Abstract
Despite encouraging clinical results with next generation drugs (MDV3100 and abiraterone) that inhibit androgen receptor (AR) signaling in patients with castration-resistant prostate cancer (CRPC), responses are variable and short-lived. There is an urgent need to understand the basis of resistance to optimize their future use. We reasoned that a radiopharmaceutical that measures intratumoral changes in AR signaling could substantially improve our understanding of AR pathway directed therapies. Expanding on previous observations, we first show that prostate-specific membrane antigen (PSMA) is repressed by androgen treatment in multiple models of AR-positive prostate cancer in an AR-dependent manner. Conversely, antiandrogens up-regulate PSMA expression. These expression changes, including increased PSMA expression in response to treatment with the antiandrogen MDV3100, can be quantitatively measured in vivo in human prostate cancer xenograft models through PET imaging with a fully humanized, radiolabeled antibody to PSMA, (64)Cu-J591. Collectively, these results establish that relative changes in PSMA expression levels can be quantitatively measured using a human-ready imaging reagent and could serve as a biomarker of AR signaling to noninvasively evaluate AR activity in patients with CRPC.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Androgen Antagonists / pharmacology
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Androgens / pharmacology
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Animals
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Antibodies, Monoclonal / chemistry
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Antibodies, Monoclonal / immunology
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Antibodies, Monoclonal / pharmacokinetics
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Antigens, Surface / genetics*
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Antigens, Surface / immunology
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Antigens, Surface / metabolism
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Benzamides
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Cell Line, Tumor
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Copper Radioisotopes / pharmacokinetics
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Dihydrotestosterone / pharmacology
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Gene Expression Regulation, Neoplastic / drug effects
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Glutamate Carboxypeptidase II / genetics*
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Glutamate Carboxypeptidase II / immunology
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Glutamate Carboxypeptidase II / metabolism
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Heterocyclic Compounds, 1-Ring / chemistry
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Humans
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Immunoblotting
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Male
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Mice
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Mice, SCID
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Neoplasms, Experimental / genetics
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Neoplasms, Experimental / metabolism
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Neoplasms, Experimental / pathology
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Nitriles
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Orchiectomy
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Phenylthiohydantoin / analogs & derivatives
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Phenylthiohydantoin / pharmacology
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Positron-Emission Tomography / methods*
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Prostate-Specific Antigen / genetics
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Prostate-Specific Antigen / metabolism
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Prostatic Neoplasms / genetics*
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Prostatic Neoplasms / metabolism
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Prostatic Neoplasms / pathology
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Radiopharmaceuticals / immunology
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Radiopharmaceuticals / pharmacokinetics
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Receptors, Androgen / genetics*
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Receptors, Androgen / metabolism
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Reverse Transcriptase Polymerase Chain Reaction
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Signal Transduction / drug effects
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Signal Transduction / genetics*
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Transplantation, Heterologous
Substances
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Androgen Antagonists
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Androgens
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Antibodies, Monoclonal
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Antigens, Surface
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Benzamides
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Copper Radioisotopes
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Heterocyclic Compounds, 1-Ring
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J591 monoclonal antibody
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Nitriles
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Radiopharmaceuticals
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Receptors, Androgen
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Dihydrotestosterone
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1,4,7,10-tetraazacyclododecane- 1,4,7,10-tetraacetic acid
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Phenylthiohydantoin
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enzalutamide
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FOLH1 protein, human
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Glutamate Carboxypeptidase II
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Prostate-Specific Antigen