REST reduction is essential for hypoxia-induced neuroendocrine differentiation of prostate cancer cells by activating autophagy signaling

Abstract

Prostate cancer (PCa) with neuroendocrine differentiation (NED) is tightly associated with hormone refractory PCa (HRPC), an aggressive form of cancer that is nearly impossible to treat. Determining the mechanism of the development of NED may yield novel therapeutic strategies for HRPC. Here, we first demonstrate that repressor element-1 silencing transcription factor (REST), a transcriptional repressor of neuronal genes that has been implicated in androgen-deprivation and IL-6 induced NED, is essential for hypoxia-induced NED of PCa cells. Bioinformatics analysis of transcriptome profiles of REST knockdown during hypoxia treatment demonstrated that REST is a master regulator of hypoxia-induced genes. Gene set enrichment analysis (GSEA) of hypoxia and REST knockdown co-upregulated genes revealed their correlation with HRPC. Consistently, gene ontology (GO) analysis showed that REST reduction potential associated with hypoxia-induced tumorigenesis, NE development, and AMPK pathway activation. Emerging reports have revealed that AMPK activation is a potential mechanism for hypoxia-induced autophagy. In line with this, we demonstrate that REST knockdown alone is capable of activating AMPK and autophagy activation is essential for hypoxia-induced NED of PCa cells. Here, making using of in vitro cell-based assay for NED, we reveal a new role for the transcriptional repressor REST in hypoxia-induced NED and characterized a sequential molecular mechanism downstream of REST resulting in AMPK phosphorylation and autophagy activation, which may be a common signaling pathway leading to NED of PCa.

REST is a crucial regulator for acquiring EMT-like and stemness phenotypes in hormone-refractory prostate cancer

“…Several laboratories including ours have demonstrated that REST is a novel regulator of human PCa cell NED910111213. The terminally differentiated NE cells are recognized as a potential cause of CRPC and apparent acquisition of stemness properties in advanced CRPC7.…”

“…NE-like cell development relies on a network of transcriptional reprogramming that controls the acquisition and maintenance of neuronal features. Recent reports including ours provide evidence showing that repressor element-1 (RE-1) silencing transcription factor (REST) expression is significantly reduced in relapsed PCa tissue912 and reduction of REST is responsible for NED of PCa cells910111213. REST was originally identified as a transcription repressor for neuron-specific genes in neuronal progenitor and non-neuronal cells14.…”

“…One recent report provided an explanation for this contradiction by suggesting a passage-dependent response, as REST deficiency impaired pluripotency of ESCs in early passage and restoration of impaired self-renewal upon prolonged culture30. In PCa, REST was found to be a mediator of AR9 and induced NED upon downregulation101112. However, whether a prolonged decrease of REST results in NE-like cells acquiring stemness is largely unknown.…”

MAOA-a novel decision maker of apoptosis and autophagy in hormone refractory neuroendocrine prostate cancer cells

“…Our recent reports show that knockdown of REST may induce NED through activation of autophagy1114, a pathway that eukaryotic cells use to degrade long-lived proteins and organelles in response to stress17. However, little is known about the underlying mechanisms for REST-mediated autophagy activation.…”

Histone demethylase PHF8 regulates hypoxia signaling through HIF1α and H3K4me3

“…Prostate cancer cells subjected to hypoxia for 3 or 7 days exhibit features of NED including neurite lengthening and the upregulation of neuronal markers such as ENO2, β-Tubulin III, CgA and ASH-1 [32–34]. We recently reproduced the hypoxic (1% O 2 for 6 days) induction of ENO2 and CgA in LNCaP cells, but we saw only partial neurite lengthening [17].…”