Background

The aim of this programme of research is development of biomarker tests for the early detection of metastatic breast cancer (BC). Altered glycosylation - a hallmark of metastatic BC - was the focus of the experimental approach used in this proteomic study.

Method

Serum samples collected as part of the DietCompLyf investigation were utilised, the samples were processed and stored in a manner ¹ compatible with down-stream proteomic analysis. Glycoproteins from pooled serum samples of patients with recurrent BC and patients with no sign of recurrence (NSR, follow-up ≥ 5 years post-diagnosis) were isolated by affinity chromatography using the carbohydrate binding protein Helix pomatia agglutinin and analysed by 2-dimensional difference gel electrophoresis (2D-DIGE) in conjunction with liquid chromatography - tandem mass spectrometry (LC-MS/MS). ELISAs were developed to verify the proteomic findings and to assess protein glycosylation in individual patient serum samples.

Results

Pregnancy zone protein, the polymeric immunoglobulin receptor and cadherin-5 emerged as potential biomarkers for metastatic BC. Relative serum levels and the glycosylation status of each of these proteins was determined by ELISA using serum samples from patients with recurrent BC (n=25) and from patients with NSR (n=23). Cadherin-5 levels were elevated in the sera from patients with recurrent BC (P = 0.019) and when HPA binding was assessed this was also elevated (P = 0.024). Cadherin-5 analysis discriminated patients with recurrent BC from those with NSR with 90% specificity ².

Conclusion

The glycoproteomic and validatory approach identified cadherin-5 as a marker of metastatic BC, with protein levels and HPA binding contributing to a test comparable to CA15.3 in terms of specificity. Further exploration of this marker is continuing using serum samples collected through the on-going, prospective, DietCompLyf study.