Date of Award

2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Cell and Molecular Pharmacology and Experimental Therapeutics

College

College of Graduate Studies

First Advisor

Richard R. Drake

Second Advisor

Anand Mehta

Third Advisor

Elizabeth Yeh

Fourth Advisor

Nancy Demore

Fifth Advisor

Lewis Frey

Abstract

Despite decades of studies documenting the association between aberrant glycosylation and breast cancer formation and progression, these investigations have failed to make a significant impact in the clinic. This highlights the inherent biological and clinical heterogeneity of breast cancers. In this thesis, we utilize MALDI mass spectrometry imaging and other glycoproteomic techniques to classify the N-glycome of clinical FFPE breast cancer samples. By doing this, we were able to identify glycosylation patterns specific to tissue regions, cancer stage and patient outcome. When analyzing tissue specific regions of tumor, stroma and necrosis, we found that the tumor regions contained high mannose and branched glycans, while the necrotic regions expressed glycans with limited branching and sialic acid modifications. After employing further glycoproteomic techniques and immunohistochemistry staining, we identified fibrinogen as the glycoprotein carrier of these necrosis specific glycans. In our next study, we classified the N-glycomes of genetically subtyped breast cancers. By analyzing tumor microarrays of HER2+ and triple negative breast cancers we were able to identify shared and differing glycosylation patterns amongst the two sub-types. Within these tumors we identified a series of high mannose glycans and highly branched fucosylated glycans that correlated with higher grade tumors. Furthermore, we also identified a series of polylactosamine glycans that displayed increased expression in advanced HER2+, triple negative and metastatic breast cancers. We further expanded on this finding by analyzing breast cancers with associated survival data and found that expression of core fucosylated polylactosamine glycan Hex8dHex1HexNAc7 was associated with significantly reduced survival in patients with Stage 1 and 2 breast cancer. Since it is known that poor survival in breast cancer is often caused by primary tumor metastasis, we compared the presence of these polylactosamine glycans in primary tumors that did and did not metastasize. By doing this, we found that expression of polylactosamine glycans significantly correlated with primary tumors that metastasized. This was validated in triple negative breast cancer tumors with known outcomes through lectin histochemistry. In conclusion, this study was the first of its kind to characterize the N-glycome of breast cancer tissues across a broad clinical spectrum, and in the process revealed novel mechanistic insights and identified a biomarker candidate that could eventually be utilized for testing a patient's susceptibility to metastasis.

Rights

All rights reserved. Copyright is held by the author.

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