Prostate cancer is the most diagnosed cancer in Australian men. Although there are effective treatments for early-stage localised prostate cancer, 1/3 of patients will progress to an incurable form of the disease known as metastatic castration-resistant prostate cancer (mCRPC). Treatment options for men with mCRPC are very limited and predicted patient survival is <2 years. Enzalutamide (ENZ) is an androgen receptor signalling inhibitor that is used clinically to treat patients with mCRPC. However, most patients develop resistance to ENZ within 8-12 months. It is well understood that prostate tumours are highly lipogenic (rely on lipids), yet it is not fully understood how changes in lipid metabolism, or other metabolic pathways, contribute to acquired ENZ resistance.
To uncover the role of rewired metabolism in the development of ENZ resistance, we performed untargeted proteomics, untargeted lipidomics and targeted and untargeted metabolomics in two prostate cancer cell lines: C4-2B cells that are sensitive to ENZ and MR49F cells that are resistant to ENZ. Using tandem mass spectrometry (LC-MS/MS) we detected >7,500 proteins across both cell lines, with 1,405 proteins that were significantly upregulated and 1,166 proteins that were significantly downregulated in ENZ-resistant cells compared with ENZ-sensitive cells. Lipidomic and metabolomic analyses detected >700 unique lipid species and metabolites in both cell lines.
Our multi-omics analyses revealed that several metabolic processes are reprogrammed in ENZ-resistant prostate cancer cells compared with ENZ-sensitive cells. Various mitochondrial antioxidant pathways were altered in ENZ-resistant cells, including polyunsaturated fatty acid synthesis, glutathione transport into mitochondria, iron metabolism and toxic aldehyde detoxification. ENZ-resistant cells were more resistant to inducers of lipid peroxidation and ferroptosis in comparison with ENZ-sensitive cells, suggesting that activation of mitochondrial antioxidant pathways may be a protective adaptation that drives ENZ resistance. Independently, enzymes and metabolites within the urea cycle were upregulated in ENZ-resistant cells, suggesting that increased ammonia detoxification through this pathway may be an important resistance mechanism against ENZ.
In conclusion, multi-omics comparison of ENZ-sensitive and ENZ-resistant mCRPC cell lines identified potential metabolic dependencies that could be exploited to overcome ENZ resistance in patients with mCRPC.