Identification and evaluation of circulating biomarkers for pancreatic cancer and their correlation with pancreatic stromal expression

Evans, Anthony (2016) Identification and evaluation of circulating biomarkers for pancreatic cancer and their correlation with pancreatic stromal expression. Doctor of Philosophy thesis, University of Liverpool.

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Abstract

Pancreatic ductal adenocarcinoma (PDAC) is the deadliest of the common cancers, with a dismal prognosis attributed in part to late diagnosis in the majority of patients. Diagnosing early stage increases the likelihood of eligibility for surgical resection, currently the only available method of cure. In this thesis I have aimed to identify serum biomarkers for the diagnosis of PDAC, as a potential means of screening for the disease in a minimally-invasive manner. A glycoprotein (dubbed Liv1) was identified as a potential diagnostic biomarker in PDAC patient sera compared to patients with chronic pancreatitis (CP), a finding that was subsequently validated in an independent cohort of samples. As a benign inflammatory disease of the pancreas, pancreatitis commonly presents concurrently with PDAC making biomarkers that can distinguish the two a rarity. In attempting to identify the cause of increased circulating Liv1 in PDAC, in situ hybridisation performed on PDAC and CP tissue specimens identified tumour cells as a source of Liv1, producing and secreting the protein into the surrounding stroma. Tissue microarray (TMA) analysis revealed stromal Liv1 was more common in PDAC patients than in CP, consistent with the pattern in sera. However, when available serum samples were matched to the tissue no direct relationship was found. Biomarker discovery work performed by other members of our group identified serum thrombospondin-1 (TSP-1) as a promising candidate biomarker for early diagnosis, decreased in sera collected up to 24 months prior to PDAC diagnosis. This observation was validated using multiple reaction monitoring, a relatively novel mass spectrometry-based method. Presented here are immunoassay results confirming the MRM data, along with serum analysis collected from a genetically engineered mouse model for PDAC suggesting that decreased TSP-1 levels may occur when PDAC is fully developed rather than at a preneoplastic stage. Finally, in light of the lack of correlation between circulating and stromal Liv1, the possibility was considered that TMAs may not be sufficient for quantifying stromal expression in PDAC. A TMA was tested as a means of quantifying components of the PDAC stroma, and revealed that prognostic analyses yielded variable results depending on what depth of the TMA was analysed. This suggests that caution should be taken when applying this technique to such a heterogeneous disease.

Item Type:	Thesis (Doctor of Philosophy)
Divisions:	Fac of Health & Life Sciences > The School of Tropical Medicine
Depositing User:	Symplectic Admin
Date Deposited:	06 Sep 2016 10:09
Last Modified:	01 Aug 2017 01:30
URI:	http://livrepository.liverpool.ac.uk/id/eprint/2048899

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