PhD defence

Glyco(proteo)mic Workflows for Cancer Biomarker Discovery

• A.B. Moran

Date

Wednesday 1 November 2023

Time

11:15 - 12:00

Location

Academy Building
Rapenburg 73
2311 GJ Leiden

Supervisor(s)

• Prof.dr. M. Wuhrer
• dr. G. Lageveen-Kammeijer (Groningen)

Summary

In prostate (PCa) and colorectal (CRC) cancer, there is a need to improve patient stratification techniques that aid diagnostic and prognostic decision-making. To fulfill this unmet clinical need, the measurement of disease-related biological parameters known as “biomarkers” from biofluids is an approach with the potential to develop non-invasive tests as well as achieve greater clinical accuracy and personalized medicine. Thus, the aim of this thesis was to develop a better understanding of biomarkers relevant to PCa and CRC as well as advancing analytical methodology and achieving methodological advancements for the purpose of biomarker discovery.
In part one of this thesis (Chapters 2 and 3), the intact proteoform profile of both urinary and seminal prostate-specific antigen (PSA) was explored using capillary electrophoresis-electrospray ionization-mass spectrometry (CE-ESI-MS). Chapter 2 focused on the development of the CE-ESI-MS method in order to explore urinary PSA proteoforms. In this sense, new insights were gained regarding cleaved and glycosylated PSA proteoforms. Additionally, Chapter 3 addressed some of the challenges associated with the data processing of intact proteoforms, namely semi-automatic proteoform annotation and quantification, thereby enhancing the throughput and accuracy of the workflow. Overall, the method is now poised for the analysis of a larger number of patient samples and our results may inform future studies regarding this protein’s proteofoms as well as any related clinical implications thereof.
In part two (Chapters 4 and 5), the potential of serum N-glycosylation as a biomarker for CRC was investigated. In Chapter 4, fluorescent labeling of total plasma released N-glycans via procainamide was combined with sialic acid-specific derivatization via ethyl esterification and amidation. This allowed the retention of all N-glycan species by reversed phase-liquid chromatography (RPLC)-MS and, in particular, α2,3- and α2,6-sialylated N-glycans were differentiated based upon retention time, precursor mass, and fragmentation spectra, and additional sialylated isomers were resolved. Chapter 5 demonstrated the application of the developed method in order to analyze serum N-glycosylation from pre- and post-operative CRC. In this chapter, previous findings with regard to specific glycosylation patterns in CRC were corroborated. It was also illustrated that pre-operative abundances of serum N-glycans may differentiate adenocarcinoma from other histological types and, in particular, differences between histological types were eradicated following surgery. Thus, these results promote the use of serum N-glycosylation signatures in order to monitor patient profiles in response to clinical interventions such as surgery.

PhD dissertations

Approximately one week after the defence, PhD dissertations by Leiden PhD students are available digitally through the Leiden Repository, that offers free access to these PhD dissertations. Please note that in some cases a dissertation may be under embargo temporarily and access to its full-text version will only be granted later.

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