Identification Pklr Metabolic Pathways and Therapeutic Roles in Promoting Neuroendocrine Differentiation of Prostate Cancer

Neuroendocrine differentiation (NED) occurs in treatment-refractory prostate cancers, and is typically associated with the loss of androgen receptor (AR) signaling, acquirement of lineage plasticity, and metastatic features. There is no conventional therapeutic approach for advanced prostate cancer patients with NE-like pathologic features thus far, because of the unknown molecular target distinct subset of patients. We propose to investigate the mechanisms underlying resistance to androgen-deprivation therapy (ADT) that contributes to the development of neuroendocrine prostate cancer (NEPC), and explore novel biomarkers and pivotal treatments responsible for advanced prostate cancer patients. Cancer cells frequently upregulate genes encode glycolytic enzymes and pyruvate kinases, which leads to glucose uptake and an altered metabolism. Although we understand that cancer may be a metabolic disease, little is known about metabolic pathways as treatment strategies in advanced prostate cancer patients. In this proposed study, we will investigate the role of a pyruvate kinase isoform, pyruvate kinase liver and red blood cell (PKLR), in ADT-resistance prostate cancer, and we will establish a causal link between the tumor-promoting effects of PKLR and NED in post ADT. Our preliminary results showed that loss of an androgen-responsive transcription factor, zinc finger and BTB domain containing 10 (ZBTB10), may associate with PKLR upregulation and NED. We also found that the upregulation of PKLR was possibly involved in promoting glucose uptake and malignant progression in prostate cancer cells following ADT. Interestingly, a G-protein-coupled receptor (GPCR), cholinergic receptor muscarinic 4 (CHRM4), might be a downstream target of PKLR. Since the activation of muscarinic receptors was reported to contribute to the progression of small-cell lung cancers, the role of CHRM4 in prostate cancer remains unknown. We will further explore the clinical relevance of how PKLR-mediated CHRM4 activation enhances prostate cancer cells to undergo mitochondrial abnormalities and NED. Activated AKT-MYCN has been reported to crosstalk with stimulated muscarinic receptor signaling, and we found that the activated AKT-MYCN associates with CHRM4, and contributes to PKLR-driven glycolysis and NED. Our study will provide a molecular basis underlying ZBTB10 loss-of-function and PKLR gain-of-function which upregulates CHRM4-AKT-MYCN signaling leading to glycolysis disorder and lineage plasticity of ADT-resistant prostate cancer. We will further study whether CHRM4 can be used as a biomarker to be exploited as a strategy for the treatment of advanced prostate cancer patients by combinatorial PKLR- and CHRM4-targeted therapeutics. Therefore, this proposed investigation will be conducted in a period of five-years as follows: Specific Aim 1: To investigate the mechanisms by which ADT enhances the oncogenic role of PKLR and promotes NE differentiation. Specific Aim 2: To understand the clinical relevance of how ADT activated PKLR is involved in therapeutic resistance and mitochondrial abnormalities of prostate cancer. Specific Aim 3: To define whether the loss of ZBTB10 is essential for PKLR induction, which leads to malignant progression and metabolic aberrations of prostate cancer. Specific Aim 4: To determine the role of CHRM4 as a potential prognostic marker of NEPC that links to PKLR activation, and explore the significant improvement of outcomes by combinatorial PKLR- and CHRM4-targeted therapeutics.