Mannose utilization under hypoxic conditions in cancer cells

  • Bibi Rehman

Student thesis: Master's Thesis


Carbohydrates serve as the body’s main source of energy through their breakdown in which energy is generated, this is known as glycolysis. Glycolysis is an essential metabolic pathway providing cellular energy for all living organisms. Normal cells as well as cancer cells rely on glycolysis for energy metabolism, however, in cancer cells glycolysis usually occurs in the absence of oxygen i.e., anaerobic glycolysis. Cells in tumour biomass live under hypoxic conditions where blood flow is restricted, thus limiting the supply of oxygen as well as glucose. The core interest is found in whether these cell types can recycle sugars from the surface glycans and whether mannose is being used as an alternative to glucose for carbon feed to promote growth and survival. Glycolysis includes many stages where several enzymes participate. The enzyme taken into consideration in this study is phosphomannose isomerase (PMI) which regulates the flux between catabolism and glycan formation. PMI is also involved in mannose metabolism and its transformation to other products such as mannose-6-phosphate (Man-6P). In this report, the kinetic study of the conversion step between mannose-6-phosphate to fructose-6-phosphate (Fru-6P) was attempted with an unsuccessful outcome. Repeatability was not feasible with the low budget for enzyme and shortage in time. Limitations discovered in methods that have previously been employed encouraged the improvement and revalidation of the method to perform simultaneous measurement of monosaccharides and their phosphoric acid esters. The present study investigated specific monosaccharide levels, glucose, and mannose, in provided cancer cell lines grown under varying conditions using analytical method high performance anion exchange column with high-performance anion-exchange chromatography/pulsed amperometric detection (HPAEC-PAD). Applying the method enabled successful quantification and profiling of mannose and glucose in these cell lines as well as exploring the conversion reaction of mannose-6-phosphate to fructose-6-phosphate to study kinetic parameters. Major findings indicated certain media was found to contain mannose whereas other contained glucose. Necrotic media, which was of major interest, was found to contain 4.45 mM glucose, however, there was no indication of mannose being present. Enzymatic activity was assessed with HPAEC-PAD by profiling mannose-6-phosphate and fructose-6-phosphate. Disruptions caused by COVID-19 and shortage in time lead to a less successful outcome where kinetic parameters could not be studied. Conversely, the conversion reaction was observed showing insufficient activity of the enzyme on mannose-6-phosphate. HPAEC-PAD with the gradient method can be considered for future analysis in such studies as profiling of these compound types i.e., sugar phosphates can be achieved with high-resolution chromatographic results. In contrast with previous research, the study agrees with the phenomenon of cancer cells in hypoxia having access to glucose as a source of nutrients and energy for growth and survival. Nevertheless, the results disagree with the initial hypothesis of cells living in hypoxia being able to recycle mannose for carbon feed. However, due to lack of evidence on this phenomenon, more study is needed to explore this discipline as it remains uncertain.
Date of Award19 Apr 2023
Original languageEnglish
SupervisorGordon Morris (Main Supervisor) & Roger Phillips (Co-Supervisor)

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