Project 3: Analysis of intrinsic and extrinsic factors that promote prostate neuroendocrine differentiation

Project Summary/Abstract The clinical use of potent anti-androgens has promoted the emergence of novel forms of castration- resistant prostate cancer (CRPC), including neuroendocrine prostate cancer (NEPC), which is highly aggressive and lethal. To date, relatively little is known about the regulatory programs for specification of rare neuroendocrine cells in the normal prostate, or how they might be recapitulated or altered during neuroendocrine differentiation in prostate cancer. Therefore, we will pursue a comparative analysis of neuroendocrine specification in the normal and transformed prostate to elucidate similarities and differences in their regulatory programs. In preliminary studies of prostate organogenesis, our findings suggest that prostate neuroendocrine cells are generated at pre-pubertal stages of organogenesis, when androgen levels are low, and that the transcription factor Ascl1 is essential for formation of prostate neuroendocrine cells. To complement these analyses, we have also performed studies of neuroendocrine differentiation in prostate tumors through single- cell RNA-sequencing of mouse CRPC tumors and organoid models to identify candidate non-cell autonomous interactions that may regulate neuroendocrine differentiation, as well as computational analyses to identify novel candidate master regulators of neuroendocrine differentiation in tumors. Importantly, we have obtained evidence for a non-cell autonomous role for extrinsic signals from the microenvironment in promoting neuroendocrine differentiation of prostate tumor cells. Based on our preliminary data, we hypothesize that neuroendocrine differentiation in both normal and tumor contexts is governed by extrinsic signals from the environment in response to low AR activity in order to regulate intrinsic pathways of neuroendocrine specification. To investigate this hypothesis, we will pursue an innovative combination of in vivo, ex vivo, molecular, and computational analyses that are organized in three synergistic specific aims: (1) Investigation of Ascl1 in prostate development and cancer to pursue comparative analyses of its role in normal and tumor contexts; (2) Investigation of intrinsic regulators of neuroendocrine differentiation in prostate cancer using computational systems approaches to identify candidate master regulators followed by their functional validation; and (3) Analysis of stromal signals that promote neuroendocrine differentiation in response to androgen deprivation to evaluate the role of candidate signaling factors from the microenvironment in modulating neuroendocrine differentiation in response to AR in organogenesis and prostate cancer. These studies will have strong translational impact through the identification of molecular targets that are specific for neuroendocrine prostate cancer. Furthermore, this project will be highly integrated with the other components of this program project through collaborative interactions with the Sawyers lab in analyzing microenvironmental signals, with the Abate-Shen lab in studies of mouse models, with Core A in analysis of human tissue samples, and Core B for statistical support and data management,