Targeting anti-androgen resistance in prostate cancer using preclinical models with physiological nutrient levels
Prostate cancer is driven by upregulated androgen receptor signalling that regulates cellular growth and metabolism. While anti-androgen therapies such as Enzalutamide can be effective against prostate cancer, 60% of patients will develop Enzalutamide resistance which is currently incurable. Since AR signalling regulates metabolism, a hallmark of cancer, we set out to characterise metabolic Enzalutamide resistance mechanisms that could be therapeutically exploited. However, therapeutic development is challenged by the poor clinical translation of anti-cancer therapies. This could be partially due to non-physiological nutrient levels in traditional cell culture media such as RPMI, which could mask therapeutic effects or resistance mechanisms. The culture media Plasmax, formulated with nutrients at physiological levels, was able to maintain the proliferation of prostate cancer cell lines comparably to traditional media in cell viability assays. Despite similar growth rates, proteomics analyses showed that physiological nutrient levels altered the expression of metabolic proteins between prostate cancer cells in RPMI and Plasmax. Metabolomics analyses demonstrated that there were changes to metabolites involved in the TCA cycle, with lower glutamine levels in Plasmax reducing downstream levels of TCA cycle metabolites. We also identified a novel metabolic resistance mechanism whereby aspartate levels were depleted in prostate cancer cells and patient-derived explants cultured with Enzalutamide in physiological media and not traditional media. This may be mediated by androgen-regulated enzymes of aspartate metabolism such as DHODH, ARG1, ASRGL1 and GOT1, which we identified through cistromic and transcriptomic analyses of prostate cancer cell lines and primary patient samples. Interestingly, blocking the uptake of aspartate via the transporter EEAT1 (UCPH-101) in combination with inhibiting DHODH (Leflunomide) to prevent pyrimidine synthesis from aspartate was effective against prostate cancer cells in Plasmax in vitro. While we identified a previously unreported anti-androgen resistance mechanism involving aspartate that could be targeted with a novel combination therapy, 2D cancer models do not represent the complexity of 3D tumours. Future directions include testing this combination therapy with a physiological explant model utilising prostate cancer patient samples and murine xenografts derived from prostate cancer cell lines.
prostate cancer, metabolism, anti-androgen resistance, physiological models, anzsrc-for: 321101 Cancer cell biology
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