An investigation of the effects of repurposed drugs on human neuroblastoma and glioblastoma cell lines

Abstract

Neuroblastoma is an aggressive and highly metastatic extracranial tumour of the sympathetic nervous system commonly seen in children, whereas, glioblastoma multiforme is an aggressive and highly proliferative intracranial tumour of the central nervous system seen more in adults. The cellular heterogeneity and molecular pathogenesis of both of these tumours have limited the development of successful treatments. The combined effects of the lipid-lowering drug, bezafibrate (BEZ) and the contraceptive drug, medroxyprogesterone acetate (MPA) (combined as BaP) has shown promising anti-cancer effects on blood cancers like myeloid leukaemia, Burkitt’s lymphoma and chronic lymphoid leukaemia, and osteosarcoma, with elevated levels of reactive oxygen species and down-regulation of lipogenic enzymes implicated in the mechanisms of action for these drug treatments. The aim of this study was to determine the effects of these combined drugs on neuronal cancers, using the SH-SY5Y neuroblastoma and U-87MG glioblastoma cell lines as model systems. BEZ treatment alone was shown to have a significant and BEZ concentration-dependent inhibitory effect on SH-SY5Y and U-87MG viable cell proliferation, whereas MPA treatment alone was shown to have very little effect on the cells. The combination of the drugs was shown to have a significant and drug concentration-dependent inhibitory effect on SH-SY5Y and U-87MG viable cell proliferation to a greater extent than BEZ treatment alone. These anti-cancerous effects were associated with increased cell death, and elevated levels of reactive oxygen species (ROS) in both cell lines after 24 hours of treatment. Levels of the lipogenic enzymes, stearoyl CoA desaturase-1 and fatty acid synthase were seen to be significantly lower in SH-SY5Y and U-87MG cells than in blood cancer cell lines. Further, oleic acid supplementation rescued SH-SY5Y neuroblastoma cells, but in serum not serum free conditions only. Oleic acid supplementation of U-87MG cells did not rescue their susceptibility to BaP treatment. Inclusion of valproic acid combined with BaP (termed VBaP) enhanced the effects of BaP treatment on SH-SY5Y and U-87MG cells, as well as U266 multiple myeloma cells. This is important, as higher concentrations of BEZ are nephrotoxic. The effects of VBaP on U-87MG cells also were explored in a 3D alginate culture system to mimic the microenvironment of the brain. In this situation, VBaP treatment still inhibited U-87MG cell growth and also was effective at inhibited established tumour spheroids. Hence, this thesis has examined whether drug repurposed drug treatments that have been established in blood cancers may also have application in neuronal cancers, and demonstrated that this is possible.