serum biomarkers is hindered by the presence of a small number of highly abundant proteins that comprise approximately 95% of serum total protein. In this study, we used pooled serum depleted of the most highly abundant proteins to reduce the dynamic range of proteins, and thereby enhance the identification of serum biomarkers using the quantitative proteomic method iTRAQ(R).


RESULTS
Medium and low abundance proteins from 6 serum pools of 10 patients each from women with serous ovarian carcinoma, and 6 non-cancer control pools were labeled with isobaric tags using iTRAQ(R) to determine the relative abundance of serum proteins identified by MS. A total of 220 unique proteins were identified and fourteen proteins were elevated in ovarian cancer compared to control serum pools, including several novel candidate ovarian cancer biomarkers: extracellular matrix protein-1, leucine-rich alpha-2 glycoprotein-1, lipopolysaccharide binding protein-1, and proteoglycan-4. Western immunoblotting validated the relative increases in serum protein levels for several of the proteins identified.


CONCLUSIONS
This study provides the first analysis of immunodepleted serum in combination with iTRAQ(R) to measure relative protein expression in ovarian cancer patients for the pursuit of serum biomarkers. Several candidate biomarkers were identified which warrant further development.
Boylan
Kristin Lm
KL
Department of Laboratory Medicine and Pathology, University of Minnesota, MMC 609, 420 Delaware St. SE, Minneapolis, MN, USA.
Andersen
John D
JD
Department of Laboratory Medicine and Pathology, University of Minnesota, MMC 609, 420 Delaware St. SE, Minneapolis, MN, USA.
Anderson
Lorraine B
LB
Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 6-155 Jackson Hall, 321 Church St SE, Minneapolis, MN, USA.
Higgins
LeeAnn
L
Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 6-155 Jackson Hall, 321 Church St SE, Minneapolis, MN, USA.
Skubitz
Amy Pn
AP
Department of Laboratory Medicine and Pathology, University of Minnesota, MMC 609, 420 Delaware St. SE, Minneapolis, MN, USA.