Androgen Receptor Signaling in Castration-Resistant Prostate Cancer Alters Hyperpolarized Pyruvate to Lactate Conversion and Lactate Levels In Vivo

Purpose: Androgen receptor (AR) signaling affects prostate cancer (PCa) growth, metabolism, and progression. Often, PCa progresses from androgen-sensitive to castration-resistant prostate cancer (CRPC) following androgen-deprivation therapy. Clinicopathologic and genomic characterizations of CRPC tumors lead to subdividing CRPC into two subtypes: (1) AR-dependent CRPC containing dysregulation of AR signaling alterations in AR such as amplification, point mutations, and/or generation of splice variants in the AR gene; and (2) an aggressive variant PCa (AVPC) subtype that is phenotypically similar to small cell prostate cancer and is defined by chemotherapy sensitivity, gain of neuroendocrine or pro-neural marker expression, loss of AR expression, and combined alterations of PTEN, TP53, and RB1 tumor suppressors. Previously, we reported patient-derived xenograft (PDX) animal models that contain characteristics of these CRPC subtypes. In this study, we have employed the PDX models to test metabolic alterations in the CRPC subtypes. Procedures: Mass spectrometry and nuclear magnetic resonance analysis along with in vivo hyperpolarized 1-[ ¹³ C]pyruvate spectroscopy experiments were performed on prostate PDX animal models. Results: Using hyperpolarized 1-[ ¹³ C]pyruvate conversion to 1-[ ¹³ C]lactate in vivo as well as lactate measurements ex vivo, we have found increased lactate production in AR-dependent CRPC PDX models even under low-hormone levels (castrated mouse) compared to AR-negative AVPC PDX models. Conclusions: Our analysis underscores the potential of hyperpolarized metabolic imaging in determining the underlying biology and in vivo phenotyping of CRPC.