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Nuclear mTOR acts as a transcriptional integrator of the androgen signaling pathway in prostate cancer progression [ChIP-seq]

ABSTRACT: Whether the nuclear fraction of mTOR plays a role in prostate cancer (PCa) and can participate in direct transcriptional crosstalk with the androgen receptor (AR) is as yet unknown. The intersection of gene expression, DNA binding-events, and metabolic studies uncovered the existence of a nuclear mTOR-AR transcriptional axis dictating the metabolic rewiring and nutrient usage of PCa cells. In human clinical specimens, nuclear localization of mTOR was significantly associated with metastasis and castration-resistant PCa (CRPC), correlating with a sustained metabolic gene program governed by mTOR in that context. This study thus uncovers an unexpected function of mTOR and underscores a paradigm shift from AR to mTOR as being the master transcriptional regulator of cell metabolism during PCa progression. We performed ChIP-seq of mTOR to study its role in LNCaP cells with or without androgen stimulation. The study was done twice independently; processed data are shown as a pool of either vehicle-treated samples or R1881-treated samples.

ORGANISM(S): Homo sapiens

PROVIDER: GSE93845 | GEO | 2017/07/18

SECONDARY ACCESSION(S): PRJNA362597

REPOSITORIES: GEO

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Project description:Androgens drive the onset and progression of prostate cancer (PCa) by modulating androgen receptor (AR) transcriptional activity. Although several microarray-based studies have identified androgen-regulated genes, here we identify in-parallel global androgen-dependent changes in both gene and alternative mRNA isoform expression by exon-level analyses of the LNCaP transcriptome. While genome-wide gene expression changes correlated well with previously-published studies, we additionally uncovered a subset of 226 novel androgen-regulated genes. Gene expression pathway analysis of this subset revealed gene clusters associated with, and including the tyrosine kinase LYN, as well as components of the mTOR (mammalian target of rapamycin) pathway, which is commonly dysregulated in cancer. We also identified 1279 putative androgen-regulated alternative events, of which 325 (~25%) mapped to known alternative splicing events or alternative first/last exons. We selected 30 androgen-dependent alternative events for RT-PCR validation, including mRNAs derived from genes encoding tumour suppressors and cell cycle regulators. Of seven positively-validating events (~23%), five events involved transcripts derived from known AR gene targets. In particular, we found a novel androgen-dependent mRNA isoform derived from an alternative internal promoter within the TSC2 tumour suppressor gene, which is predicted to encode a protein lacking an interaction domain required for mTOR inhibition. We confirmed that expression of the alternative TSC2 mRNA isoform was directly regulated by androgens. Furthermore, by chromatin immunoprecipitation, we observed recruitment of AR to the alternative promoter region at early timepoints following androgen stimulation, which correlated with expression of alternative transcripts. Together, our data suggest that alternative mRNA isoform expression might mediate the cellular response to androgens, and may have roles in clinical PCa. Total 8 samples were analysed. 4 control (LNCaP cells grown in RPMI-1640 media with charcoal-stripped 10% FBS devoid of steroids) and 4 treatment (LNCaP cells grown in media devoid of steroid, and subsequently treated with 10nM R1881 synthetic androgen analogue for 24 hours).

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Nuclear mTOR acts as a transcriptional integrator of the androgen signaling pathway in prostate cancer progression [ChIP-seq]

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