title: Identification of novel androgen-regulated pathways and mRNA isoforms through genome-wide exon-specific profiling of the LNCaP transcriptome.
abstract: 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 alternative promoters of 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 this alternative TSC2 mRNA isoform was directly regulated by androgens, and chromatin immunoprecipitation indicated 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.
authors.affiliation: Institute of Human Genetics, Newcastle University, Newcastle-upon-Tyne, United Kingdom.
authors.forename: Prabhakar
authors.initials: P
authors.lastname: Rajan
authors.forename: Caroline
authors.initials: C
authors.lastname: Dalgliesh
authors.forename: Phillippa J
authors.initials: PJ
authors.lastname: Carling
authors.forename: Thomas
authors.initials: T
authors.lastname: Buist
authors.forename: Chaolin
authors.initials: C
authors.lastname: Zhang
authors.forename: Sushma N
authors.initials: SN
authors.lastname: Grellscheid
authors.forename: Kelly
authors.initials: K
authors.lastname: Armstrong
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Stockley
authors.forename: Cedric
authors.initials: C
authors.lastname: Simillion
authors.forename: Luke
authors.initials: L
authors.lastname: Gaughan
authors.forename: Gabriela
authors.initials: G
authors.lastname: Kalna
authors.forename: Michael Q
authors.initials: MQ
authors.lastname: Zhang
authors.forename: Craig N
authors.initials: CN
authors.lastname: Robson
authors.forename: Hing Y
authors.initials: HY
authors.lastname: Leung
authors.forename: David J
authors.initials: DJ
authors.lastname: Elliott
mesh_terms: D000728:Androgens / Q000494:pharmacology*; D045744:Cell Line, Tumor; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D005091:Exons / Q000235:genetics*; D020869:Gene Expression Profiling; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D052138:Genes, Neoplasm / Q000235:genetics; D015894:Genome, Human / Q000235:genetics*; D006801:Humans; D008024:Ligands; D008297:Male; D011401:Promoter Regions, Genetic / Q000235:genetics; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000473:pathology; D059368:RNA Isoforms / Q000235:genetics / Q000378:metabolism; D011944:Receptors, Androgen / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects* / Q000235:genetics; D059467:Transcriptome / Q000235:genetics*; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C410798:AR protein, human; D000728:Androgens; D008024:Ligands; D059368:RNA Isoforms; D011944:Receptors, Androgen; C000624653:TSC2 protein, human; D000077005:Tuberous Sclerosis Complex 2 Protein; D025521:Tumor Suppressor Proteins