Evidence of Altered Glycosylation of Serum Proteins Prior to Pancreatic Cancer Diagnosis.

Shibu Krishnan,Joy Cuenco,Aleksandra Gentry-Maharaj,Stephen Pereira,John Timms,Harry Whitwell,Marco Gaspari,Usha Menon

doi:10.3390/ijms18122670

Abstract

Biomarkers for the early detection of pancreatic cancer are urgently needed. The aim of this pilot study was to evaluate changes in serum N-glycoproteins and their glycosylation status prior to clinical presentation of pancreatic cancer that may be potential biomarkers. Prediagnosis serum samples pooled according to five time-to-diagnosis groups and a non-cancer control pool were digested with trypsin, labelled with mass tags, and subjected to titanium dioxide capture, deglycosylation, and 2D-LC-MS/MS profiling. Unbound peptides were profiled in parallel. Across the sample groups, 703 proteins were quantified and 426 putative sites of N-glycosylation were identified with evidence of several novel sites. Altered proteins with biomarker potential were predominantly abundant inflammatory response, coagulation, and immune-related proteins. Whilst glycopeptide profiles largely paralleled those of their parent proteins, there was evidence of altered N-glycosylation site occupancy or sialic acid content prior to diagnosis for some proteins, most notably of immunoglobulin gamma chains. α-1-Antitrypsin was tested as a biomarker, but found not to complement carbohydrate antigen 19-9 (CA19-9) in early detection of cancer. In conclusion, we provide preliminary evidence of altered glycosylation of several serum proteins prior to pancreatic cancer diagnosis, warranting further investigation of these proteins as early biomarkers. These changes may be largely driven by inflammatory processes that occur in response to tumour formation and progression.

Highlights

Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer death and has the lowest five year survival rate for any solid tumour (3–6%) [1,2]
Prediagnosis serum samples sourced from the UK Collaborative Trial of Ovarian Cancer Screening (UKCTOCS) were
Using a TiO2-based enrichment strategy linked to quantitative LC-MS/MS by TMT labelling, we have compared serum protein and glycopeptide profiles of noncancer controls with those of women who went on to be diagnosed with PDAC

Summary

Introduction

Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer death and has the lowest five year survival rate for any solid tumour (3–6%) [1,2]. The serum marker carbohydrate antigen 19-9 (CA19-9) [3,4,5] is the only biomarker used routinely in the management of PDAC for monitoring treatment response It has a 79–81% sensitivity and 82–90% specificity [6], is often elevated in benign pancreatobiliary diseases such as obstructive jaundice, pancreatitis, and cholangitis [7,8,9]. 8–10% of the Caucasian population with the Lewis a−b− genotype do not express CA19-9; these individuals lack the FUT2 and FUT3 fucosyltransferases, and fail to generate the CA19-9 epitope which is the sialylated Lewis A blood group antigen [8,10] For these reasons, serum CA19-9 is not recommended for diagnosis of PDAC. The clinical utility of most reported markers has yet to be determined and requires multicenter validation

Methods

Results

Conclusion