Stromal epigenetic alterations drive metabolic and neuroendocrine prostate cancer reprogramming
Rajeev Mishra, … , Edwin M. Posadas, Neil A. Bhowmick
Rajeev Mishra, … , Edwin M. Posadas, Neil A. Bhowmick
Published July 26, 2018
Citation Information: J Clin Invest. 2018;128(10):4472-4484. https://doi.org/10.1172/JCI99397.
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Research Article Cell biology Metabolism

Stromal epigenetic alterations drive metabolic and neuroendocrine prostate cancer reprogramming

Abstract

Prostate cancer is an androgen-dependent disease subject to interactions between the tumor epithelium and its microenvironment. Here, we found that epigenetic changes in prostatic cancer-associated fibroblasts (CAF) initiated a cascade of stromal-epithelial interactions. This facilitated lethal prostate cancer growth and development of resistance to androgen signaling deprivation therapy (ADT). We identified a Ras inhibitor, RASAL3, as epigenetically silenced in human prostatic CAF, leading to oncogenic Ras activity driving macropinocytosis-mediated glutamine synthesis. Interestingly, ADT further promoted RASAL3 epigenetic silencing and glutamine secretion by prostatic fibroblasts. In an orthotopic xenograft model, subsequent inhibition of macropinocytosis and glutamine transport resulted in antitumor effects. Stromal glutamine served as a source of energy through anaplerosis and as a mediator of neuroendocrine differentiation for prostate adenocarcinoma. Antagonizing the uptake of glutamine restored sensitivity to ADT in a castration-resistant xenograft model. In validating these findings, we found that prostate cancer patients on ADT with therapeutic resistance had elevated blood glutamine levels compared with those with therapeutically responsive disease (odds ratio = 7.451, P = 0.02). Identification of epigenetic regulation of Ras activity in prostatic CAF revealed RASAL3 as a sensor for metabolic and neuroendocrine reprogramming in prostate cancer patients failing ADT.

Authors

Rajeev Mishra, Subhash Haldar, Veronica Placencio, Anisha Madhav, Krizia Rohena-Rivera, Priyanka Agarwal, Frank Duong, Bryan Angara, Manisha Tripathi, Zhenqiu Liu, Roberta A. Gottlieb, Shawn Wagner, Edwin M. Posadas, Neil A. Bhowmick

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Figure 1

Epigenetic downregulation of RASAL3 in prostatic CAF.

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Epigenetic downregulation of RASAL3 in prostatic CAF. (A) Heatmap summar...
(A) Heatmap summarizing DNA methylation levels of CpG repeats (blue color indicates hypomethylation, and brown represents hypermethylation). Top 20 methylated genes significantly differentially expressed between NAF and CAF. Each column represents a fibroblast sample, and each row represents the methylation level of indicated gene (n = 5). (B) Top: University of California at Santa Cruz Genome Browser screen shot of the indicated region of chromosome 19 showing the positions of the RASAL3 gene, histone 3 lysine 27 acetylation, and human mRNA. Bottom: locations of predicted CpG sites in exon 2 by bisulfite sequencing, represented as black (methylated) or white circle (unmethylated, n = 5). The number of methylated CpGs divided by the total number of true CpGs analyzed is given as a percentage on the pie chart. (C) Box plots representing the difference in methylation states of the RASAL3 gene promoter between NAF and CAF as measured by RRBS analysis (n = 5). (D) RASAL3 mRNA expression in a panel of primary fibroblast was examined by quantitative RT-PCR, normalizing to GAPDH mRNA expression. rel. mRNA expr., relative mRNA expression. (E and F) Box plots show relative gene expression level (log2) of the RASAL3 in normal and PCa patients from indicated data sets. Data represent mean ± SD. *P < 0.05, 2-tailed Student’s t test.