Detection of differential levels of proteins in the urine of patients with endometrial cancer: analysis using two-dimensional gel electrophoresis and o-glycan binding lectin

Abstract

Cancers can cause some proteins to be aberrantly excreted or released in the urine, which can be used as biomarkers. To screen for potential biomarkers for endometrial cancer (ECa), the urinary proteins from patients who were newly diagnosed with early stage ECa and untreated controls were separated using two-dimensional gel electrophoresis (2-DE) and followed by image analysis. The altered levels of zinc alpha-2 glycoprotein, alpha 1-acid glycoprotein, and CD59 were detected in the patients compared to the controls. In addition, the urine of the ECa patients was also found to contain relatively lower levels of a fragment of nebulin when the 2-DE separated urinary proteins were probed using champedak galactose binding (CGB) lectin. The different levels of the nebulin fragment were further validated by subjecting the urinary protein samples to CGB lectin affinity chromatography and analysis of the bound fractions by LC-MS/MS. Our data is suggestive of the potential use of the differentially expressed urinary proteins as biomarkers for ECa although this requires further extensive validation on clinically representative populations.

Keywords: 2-dimensional gel electrophoresis; biomarker; champedak galactose binding lectin; endometrial cancer; proteomics; urine.

Figure 1

Typical two-dimensional gel electrophoresis (2-DE) urinary protein profiles. The labeled spot clusters are proteins which consistently appeared in profiles of control subjects. Panels (A) and (B) refer to the profiles of a control subject and a patient with stage IB endometrial cancer (ECa), respectively.

Figure 2

Typical 2-DE urinary O-glycoprotein profiles. Panels (A) and (B) refer to 2-DE urinary O-glycoprotein profiles of a control subject and a patient with stage IB ECa, respectively. Spot clusters that are marked in boxes are proteins, which were consistently detected by CGB lectin. NEB refers to nebulin. The acidic side of the membranes is to the left and the relative molecular mass declines from the top.