ABSTRACT
Prostate cancer is the second leading cause of cancer related deaths in US men, largely because of metastasis, which is ultimately fatal. A better understanding of metastasis biology will lead to improved prognostication and therapeutics. We previously reported 11q13.1 gain was independently predictive of recurrence after radical prostatectomy. Multiple endocrine neoplasia I (MEN1) maps to this region of copy number gain in aggressive prostate tumors and was shown to be the only gene at this locus at increased expression in prostate cancer. Here, we demonstrate an oncogenic role for MEN1 in prostate cancer using a variety of independent assays.
Subject(s)
Biomarkers, Tumor/genetics , Prostatic Neoplasms/genetics , Proto-Oncogene Proteins/genetics , Cell Line, Tumor , Humans , Immunohistochemistry , In Situ Hybridization, Fluorescence , Male , Oligonucleotide Array Sequence Analysis , RNA, Small Interfering , Reverse Transcriptase Polymerase Chain Reaction , Tissue Array AnalysisABSTRACT
The hormone-activated glucocorticoid receptor (GR), through its N- and C-terminal transcriptional activation functions AF-1 and AF-2, controls the transcription of target genes presumably through interaction(s) with transcriptional regulatory factors. Utilizing a modified yeast two-hybrid approach, we have identified the tumor susceptibility gene 101 (TSG101) and the vitamin D receptor-interacting protein 150 (DRIP150) as proteins that interact specifically with a functional GR AF-1 surface. In yeast and mammalian cells, TSG101 represses whereas DRIP150 enhances GR AF-1-mediated transactivation. Thus, GR AF-1 is capable of recruiting both positive and negative regulatory factors that differentially regulate GR transcriptional enhancement. In addition, we show that another member of the DRIP complex, DRIP205, interacts with the GR ligand binding domain in a hormone-dependent manner and facilitates GR transactivation in concert with DRIP150. These results suggest that DRIP150 and DRIP205 functionally link GR AF-1 and AF-2, and represent important mediators of GR transcriptional enhancement.
Subject(s)
Gene Expression Regulation , Receptors, Glucocorticoid/genetics , Trans-Activators , Transcriptional Activation , Animals , Cell Line , DNA-Binding Proteins/chemistry , DNA-Binding Proteins/metabolism , Endosomal Sorting Complexes Required for Transport , Glucocorticoids/metabolism , HeLa Cells , Humans , Nuclear Proteins/metabolism , Protein Binding , Receptors, Glucocorticoid/chemistry , Receptors, Glucocorticoid/metabolism , Transcription Factors/chemistry , Transcription Factors/metabolism , Two-Hybrid System TechniquesABSTRACT
Glucocorticoids act through the glucocorticoid receptor (GR), which can function as a transcriptional activator or repressor, to elicit cytostatic and cytotoxic effects in a variety of cells. The molecular mechanisms regulating these events and the target genes affected by the activated receptor remain largely undefined. Using cultured human osteosarcoma cells as a model for the GR antiproliferative effect, we demonstrate that in U20S cells, GR activation leads to irreversible growth inhibition, apoptosis, and repression of Bcl2. This cytotoxic effect is mediated by GR's transcriptional repression function, since transactivation-deficient mutants and ligands still bring about apoptosis and Bcl2 down-regulation. In contrast, the antiproliferative effect of GR in SAOS2 cells is reversible, does not result in apoptosis or repression of Bcl2, and is a function of the receptor's ability to stimulate transcription. Thus, the cytotoxic versus cytostatic outcome of glucocorticoid treatment is cell context dependent. Interestingly, the cytostatic effect of glucocorticoids in SAOS2 cells involves multiple GR activation surfaces. GR mutants and ligands that disrupt individual transcriptional activation functions (activation function 1 [AF-1] and AF-2) or receptor dimerization fail to fully inhibit cellular proliferation and, remarkably, discriminate between the targets of GR's cytostatic action, the cyclin-dependent kinase inhibitors p21(Cip1) and p27(Kip1). Induction of p21(Cip1) is agonist dependent and requires AF-2 but not AF-1 or GR dimerization. In contrast, induction of p27(Kip1) is agonist independent, does not require AF-2 or AF-1, but depends on GR dimerization. Our findings indicate that multiple GR transcriptional regulatory mechanisms that employ distinct receptor surfaces are used to evoke either the cytostatic or cytotoxic response to glucocorticoids.
