DOI

https://doi.org/10.25772/4N20-2A18

Defense Date

2021

Document Type

Thesis

Degree Name

Master of Science

Department

Biology

First Advisor

Santiago Lima

Abstract

Sphingolipids play a crucial role in signaling, membrane structure, and migration, making them important molecules in cancer development, metastasis, and drug resistance. While some sphingolipids have been associated with pro-apoptotic or pro-survival behaviors, the role of many sphingolipids in cancer remains poorly defined. Chapter 1 of this study investigated the impact of three enzymes that compose most of the ceramide to Lc3 ceramide pathway – UGCG, GBA, and B3GNT5 – and how their alteration impacts chemoresistance and basal membrane invasion in vitro. It was found that the CΒE-induced inhibition of GBA, which converts glucosylceramide to ceramide, has no effects on invasion or on chemotherapeutic resistance to cisplatin or vinorelbine. UGCG, which converts ceramide to glucosylceramide, can be inhibited by eliglustat and PPMP. PPMP treatment at higher concentrations caused decreased viability in lung adenocarcinoma compared to lung squamous carcinoma, and when in combination with vinorelbine, PPMP caused reduced viability in colon adenocarcinoma, a trend not seen in colon carcinoma. Changes in cellular behavior demonstrated in response to PPMP, but not eliglustat, suggest that the response may be attributed to the off-target inhibition of ACS, and not UGCG itself. Interestingly, both PPMP and high concentrations of eliglustat increased levels of transwell invasion in colon adenocarcinoma. CRISPR-Cas9 induced partial knockout of B3GNT5, which is the sole enzyme converting lactosylceramide to Lc3 ceramide, did not affect transwell invasion, but it did result in higher resistance to vinorelbine in combination with PPMP. An acyl-chain analysis of sphingolipid species in the altered cell line found increased C24:1 at all tested species, and increased glucosylceramide and lactosylceramide. Chapter 2 of this study analyzed sphingolipid acyl chain length in normal and tumor head and neck tissue, finding C16, C24:1, and C24 are significantly raised in tumor tissue, with C24:1 Cer and MonoHex significantly increased only in African Americans. Comparison of normal tissues indicated that Caucasians had significantly more C16 LacCer and C24:1 Cer than African Americans, which could be correlated to poorer head and neck cancer prognosis in African Americans. In tumor tissue, C16 SM and C24:1 LacCer were significantly higher in females than males. Together, these two chapters further cancer sphingolipid research by recognizing PPMP and vinorelbine as a potential co-treatment to increased chemotherapeutic cytotoxicity, discovering that reduced B3GNT5 raises GlcCer levels in cervical cancer, and identifying acyl chain lengths that may serve as future markers of cancer diagnosis and prognosis.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

8-17-2021

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