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Title: Towards a small molecule inhibitor of Lactate Dehydrogenase-A
Author: Lomas, Andrew Philip
ISNI:       0000 0004 2728 113X
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2011
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Lactate Dehydrogenase-A (LDH-A) is up-regulated in a broad array of cancers and is associated with poor prognosis. Involved in the hypoxic response, LDH-A is a HIF-1 target and is responsible for the enzymatic reduction of pyruvate to lactate. This is important for several reasons, chiefly (1) the regeneration of NAD+ which feeds back into earlier glycolytic stages and (2) the depletion of intracellular pyruvate concentrations. High intracellular pyruvate is known to inhibit HDACs and is associated with increased apoptosis. LDH-A is also known to be controlled by oncogenes such as c-Myc suggesting an oncogenic role. Studies have shown that the knock-out of LDH-A reduces proliferation and tumourgenicity, and stimulates the mitochondria. This thesis therefore had three aims: firstly, to validate LDH-A inhibition and elucidate its full nature in terms of the implications for tumour survival; secondly, to ascertain the role of LDH-B in order to determine whether selectivity towards LDH-A would be a necessary feature of any small molecule; lastly, to recapitulate siRNA mediated LDH-A inhibition with small molecule inhibitors that had the potential for clinical application. The thesis examined both clinical data and a broad panel of cultured cancer cell types in order to select appropriate model in which to validate siRNA mediated inhibition of LDH-A and LDH-B. After it was demonstrated that LDH-A inhibition reduced the growth of cultured cells, a range of techniques were used to quantify this reduced growth in terms of cell death and changes in metabolism. Further to this, literature studies had proposed a role for LDH-B in maintaining lactate fuelled tumour growth; however, this thesis shows that in the cell lines studied, lactate-fuelled tumour growth was an LDH-A dependent phenomenon. Finally, a high throughput assay system was designed and validated and a library of small molecules was selected, synthesized, and screened in order to identify selective inhibitors of LDH-A.
Supervisor: Harris, Adrian L. ; Russell, Angela J. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Chemistry ; Medicinal Chemistry ; Pharmacology ; Oncology ; Chemical Biology ; breast cancer ; tumour metabolism ; Warburg effect ; synthesis ; rational drug design