Introduction: Metabolic approaches to identifying tumor susceptibilities leads to improved eradication. Androgen deprivation therapy (ADT) is a primary approach to advanced hormone sensitive (HS) prostate cancer (PC), and recent data suggests it induces unique sensitivities to adjuvant therapy. Cell oxidation-reduction (redox) is a measure of metabolism and is often altered in malignancy due to changing metabolic demands. We sought to determine the sensitivity of PC cells following ADT to inhibition of key bio-energetic pathways via a concerted metabolic approach.
Methods: HSPC cells were treated with androgen deficient media for 4 and 8 days and compared to respective controls. Western blot analysis was performed for key regulatory enzymes and transporters in fatty acid (FA) and glutamine (Gln) metabolism. Intra-cellular Gln/glutamate was quantified using Mass Spectrometry and metabolite detection assays (Promega). Seahorse Mito Fuel Flex assay determined contributions of individual pathways to basal mitochondrial fuel oxidation. To assess the importance of individual pathways in ADT cells compared to control, 8 inhibitors were individually applied, followed by Optical Metabolite Imaging (OMI) to calculate changes in the redox ratio.
Results: ADT treated cells showed increased expression of Gln transporters ASCT1 (p=0.04) and ASCT2 (p=0.001) at 4 days. Intra-cell Gln was also found to be significantly elevated in ADT treated cells (p=0.02). Paradoxically, ADT treatment was found to significantly decrease multiple key regulators in fatty acid metabolism. In ADT versus control, Seahorse analysis revealed a significantly depressed rate of mitochondrial oxidation, a reduced dependency on glucose (p=<0.001) and increased capacity to utilize Gln (p=<0.001) and FA (p=0.004). OMI following inhibition of glycolysis, glutaminolysis, and FA oxidation showed significant changes in the redox ratio in control cells, but not in those treated with ADT (Figure).
Conclusions: ADT-treated cells display an overall depression of mitochondrial oxidation with an increased capacity for Gln and FA utilization. Single pathway inhibition minimally alters cellular redox ratio indicating remarkable energy adaptability in ADT-treated PC cells. This unique metabolic profile presents a challenge for therapeutic targeting. Source of
Funding: Urology Care Foundation/ AUA Research Scholar Program (T.K.), DOD PCRP PC 150221.