Reprogramming neuroblastoma by diet-enhanced polyamine depletion

Neuroblastoma is a highly lethal childhood tumor derived from differentiation-arrested neural crest cells1,2. Like all cancers, its growth is fueled by metabolites obtained from either circulation or local biosynthesis3,4. Neuroblastomas depend on local polyamine biosynthesis, with the inhibitor difluoromethylornithine showing clinical activity5. Here we show that such inhibition can be augmented by dietary restriction of upstream amino acid substrates, leading to disruption of oncogenic protein translation, tumor differentiation, and profound survival gains in the TH-MYCN mouse model. Specifically, an arginine/proline-free diet decreases the polyamine precursor ornithine and augments tumor polyamine depletion by difluoromethylornithine. This polyamine depletion causes ribosome stalling, unexpectedly specifically at adenosine-ending codons. Such codons are selectively enriched in cell cycle genes and low in neuronal differentiation genes. Thus, impaired translation of these codons, induced by the diet-drug combination, favors a pro-differentiation proteome. These results suggest that the genes of specific cellular programs have evolved hallmark codon usage preferences that enable coherent translational rewiring in response to metabolic stresses, and that this process can be targeted to activate differentiation of pediatric cancers.

Performance Characteristics of Mass Spectrometry-Based Analytical Procedures for Quantitation of Nitrosamines in Pharmaceuticals: Insights from an Inter-laboratory Study

With the discovery of carcinogenic nitrosamine impurities in pharmaceuticals in 2018 and subsequent regulatory requirements for risk assessment for nitrosamine formation during pharmaceutical manufacturing processes, storage or from contaminated supply chains, effective testing of nitrosamines has become essential to ensure the quality of drug substances and products. Mass spectrometry has been widely applied to detect and quantify trace amounts of nitrosamines in pharmaceuticals. As part of an effort by regulatory authorities to assess the measurement variation in the determination of nitrosamines, an inter-laboratory study was performed by the laboratories from six regulatory agencies with each of the participants using their own analytical procedures to determine the amounts of nitrosamines in a set of identical samples. The results demonstrated that accurate and precise quantitation of trace level nitrosamines can be achieved across multiple analytical procedures and provided insight into the performance characteristics of mass spectrometry-based analytical procedures in terms of accuracy, repeatability and reproducibility.

ADAMTS-7 Modulates Atherosclerotic Plaque Formation by Degradation of TIMP-1

BACKGROUND

The ADAMTS7 locus was genome-wide significantly associated with coronary artery disease. Lack of the ECM (extracellular matrix) protease ADAMTS-7 (A disintegrin and metalloproteinase-7) was shown to reduce atherosclerotic plaque formation. Here, we sought to identify molecular mechanisms and downstream targets of ADAMTS-7 mediating the risk of atherosclerosis.

METHODS

Targets of ADAMTS-7 were identified by high-resolution mass spectrometry of atherosclerotic plaques from Apoe-/- and Apoe-/-Adamts7-/- mice. ECM proteins were identified using solubility profiling. Putative targets were validated using immunofluorescence, in vitro degradation assays, coimmunoprecipitation, and Förster resonance energy transfer-based protein-protein interaction assays. ADAMTS7 expression was measured in fibrous caps of human carotid artery plaques.

RESULTS

In humans, ADAMTS7 expression was higher in caps of unstable as compared to stable carotid plaques. Compared to Apoe-/- mice, atherosclerotic aortas of Apoe-/- mice lacking Adamts-7 (Apoe-/-Adamts7-/-) contained higher protein levels of Timp-1 (tissue inhibitor of metalloprotease-1). In coimmunoprecipitation experiments, the catalytic domain of ADAMTS-7 bound to TIMP-1, which was degraded in the presence of ADAMTS-7 in vitro. ADAMTS-7 reduced the inhibitory capacity of TIMP-1 at its canonical target MMP-9 (matrix metalloprotease-9). As a downstream mechanism, we investigated collagen content in plaques of Apoe-/- and Apoe-/-Adamts7-/- mice after a Western diet. Picrosirius red staining of the aortic root revealed less collagen as a readout of higher MMP-9 activity in Apoe-/- as compared to Apoe-/- Adamts7-/- mice. To facilitate high-throughput screening for ADAMTS-7 inhibitors with the aim of decreasing TIMP-1 degradation, we designed a Förster resonance energy transfer-based assay targeting the ADAMTS-7 catalytic site.

CONCLUSIONS

ADAMTS-7, which is induced in unstable atherosclerotic plaques, decreases TIMP-1 stability reducing its inhibitory effect on MMP-9, which is known to promote collagen degradation and is likewise associated with coronary artery disease. Disrupting the interaction of ADAMTS-7 and TIMP-1 might be a strategy to increase collagen content and plaque stability for the reduction of atherosclerosis-related events.

Clostridium scindens secretome suppresses virulence gene expression of Clostridioides difficile in a bile acid-independent manner

Clostridioides difficile infection (CDI) is a major health concern and one of the leading causes of hospital-acquired diarrhea in many countries. C. difficile infection is challenging to treat as C. difficile is resistant to multiple antibiotics. Alternative solutions are needed as conventional treatment with broad-spectrum antibiotics often leads to recurrent CDI. Recent studies have shown that specific microbiota-based therapeutics such as bile acids (BAs) are promising approaches to treat CDI. Clostridium scindens encodes the bile acid-induced (bai) operon that carries out 7-alpha-dehydroxylation of liver-derived primary BAs to secondary BAs. This biotransformation is thought to increase the antibacterial effects of BAs on C. difficile. Here, we used an automated multistage fermentor to study the antibacterial actions of C. scindens and BAs on C. difficile in the presence/absence of a gut microbial community derived from healthy human donor fecal microbiota. We observed that C. scindens inhibited C. difficile growth when the medium was supplemented with primary BAs. Transcriptomic analysis indicated upregulation of C. scindens bai operon and suppressed expression of C. difficile exotoxins that mediate CDI. We also observed BA-independent antibacterial activity of the secretome from C. scindens cultured overnight in a medium without supplementary primary BAs, which suppressed growth and exotoxin expression in C. difficile mono-culture. Further investigation of the molecular basis of our observation could lead to a more specific treatment for CDI than current approaches. IMPORTANCE There is an urgent need for new approaches to replace the available treatment options against Clostridioides difficile infection (CDI). Our novel work reports a bile acid-independent reduction of C. difficile growth and virulence gene expression by the secretome of Clostridium scindens. This potential treatment combined with other antimicrobial strategies could facilitate the development of alternative therapies in anticipation of CDI and in turn reduce the risk of antimicrobial resistance.

Independent control of COVID-19 vaccines by EU Official Control Authority Batch Release: challenges, strengths and successes

Vaccines have been a key tool in stemming the tide of the COVID-19 pandemic. The rapid development of effective vaccines against COVID-19, together with their regulatory approval and wide scale distribution has been achieved in an impressively short period thanks to the intense efforts of many. In parallel to vaccine development, the EU considered it important to prepare for the independent control of the COVID-19 vaccines, including testing, to help ensure that only vaccines that comply with the approved quality requirements reach the public and to help improve/increase public confidence in the vaccines. The existing EU Official Control Authority Batch Release (OCABR) system, co-ordinated by the European Directorate for the Quality of Medicines and HealthCare (EDQM), was able to effectively respond to the need, through rapid co-ordination, work-sharing, advance planning and early interaction with manufacturers, the Coalition for Epidemic Preparedness Innovation (CEPI) and regulatory authorities. The Official Medicines Control Laboratories (OMCLs) involved in the OCABR activity, using the strength of the established system in the OCABR network and adaptations to the crisis conditions, were ready to release the first COVID-19 vaccine batches, after protocol review and testing, at the time of the conditional marketing authorisation for each of the COVID-19 vaccines, with no delay for batches reaching the public. Thanks to the dedication of resources by the EU and national authorities as well as by the EDQM, this was done without impacting the release of the other vaccines and human blood and plasma derived medicinal products, essential for public health. Transparency and communication of practices were important factors to support reliance on the OCABR outcome in non-EU countries, with the goal to improve access to vaccines in Europe and beyond. An overview of the process, legal background, challenges and successes of OCABR for COVID-19 vaccines as well as a look at the international perspective and lessons learned is provided.

Comprehensive chromatin proteomics resolves functional phases of pluripotency and identifies changes in regulatory components

The establishment of cellular identity is driven by transcriptional and epigenetic regulators of the chromatin proteome - the chromatome. Comprehensive analyses of the chromatome composition and dynamics can therefore greatly improve our understanding of gene regulatory mechanisms. Here, we developed an accurate mass spectrometry (MS)-based proteomic method called Chromatin Aggregation Capture (ChAC) followed by Data-Independent Acquisition (DIA) and analyzed chromatome reorganizations during major phases of pluripotency. This enabled us to generate a comprehensive atlas of proteomes, chromatomes, and chromatin affinities for the ground, formative and primed pluripotency states, and to pinpoint the specific binding and rearrangement of regulatory components. These comprehensive datasets combined with extensive analyses identified phase-specific factors like QSER1 and JADE1/2/3 and provide a detailed foundation for an in-depth understanding of mechanisms that govern the phased progression of pluripotency. The technical advances reported here can be readily applied to other models in development and disease.

Unscheduled DNA replication in G1 causes genome instability and damage signatures indicative of replication collisions

DNA replicates once per cell cycle. Interfering with the regulation of DNA replication initiation generates genome instability through over-replication and has been linked to early stages of cancer development. Here, we engineer genetic systems in budding yeast to induce unscheduled replication in a G1-like cell cycle state. Unscheduled G1 replication initiates at canonical S-phase origins. We quantifiy the composition of replisomes in G1- and S-phase and identified firing factors, polymerase α, and histone supply as factors that limit replication outside S-phase. G1 replication per se does not trigger cellular checkpoints. Subsequent replication during S-phase, however, results in over-replication and leads to chromosome breaks and chromosome-wide, strand-biased occurrence of RPA-bound single-stranded DNA, indicating head-to-tail replication collisions as a key mechanism generating genome instability upon G1 replication. Low-level, sporadic induction of G1 replication induces an identical response, indicating findings from synthetic systems are applicable to naturally occurring scenarios of unscheduled replication initiation.

Abstract P1110: Identification Of Timp-1 As A Downstream Target Of The Coronary Artery Disease Risk Factor Adamts-7 In Atherosclerosis

Background: The gene encoding the extracellular matrix (ECM) protease ADAMTS-7 was associated with coronary artery disease (CAD) in genome-wide association studies. ADAMTS-7 is expressed at all stages in human plaques and mice lacking Adamts-7 displayed reduced atherosclerotic plaque formation. While these findings render ADAMTS-7 a promising therapeutic target, the underlying mechanisms remain unknown.

Methods and Results: Here, we sought to identify downstream mechanisms of ADAMTS-7 in atherosclerotic plaque formation. Targets of Adamts-7 were identified by high-resolution mass spectrometry of atherosclerotic plaques in Apoe-/- and Apoe-/-Adamts7-/- mice. ECM proteins were identified using solubility profiling. The endogenous inhibitor of matrix metalloproteinases (MMP) Timp-1 was identified as a novel target of Adamts-7. Adamts-7 and Timp-1 were found to be co-localized in atherosclerotic plaques and co-immunoprecipitation (Co-IP) studies revealed TIMP-1 as the first putative target to bind to the catalytic domain of ADAMTS-7. In vitro degradation assays demonstrated that ADAMTS-7 degrades TIMP-1. Co-IP furthermore revealed less binding of TIMP-1 to its canonical target MMP-9 when ADAMTS-7 was present. In line, scaffolding and degradation of TIMP-1 by ADAMTS-7 impaired TIMP-1-mediated inhibition of MMP-9 in vitro. As a downstream mechanism, we investigated collagen content in atherosclerotic plaques of Apoe-/- and Apoe-/- Adamts7-/- mice after Western diet. Collagen stainings of the aortic root revealed less collagen as a readout of higher MMP-9 activity in Apoe-/- as compared to Apoe-/- Adamts7-/- mice. Since ADAMTS-7 might exert its pro-atherogenic effects through interaction with TIMP-1, we established a TIMP-1-ADAMTS-7-interaction assay based on Förster resonance energy transfer (FRET) to identify inhibitors of this protein-protein interaction.

Conclusion and Outlook: TIMP-1 represents a novel downstream target of ADAMTS-7 that can explain the role of this novel risk factor in CAD. Our FRET-based protein-protein interaction assay may be used for high-throughput screening to identifiy inhibitors and prevent the initiation or slow the progression of atherosclerosis.

TET1 regulates gene expression and repression of endogenous retroviruses independent of DNA demethylation

DNA methylation (5-methylcytosine (5mC)) is critical for genome stability and transcriptional regulation in mammals. The discovery that ten-eleven translocation (TET) proteins catalyze the oxidation of 5mC to 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC) revolutionized our perspective on the complexity and regulation of DNA modifications. However, to what extent the regulatory functions of TET1 can be attributed to its catalytic activity remains unclear. Here, we use genome engineering and quantitative multi-omics approaches to dissect the precise catalytic vs. non-catalytic functions of TET1 in murine embryonic stem cells (mESCs). Our study identifies TET1 as an essential interaction hub for multiple chromatin modifying complexes and a global regulator of histone modifications. Strikingly, we find that the majority of transcriptional regulation depends on non-catalytic functions of TET1. In particular, we show that TET1 is critical for the establishment of H3K9me3 and H4K20me3 at endogenous retroviral elements (ERVs) and their silencing that is independent of its canonical role in DNA demethylation. Furthermore, we provide evidence that this repression of ERVs depends on the interaction between TET1 and SIN3A. In summary, we demonstrate that the non-catalytic functions of TET1 are critical for regulation of gene expression and the silencing of endogenous retroviruses in mESCs.

International Regulatory Collaboration on the Analysis of Nitrosamines in Metformin-Containing Medicines

Recalls of some batches of metformin have occurred due to the detection of N-nitrosodimethylamine (NDMA) in amounts above the acceptable intake (AI) of 96 ng per day. Prior to the recalls, an international regulatory laboratory network had been monitoring drugs for nitrosamine impurities with each laboratory independently developing and validating multiple analytical procedures to detect and measure nitrosamines in metformin drugs used in their jurisdictions. Here, we provide an overview of the analysis of metformin active pharmaceutical ingredients (APIs) and drug products with 1090 samples (875 finished dosage forms (FDFs) and 215 API samples) tested beginning in November of 2019 through July of 2020. Samples were obtained internationally by a variety of approaches, including purchased, received from firms via information requests or selected by regional regulatory authorities (either at wholesalers or during GMP inspections). Only one nitrosamine (NDMA) was detected and was only present in some batches of metformin products. For API samples, 213 out of 215 lots tested had no measurable level of NDMA. For FDF samples tested, the number of batches with NDMA above the AI amount for patient safety was 17.8% (156/875). Based on these data, although the presence of NDMA was of concern, 82.2% of the samples of metformin drug products tested met quality and safety standards for patients. Regulatory agencies continue to collaborate extensively and work with marketing authorization holders to understand root causes of nitrosamine formation and agree on corrective actions to mitigate the presence of NDMA in future metformin batches.

Defining the RBPome of primary T helper cells to elucidate higher-order Roquin-mediated mRNA regulation

Post-transcriptional gene regulation in T cells is dynamic and complex as targeted transcripts respond to various factors. This is evident for the Icos mRNA encoding an essential costimulatory receptor that is regulated by several RNA-binding proteins (RBP), including Roquin-1 and Roquin-2. Here, we identify a core RBPome of 798 mouse and 801 human T cell proteins by utilizing global RNA interactome capture (RNA-IC) and orthogonal organic phase separation (OOPS). The RBPome includes Stat1, Stat4 and Vav1 proteins suggesting unexpected functions for these transcription factors and signal transducers. Based on proximity to Roquin-1, we select ~50 RBPs for testing coregulation of Roquin-1/2 targets by induced expression in wild-type or Roquin-1/2-deficient T cells. Besides Roquin-independent contributions from Rbms1 and Cpeb4 we also show Roquin-1/2-dependent and target-specific coregulation of Icos by Celf1 and Igf2bp3. Connecting the cellular RBPome in a post-transcriptional context, we find contributions from multiple RBPs to the prototypic regulation of mRNA targets by individual trans-acting factors.

An extensive RNA binding protein atlas (RBPome) for primary T cells would be a useful resource. Here the authors use two different methods to characterise the mouse and human T cell RBPome and show regulation of Roquin-1/2 dependent and independent pathways.

Phosphorylation of the HP1β hinge region sequesters KAP1 in heterochromatin and promotes the exit from naïve pluripotency

Heterochromatin binding protein HP1β plays an important role in chromatin organization and cell differentiation, however the underlying mechanisms remain unclear. Here, we generated HP1β^−/− embryonic stem cells and observed reduced heterochromatin clustering and impaired differentiation. We found that during stem cell differentiation, HP1β is phosphorylated at serine 89 by CK2, which creates a binding site for the pluripotency regulator KAP1. This phosphorylation dependent sequestration of KAP1 in heterochromatin compartments causes a downregulation of pluripotency factors and triggers pluripotency exit. Accordingly, HP1β^−/− and phospho-mutant cells exhibited impaired differentiation, while ubiquitination-deficient KAP1^−/− cells had the opposite phenotype with enhanced differentiation. These results suggest that KAP1 regulates pluripotency via its ubiquitination activity. We propose that the formation of subnuclear membraneless heterochromatin compartments may serve as a dynamic reservoir to trap or release cellular factors. The sequestration of essential regulators defines a novel and active role of heterochromatin in gene regulation and represents a dynamic mode of remote control to regulate cellular processes like cell fate decisions.

Identification of permissive amber suppression sites for efficient non-canonical amino acid incorporation in mammalian cells

The genetic code of mammalian cells can be expanded to allow the incorporation of non-canonical amino acids (ncAAs) by suppressing in-frame amber stop codons (UAG) with an orthogonal pyrrolysyl-tRNA synthetase (PylRS)/tRNAPylCUA (PylT) pair. However, the feasibility of this approach is substantially hampered by unpredictable variations in incorporation efficiencies at different stop codon positions within target proteins. Here, we apply a proteomics-based approach to quantify ncAA incorporation rates at hundreds of endogenous amber stop codons in mammalian cells. With these data, we compute iPASS (Identification of Permissive Amber Sites for Suppression; available at www.bultmannlab.eu/tools/iPASS), a linear regression model to predict relative ncAA incorporation efficiencies depending on the surrounding sequence context. To verify iPASS, we develop a dual-fluorescence reporter for high-throughput flow-cytometry analysis that reproducibly yields context-specific ncAA incorporation efficiencies. We show that nucleotides up- and downstream of UAG synergistically influence ncAA incorporation efficiency independent of cell line and ncAA identity. Additionally, we demonstrate iPASS-guided optimization of ncAA incorporation rates by synonymous exchange of codons flanking the amber stop codon. This combination of in silico analysis followed by validation in living mammalian cells substantially simplifies identification as well as adaptation of sites within a target protein to confer high ncAA incorporation rates.

A proteomic atlas of the neointima identifies novel druggable targets for preventive therapy

Aims 

In-stent restenosis is a complication after coronary stenting associated with morbidity and mortality. Here, we sought to investigate the molecular processes underlying neointima formation and to identify new treatment and prevention targets.

Methods and results 

Neointima formation was induced by wire injury in mouse femoral arteries. High-accuracy proteomic measurement of single femoral arteries to a depth of about 5000 proteins revealed massive proteome remodelling, with more than half of all proteins exhibiting expression differences between injured and non-injured vessels. We observed major changes in the composition of the extracellular matrix and cell migration processes. Among the latter, we identified the classical transient receptor potential channel 6 (TRPC6) to drive neointima formation. While Trpc6  ^−/− mice presented reduced neointima formation compared to wild-type mice (1.44 ± 0.39 vs. 2.16 ± 0.48, P = 0.01), activating or repressing TRPC6 in human vascular smooth muscle cells resulted in increased [vehicle 156.9 ± 15.8 vs. 1-oleoyl-2-acetyl-sn-glycerol 179.1 ± 8.07 (10³ pixels), P = 0.01] or decreased migratory capacity [vehicle 130.0 ± 26.1 vs. SAR7334 111.4 ± 38.0 (10³ pixels), P = 0.04], respectively. In a cohort of individuals with angiographic follow-up (n = 3068, males: 69.9%, age: 59 ± 11 years, follow-up 217.1 ± 156.4 days), homozygous carriers of a common genetic variant associated with elevated TRPC6 expression were at increased risk of restenosis after coronary stenting (adjusted odds ratio 1.49, 95% confidence interval 1.08–2.05; P = 0.01).

Conclusions 

Our study provides a proteomic atlas of the healthy and injured arterial wall that can be used to define novel factors for therapeutic targeting. We present TRPC6 as an actionable target to prevent neointima formation secondary to vascular injury and stent implantation.

Transcription Factor MAFF (MAF Basic Leucine Zipper Transcription Factor F) Regulates an Atherosclerosis Relevant Network Connecting Inflammation and Cholesterol Metabolism

BACKGROUND

Coronary artery disease (CAD) is a multifactorial condition with both genetic and exogenous causes. The contribution of tissue-specific functional networks to the development of atherosclerosis remains largely unclear. The aim of this study was to identify and characterize central regulators and networks leading to atherosclerosis.

METHODS

Based on several hundred genes known to affect atherosclerosis risk in mouse (as demonstrated in knockout models) and human (as shown by genome-wide association studies), liver gene regulatory networks were modeled. The hierarchical order and regulatory directions of genes within the network were based on Bayesian prediction models, as well as experimental studies including chromatin immunoprecipitation DNA-sequencing, chromatin immunoprecipitation mass spectrometry, overexpression, small interfering RNA knockdown in mouse and human liver cells, and knockout mouse experiments. Bioinformatics and correlation analyses were used to clarify associations between central genes and CAD phenotypes in both human and mouse.

RESULTS

The transcription factor MAFF (MAF basic leucine zipper transcription factor F) interacted as a key driver of a liver network with 3 human genes at CAD genome-wide association studies loci and 11 atherosclerotic murine genes. Most importantly, expression levels of the low-density lipoprotein receptor (LDLR) gene correlated with MAFF in 600 CAD patients undergoing bypass surgery (STARNET [Stockholm-Tartu Atherosclerosis Reverse Network Engineering Task]) and a hybrid mouse diversity panel involving 105 different inbred mouse strains. Molecular mechanisms of MAFF were tested in noninflammatory conditions and showed positive correlation between MAFF and LDLR in vitro and in vivo. Interestingly, after lipopolysaccharide stimulation (inflammatory conditions), an inverse correlation between MAFF and LDLR in vitro and in vivo was observed. Chromatin immunoprecipitation mass spectrometry revealed that the human CAD genome-wide association studies candidate BACH1 (BTB domain and CNC homolog 1) assists MAFF in the presence of lipopolysaccharide stimulation with respective heterodimers binding at the MAF recognition element of the LDLR promoter to transcriptionally downregulate LDLR expression.

CONCLUSIONS

The transcription factor MAFF was identified as a novel central regulator of an atherosclerosis/CAD-relevant liver network. MAFF triggered context-specific expression of LDLR and other genes known to affect CAD risk. Our results suggest that MAFF is a missing link between inflammation, lipid and lipoprotein metabolism, and a possible treatment target.

The glucocorticoid receptor recruits the COMPASS complex to regulate inflammatory transcription at macrophage enhancers

Glucocorticoids (GCs) are effective anti-inflammatory drugs; yet, their mechanisms of action are poorly understood. GCs bind to the glucocorticoid receptor (GR), a ligand-gated transcription factor controlling gene expression in numerous cell types. Here, we characterize GR’s protein interactome and find the SETD1A (SET domain containing 1A)/COMPASS (complex of proteins associated with Set1) histone H3 lysine 4 (H3K4) methyltransferase complex highly enriched in activated mouse macrophages. We show that SETD1A/COMPASS is recruited by GR to specific cis-regulatory elements, coinciding with H3K4 methylation dynamics at subsets of sites, upon treatment with lipopolysaccharide (LPS) and GCs. By chromatin immunoprecipitation sequencing (ChIP-seq) and RNA-seq, we identify subsets of GR target loci that display SETD1A occupancy, H3K4 mono-, di-, or tri-methylation patterns, and transcriptional changes. However, our data on methylation status and COMPASS recruitment suggest that SETD1A has additional transcriptional functions. Setd1a loss-of-function studies reveal that SETD1A/COMPASS is required for GR-controlled transcription of subsets of macrophage target genes. We demonstrate that the SETD1A/COMPASS complex cooperates with GR to mediate anti-inflammatory effects.

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GR’s transcriptional complex in macrophages includes COMPASS proteins

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GR ligand changes SETD1A chromatin occupancy in activated macrophages

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Subsets of GR target sites show COMPASS binding and H3K4 methylation dynamics

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SETD1A is required for some of GR’s anti-inflammatory actions

Collaborative study for the establishment of Ph. Eur. Human albumin (molecular size) Biological Reference Preparation batches 1, 2 and 3

To comply with European Pharmacopoeia (Ph. Eur.) monograph Human albumin solution (0255), albumin solutions have to be tested for molecular-size distribution by size-exclusion chromatography (SEC). However, differences in interpretation of the test results continue to be observed among albumin manufacturers in Europe. A collaborative study was run by the European Directorate for the Quality of Medicines & HealthCare (EDQM), under the aegis of the Biological Standardisation Programme (BSP), to support the revision of Ph. Eur. monograph 0255 and to establish a Biological Reference Preparation (BRP) for use in the molecular-size distribution test. In 2019, Ph. Eur. Expert Group 6B proposed to include an analytical improvement of the SEC procedure in the monograph, which was then submitted for public enquiry. This publication describes the evaluation of three candidate BRPs to serve as a tool for both the system suitability test (SST) and albumin monomer and dimer peak identification according to the proposed revised methodology. Three Official Medicines Control Laboratories (OMCLs) involved in the official batch release of human albumin solution took part in the study. Based on the study results, the candidate BRPs were found suitable for purpose and were adopted by the Ph. Eur. Commission as Ph. Eur. Human albumin (molecular size) BRP batches 1, 2 and 3 concomitantly with the revised monograph Human albumin solution (0255) in November 2020.

Recent evolution of a TET-controlled and DPPA3/STELLA-driven pathway of passive DNA demethylation in mammals

Genome-wide DNA demethylation is a unique feature of mammalian development and naïve pluripotent stem cells. Here, we describe a recently evolved pathway in which global hypomethylation is achieved by the coupling of active and passive demethylation. TET activity is required, albeit indirectly, for global demethylation, which mostly occurs at sites devoid of TET binding. Instead, TET-mediated active demethylation is locus-specific and necessary for activating a subset of genes, including the naïve pluripotency and germline marker Dppa3 (Stella, Pgc7). DPPA3 in turn drives large-scale passive demethylation by directly binding and displacing UHRF1 from chromatin, thereby inhibiting maintenance DNA methylation. Although unique to mammals, we show that DPPA3 alone is capable of inducing global DNA demethylation in non-mammalian species (Xenopus and medaka) despite their evolutionary divergence from mammals more than 300 million years ago. Our findings suggest that the evolution of Dppa3 facilitated the emergence of global DNA demethylation in mammals.

Anti-inflammatory functions of the glucocorticoid receptor require DNA binding

The glucocorticoid receptor is an important immunosuppressive drug target and metabolic regulator that acts as a ligand-gated transcription factor. Generally, GR’s anti-inflammatory effects are attributed to the silencing of inflammatory genes, while its adverse effects are ascribed to the upregulation of metabolic targets. GR binding directly to DNA is proposed to activate, whereas GR tethering to pro-inflammatory transcription factors is thought to repress transcription. Using mice with a point mutation in GR’s zinc finger, that still tether via protein–protein interactions while being unable to recognize DNA, we demonstrate that DNA binding is essential for both transcriptional activation and repression. Performing ChIP-Seq, RNA-Seq and proteomics under inflammatory conditions, we show that DNA recognition is required for the assembly of a functional co-regulator complex to mediate glucocorticoid responses. Our findings may contribute to the development of safer immunomodulators with fewer side effects.

Atomic-resolution mapping of transcription factor-DNA interactions by femtosecond laser crosslinking and mass spectrometry

Transcription factors (TFs) regulate target genes by specific interactions with DNA sequences. Detecting and understanding these interactions at the molecular level is of fundamental importance in biological and clinical contexts. Crosslinking mass spectrometry is a powerful tool to assist the structure prediction of protein complexes but has been limited to the study of protein-protein and protein-RNA interactions. Here, we present a femtosecond laser-induced crosslinking mass spectrometry (fliX-MS) workflow, which allows the mapping of protein-DNA contacts at single nucleotide and up to single amino acid resolution. Applied to recombinant histone octamers, NF1, and TBP in complex with DNA, our method is highly specific for the mapping of DNA binding domains. Identified crosslinks are in close agreement with previous biochemical data on DNA binding and mostly fit known complex structures. Applying fliX-MS to cells identifies several bona fide crosslinks on DNA binding domains, paving the way for future large scale ex vivo experiments.

Kreuth V initiative: European consensus proposals for treatment of hemophilia using standard products, extended half-life coagulation factor concentrates and non-replacement therapies

This report contains the updated consensus recommendations for optimal hemophilia care produced in 2019 by three Working Groups (WG) on behalf of the European Directorate for Quality of Medicines and Healthcare in the frame of the Kreuth V Initiative. WG1 recommended access to prophylaxis for all patients, the achievement of plasma factor trough levels of at least 3-5% when extended half-life factor VIII (FVIII) and FIX products are used, a personalized treatment regimen, and a choice of chromogenic assays for treatment monitoring. It was also emphasized that innovative therapies should be supervised by hemophilia comprehensive care centers. WG2 recommended mandatory collection of postmarketing data to assure the long-term safety and efficacy of new hemophilia therapies, the establishment of national patient registries including the core data recommended by the European Medicines Agency and the International Society on Thrombosis and Haemostasis, with adequate support under public control, and greater collaboration to facilitate a comprehensive data evaluation throughout Europe. WG3 discussed methodological aspects of hemophilia care in the context of access decisions, particularly for innovative therapies, and recommended that clinical studies should be designed to provide the quality of evidence needed by regulatory authorities, HTA bodies and healthcare providers. The dialogue between all stakeholders in hemophilia care and patient organizations should be fostered to implement these recommendations.

Drosophila SWR1 and NuA4 complexes are defined by DOMINO isoforms

Histone acetylation and deposition of H2A.Z variant are integral aspects of active transcription. In Drosophila, the single DOMINO chromatin regulator complex is thought to combine both activities via an unknown mechanism. Here we show that alternative isoforms of the DOMINO nucleosome remodeling ATPase, DOM-A and DOM-B, directly specify two distinct multi-subunit complexes. Both complexes are necessary for transcriptional regulation but through different mechanisms. The DOM-B complex incorporates H2A.V (the fly ortholog of H2A.Z) genome-wide in an ATP-dependent manner, like the yeast SWR1 complex. The DOM-A complex, instead, functions as an ATP-independent histone acetyltransferase complex similar to the yeast NuA4, targeting lysine 12 of histone H4. Our work provides an instructive example of how different evolutionary strategies lead to similar functional separation. In yeast and humans, nucleosome remodeling and histone acetyltransferase complexes originate from gene duplication and paralog specification. Drosophila generates the same diversity by alternative splicing of a single gene.

Cistromic Reprogramming of the Diurnal Glucocorticoid Hormone Response by High-Fat Diet

The glucocorticoid receptor (GR) is a potent metabolic regulator and a major drug target. While GR is known to play integral roles in circadian biology, its rhythmic genomic actions have never been characterized. Here we mapped GR's chromatin occupancy in mouse livers throughout the day and night cycle. We show how GR partitions metabolic processes by time-dependent target gene regulation and controls circulating glucose and triglycerides differentially during feeding and fasting. Highlighting the dominant role GR plays in synchronizing circadian amplitudes, we find that the majority of oscillating genes are bound by and depend on GR. This rhythmic pattern is altered by high-fat diet in a ligand-independent manner. We find that the remodeling of oscillatory gene expression and postprandial GR binding results from a concomitant increase of STAT5 co-occupancy in obese mice. Altogether, our findings highlight GR's fundamental role in the rhythmic orchestration of hepatic metabolism.

Multi-level Proteomics Identifies CT45 as a Chemosensitivity Mediator and Immunotherapy Target in Ovarian Cancer

Most high-grade serous ovarian cancer (HGSOC) patients develop resistance to platinum-based chemotherapy and recur, but 15% remain disease free over a decade. To discover drivers of long-term survival, we quantitatively analyzed the proteomes of platinum-resistant and -sensitive HGSOC patients from minute amounts of formalin-fixed, paraffin-embedded tumors. This revealed cancer/testis antigen 45 (CT45) as an independent prognostic factor associated with a doubling of disease-free survival in advanced-stage HGSOC. Phospho- and interaction proteomics tied CT45 to DNA damage pathways through direct interaction with the PP4 phosphatase complex. In vitro, CT45 regulated PP4 activity, and its high expression led to increased DNA damage and platinum sensitivity. CT45-derived HLA class I peptides, identified by immunopeptidomics, activate patient-derived cytotoxic T cells and promote tumor cell killing. This study highlights the power of clinical cancer proteomics to identify targets for chemo- and immunotherapy and illuminate their biological roles.

Functional identity of hypothalamic melanocortin neurons depends on Tbx3

Heterogeneous populations of hypothalamic neurons orchestrate energy balance via the release of specific signatures of neuropeptides. However, how specific intracellular machinery controls peptidergic identities and function of individual hypothalamic neurons remains largely unknown. The transcription factor T-box 3 (Tbx3) is expressed in hypothalamic neurons sensing and governing energy status, whereas human TBX3 haploinsufficiency has been linked with obesity. Here, we demonstrate that loss of Tbx3 function in hypothalamic neurons causes weight gain and other metabolic disturbances by disrupting both the peptidergic identity and plasticity of Pomc/Cart and Agrp/Npy neurons. These alterations are observed after loss of Tbx3 in both immature hypothalamic neurons and terminally differentiated mouse neurons. We further establish the importance of Tbx3 for body weight regulation in Drosophila melanogaster and show that TBX3 is implicated in the differentiation of human embryonic stem cells into hypothalamic Pomc neurons. Our data indicate that Tbx3 directs the terminal specification of neurons as functional components of the melanocortin system and is required for maintaining their peptidergic identity. In summary, we report the discovery of a key mechanistic process underlying the functional heterogeneity of hypothalamic neurons governing body weight and systemic metabolism.

E47 modulates hepatic glucocorticoid action

Glucocorticoids (GCs) are effective drugs, but their clinical use is compromised by severe side effects including hyperglycemia, hyperlipidemia and obesity. They bind to the Glucocorticoid Receptor (GR), which acts as a transcription factor. The activation of metabolic genes by GR is thought to underlie these adverse effects. We identify the bHLH factor E47 as a modulator of GR target genes. Using mouse genetics, we find that E47 is required for the regulation of hepatic glucose and lipid metabolism by GR, and that loss of E47 prevents the development of hyperglycemia and hepatic steatosis in response to GCs. Here we show that E47 and GR co-occupy metabolic promoters and enhancers. E47 is needed for the efficient recruitment of GR and coregulators such as Mediator to chromatin. Altogether, our results illustrate how GR and E47 regulate hepatic metabolism, and might provide an entry point for novel therapies with reduced side effects.

Glucocorticoids (GCs) are widely used anti-inflammatory drugs; however, long-term treatment causes metabolic side effects. Here, the authors show that E47 is a modulator of glucocorticoid receptor activity for a subset of target genes in mouse liver, and that loss of E47 protects mice from hyperglycemia and hepatic steatosis in response to GCs.

Rapid proteomic analysis for solid tumors reveals LSD1 as a drug target in an end-stage cancer patient

Recent advances in mass spectrometry (MS)-based technologies are now set to transform translational cancer proteomics from an idea to a practice. Here, we present a robust proteomic workflow for the analysis of clinically relevant human cancer tissues that allows quantitation of thousands of tumor proteins in several hours of measuring time and a total turnaround of a few days. We applied it to a chemorefractory metastatic case of the extremely rare urachal carcinoma. Quantitative comparison of lung metastases and surrounding tissue revealed several significantly upregulated proteins, among them lysine-specific histone demethylase 1 (LSD1/KDM1A). LSD1 is an epigenetic regulator and the target of active development efforts in oncology. Thus, clinical cancer proteomics can rapidly and efficiently identify actionable therapeutic options. While currently described for a single case study, we envision that it can be applied broadly to other patients in a similar condition.

Compartment-resolved Proteomic Analysis of Mouse Aorta during Atherosclerotic Plaque Formation Reveals Osteoclast-specific Protein Expression

Atherosclerosis leads to vascular lesions that involve major rearrangements of the vascular proteome, especially of the extracellular matrix (ECM). Using single aortas from ApoE knock out mice, we quantified formation of plaques by single-run, high-resolution mass spectrometry (MS)-based proteomics. To probe localization on a proteome-wide scale we employed quantitative detergent solubility profiling. This compartment- and time-resolved resource of atherogenesis comprised 5117 proteins, 182 of which changed their expression status in response to vessel maturation and atherosclerotic plaque development. In the insoluble ECM proteome, 65 proteins significantly changed, including relevant collagens, matrix metalloproteinases and macrophage derived proteins. Among novel factors in atherosclerosis, we identified matrilin-2, the collagen IV crosslinking enzyme peroxidasin as well as the poorly characterized MAM-domain containing 2 (Mamdc2) protein as being up-regulated in the ECM during atherogenesis. Intriguingly, three subunits of the osteoclast specific V-ATPase complex were strongly increased in mature plaques with an enrichment in macrophages thus implying an active de-mineralization function.

EPOP Functionally Links Elongin and Polycomb in Pluripotent Stem Cells

The cellular plasticity of pluripotent stem cells is thought to be sustained by genomic regions that display both active and repressive chromatin properties. These regions exhibit low levels of gene expression, yet the mechanisms controlling these levels remain unknown. Here, we describe Elongin BC as a binding factor at the promoters of bivalent sites. Biochemical and genome-wide analyses show that Elongin BC is associated with Polycomb Repressive Complex 2 (PRC2) in pluripotent stem cells. Elongin BC is recruited to chromatin by the PRC2-associated factor EPOP (Elongin BC and Polycomb Repressive Complex 2 Associated Protein, also termed C17orf96, esPRC2p48, E130012A19Rik), a protein expressed in the inner cell mass of the mouse blastocyst. Both EPOP and Elongin BC are required to maintain low levels of expression at PRC2 genomic targets. Our results indicate that keeping the balance between activating and repressive cues is a more general feature of chromatin in pluripotent stem cells than previously appreciated.

[Relevance of Vascular Trauma in Trauma Care - Impact on Clinical Course and Mortality]

There is a lack of evidence as to the relevance of vascular trauma (VT) in patients with severe injuries. Therefore, we reviewed registry data in the present study in order to systematically objectify the effect of VT in these patients. This study aimed to provide an adequate picture of the relevance of vascular trauma and to identify adverse prognostic factors. In a retrospective analysis of records from the TraumaRegister DGU® (TR-DGU) in two subgroups with moderate and severe VT, we examined the records for differences in terms of morbidity, mortality, follow-up and prognostic parameters compared to patients without VT with the same ISS. From a total of 42,326 patients, 2,961 (7 %) had a VT, and in 2,437 cases a severe VT (AIS ≥ 3) was diagnosed (5.8 %). In addition to a higher incidence of shock and a 2 to 3-fold increase in fluid replacement and erythrocyte transfusion, patients with severe VT had a 60 % higher rate of multiple organ failure, and in-hospital mortality was twice as high (33.8 %). The massively increased early mortality (8.0 vs. 25.2 %) clearly illustrates how severely injured patients are placed at risk by the presence of a relevant VT with a comparable ISS. In our opinion, due to an unexpected poor prognosis in the TR-DGU data for vascular injuries, increased attention is required in the care of severely injured patients. Based on our comprehensive analysis of negative prognostic factors, a further adjustment to the standards of vascular medicine could be advisable. The influence of the level of care provided by the admitting hospital and the relevance of a further hospital transfer to prognosis and clinical outcome is currently being analysed.

Proteomics to study DNA-bound and chromatin-associated gene regulatory complexes

High-resolution mass spectrometry (MS)-based proteomics is a powerful method for the identification of soluble protein complexes and large-scale affinity purification screens can decode entire protein interaction networks. In contrast, protein complexes residing on chromatin have been much more challenging, because they are difficult to purify and often of very low abundance. However, this is changing due to recent methodological and technological advances in proteomics. Proteins interacting with chromatin marks can directly be identified by pulldowns with synthesized histone tails containing posttranslational modifications (PTMs). Similarly, pulldowns with DNA baits harbouring single nucleotide polymorphisms or DNA modifications reveal the impact of those DNA alterations on the recruitment of transcription factors. Accurate quantitation – either isotope-based or label free – unambiguously pinpoints proteins that are significantly enriched over control pulldowns. In addition, protocols that combine classical chromatin immunoprecipitation (ChIP) methods with mass spectrometry (ChIP-MS) target gene regulatory complexes in their in-vivo context. Similar to classical ChIP, cells are crosslinked with formaldehyde and chromatin sheared by sonication or nuclease digested. ChIP-MS baits can be proteins in tagged or endogenous form, histone PTMs, or lncRNAs. Locus-specific ChIP-MS methods would allow direct purification of a single genomic locus and the proteins associated with it. There, loci can be targeted either by artificial DNA-binding sites and corresponding binding proteins or via proteins with sequence specificity such as TAL or nuclease deficient Cas9 in combination with a specific guide RNA. We predict that advances in MS technology will soon make such approaches generally applicable tools in epigenetics.

ADP-ribose-derived nuclear ATP synthesis by NUDIX5 is required for chromatin remodeling

Key nuclear processes in eukaryotes, including DNA replication, repair, and gene regulation, require extensive chromatin remodeling catalyzed by energy-consuming enzymes. It remains unclear how the ATP demands of such processes are met in response to rapid stimuli. We analyzed this question in the context of the massive gene regulation changes induced by progestins in breast cancer cells and found that ATP is generated in the cell nucleus via the hydrolysis of poly(ADP-ribose) to ADP-ribose. In the presence of pyrophosphate, ADP-ribose is used by the pyrophosphatase NUDIX5 to generate nuclear ATP. The nuclear source of ATP is essential for hormone-induced chromatin remodeling, transcriptional regulation, and cell proliferation.

Establishment of hepatitis A vaccine (inactivated, non-adsorbed) BRP batches 2 and 3

The current hepatitis A vaccine (HAV), inactivated, non-adsorbed, European Pharmacopoeia (Ph. Eur.) Biological Reference Preparation (BRP) is used for the in vitro potency assay of HAV as prescribed by the Ph. Eur. general chapter 2.7.14 Assay of hepatitis A vaccine. This reference preparation was calibrated in 2008 through an international collaborative study and was assigned a potency of 12 IU/mL. During use of this BRP it appeared to be inapplicable in certain cases due to a low nominal antigen content. Consequently, the European Directorate for the Quality of Medicines and HealthCare (EDQM) established replacement batches for this BRP, calibrated against the 1(st) WHO International Standard (IS) for HAV (inactivated), using the standard in vitro ELISA (enzyme-linked immunosorbent assay) method validated previously. The results of the study showed that the candidate BRPs were suitable for the intended purpose, and following completion of the study, they were adopted in November 2014 by the Ph. Eur. Commission as HAV (inactivated, non-adsorbed) BRP batches 2 and 3, with an assigned potency of 1350 IU/mL, for in vitro antigen content determination by ELISA. As the amount of material in each vial largely exceeds the amount required for the performance of a single assay, the BRPs are to be aliquoted by users as single-use aliquots and refrozen below -50 °C prior to their use as reference preparations.

Establishment of the Ph. Eur. erythropoietin chemical reference substance batch 1

The Erythropoietin (EPO) European Pharmacopoeia (Ph. Eur.) Biological Reference Preparation (BRP) batch 3 was calibrated in 2006 by in vivo bioassay and was used as a reference preparation for these assays as well as for the physicochemical methods in the Ph. Eur. monograph Erythropoietin concentrated solution (1316). In order to avoid the frequent replacement of this standard and thus reduce the use of animals, a new EPO Chemical Reference Substance (CRS) was established to be used solely for the physicochemical methods. Here we report the outcome of a collaborative study aimed at demonstrating the suitability of the candidate CRS (cCRS) as a reference for the physicochemical methods in the Ph. Eur. monograph. Results from the study demonstrated that for the physicochemical methods currently required in the monograph (capillary zone electrophoresis (CZE), polyacrylamide gel electrophoresis (PAGE)/immunoblotting and peptide mapping), the cCRS is essentially identical to the existing BRP. However, data also indicated that, for the physicochemical methods under consideration for inclusion in a revised monograph (test for oxidised forms and glycan mapping), the suitability of the cCRS as a reference needs to be confirmed with additional work. Further to completion of the study, the Ph. Eur. Commission adopted the cCRS as "Erythropoietin for physicochemical tests CRS batch 1" to be used for CZE, PAGE/immunoblotting and peptide mapping.

Quality standards of the European Pharmacopoeia

ETHNOPHARMACOLOGICAL RELEVANCE

The European Pharmacopoeia (Ph. Eur.) provides a legal and scientific reference for the quality control of medicines. It is legally binding in the 38 signatory parties of the Convention on the elaboration of a European Pharmacopoeia (37 member states and the European Union).

MATERIALS AND METHODS

The requirements for a specific herbal drug are prescribed in the corresponding individual monograph and the relevant general monographs. Criteria for pesticides and heavy metals for example are defined in the general monograph on Herbal drugs. The Ph. Eur. also provides general methods including methods for determination of aflatoxins B1 and ochratoxin A. Screening methods for aristolochic acids are applied for herbal drugs that may be subject to adulteration or substitution with plant material containing aristolochic acids.

CONCLUSION

The Ph. Eur. collaborate in many areas with the European Medicines Agency (EMA) to ensure close collaboration as regards the respective work programmes and approach.

PLK1 signaling in breast cancer cells cooperates with estrogen receptor-dependent gene transcription

Polo-like kinase 1 (PLK1) is a key regulator of cell division and is overexpressed in many types of human cancers. Compared to its well-characterized role in mitosis, little is known about PLK1 functions in interphase. Here, we report that PLK1 mediates estrogen receptor (ER)-regulated gene transcription in human breast cancer cells. PLK1 interacts with ER and is recruited to ER cis-elements on chromatin. PLK1-coactivated genes included classical ER target genes such as Ps2, Wisp2, and Serpina3 and were enriched in developmental and tumor-suppressive functions. Performing large-scale phosphoproteomics of estradiol-treated MCF7 cells in the presence or absence of the specific PLK1 inhibitor BI2536, we identified several PLK1 end targets involved in transcription, including the histone H3K4 trimethylase MLL2, the function of which on ER target genes was impaired by PLK1 inhibition. Our results propose a mechanism for the tumor-suppressive role of PLK1 in mammals as an interphase transcriptional regulator.

A single glycine-alanine exchange directs ligand specificity of the elephant progestin receptor

The primary gestagen of elephants is 5α-dihydroprogesterone (DHP), which is unlike all other mammals studied until now. The level of DHP in elephants equals that of progesterone in other mammals, and elephants are able to bind DHP with similar affinity to progesterone indicating a unique ligand-binding specificity of the elephant progestin receptor (PR). Using site-directed mutagenesis in combination with in vitro binding studies we here report that this change in specificity is due to a single glycine to alanine exchange at position 722 (G722A) of PR, which specifically increases DHP affinity while not affecting binding of progesterone. By conducting molecular dynamics simulations comparing human and elephant PR ligand-binding domains (LBD), we observed that the alanine methyl group at position 722 is able to push the DHP A-ring into a position similar to progesterone. In the human PR, the DHP A-ring position is twisted towards helix 3 of PR thereby disturbing the hydrogen bond pattern around the C3-keto group, resulting in a lower binding affinity. Furthermore, we observed that the elephant PR ligand-binding pocket is more rigid than the human analogue, which probably explains the higher affinity towards both progesterone and DHP. Interestingly, the G722A substitution is not elephant-specific, rather it is also present in five independent lineages of mammalian evolution, suggesting a special role of the substitution for the development of distinct mammalian gestagen systems.

Data extraction from proteomics raw data: an evaluation of nine tandem MS tools using a large Orbitrap data set

In shot-gun proteomics raw tandem MS data are processed with extraction tools to produce condensed peak lists that can be uploaded to database search engines. Many extraction tools are available but to our knowledge, a systematic comparison of such tools has not yet been carried out. Using raw data containing more than 400,000 tandem MS spectra acquired using an Orbitrap Velos we compared 9 tandem MS extraction tools, freely available as well as commercial. We compared the tools with respect to number of extracted MS/MS events, fragment ion information, number of matches, precursor mass accuracies and agreement in-between tools. Processing a primary data set with 9 different tandem MS extraction tools resulted in a low overlap of identified peptides. The tools differ by assigned charge states of precursors, precursor and fragment ion masses, and we show that peptides identified very confidently using one extraction tool might not be matched when using another tool. We also found a bias towards peptides of lower charge state when extracting fragment ion data from higher resolution raw data without deconvolution. Collecting and comparing the extracted data from the same raw data allow adjusting parameters and expectations and selecting the right tool for extraction of tandem MS data.

Characterisation of steroid receptor expression in the human prostate carcinoma cell line 22RV1 and quantification of androgen effects on mRNA regulation of prostate-specific genes

In this study, the effect of natural androgens on the expression of androgen-regulated genes in the human prostate carcinoma cell line 22RV1 was characterised. To clarify the usefulness of the cells for in vitro studies concerning activation of androgen responsive genes by various steroidal compounds steroid receptor expression patterns had to be characterised intensively. Expression of androgen receptor (AR), estrogen receptor alpha (ERalpha) and beta (ERbeta), progestin receptor (PR) and glucocorticoid receptor alpha and beta was investigated by the means of RT-PCR, immunocytochemistry, ligand binding or Western blot. 22RV1 cells were proved to express androgen receptor and less glucocorticoid receptor beta on mRNA level. The confirmed mutation of the androgen receptor at codon H874 slightly apart from the steroid binding pocket seemed not to cause alteration of natural steroid hormone binding. mRNA expression of all progestin and estrogen receptor isoforms as well as glucocorticoid receptor alpha could not be detected. To study functional relevance of above-mentioned findings nine androgen-regulated genes were chosen to characterise the cell line and to determine androgenic effects using highly sensitive real-time RT-PCR. Addition of the three natural steroids dihydrotestosterone (DHT), testosterone, and 19-nortestosterone significantly influenced mRNA expression profiles. All compounds under study showed clear time-dependent and androgen-specific effects on transcriptional level. The results demonstrate that the cultivated human prostate carcinoma epithelial cells have a hormonal sensitivity correlated with the presence of specific receptors and can, therefore, serve as a selective model to study hormone action.