Elevated NCOR1 disrupts a network of dietary-sensing nuclear receptors in bladder cancer cells

Increasingly invasive bladder cancer cells lines displayed insensitivity toward a panel of dietary-derived ligands for members of the nuclear receptor superfamily. Insensitivity was defined through altered gene regulatory actions and cell proliferation and reflected both reduced receptor expression and elevated nuclear receptor corepressor 1 (NCOR1) expression. Stable overexpression of NCOR1 in sensitive cells (RT4) resulted in a panel of clones that recapitulated the resistant phenotype in terms of gene regulatory actions and proliferative responses toward ligand. Similarly, silencing RNA approaches to NCOR1 in resistant cells (EJ28) enhanced ligand gene regulatory and proliferation responses, including those mediated by peroxisome proliferator-activated receptor (PPAR) gamma and vitamin D receptor (VDR) receptors. Elevated NCOR1 levels generate an epigenetic lesion to target in resistant cells using the histone deacetylase inhibitor vorinostat, in combination with nuclear receptor ligands. Such treatments revealed strong-additive interactions toward the PPARgamma, VDR and Farnesoid X-activated receptors. Genome-wide microarray and microfluidic quantitative real-time, reverse transcription-polymerase chain reaction approaches, following the targeting of NCOR1 activity and expression, revealed the selective capacity of this corepressor to govern common transcriptional events of underlying networks. Combined these findings suggest that NCOR1 is a selective regulator of nuclear receptors, notably PPARgamma and VDR, and contributes to their loss of sensitivity. Combinations of epigenetic therapies that target NCOR1 may prove effective, even when receptor expression is reduced.

The developing role of receptors and adaptors

The response of a cell to the myriad of signals that it receives is varied, and it is dependent on many different factors. The most-studied responses involve growth-factor signalling and these signalling cascades have become key targets for cancer therapy. Recent reports have indicated that growth-factor receptors and associated adaptors can accumulate in the nucleus. Are there novel functions for these proteins that might affect our understanding of their role in cancer and have implications for drug resistance?

The androgen receptor controls expression of the cancer-associated sTn antigen and cell adhesion through induction of ST6GalNAc1 in prostate cancer

Patterns of glycosylation are important in cancer, but the molecular mechanisms that drive changes are often poorly understood. The androgen receptor drives prostate cancer (PCa) development and progression to lethal metastatic castration-resistant disease. Here we used RNA-Seq coupled with bioinformatic analyses of androgen-receptor (AR) binding sites and clinical PCa expression array data to identify ST6GalNAc1 as a direct and rapidly activated target gene of the AR in PCa cells. ST6GalNAc1 encodes a sialytransferase that catalyses formation of the cancer-associated sialyl-Tn antigen (sTn), which we find is also induced by androgen exposure. Androgens induce expression of a novel splice variant of the ST6GalNAc1 protein in PCa cells. This splice variant encodes a shorter protein isoform that is still fully functional as a sialyltransferase and able to induce expression of the sTn-antigen. Surprisingly, given its high expression in tumours, stable expression of ST6GalNAc1 in PCa cells reduced formation of stable tumours in mice, reduced cell adhesion and induced a switch towards a more mesenchymal-like cell phenotype in vitro. ST6GalNAc1 has a dynamic expression pattern in clinical datasets, beingsignificantly up-regulated in primary prostate carcinoma but relatively down-regulated in established metastatic tissue. ST6GalNAc1 is frequently upregulated concurrently with another important glycosylation enzyme GCNT1 previously associated with prostate cancer progression and implicated in Sialyl Lewis X antigen synthesis. Together our data establishes an androgen-dependent mechanism for sTn antigen expression in PCa, and are consistent with a general role for the androgen receptor in driving important coordinate changes to the glycoproteome during PCa progression.

The Early Effects of Rapid Androgen Deprivation on Human Prostate Cancer

The androgen receptor (AR) is the dominant growth factor in prostate cancer (PCa). Therefore, understanding how ARs regulate the human transcriptome is of paramount importance. The early effects of castration on human PCa have not previously been studied 27 patients medically castrated with degarelix 7 d before radical prostatectomy. We used mass spectrometry, immunohistochemistry, and gene expression array (validated by reverse transcription-polymerase chain reaction) to compare resected tumour with matched, controlled, untreated PCa tissue. All patients had levels of serum androgen, with reduced levels of intraprostatic androgen at prostatectomy. We observed differential expression of known androgen-regulated genes (TMPRSS2, KLK3, CAMKK2, FKBP5). We identified 749 genes downregulated and 908 genes upregulated following castration. AR regulation of α-methylacyl-CoA racemase expression and three other genes (FAM129A, RAB27A, and KIAA0101) was confirmed. Upregulation of oestrogen receptor 1 (ESR1) expression was observed in malignant epithelia and was associated with differential expression of ESR1-regulated genes and correlated with proliferation (Ki-67 expression).

PATIENT SUMMARY: This first-in-man study defines the rapid gene expression changes taking place in prostate cancer (PCa) following castration. Expression levels of the genes that the androgen receptor regulates are predictive of treatment outcome. Upregulation of oestrogen receptor 1 is a mechanism by which PCa cells may survive despite castration.

Choline Kinase Alpha as an Androgen Receptor Chaperone and Prostate Cancer Therapeutic Target

BACKGROUND: The androgen receptor (AR) is a major drug target in prostate cancer (PCa). We profiled the AR-regulated kinome to identify clinically relevant and druggable effectors of AR signaling.

METHODS: Using genome-wide approaches, we interrogated all AR regulated kinases. Among these, choline kinase alpha (CHKA) expression was evaluated in benign (n = 195), prostatic intraepithelial neoplasia (PIN) (n = 153) and prostate cancer (PCa) lesions (n = 359). We interrogated how CHKA regulates AR signaling using biochemical assays and investigated androgen regulation of CHKA expression in men with PCa, both untreated (n = 20) and treated with an androgen biosynthesis inhibitor degarelix (n = 27). We studied the effect of CHKA inhibition on the PCa transcriptome using RNA sequencing and tested the effect of CHKA inhibition on cell growth, clonogenic survival and invasion. Tumor xenografts (n = 6 per group) were generated in mice using genetically engineered prostate cancer cells with inducible CHKA knockdown. Data were analyzed with χ(2) tests, Cox regression analysis, and Kaplan-Meier methods. All statistical tests were two-sided.

RESULTS: CHKA expression was shown to be androgen regulated in cell lines, xenografts, and human tissue (log fold change from 6.75 to 6.59, P = .002) and was positively associated with tumor stage. CHKA binds directly to the ligand-binding domain (LBD) of AR, enhancing its stability. As such, CHKA is the first kinase identified as an AR chaperone. Inhibition of CHKA repressed the AR transcriptional program including pathways enriched for regulation of protein folding, decreased AR protein levels, and inhibited the growth of PCa cell lines, human PCa explants, and tumor xenografts.

CONCLUSIONS: CHKA can act as an AR chaperone, providing, to our knowledge, the first evidence for kinases as molecular chaperones, making CHKA both a marker of tumor progression and a potential therapeutic target for PCa.

Drug induced gingival overgrowth: A role for Protease Activated Receptors?

Background: Protease activated receptors (PAR) belong to a subfamily of G protein coupled receptors. They consist of seven transmembrane domains but are not classical receptors as their agonist is a circulating serine proteinase. This proteinase cleaves an N-terminal extracellular domain of the receptor to reveal a new N-terminal tethered ligand which binds intramolecularly, thus converting an extracellular proteolytic event into a transmembrane signal. Therefore, the cleavage and activation of PARs provide a mechanism whereby proteinases can directly influence the inflammatory response. Gingival hyperplasia or gingival enlargement is a side effect of some drugs such as cyclosporine, a potent immunosuppressant. To date, the potential role of PAR in the inflammation associated with the pathogenesis of gingival overgrowth has not been studied. Objectives: The present study was designed to determine whether proteinases derived from extracts of cyclosporine induced hyperplasia were capable of activating PAR in vitro. Methods: Cell lysates were derived from tissue obtained from gingival overgrowth of patients requiring surgical excision. Cell lines over-expressing PARs were maintained in Dulbecco's modified Eagle's medium (DMEM), containing 10% foetal calf serum (FCS) in 5% CO2. The cells were treated with gingival overgrowth lysates and agonist stimulated calcium release from the cells was recorded using the Fluo-4-Direct™ Calcium Assay Kit from Invitrogen, according to manufacturer's instructions. Results: Calcium release by activated PAR on tumour cells was detected in those treated with gingival hyperplasia lysates. Samples from healthy gingival fibroblasts did not elicit this response. Conclusions: The identification of mediators of the molecular events central to the inflammatory phenotype elicited by gingival hyperplasia is important. To this end, our experiments show that in vitro, enzymes derived from overgrown gingival tissue are capable of activating PAR and thereby provide evidence for the potential role of PAR in sustaining gingival hyperplasia.

Immunocytochemical Localization of Substance P Receptors (NK-1 Receptors) in Human Gingival Tissue

Substance P (SP) is a member of the structurally related family of neuropeptides known as the tachykinins. In addition to neurotransmitter roles, the tachykinins are also known to modulate local inflammation which depends on signalling between the neuropeptide molecules and target cells and tissues. SP mediates its effects through a specific receptor, known as the substance P receptor or the neurokinin 1 (NK-1) receptor. The NK-1 receptor is a G-protein associated integral membrane protein and although it has been studied in a wide range of tissues, to date there has been no published data on the localisation of the NK-1 receptor in human gingival tissue. Objective: The aim of this study was to examine the distribution of the NK-1 receptor in human gingival tissue using immunocytochemistry. Method: Gingival tissue was obtained from patients undergoing periodontal surgery. Tissue was fixed in paraformaldehyde and embedded in wax for sectioning. Sections were dewaxed in xylene and then rehydrated in alcohols and phosphate buffered saline. Rehydrated sections were probed with rabbit polyclonal antibody to human NK-1 receptor which was subsequently detected using anti-rabbit horseradish peroxidase conjugate and diaminobenzidine as substrate. Results: Immunocytochemistry revealed that the NK-1 receptor was distributed along nerve fibres and blood vessel endothelial cells, suggesting these areas are main targets for the actions of SP via the NK-1 receptor. Conclusion: This is the first immunocytochemical report of NK-1 receptors in human gingival tissue and provides evidence for possible NK-1 mediated biological effects of SP in human gingival tissue from periodontitis patients.

Neuropeptide Receptors in the Dental Pulp

Objectives: The inflammatory response to pulpal injury or infection has major clinical significance. The aim of the study is to investigate the presence and regulation of expression of neuropeptide receptors on human pulp fibroblasts and whole pulp tissue. This study will investigate the expression of Substance P (NK-1) and Neuropeptide Y (NPY-Y1) receptors on pulp fibroblasts, determine the effects of Transforming Growth Factor Beta-1 (TGF-b1) and Interleukin 1-Beta (IL-1b) on the expression of NK-1 and NPY-Y1 receptors on pulp fibroblasts and examine the levels of receptor expression in whole pulp samples. Methods: Primary pulp fibroblast cell lines were obtained from patients undergoing extractions for orthodontic reasons. The cells were grown to confluence and stimulated for 5 days with IL-1b or TGF-b1. Pulp tissue fragments were obtained from freshly extracted sound and carious teeth, snap frozen in liquid nitrogen and cracked open using a vice. The monolayer was removed with cell scrapers and pelleted. The cell membranes of the cultured cells and the whole tissue were isolated using a Mem-PER® Eukaryotic Membrane Protein Extraction Reagent Kit (Pierce, UK). The membrane proteins were separated by SDS-PAGE and Western blotting was used to detect the presence of NK-1 and NPY-Y1. Results: Initial results demonstrated the presence of NK-1 and NPY-Y1 in cultured pulp fibroblasts. Following the 5 day incubation with TGF-b1, the cells appeared not to express NK-1. IL-1b had a slight stimulatory effect on NK-1 expression. The NPY-Y1 expression was not affected by either TGF-b1 or IL-1b. In whole pulp samples, levels of NK-1 were increased in carious teeth compared to caries-free teeth. The NPY-Y1 levels were similar in carious and non-carious teeth. Conclusion: These findings give an insight into how pulp cells react to inflammatory stimuli with regards to neuropeptide receptor expression and their roles in health and disease