Tivozanib for the treatment of renal cell carcinoma: patient selection and perspectives

Tivozanib is an oral selective vascular endothelial growth factors receptor (VEGFR) tyrosine kinase inhibitor that is recently approved by the European Medicines Agency for the treatment of previously untreated patients with metastatic renal cell carcinoma (mRCC) as well as for those patients with disease progression during or after cytokine therapy. Nowadays, in first-line and second-line treatment of mRCC, there is an abundance of options, mainly consisting of VEGFR-directed tyrosinekinase inhibitors. This review focusses on the role of tivozanib with respect to patient selection and future perspectives in this fast-changing landscape.

QIL1-dependent assembly of MICOS complex-lethal mutation in C19ORF70 resulting in liver disease and severe neurological retardation

Seven subunits of the mitochondrial contact site and cristae junction (CJ) organizing system (MICOS) in humans have been recently described in function and structure. QIL1 (also named MIC13) is a small complex that is crucial for the maintenance and assembling of MICOS. A novel mutation of an essential splice site in the C19orf70 gene encoding QIL1 induces severe mitochondrial encephalopathy, hepatopathy and lactate acidosis consistent with psychomotor retardation. In addition, bilateral kidney stones were observed. Disassembly of MICOS complex subunits displays lack of MIC10-MIC26-MIC27-QIL1 subcomplex, resulting in aberrant cristae structure and a loss of cristae junctions and contact sites. In liver and muscle tissue, the activity of the respiratory chain complexes (OXPHOS) was severely impaired. Defects in MICOS complex do not only affect mitochondrial architecture, but also mitochondrial fusion, metabolic signalling, lipid trafficking and cellular electric homeostasis.

Validation of the Chowdhury overall survival score in patients with melanoma brain metastasis treated with Gamma Knife Radiosurgery

Melanoma brain metastases (MBM) are common in patients with stage IV disease. For Gamma Knife radiosurgery (GKRS) on MBM, risk scores such as RPA and melanoma-GPA aid to identify prognostic subgroups. This study aimed to validate the overall survival (OS) risk score developed by Chowdhury et al. in our center's patient cohort. A total of 104 MBM patients were treated with GKRS between 1/1/2002 and 31/12/2014 in our institution. Patients were categorized according to RPA, melanoma-GPA and Chowdhury OS score. The Kaplan-Meier method was used to estimate overall survival, and predicted survival probabilities were calculated for calibration. Cox proportional hazards regressions were performed to identify additional risk factors. Overall, median follow-up time was 80 months, while median OS (mOS) after GKRS was 6 months. Stratified according to the Chowdhury OS score, mOS in the high, medium and low risk group was 3.4, 7.1, and 10.0 months, respectively. The addition of other patient or disease characteristics to the Chowdhury OS model did not improve its performance. The C-index of the melanoma-GPA was 0.46 while the Chowdhury OS had an index of 0.67. In comparison with the RPA and melanoma-GPA, the Chowdhury OS score more accurately distinguished between separate risk groups among patients with MBM treated with GKRS. Contrary to the original study by Chowdhury, follow-up time was sufficient here for the low-risk group to reach the mOS time of 10 months.

Mining for mitochondrial mechanisms: Linking known syndromes to mitochondrial function

Mitochondrial disorders (MDs) are caused by defects in 1 or multiple complexes of the oxidative phosphorylation (OXPHOS) machinery. MDs are associated with a broad range of clinical signs and symptoms, and have considerable clinical overlap with other neuromuscular syndromes. This overlap might be due to involvement of mitochondrial pathways in some of these non-mitochondrial syndromes. Here, we give an overview of around 25 non-mitochondrial syndromes, diagnosed in patients who were initially suspected to have a MD on the basis of clinical and biochemical parameters. In addition, we highlight the mitochondrial connections of 6 of these non-mitochondrial syndromes (eg, Rett syndrome and Dravet syndrome) diagnosed in multiple patients. Further research to unravel the interplay between these genes and mitochondria may help to increase knowledge on these syndromes. Additionally, it may open new avenues for research on pathways interacting with mitochondrial function in order to find new targets for therapeutics to treat MDs. The data presented in this review underline the importance of careful assessment of clinical, genetic, and biochemical data in all patients suspected of a neuromuscular syndrome, and highlights the importance of the role of clinical geneticists, physicians, and clinical biochemists in recognizing the possible mitochondrial connection of non-mitochondrial syndromes.

[Serious complications during treatment with methotrexate: also in chronic low-dosage use]

Methotrexate is a frequently prescribed drug and is considered to be safe at a low dosage. However, serious complications may occur during treatment. In this article we describe a 78-year-old male who used low-dose methotrexate for psoriatic arthritis. He died of multi-organ failure caused by sepsis and methotrexate intoxication as a result of deteriorating renal function. The second patient was a 56-year-old male who used low-dose methotrexate for rheumatoid arthritis. This patient developed pancytopenia and methotrexate pneumonitis during treatment with methotrexate. We recommend the frequent monitoring of blood count and renal and liver function tests to detect early deterioration. Furthermore, doctors should be aware of conditions and factors predisposing to methotrexate intoxication, such as impaired kidney function and co-medication. If methotrexate intoxication is suspected, intravenous folinic acid should be administered immediately.

A lethal neonatal phenotype of mitochondrial short-chain enoyl-CoA hydratase-1 deficiency

Short-chain enoyl-CoA hydratase (SCEH) is a mitochondrial enzyme involved in the oxidation of fatty acids and the catabolic pathway of valine and, to a lesser extent, isoleucine. Deficiency of this enzyme was recently shown to cause an early childhood Leigh syndrome phenotype. The few reported patients were compound heterozygotes for two missense or missense with truncating variants in ECHS1 that encodes SCEH. We describe two siblings with severe refractory lactic acidosis and death within the first 2 days of life. Following negative clinical whole-exome and whole-genome sequencing, we resorted to autozygome/exome analysis on research basis and identified a homozygous splice site mutation (c.88+5G>A) in the two cases. Analysis of cDNA confirmed complete replacement of the normal transcript with an aberrant transcript (r.88_89ins 88+1_88+11) predicting premature truncation of the protein [p.(Ala31Glufs*23)]. Furthermore, quantitative reverse transcriptase polymerase chain reaction (RTPCR) showed marked reduction in ECHS1, most likely nonsense-mediated decay (NMD)-mediated. This is the first report of homozygosity for a truncating mutation in ECHS1, which may explain the severe phenotype. Our report highlights the need to consider SCEH deficiency in patients with lethal neonatal lactic acidosis, and the potentially limited sensitivity of untargeted genomic sequencing towards non-canonical splicing mutations, which may explain at least some of the 'negative' cases on clinical exome/genome sequencing.

Leigh-Like Syndrome Due to Homoplasmic m.8993T>G Variant with Hypocitrullinemia and Unusual Biochemical Features Suggestive of Multiple Carboxylase Deficiency (MCD)

Leigh syndrome (LS), or subacute necrotizing encephalomyelopathy, is a genetically heterogeneous, relentlessly progressive, devastating neurodegenerative disorder that usually presents in infancy or early childhood. A diagnosis of Leigh-like syndrome may be considered in individuals who do not fulfil the stringent diagnostic criteria but have features resembling Leigh syndrome.We describe a unique presentation of Leigh-like syndrome in a 3-year-old boy with elevated 3-hydroxyisovalerylcarnitine (C5-OH) on newborn screening (NBS). Subsequent persistent plasma elevations of C5-OH and propionylcarnitine (C3) as well as fluctuating urinary markers were suggestive of multiple carboxylase deficiency (MCD). Normal enzymology and mutational analysis of genes encoding holocarboxylase synthetase (HLCS) and biotinidase (BTD) excluded MCD. Biotin uptake studies were normal excluding biotin transporter deficiency. His clinical features at 13 months of age comprised psychomotor delay, central hypotonia, myopathy, failure to thrive, hypocitrullinemia, recurrent episodes of decompensation with metabolic keto-lactic acidosis and an episode of hyperammonemia. Biotin treatment from 13 months of age was associated with increased patient activity, alertness, and attainment of new developmental milestones, despite lack of biochemical improvements. Whole exome sequencing (WES) analysis failed to identify any other variants which could likely contribute to the observed phenotype, apart from the homoplasmic (100%) m.8993T>G variant initially detected by mitochondrial DNA (mtDNA) sequencing.Hypocitrullinemia has been reported in patients with the m.8993T>G variant and other mitochondrial disorders. However, persistent plasma elevations of C3 and C5-OH have previously only been reported in one other patient with this homoplasmic mutation. We suggest considering the m.8993T>G variant early in the diagnostic evaluation of MCD-like biochemical disturbances, particularly when associated with hypocitrullinemia on NBS and subsequent confirmatory tests. An oral biotin trial is also warranted.

Natural disease course and genotype-phenotype correlations in Complex I deficiency caused by nuclear gene defects: what we learned from 130 cases

Mitochondrial complex I is the largest multi-protein enzyme complex of the oxidative phosphorylation system. Seven subunits of this complex are encoded by the mitochondrial and the remainder by the nuclear genome. We review the natural disease course and signs and symptoms of 130 patients (four new cases and 126 from literature) with mutations in nuclear genes encoding structural complex I proteins or those involved in its assembly. Complex I deficiency caused by a nuclear gene defect is usually a non-dysmorphic syndrome, characterized by severe multi-system organ involvement and a poor prognosis. Age at presentation may vary, but is generally within the first year of life. The most prevalent symptoms include hypotonia, nystagmus, respiratory abnormalities, pyramidal signs, dystonia, psychomotor retardation or regression, failure to thrive, and feeding problems. Characteristic symptoms include brainstem involvement, optic atrophy and Leigh syndrome on MRI, either or not in combination with internal organ involvement and lactic acidemia. Virtually all children ultimately develop Leigh syndrome or leukoencephalopathy. Twenty-five percent of the patients died before the age of six months, more than half before the age of two and 75 % before the age of ten years. Some patients showed recovery of certain skills or are still alive in their thirties . No clinical, biochemical, or genetic parameters indicating longer survival were found. No clear genotype-phenotype correlations were observed, however defects in some genes seem to be associated with a better or poorer prognosis, cardiomyopathy, Leigh syndrome or brainstem lesions.

A Diagnostic Algorithm for Mitochondrial Disorders in Estonian Children

Mitochondrial disorders are a heterogeneous group of disorders affecting energy production of the body. Different consensus diagnostic criteria for mitochondrial disorders in childhood are available - Wolfson, Nijmegen and modified Walker criteria. Due to the extreme complexity of mitochondrial disorders in children, we decided to develop a diagnostic algorithm, applicable in clinical practice in Estonia, in order to identify patients with mitochondrial disorders among pediatric neonatology and neurology patients. Additionally, it was aimed to evaluate the live-birth prevalence of mitochondrial disorders in childhood. During the study period (2003-2009), a total of 22 children were referred to a muscle biopsy in suspicion of mitochondrial disorder based on the preliminary biochemical, metabolic and instrumental investigations. Enzymatic and/or molecular analysis confirmed mitochondrial disease in 5 of them - an SCO2 gene (synthesis of cytochrome c oxidase, subunit 2) defect, 2 cases of pyruvate dehydrogenase complex deficiency and 2 cases of combined complex I and IV deficiency. The live-birth prevalence for mitochondrial defects observed in our cohort was 1/20,764 live births. Our epidemiological data correlate well with previously published epidemiology data on mitochondrial diseases in childhood from Sweden and Australia, but are lower than in Finland.

Sequence variants in four candidate genes (NIPSNAP1, GBAS, CHCHD1 and METT11D1) in patients with combined oxidative phosphorylation system deficiencies

The oxidative phosphorylation (OXPHOS) system, comprising five enzyme complexes, is located in the inner membrane of mitochondria and is the final biochemical pathway in oxidative ATP production. Defects in this energy-generating system can cause a wide range of clinical symptoms; these diseases are often progressive and multisystemic. Numerous genes have been implicated in OXPHOS deficiencies and many mutations have been described. However, in a substantial number of patients with decreased enzyme activities of two or more OXPHOS complexes, no mutations in the mitochondrial DNA or in nuclear genes known to be involved in these disorders have been found. In this study, four nuclear candidate genes--NIPSNAP1, GBAS, CHCHD1 and METT11D1--were screened for mutations in 22 patients with a combined enzymatic deficiency of primarily the OXPHOS complexes I, III and IV to determine whether a mutation in one of these genes could explain the mitochondrial disorder. For each variant not yet reported as a polymorphism, 100 control samples were screened for the presence of the variant. This way we identified 14 new polymorphisms and 2 presumably non-pathogenic mutations. No mutations were found that could explain the mitochondrial disorder in the patients investigated in this study. Therefore, the genetic defect in these patients must be located in other nuclear genes involved in mtDNA maintenance, transcription or translation, in import, processing or degradation of nuclear encoded mitochondrial proteins, or in assembly of the OXPHOS system.

Coenzyme Q(10) is decreased in fibroblasts of patients with methylmalonic aciduria but not in mevalonic aciduria

The content of coenzyme Q(10) (CoQ(10)) was examined in skin fibroblasts of 10 patients with mevalonic aciduria (MVA) and of 22 patients with methylmalonic aciduria (MMA). Patients with these inborn errors of metabolism are thought to be at risk for CoQ(10) depletion either by direct inhibition of the proximal pathway of CoQ(10) synthesis (MVA) or indirectly by inhibition of mitochondrial energy metabolism (MMA). We demonstrated that CoQ(10) concentrations were not significantly different from controls in MVA patients, suggesting that there may be upregulatory effects. On the other hand the CoQ(10) content in fibroblasts of patients with MMA was significantly reduced.

Normal biochemical analysis of the oxidative phosphorylation (OXPHOS) system in a child with POLG mutations: a cautionary note

We report a 5-year-old child carrying polymerase gamma (POLG1) mutations, but strikingly normal oxidative phosphorylation analysis in muscle, fibroblasts and liver. Mutations in POLG1 have so far been described in children with severe combined oxidative phosphorylation (OXPHOS) deficiencies and with the classical Alpers-Huttenlocher syndrome. The patient presented with a delayed psychomotor development and ataxia during the first two years of life. From the third year of life he developed epilepsy and regression in development, together with symptoms of visual impairment and sensorineuronal deafness. Cerebrospinal fluid showed elevated lactic acid and protein concentrations. An elder brother had died due to combined OXPHOS deficiencies. Despite the clinical similarity with the elder brother, except for liver involvement, the OXPHOS system analysis in a frozen muscle biopsy was normal. For this reason a fresh muscle biopsy was performed, which has the advantage of the possibility of measuring the substrate oxidation rates and ATP production, part of the mitochondrial energy-generating system (MEGS). During the same session, biopsies of liver and fibroblasts were taken. These three tissues showed normal measurements of the MEGS capacity. Based on the phenotype of Alpers-Huttenlocher syndrome in the elder brother, we decided to screen the POLG1 gene. Mutation analysis showed compound heterozygosity with two known mutations, A467T and G848S. The normal MEGS capacity in this patient expands the already existing complexity and heterogeneity of the childhood POLG1 patients and, on the basis of the high frequency of POLG1 mutations in childhood, warrants a liberal strategy with respect to mutation analysis.

MR spectroscopy of the brain in Leigh syndrome

Brain magnetic resonance spectroscopy in two patients with Leigh syndrome revealed the presence of lactate in gray and white matter brain tissue and relatively high choline levels in the white matter. The latter observation, most probably related to an ongoing demyelination process, underlines specific involvement of white matter metabolism in Leigh syndrome even in cases without involvement of the white matter as visualized on MRI. Magnetic resonance spectroscopy might thus be of help in differentiating Leigh syndrome from a range of other mitochondrial diseases, such as ophthalmoplegia and Kearns-Sayre syndrome, showing lack of lactate in brain tissues appearing normal on MRI.

Early cardiac involvement in children carrying the A3243G mtDNA mutation

The phenotypic spectrum of the mitochondrial A3243G DKA mutation is highly variable, particularly when occuring in childhood. In contrast to the classical presentation in adulthood (MELAS syndrome; mitochondria! myopathy, encephalopathy, lactic acidosis and stroke-like episodes) children show a different pattern of symptoms, often without the typical encephalopathy or psychomotor regression. We present six children carrying the A3243G mtDNA mutation with a heteroplasmy above 50 % in muscle tissue. The age of diagnosis ranged from 2 weeks up to 14.5 years. The clinical presentation was rather non-specific including muscle weakness, developmental delay and epilepsy. In this small pediatric group we detected presymptomatic cardiac involvement in five out of six children already at an early stage of disease. The cardiac pathology included cardiomyopathy and biventricular hypertrophy with rhythm disturbances (for example long QT-syndrome). The observed cardiac changes do not always increase the risk of cardiac deterioration; however, two of our patients died early on.

CONCLUSION

We hypothesize that the A3243G mutation might be underdiagnosed, as patients could suffer from an unexplained cardiac death before the diagnosis is made. We advise performing regular repeated ECGs and echocardiography in all children carrying a A3243G mtDNA mutation independently from the presence of cardiac symptoms.

Mitochondrial disease criteria: diagnostic applications in children

BACKGROUND

Based on a previous prospective clinical and biochemical study, a consensus mitochondrial disease scoring system was established to facilitate the diagnosis in patients with a suspected mitochondrial disorder.

OBJECTIVE

To evaluate the specificity of the diagnostic system, we applied the mitochondrial disease score in 61 children with a multisystem disease and a suspected oxidative phosphorylation disorder who underwent a muscle biopsy and were consecutively diagnosed with a genetic mutation.

METHODS

We evaluated data of 44 children diagnosed with a disorder in oxidative phosphorylation, carrying a mutation in the mitochondrial or nuclear DNA. We compared them with 17 children who, based on the clinical and metabolic features, also had a muscle biopsy but were finally diagnosed with a nonmitochondrial multisystem disorder by further genetic analysis.

RESULTS

All children with a genetically established diagnosis of a primary oxidative phosphorylation disorder had a mitochondrial disease score above 6 (probable mitochondrial disorder), and 73% of the children had a score above 8 (definite mitochondrial disorder) at evaluation of the muscle biopsy. In the nonmitochondrial multisystem disorder group, the score was significantly lower, and no patients reached a score comparable with a definite respiratory chain disorder.

CONCLUSIONS

The mitochondrial disease criteria system has a high specificity to distinguish between mitochondrial and other multisystem disorders. The method could also be applied in children with a suspected mitochondrial disorder, prior to performing a muscle biopsy.

Skeletal muscle ultrasonography in children with a dysfunction in the oxidative phosphorylation system

OBJECTIVE

The aim of this prospective study was to investigate the diagnostic value of quantitative skeletal muscle ultrasonography in children suspected of having a mitochondrial disorder.

METHODS

Muscle thickness and quantitatively determined echo intensity of four muscles were established in 53 children with symptoms indicative of a mitochondrial disorder.

RESULTS

A sensitivity of 25 to 46 % was found, depending on the chosen cut-off point (abnormal or borderline abnormal), with a specificity of 85 to 100 %. Except for one, all abnormal ultrasound scans were found in children over five years of age. Within the group of patients with a mitochondrial disorder, a significant correlation was found between muscle echo intensity and age (r = 0.38; p = 0.047).

CONCLUSIONS

We conclude that skeletal muscle ultrasound can be of additional value in the diagnosis of children with suspected mitochondrial disorders, especially in children over five years of age. With its low sensitivity, it is not suitable for screening purposes. However, since all abnormal ultrasound scans were found in children with a mitochondrial disorder, and no significant correlation with the MDC score was found, muscle ultrasound can be used complementary to this scoring system to facilitate the decision-making in pursuing further invasive diagnostics.

Development of an androgen reporter gene assay (AR-LUX) utilizing a human cell line with an endogenously regulated androgen receptor

The aim of the work described in this report is to develop and characterize a cell-based androgen reporter assay. For this purpose, the androgen receptor (AR) expressing human breast cancer cell line T47D was stably transfected with a luciferase gene under transcriptional control of the PB-ARE-2 androgen response element. The application of this cell line in an endogenous Androgen Receptor-mediated LUciferase eXpression assay (AR-LUX) was validated. An EC50 value of 86 pM was determined for the standard androgen R1881 with a detection limit of 46 pM. Other androgens like dihydrotestosterone, 17beta-trenbolone, and bolasterone also induced luciferase expression, while anti-androgens suppressed these responses. As expected, AR-mediated responses were also elicited by high concentrations of the steroids progesterone, 17beta-estradiol, d-aldosterone, and dexamethasone, with observed EC50 values 10 to 350,000 times higher than that for R1881. A unique feature of the AR-LUX assay is that effects on modulation of active endogenous AR-levels are reliably reflected in the luciferase induction response, as exemplified by vitamin D, all-trans-retinoic acid, epigallocatechin gallate, and forskolin. This feature is especially useful when assessing complex mixtures, e.g., environmental samples or natural compound libraries. From these data it is concluded that the AR-LUX assay is a reliable in vitro test system for the detection and quantification of AR-mediated biological effects. The 96-well plate format makes the assay particularly suitable for high-throughput screening.

The antiinflammatory drug sulfasalazine inhibits tumor necrosis factor alpha expression in macrophages by inducing apoptosis

OBJECTIVE

Sulfasalazine (SSZ) is a commonly used drug in the treatment of inflammatory diseases such as rheumatoid arthritis and Crohn's disease. In both diseases, the proinflammatory cytokine tumor necrosis factor alpha (TNFalpha) plays a prominent role. In these studies, we investigated the mechanism by which SSZ inhibits TNFalpha expression in macrophages and macrophage-like cell lines.

METHODS

Monocyte-derived macrophages and several macrophage-like cell lines were exposed to SSZ in vitro, and the effect on TNFalpha expression was monitored by reverse transcriptase-polymerase chain reaction and Western blot analysis. In addition, the effects of SSZ in vivo were examined by intraperitoneally injecting mice with SSZ, after which peritoneal cells were harvested and examined using various staining methods.

RESULTS

Preincubation of macrophages with SSZ, but not with methotrexate, inhibited lipopolysaccharide (LPS)-induced TNFalpha expression. Inhibition of TNFalpha expression by SSZ coincided with the induction of apoptosis, as judged by the appearance of morphologic changes typical of apoptosis, such as nuclear condensation and fragmentation. Induction of apoptosis by SSZ was confirmed by TUNEL analysis and by the detection of cleaved U1-70K, a substrate of caspase 3. Intraperitoneal injections of SSZ in mice resulted in the induction of apoptosis of peritoneal cells within a few hours. SSZ-induced cleavage of the U1-70K protein was inhibited by Zn2+ and by specific inhibitors of caspases 3 and 8, but not caspases 1 and 9. Interestingly, the reduced expression of LPS-induced TNFalpha in the presence of SSZ was restored by inhibition of caspase 8.

CONCLUSION

Inhibition of TNFalpha expression in macrophages by SSZ is due to the induction of apoptosis and involves the activation of caspase 8.

Cell death: a trigger of autoimmunity?

Systemic autoimmune diseases are characterized by the production of antibodies against a broad range of self-antigens. Recent evidence indicates that the majority of these autoantigens are modified in various ways during cell death. This has led to the hypothesis that the primary immune response in the development of autoimmunity is directed to components of the dying cell. In this article, we summarize data on the modification of autoantigens during cell death and the possible consequences of this for autoimmunity.

Superinduction of interleukin 8 mRNA in activated monocyte derived macrophages from rheumatoid arthritis patients

OBJECTIVE

Synovial inflammation in patients with rheumatoid arthritis (RA) is characterised by the presence of large numbers of highly activated monocytes and macrophages. The importance of these cells in the aethiopathogenesis and prognosis of RA is increasingly recognised. The object of this report is to determine whether monocytes and monocyte derived macrophages of RA patients produce increased cytokine mRNA levels.

METHODS

Monocyte derived macrophages from RA patients and healthy controls were cultured either in the absence or presence of lipopolysaccharide. The expression levels of the mRNAs encoding GAPDH, interleukin 1beta (IL1beta), IL8, and alpha(2) macroglobulin in these cells were analysed by reverse transcriptase-polymerase chain reaction (RT-PCR).

RESULTS

Activated monocyte derived macrophages from RA patients produce significantly higher IL8 mRNA levels than activated macrophages from healthy controls. By contrast, resting RA and control macrophages produce similar levels of IL8 mRNA. Culturing of activated macrophages in the presence of RA or control sera has no effect on the expression levels of IL8 mRNA. No significant differences between RA and control macrophages were observed in the expression levels of IL1beta and alpha(2) macroglobulin mRNAs.

CONCLUSION

These data indicate that the increased IL8 mRNA production capacity of RA macrophages upon activation is an intrinsic property of these cells, and is not attributable to factors present in the circulation. Based on these observations, it is postulated that this innate hyper-responsiveness of RA macrophages contributes to the high IL8 levels present in the synovial fluid of rheumatoid joints, and is implicated in the chemotactic gradient leading to the homing of leucocytes to the joints.

Peripheral blood monocytes of rheumatoid arthritis patients do not express elevated TNF alpha, IL-1beta, and IL-8 mRNA levels. A comparison of monocyte isolation procedures

We have compared three monocyte isolation procedures for their suitability in the analysis of cytokine mRNA expression in circulating monocytes. Monocytes were isolated from peripheral blood (1) using antiCD14 coated magnetic beads, (2) by Ficoll centrifugation, or (3) by Ficoll centrifugation followed by plastic adherence. The effect of the isolation procedure on the cytokine mRNA expression levels of the isolated monocytes was evaluated by RT-PCR. Results show that the expression of cytokine mRNAs determined in monocytes isolated using antiCD14 coated magnetized beads reflects best the cytokine mRNA levels in circulating monocytes. We subsequently applied this method to the analysis of cytokine mRNA expression levels in rheumatoid arthritis and control monocytes, which revealed that RA and control monocytes isolated by antiCD14 beads produce similar, very low TNF alpha, IL-1beta, and IL-8 mRNA levels.

Expression of macrophage-derived chemokine (MDC) mRNA in macrophages is enhanced by interleukin-1beta, tumor necrosis factor alpha, and lipopolysaccharide

A cDNA encoding the C-C chemokine MDC was isolated from a human macrophage cDNA library by differential hybridization using monocyte- and macrophage-specific cDNA probes. During monocyte to macrophage differentiation in vitro, MDC expression is first detected after 1 day of culturing and reaches maximum levels after 6 days when macrophages have fully matured, as judged from the expression of known macrophage marker genes. Exposure of macrophages to lipopolysaccharide (LPS) results in a dose-dependent increase in MDC mRNA levels, with maximum induction occurring after 6-8 h, whereas expression levels of macrophage inflammatory protein-1alpha (MIP-1alpha), MIP-2, interleukin-1beta (IL-1beta), and tumor necrosis factor alpha (TNF-alpha) respond much faster to LPS. Furthermore, MDC expression in macrophages is enhanced by the inflammatory mediators TNF-alpha and IL-1beta. Similar to other TNF-alpha/IL-1beta-inducible genes, costimulation of macrophages with both cytokines leads to higher MDC expression levels than stimulation with a single cytokine. By contrast, both resting and activated monocytes do not express MDC mRNA.

A functional Sp1 binding site is essential for the activity of the adult liver-specific human insulin-like growth factor II promoter

The human gene encoding insulin-like growth factor II contains four promoters (P1-P4) that are differentially activated in various tissues during development. Expression of insulin-like growth factor II in adult liver tissue is directed by P1, which is activated by liver-enriched members of the CCAAT/enhancer binding protein family of transcription factors. In the present report we show that the region around -48 relative to the transcription start site contains a high affinity Sp1 binding site. This was demonstrated by electrophoretic mobility shift assays using nuclear extracts from Hep3B hepatoma cells and with specific antibodies directed against Sp1. Competition electrophoretic mobility shift assays revealed that the Sp1 binding site of P1 and a consensus Sp1 binding site bind Sp1 with comparable efficiencies. Mutation of the Sp1 binding site results in an 85% decrease in P1 promoter activity in transient transfection assays using two different cell lines, COS-7 and Hep3B. Investigation of P1 mutants in which the spacing of the Sp1 binding site and the transcription start site was increased showed that the role of the Sp1 binding site in regulation of P1 is position dependent. Interestingly, the Sp1-responsive element cannot be exchanged by a functional TATA box. Activation of P1 by transactivators CCAAT/enhancer binding protein-beta and hepatocyte nuclear factor-3beta is strongly impaired after mutation of the Sp1 binding site. These results demonstrate that the specific presence of a binding site for the ubiquitously expressed transcription factor Sp1 is of eminent importance for efficient activation of P1 by liver-enriched transactivators.

The liver-specific promoter of the human insulin-like growth factor-II gene contains two negative regulatory elements

The adult liver-specific IGF-II promoter P1 is activated by CCAAT/Enhancer Binding Proteins alpha and beta. Here we present evidence that promoter P1, in addition to positively regulating elements, contains two elements of 67 nucleotides that form an inverted repeat (IR) and suppress P1 activity. The two IR elements are specifically bound by a protein (inverted repeat binding factor, IRBF). The amounts of IRBF in various cell lines correlate with the levels of suppression of P1 activity, suggesting that this factor is responsible for the suppression of P1 mediated by the IR elements.

Postnatal liver-specific expression of human insulin-like growth factor-II is highly stimulated by the transcriptional activators liver-enriched activating protein and CCAAT/enhancer binding protein-alpha

Transcription of the human gene encoding insulin-like growth factor II (IGF-II) is directed by four promoters (P1-P4), which are active in a tissue- and development-dependent manner. High levels of IGF-II in postnatal serum are due to activation of P1 in the liver. Since liver tissue contains high levels of the bZIP factors, liver-enriched activating protein (LAP), the CCAAT/enhancer binding protein-alpha (C/EBP alpha), and the D-element binding protein (DBP), and since P1 contains a functional C/EBP alpha binding site (P1 CBS), we have examined the role of these transcription factors in the activation of IGF-II P1. Transient transfection experiments reveal that P1 can be activated up to 15-fold by LAP and up to 6-fold by C/EBP alpha but can not be activated by DBP. Electrophoretic mobility shift assays with liver nuclear extract show that P1 CBS is predominantly bound by LAP and C/EBP alpha. Mutational analysis of P1 CBS indicates that DBP binding is prevented by one distinct G-C base pair in the P1 CBS element. The P1 CBS element is a high affinity binding site, which was demonstrated by comparing P1 CBS with other LAP-C/EBP alpha binding sites employing quantitative electrophoretic mobility shift assay. These results indicate that LAP and C/EBP alpha are major contributors to the postnatal liver-specific activation of the human IGF-II promoter P1.

Transcriptional and post-transcriptional regulation of the human IGF-II gene expression

The human insulin-like growth factor II (IGF-II) gene consists of nine exons and has four promoters (P1-4). The promoters exhibit a tissue-specific and developmental stage-dependent expression pattern. In fetal liver promoters P2-4 are expressed, but after birth these promoters are shut off and another promoter, P1, is activated. We have investigated some properties of the human promoters P1 and P3 and identified a number of sequence elements, that are recognized by transcription factors. Promoter P1 is stimulated by the liver-enriched transcription factors C/EBP and LAP, whereas in the proximal region of P3 we have identified several elements that are recognized by transcription factors, including krox20/egr2 and krox24/erg1. Besides transcriptional regulation of expression also regulation at the post-transcriptional level occurs. We have found that the IGF-II mRNAs are subjected to site-specific endonucleolytic cleavage yielding a labile 5' specific fragment and a stable polyadenylated 3' specific cleavage product of 1.8 kb. Two widely separated sequence elements within the last exon were identified that are able to interact and yield a double-stranded stem structure. It is likely that this structure is essential for post-transcriptional cleavage of IGF-II mRNAs.

Transcriptional regulation of the major promoters of the human IGF-II gene

The human insulin-like growth factor-II (IGF-II) gene constitutes a complex transcriptional unit that is controlled by four different promoters preceding multiple 5'-untranslated exons. Expression of the IGF-II gene is development and tissue specific and yields a family of mRNAs that all encode preproIGF-II. We have analyzed the sequences and factors involved in the transcriptional activation of promoters P1 and P3. Detailed analysis revealed several characteristic elements and protein binding sequences. P1, which is expressed only in adult liver tissue, contains a region that can be specifically activated by the CCAAT/enhancer binding protein (C/EBP). P3 consists of a proximal promoter region that supports general transcription, whereas cell-specific elements are located upstream.

The liver-specific promoter of the human insulin-like growth factor II gene is activated by CCAAT/enhancer binding protein (C/EBP)

The human gene coding for insulin-like growth factor II (IGF-II) contains four promoters (P1-P4), that are subjected to tissue-specific and development-dependent regulation. Expression of promoter P1 is detected only in adult liver tissue, whereas promoter P3 is the major IGF-II promoter in fetal liver and is further expressed in other fetal tissues and in adult non-hepatic tissues. C/EBP is a tissue- and development-specific transcription factor that is expressed predominantly in adult liver, adipose tissue and lung. The effect of C/EBP on the expression of constructs containing IGF-II promoter P1 or P3 linked to the luciferase gene was investigated in cotransfection assays using Hep3B cells. We found that promoter P1 can be activated by C/EBP, whereas this transcription factor has no effect on the expression of promoter P3. By gel retardation and DNasel footprinting it was demonstrated that C/EBP can bind to a region of P1 located between 82 and 109 basepairs upstream of the cap site. Furthermore, we showed that deletion of this C/EBP binding region strongly reduces the ability of C/EBP to stimulate transcription from P1. These results indicate that C/EBP is a major component in the specific activation of the human IGF-II promoter P1 in adult liver.

Gene amplification in a human osteosarcoma cell line results in the persistence of the original chromosome and the formation of translocation chromosomes

Although gene amplification, a process that is markedly enhanced in tumor cells, has been studied in many different cell systems, there is still controversy about the mechanism(s) involved in this process. It is still unclear what happens to the DNA sequences that become amplified, whether they remain present at their original location (conservative gene amplification) or whether gene amplification necessarily results in a deletion at the original location (non-conservative gene amplification). We have studied gene amplification in a human osteosarcoma cell line, starting from a cell clone which contains only one copy of a plasmid integrate. Independent amplificants, originating from this clone and containing elevated plasmid copy numbers, were isolated and analyzed. Based on previous observations, encompassing the persistence of single-copy DNA sequences besides amplified DNA sequences clustered at a different location in the independent amplificants, we proposed an amplification pathway including a local duplication step and transposition of the duplicated DNA to other chromosomal positions. Now we have extended our study to more independent amplificants. We prove that the single-copy plasmid-containing chromosomes in the different amplificants and the single-copy plasmid-containing chromosome in the original parental cell clone are indeed identical, namely a translocation chromosome composed of at least three parts of which two originate from chromosomes 14 and 17. We show that the unit of amplification and the unit of the proposed transposition event are at least 1.5 Mb. We also demonstrate that the amplified DNA sequences, present at genomic locations other than the original single-copy DNA sequences, are preferentially associated with chromosome 16. We find that the amplified DNA sequences are often located at or near a site of chromosome translocation involving chromosome 16. In one cell clone we detect the amplified DNA sequences in most of the cells to be located within a complete chromosome 16 while in a minority of cells the amplified sequences are located at or near a breakpoint on a translocation chromosome 16. This indicates that this amplification region is highly unstable and frequently gives rise to translocation events.