Abstract
Copper-ionophores that elevate intracellular bioavailable copper display significant therapeutic utility against prostate cancer cells in vitro and in TRAMP (Transgenic Adenocarcinoma of Mouse Prostate) mice. However, the pharmacological basis for their anticancer activity remains unclear, despite impending clinical trails. Herein we show that intracellular copper levels in prostate cancer, evaluated in vitro and across disease progression in TRAMP mice, were not correlative with copper-ionophore activity and mirrored the normal levels observed in patient prostatectomy tissues (Gleason Score 7 & 9). TRAMP adenocarcinoma cells harbored markedly elevated oxidative stress and diminished glutathione (GSH)-mediated antioxidant capacity, which together conferred selective sensitivity to prooxidant ionophoric copper. Copper-ionophore treatments [CuII(gtsm), disulfiram & clioquinol] generated toxic levels of reactive oxygen species (ROS) in TRAMP adenocarcinoma cells, but not in normal mouse prostate epithelial cells (PrECs). Our results provide a basis for the pharmacological activity of copper-ionophores and suggest they are amendable for treatment of patients with prostate cancer. Additionally, recent in vitro and mouse xenograft studies have suggested an increased copper requirement by prostate cancer cells. We demonstrated that prostate adenocarcinoma development in TRAMP mice requires a functional supply of copper and is significantly impeded by altered systemic copper distribution. The presence of a mutant copper-transporting Atp7b protein (tx mutation: A4066G/Met1356Val) in TRAMP mice changed copper-integration into serum and caused a remarkable reduction in prostate cancer burden (64% reduction) and disease severity (grade), abrogating adenocarcinoma development. Implications for current clinical trials are discussed.
Highlights
Prostate cancer is a major cause of morbidity and mortality among elderly men worldwide and is rapidly becoming more prevalent as life expectancy increases [1, 2]
Our results provide a basis for the pharmacological activity of copper-ionophores and suggest they are amendable for treatment of patients with prostate cancer
We recently established that prostate cancer cells, both in vitro and in the orthotopic TRAMP mouse model, are remarkably sensitive to a family of lipophilic compounds categorized as copper-ionophores [7,8,9]
Summary
Prostate cancer is a major cause of morbidity and mortality among elderly men worldwide and is rapidly becoming more prevalent as life expectancy increases [1, 2]. Treatment regimes are disease stage-dependent and can include combinations of radical prostatectomy, brachytherapy www.impactjournals.com/oncotarget (implanted radioactive seeds) and androgen deprivation (hormone therapy). These therapies are often not curative and the majority of patients relapse into castration-resistant (hormone-refractory) disease. We recently established that prostate cancer cells, both in vitro and in the orthotopic TRAMP mouse model, are remarkably sensitive to a family of lipophilic compounds categorized as copper-ionophores [7,8,9]. The differential response between normal (healthy) and cancerous cells to select copper-ionophores is the basis for their development against a variety of cancer types, including melanoma and breast cancer [13,14,15]. The pharmacological mechanism responsible for their selective toxicity against cancerous cells remains unclear
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