Targeting the prostate cancer metabolome with novel trojan horse compounds.

Abstract

Prostate cancer (PCa) is the second most common cancer diagnosed in males worldwide, and the incidence of this disease is predicted to double globally by 2030. In Ireland, PCa accounts for nearly 16% of all invasive cancers diagnosed annually. While approximately 70% of all prostate cancer patients display an initial response to androgen ablation therapy, eventually patients become unresponsive to further anti-androgen therapy. With this, the androgen independent prostate cancer is considered incurable. Cancer cells tend to employ aerobic glycolysis, the ?Warburg effect? to meet their energy demands. Although, much more inefficient in terms of ATP production when compared to Oxidative Phosphorylation (OxPhos) employed by normal cells, this process is quicker and tends to use glucose 100 times faster. Our group in collaboration with University of South Australia has developed a unique `Trojan Horse? chemotherapeutic strategy that exploits the Warburg effect to target the prostate cancer metabolome and multiple aspects of the disease biology. The approach involves generating a series of compounds by complexing Vitamin C and Vitamin K3 with sugars and lipids. A panel of prostate cancer cell lines (LNCAP, PC3, DU154) representing varying stages of disease progression and a non-malignant cell line (PNT-1a) were tested with 10 Trojan Horse (TH) compounds to determine the cytotoxicity of the compounds under 3 physiological glucose conditions. Three TH compounds; two glucose Menadione and one lipid Menadione based demonstrated significant cytotoxic effects. To evaluate the effects of these compounds on the PCa metabolome, the metabolic bioenergetic profiles of the panel of cell lines mentioned above were examined with the seahorse XFe2 Bioanalyzer following treatments with the three TH compounds. Flow cytometry and immunofluorescence-based assays were performed in parallel to determine levels of reactive oxygen species (ROS) and measure changes in mitochondrial membrane potential. LC-MS analysis was also performed to identify metabolites which could map specific metabolic phenotypes displayed by the cell lines. The androgen independent cell lines PC3 and Du145 displayed a greater reliance on glycolysis for ATP production which shifted marginally towards energy production by OxPhos following treatment with TH compounds. LNCAP the androgen dependent cell line was heavily dependent on OxPhos, and no change was observed in its metabolic capacity following treatment with TH compounds. An increase in reactive oxygen species (ROS) levels and alterations in mitochondrial membrane potential (MMP) were observed following TH treatments, but not to the levels expected. The results of the metabolomic analysis were in agreement with the metabolic bioenergetic profiles displayed by the cell lines pre and post TH treatment. LC-MS analysis also identified a significant increase in ROS scavenging amino acids which would account for the lower ROS levels and changes in MMP following TH treatments. The findings highlight the differences in metabolic phenotypes between androgen dependent and independent PCa and indicate a role for metabolic targeting by TH compounds.