Detection of cadherin-17 in human colon cancer LIM1215 cell secretome and tumour xenograft-derived interstitial fluid and plasma.

Colorectal cancer (CRC), one of the most prevalent cancers in the western world, is treatable if detected early. However, 70% of CRC is detected at an advanced stage. This is largely due to the inadequacy of current faecal occult blood screening testing and costs involved in conducting population-based colonoscopy, the 'gold standard' for CRC detection. Another biomarker for CRC, carcinoembryonic antigen, while useful for monitoring CRC recurrence, is ineffective, lacking the specificity required early detection of CRC. For these reasons there is a need for more effective blood-based markers for early CRC detection. In this study we targeted glycoproteins secreted from the human colon carcinoma cell line LIM1215 as a source of potential CRC biomarkers. Secreted candidate glycoproteins were confirmed by MS and validated by Western blot analysis of tissue/tumour interstitial fluid (Tif) from LIM1215 xenograft tumours grown in immunocompromised mice. Overall, 39 glycoproteins were identified in LIM1215 culture media (CCM) and 5 glycoproteins in LIM1215 tumour xenograft Tif; of these, cadherin-17 (CDH17), galectin-3 binding protein (LGALS3BP), and tyrosine-protein kinase-like 7 (PTK7) were identified in both CM and glycosylation motifs. Swiss-Prot was used to annotate Tif. Many of the glycoproteins identified in this study (e.g., AREG, DSG2, EFNA1, EFNA3, EFNA4, EPHB4, ST14, and TIMP1) have been reported to be implicated in CRC biology. Interestingly, the cadherin-17 ectodomain, but not full length cadherin-17, was identified in CM, Tif and plasma derived from mice bearing the LIM1215 xenograft tumour. To our knowledge, this is the first report of the cadherin-17 ectodomain in plasma. In this study, we report for the first time that the presence of full-length cadherin-17 in exosomes released into the CM. This article is part of a Special Issue entitled: An Updated Secretome.