Recent advances in understanding progression to castration-resistant prostate cancer (CRPC) has led to development of therapeutics that slightly increase overall survival; however, the majority of patients with CRPC succumb to disease within 2-3 years, indicating the need for metrics of precision medicine, and development of additional therapeutics. Here, we propose an ambitious approach to stratify and enhance treatment for metastatic CRPC to improve therapeutic outcomes, based on cell cycle alterations that we recently discovered. The studies described will explore untouched territory with regard to PCa targeted therapy based management, and will provide the first assessment of treatment based on subtyping in this disease context. Moreover, the studies described could provide the first biomarker with which to stratify prostate cancer treatment, and to improve therapy for patients with advanced disease. Our collective findings strongly suggest that alterations in the RB-cyclin D1/CDK4 axis play major roles in disease progression, and molecular investigation of these alterations provide a rational basis for disease stratification and improved management of advanced PCa. This postulate will be challenged in carefully planned specific aim. First, building on 2 funded clinical trials, we will use biopsy material, novel models of disease, and co-clinical trials to challenge the hypothesis that the RB-cyclin D1/CDK4 axis can be developed as biomarkers of response and as metrics for treatment stratification (Aim 1). These studies have the potential for near-term patient benefit, and could identify the first biomarker for personalized medicine in advanced PCa. Second, robust models will be used to interrogate the molecular basis of responsiveness to therapeutic directed toward alterations in RB and/or cyclin D1 status (Aim 2). Studies planned will provide critical information as to specificity and clinical placement of RB and cyclin D1- alteration dependent interventions. Finally, targeting the Rb-cyclin D1/CDK4 axis forces reliance of tumor cells on G2/M cyclin dependent kinases?plans were thereby developed to leverage this cell cycle dependence, with a goal toward discovery of new means to maximize efficacy of treatment for cells with RB-cyclin D1/CDK4 alterations (Aim 3). These collective aims build off the unique collaboration amongst a leader in clinical management of advanced PCa and a pioneer of novel clinical trials (Dr. Kelly), and a leading AR biologist with significant expertise in studying cell cycle regulation and PCa-associated cell cycle alterations (Dr. Knudsen), and an expert in clinical targeting of cell cycle alterations (Dr. O?Dwyer). As proposed, this project has the capacity to illuminate the means by which perturbations Rb-cyclin D1 alterations alter disease progression and therapeutic response in human disease, and to dramatically alter PCa management.

Public Health Relevance

At present, all patients with metastatic PCa are treated identically, without selection for appropriate therapeutic regimens based on tumor profiling. Recent studies from our laboratory and others strongly suggest that G1-S alterations, particularly as associated with RB and cyclin D1, are major effectors of disease progression; conversely, these alterations provide new opportunities for tumor stratification, precision medicine, and development of effective treatment regimens for tumors with these alterations. The proposal described in Project 5 is supported by robust preclinical and clinical data, and put forward the postulate that modeling, clinical analyses, and functional characterization of G1-S alterations in advanced PCa will allow for application of precision medicine, both in the context of targeting cell cycle-associated driver mutations and through induction of synthetic lethality.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Special Emphasis Panel (ZRG1)
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Mckee, Tawnya C
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Thomas Jefferson University
Schools of Medicine
United States
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Thangavel, Chellappagounder; Boopathi, Ettickan; Liu, Yi et al. (2018) Therapeutic Challenge with a CDK 4/6 Inhibitor Induces an RB-Dependent SMAC-Mediated Apoptotic Response in Non-Small Cell Lung Cancer. Clin Cancer Res 24:1402-1414
Shafi, Ayesha A; Schiewer, Matthew J; de Leeuw, Renée et al. (2018) Patient-derived Models Reveal Impact of the Tumor Microenvironment on Therapeutic Response. Eur Urol Oncol 1:325-337
de Leeuw, Renée; McNair, Christopher; Schiewer, Matthew J et al. (2018) MAPK Reliance via Acquired CDK4/6 Inhibitor Resistance in Cancer. Clin Cancer Res 24:4201-4214
McNair, Christopher; Xu, Kexin; Mandigo, Amy C et al. (2018) Differential impact of RB status on E2F1 reprogramming in human cancer. J Clin Invest 128:341-358