Haptoglobin-alpha subunit as potential serum biomarker in ovarian cancer: identification and characterization using proteomic profiling and mass spectrometry.
OBJECTIVE
The objective of this study was to identify and characterize new serum biomarkers in ovarian cancer patients using mass spectrometric protein profiling and specific immunological assays.


METHODS
Serum samples from 80 cancer patients and 91 healthy women were analyzed by surface enhanced laser desorption and ionization-mass spectrometry (MS) profiling. A candidate biomarker was purified by affinity chromatography, and its sequence was determined by liquid chromatography-tandem MS. An antibody was generated from the synthesized peptide for quantitative validation in the cases and controls. CA125 was determined and compared with the same set of specimens.


RESULTS
Using surface enhanced laser desorption and ionization, we found a serum biomarker at approximately 11700 Da, which had peak intensity significantly higher in cases (1.366) compared with controls (0.208, P = 0.002), and subsequently identified this as the alpha chain of haptoglobin. ELISA indicated that Hp-alpha was </=2-fold higher in cancer serum compared with normal, benign tumor, and other gynecological cancers (P < 0.05) and had 64% sensitivity at 90% specificity alone and 91% sensitivity and 95% specificity if combined with CA125.


CONCLUSIONS
Haptoglobin-derived alpha subunit is a potential marker for ovarian cancer that is complementary to CA125. MS-based protein profiling is a valuable tool for screening protein markers and useful to detect post-translational modification of tumor-associated proteins or abnormal metabolic products. However, confirmation of protein identity with specific antibodies is crucial for clinical application and functional studies.
Ye
Bin
B
Department of Obstetrics & Gynecology, Brigham and Women's Hospital, Dana-Farber Cancer Institute, Dana-Farber Harvard Cancer Center, Boston, MA 02115, USA. Bin-Ye@hms.harvard.edu
Cramer
Daniel W
DW
Skates
Steven J
SJ
Gygi
Steven P
SP
Pratomo
Vanessa
V
Fu
Lanfei
L
Horick
Nora K
NK
Licklider
Larry J
LJ
Schorge
John O
JO
Berkowitz
Ross S
RS
Mok
Samuel C
SC
D000595:Amino Acid Sequence; D014408:Biomarkers, Tumor / Q000097:blood*; D001710:Biotin / Q000378:metabolism; D015153:Blotting, Western; D018394:CA-125 Antigen / Q000097:blood; D019281:Dimerization; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005833:Genital Neoplasms, Female / Q000097:blood; D006242:Haptoglobins / Q000096:biosynthesis*; D006801:Humans; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D020411:Oligonucleotide Array Sequence Analysis; D010051:Ovarian Neoplasms / Q000097:blood* / Q000175:diagnosis*; D010455:Peptides / Q000737:chemistry; D040901:Proteomics / Q000379:methods; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013997:Time Factors
D014408:Biomarkers, Tumor; D018394:CA-125 Antigen; C485359:HP protein, human; D006242:Haptoglobins; D010455:Peptides; D001710:Biotin