Abstracts Category : Other

Improvingbreast cancer therapy through oestrone analogue and glycolysisinhibitor synergism

by Roxette Dianne Anderson

Introduction: In South Africa, breast cancer has thehighest prevalence with a life time risk of 1 in every 9 womenbeing diagnosed annually. There are four sub-types of breast cancerand according to the stage of the cancer, various treatmentregimens are prescribed. A major obstacle is that majority ofcancers have developed multi-drug resistance and new treatmentregimens need to be developed in order to obtain therapeuticefficacy. Cancer cells use aerobic glycolytic metabolism forenergy generation and inhibition of this pathway increasessensitivity of the cells to anti-neoplasic treatments.2-Deoxyglucose (2-DG) competes with and inhibits glucose uptakeinhibiting the glycolytic pathway which can result indepolarisation of the mitochondrial membrane potential releasingcytochrome c. Two 2-Methoxyestradiol (2-ME) derivatives, ESE-15-ol and ESE-16 have shown to be promising anti-cancer agents andcombination therapy could allow the use of these compounds with adecreased side effect profile. The combination of these compoundswith 2-DG was therefore investigated. Aim: To investigatecombinations of two oestrone analogues and the glycolysis inhibitor2- deoxyglucose for potential synergistic effects using a cellenumeration assay, mitochondrial membrane potential and cell cycleanalysis, on breast cancer cells in an in vitro setting. Cellapoptosis, necrosis and autophagy pathways were assessed toindicate the mechanism of cytotoxicity. Methods: The breastcancer MCF-7 and non-tumorigenic MCF-12A cell line were used.Cells were exposed to ESE-15-ol, ESE-16 and 2-DG alone and incombination. Mechanistic studies were performed using the variousresearch methodologies including the sulforhodamine B assay forcell enumeration, Annexin-V FITC and propidium iodide labeling forapoptosis/necrosis studies, PlasDIC and light microscopy formorphological analysis, propidium iodide staining for cell cycleprogression, JC-1 for mitochondrial membrane potential studies,transmission electron microscopy and western blotting for theanalysis of autophagy. Results: A GI50 of 34.1 nM was reported forMCF-7 cells after treatment with ESE-15-ol, 141 nM for ESE-16 and1.3 mM 2-DG. The GI50 of ESE-15-ol treated MCF-12A cells was 141nM, 140.1 nM for ESE-16 treated cells and 1.7 mM for 2-DG. ESE-16had the greatest effect on cell viability in MCF-7 cells and ashift from an inhibitory effect to the initiation of cell deathwas evident after treatment of 100 nM of ESE-15-ol and ESE-16.2-DG had a lower cytotoxic effect than the oestrone analogues. TheMCF-12A cell line was less susceptible to the experimentalcompounds. The combination of the oestrone analogues with 2-DGelicited a greater effect on cell enumeration than each of thecompounds alone with a less pronounced effect on the MCF- 12A cellline in comparison to the MCF-7 cells. The experimental compoundsinitiated apoptosis with ESE-16 eliciting a greater effect thanESE-15-ol. The combination of the oestrone analogues with 2-DGresulted inAdvisors/Committee Members: Cromarty, Allan Duncan (advisor), Joubert, Annie M. (coadvisor), Van Tonder, Alet (coadvisor).