Identification of potential mechanisms of action of 3ʹ,4ʹ,5ʹ-trimethoxyflavonol in the inhibition of prostate cancer

3ʹ,4ʹ,5ʹ-Trimethoxyflavonol (TMFol), a synthetic analogue of the naturally occurring flavonols quercetin and fisetin, has demonstrated putative anti-cancer activity in the prostate. The mechanisms of action that are engaged are largely unknown. Therefore, the work presented in this thesis investigated the mechanisms used by TMFol to compromise cell proliferation in prostate cell lines 22Rv1, PC-3 and PNT2. Furthermore, it investigated the effect of TMFol on prostate cancer development and progression in two separate transgenic models, PBCre4p53floxRbflox and PBCre4Ptenflox mice. Apoptosis and cell cycle distribution were analysed by flow cytometry, while biochemical assays, Western blots, histological evaluations or qPCR were used to analyse senescence, changes in prostate metabolism and the effect of TMFol on mice. TMFol inhibited cell proliferation in vitro without inducing apoptosis. However the reduction in tumour growth in 22Rv1 xenografts, that were fed a 0.2 % TMFol diet, was associated with a significant increase in cleaved caspase-3 staining, an indicator of apoptosis. There was S phase arrest in the PC-3 and PNT2 cells, while there was an increase in senescence-associated β-galactosidase activity in both 22Rv1 and PC-3 cells. TMFol also caused a significant increase in the protein expression of p21 and p53 in 22Rv1 cells. TMFol significantly inhibited the expression of acetyl-CoA carboxylase at the protein and mRNA levels and the expression and activity of mitochondrial aconitase, which could result in the inhibition of fatty acid synthesis and citrate oxidation, respectively. PBCre4p53floxRbflox and PBCre4Ptenflox mice fed a 0.2 % TMFol diet did not display any evidence of tumours in the prostate, but there was no significant difference in the PIN development between the mice on the control diet and those on the TMFol diet. Taken together, TMFol has the potential to induce cell cycle arrest, apoptosis and senescence and to inhibit fatty acid synthesis and citrate oxidation in prostate cancer cells.