Resistance to androgen receptor signaling inhibition does not necessitate development of neuroendocrine prostate cancer.

W Nathaniel Brennen,Srinivasan Yegnasubramanian,Lizamma Antony,Angelo M De Marzo,William B Isaacs,Jody E Hooper,Susan L Dalrymple,Peter S Nelson,Radhika A Patel,Alan K Meeker,John T Isaacs,William G Nelson,Jianfeng Xu,Ilsa M Coleman,Yezi Zhu,Roshan Chikarmane,Brian Hanratty,Eva Corey,S Lilly Zheng,Michael C Haffner,Jun Luo

doi:10.1172/jci.insight.146827

Abstract

Resistance to AR signaling inhibitors (ARSis) in a subset of metastatic castration-resistant prostate cancers (mCRPCs) occurs with the emergence of AR– neuroendocrine prostate cancer (NEPC) coupled with mutations/deletions in PTEN, TP53, and RB1 and the overexpression of DNMTs, EZH2, and/or SOX2. To resolve whether the lack of AR is the driving factor for the emergence of the NE phenotype, molecular, cell, and tumor biology analyses were performed on 23 xenografts derived from patients with PC, recapitulating the full spectrum of genetic alterations proposed to drive NE differentiation. Additionally, phenotypic response to CRISPR/Cas9-mediated AR KO in AR+ CRPC cells was evaluated. These analyses document that (a) ARSi-resistant NEPC developed without androgen deprivation treatment; (b) ARS in ARSi-resistant AR+/NE+ double-positive “amphicrine” mCRPCs did not suppress NE differentiation; (c) the lack of AR expression did not necessitate acquiring a NE phenotype, despite concomitant mutations/deletions in PTEN and TP53, and the loss of RB1 but occurred via emergence of an AR–/NE– double-negative PC (DNPC); (d) despite DNPC cells having homogeneous genetic driver mutations, they were phenotypically heterogeneous, expressing basal lineage markers alone or in combination with luminal lineage markers; and (e) AR loss was associated with AR promoter hypermethylation in NEPCs but not in DNPCs.

Highlights

The normal adult human prostate is composed of a simple stratified epithelium, the homeostasis of which is maintained via adult stem/progenitor cell turnover producing a steady-state, self-renewing condition [1]
It has been proposed that AR signaling inhibitors (ARSis) treatment of patients with metastatic castration-resistant prostate cancers (mCRPCs) drives ARPCs into a more aggressive and lethal AR– neuroendocrine prostate cancer (NEPC) phenotype [28, 31,32,33,34]
It has been suggested that such differentiation into NEPC requires the loss of AR signaling (ARS) in combination with mutations in PTEN, RB1, and TP53 together with the overexpression of DNMTs, EZH2, and/or SOX2 [28, 31,32,33,34, 63]

Summary

Introduction

The normal adult human prostate is composed of a simple stratified epithelium, the homeostasis of which is maintained via adult stem/progenitor cell turnover producing a steady-state, self-renewing condition [1]. It is proposed that a rare subset (i.e., 0.59%) of adult prostate basal cells comprises the epithelial stem/progenitor cells, which coexpress the full spectrum of prostate epithelial cell markers (i.e., keratin 5 [KRT5], KRT6A, KRT8, KRT14, KRT18, and KRT19; the transcription factor p63; glutathione-S-transferase π [GSTP1]), but not AR [2, 6] This is supported by the fact that the growth fraction in basal cells based upon Ki67 expression is quite low (i.e., 1.65% ± 0.12% positive), it is 12-fold higher than the growth fraction in luminal cells Consistent with this basal location for the proliferating epithelial stem/progenitor cells is the nuclear expression of c-MYC by AR– cells within this compartment in benign human glands (Figure 1B)

Methods

Results

Conclusion