Epithelial ovarian cancer kills almost 16 000 women each year in part due to late stage of presentation and lack of reliable
biomarkers for disease detection. CA-125, the currently accepted
serum marker, alone lacks the sensitivity for early stage diagnosis, as only 50% of early stage cases are detected with this marker. Although more early stage cases may be detected by
lysophosphatidic acid, this marker is also elevated in other
cancers. One major objective of the NCI-FDA Tissue Proteomics Initiative has been to combine the technique of
laser capture microdissection (LCM) of epithelial
tumor cells in human tissue specimens with two-dimensional gel electrophoresis (2-D PAGE) to identify
proteins that may serve as invasive
ovarian cancer-specific
biomarkers for early detection and/or new therapeutic targets. We performed 2-D PAGE on lysates from five microdissected ovarian
tumors (three invasive
ovarian cancers and two noninvasive, low malignant potential (LMP) ovarian
tumors). We then compared
silver stained 2-D
gels created from microdissected lysates with
SYPRO-Ruby stained 2-D PAGE profiles of the patient-matched undissected bulk
tumor lysates from all five patients. Twenty-three
proteins were consistently differentially expressed between both the LMP and three invasive ovarian
tumors in the limited study set. Thirteen were uniquely present in all three of the invasive
ovarian cancer cases and absent or underexpressed in the two LMP cases. Ten were uniquely present in the LMP cases but absent or underexpressed in all invasive
ovarian cancer cases. Credentialing and preliminary target validation of the mass spectrometry identified
proteins cut from the Ruby-red stained
gels was performed by LCM coupled Western blot and reverse-phase array technology in a study set of six cases (the aforementioned five cases used in the 2-D PAGE profiling component of the study plus one additional LMP case). The analysis revealed that the 52 kDa
FK506 binding protein, Rho
G-protein dissociation inhibitor (
RhoGDI), and
glyoxalase I are found to be uniquely overexpressed in invasive human
ovarian cancer when compared to the LMP form of this
cancer. The direct comparison of LCM generated proteomic profiles of invasive vs. LMP
ovarian cancer may more directly generate important markers for early detection and/or therapeutic targets unique to the invasive phenotype.