AbstractProstate cancer is the second most common cancer in males worldwide and the fifth most common cause of cancer death among men. Identifying drugs which prevent prostate cancer initiation and development is a major goal in the field of cancer research, with a large focus on repositioning established medicines to reduce the time and cost of drug development and decrease adverse side effects in patients. Epidemiological and in vitro studies suggest that aspirin (NSAID) and metformin (first-line agent in type II diabetes) are negatively associated with prostate cancer risk and mortality although considering their overlapping function, it is perhaps surprising that little is known about using these drugs in combination for the prevention or treatment of prostate cancer.
The aim of this PhD thesis was to assesses the effect of aspirin and metformin on prostate cell proliferation and migration to determine whether the drugs in combination have the potential to reduce tumour growth and prevent the formation of secondary cancer sites. Four prostate cell lines: prostate epithelial cells, PNT2 and three cancer cell lines; PC3, DU145 and LNCaP were treated with therapeutic concentrations of aspirin (up to 2 mM) and metformin (up to 30 µM). Cell counting, tritiated thymidine incorporation assays and western blotting measured changes in cell growth and markers of proliferation, while annexin V and Q-VD-OPh assays measured apoptosis. In addition, PC3 cells were grown as 3D spheroids to observe the effect of the drugs in a model which better represents the cell to cell interactions and surrounding environment seen in vivo. Wound healing assays were used to examine drug induced changes in cell migration and western blotting and qPCR assessed associated changes in key signalling molecules.
The results show that aspirin alone was highly effective at inhibiting 2D culture cell proliferation and inducing cell death in the androgen dependent, p53 positive LNCaP cell line while therapeutic concentrations of metformin had no effect on either of these outputs. In the more advanced androgen independent, p53 negative, PTEN negative PC3 cell line treatment with aspirin alone decreased cell proliferation while cells were unresponsive to metformin. Together the drugs additively inhibited cell proliferation in 2D culture and importantly the combination decreased spheroid growth in 3D cell culture more than when dosed with each drug individually. With the non-tumorigenic PNT2s, neither metformin nor aspirin significantly affected cell proliferation or apoptosis, highlighting the possibility that the drugs more readily target cancer cells as reported in other studies. Both aspirin and metformin reduced the migratory capacity of the highly invasive PC3 cells, promoting a more epithelial phenotype as seen with an increase in E-cadherin and a decrease in N-cadherin, Slug and MMP-9. This effect was enhanced when the drugs were used in combination although it was not additive.
In conclusion, the data presented in this thesis supports the use of aspirin and metformin in combination to reduce prostate cancer proliferation and cell migration in a subset of cancers. As aspirin and metformin appear to target two distinct cancer hallmarks they have a greater chance of efficacy in heterogenous tumours, creating a strong therapeutic argument for this drug combination.
|Date of Award||19 Mar 2019|
|Supervisor||Claire M Perks (Supervisor), Ann C Williams (Supervisor), Jeff M. P. Holly (Supervisor) & Richard M Martin (Supervisor)|