Paracetamol is the drug for which the Dutch Poisons Information Centre (DPIC) receives the most i... more Paracetamol is the drug for which the Dutch Poisons Information Centre (DPIC) receives the most information requests. The protocol for the treatment of single acute oral paracetamol intoxications is clear, however, ambiguity exists concerning the treatment of intoxications with repeated supratherapeutic doses of paracetamol. Paracetamol intoxications with liquid preparations, extendedrelease tablets, exposure routes other than oral, and repeated supratherapeutic ingestions require a tailored approach. An increased risk of liver damage due to paracetamol intoxication has to be taken into account for patients who consume excessive levels of alcohol, are malnourished or have a preexisting liver condition. The decision tree of the DPIC is a helpful tool to swiftly attain a risk assessment and treatment plan for most types of paracetamol intoxication. Conflict of interest and financial support: none declared.
Abstract Introduction The synthesis of clandestine drugs is a widespread worldwide phenomenon, wi... more Abstract Introduction The synthesis of clandestine drugs is a widespread worldwide phenomenon, with clandestine drug laboratories occurring both in rural and urban areas. There is considerable unfamiliarity among medical professionals about the health risks that are associated with chemicals used in clandestine drug laboratories. Objective To evaluate the adverse health effects resulting from exposure to chemicals involved in the production of clandestine drugs. Methods The US National Library of Medicine PubMed database and the Excerpta Medica database (EMBASE) were searched from their date of inception to October 26, 2021 using combinations of relevant search terms. This yielded 1,558 unique articles, which were subjected to two eligibility criteria: (i) exposure to clandestine drug laboratory chemicals resulting in adverse health effects; (ii) subjects were human. A total of 22 unique articles were retrieved, consisting of 10 reviews, eight case reports/series and four retrospective studies. Further searches among the references cited in these publications yielded another seven case reports/series and six retrospective studies. Results Inhalation: Surveillance studies reported respiratory symptoms (including cough, throat irritation, nasal irritation, and dyspnea) in 59% (n = 1,657 of 2,803) of those exposed. The case reports/series described respiratory symptoms in 43% of the cases (n = 36 of 84). Lung edema was reported occasionally (n = 2). Eye exposure : Surveillance studies reported eye irritation and burns in 23% (n = 647 of 2,803) of those exposed. The case reports/series described ocular adverse events in 36% of the cases (n = 30 of 84). More severe ocular effects, such as corneal damage and conjunctival necrosis, were reported after direct eye contact with caustic fluids. Skin exposure : Surveillance studies reported dermal effects, ranging from skin irritation to severe burns, in 6% of those exposed (n = 174 of 2,803). The case reports/series described dermal effects in 30% of the cases (n = 25 of 84). Ingestion : Gastrointestinal burns were observed after ingestion of caustic substances in 5% of the patients reported in the case reports/series (n = 4 of 84). Systemic effects : Surveillance studies reported headache and dizziness in 31% (n = 882 of 2,803) and 7% (n = 187 of 2,803) of those exposed, respectively. The case reports/series described sympathomimetic effects, including mydriasis, hypertension, tachycardia, in 4% of the cases (n = 3 of 84). Fatalities : Surveillance studies reported death in 1% of those exposed (n = 29 of 2803). Ten percent of the people reported in the cases report/series died (n = 8 of 84). Death was reported after inhalation of phosphine (n = 5), hydrogen sulfide (n = 1), methanol (n = 1), and after ingestion of sulfuric acid (n = 1). Conclusions Exposure to chemicals involved in the production of clandestine drugs mostly resulted in mild to moderate respiratory, ocular or dermal effects, usually caused by caustic chemicals or solvents. Systemic effects were generally mild, but severe symptoms and eight deaths were reported after exposure to phosphine, hydrogen sulfide, methanol and sulfuric acid.
Lipid overload and adipocyte dysfunction are key to the development of insulin resistance and can... more Lipid overload and adipocyte dysfunction are key to the development of insulin resistance and can be induced by a high-fat diet. CD1d-restricted invariant natural killer T (iNKT) cells have been proposed as mediators between lipid overload and insulin resistance, but recent studies found decreased iNKT cell numbers and marginal effects of iNKT cell depletion on insulin resistance under high-fat diet conditions. Here, we focused on the role of iNKT cells under normal conditions. We showed that iNKT cell–deficient mice on a low-fat diet, considered a normal diet for mice, displayed a distinctive insulin resistance phenotype without overt adipose tissue inflammation. Insulin resistance was characterized by adipocyte dysfunction, including adipocyte hypertrophy, increased leptin, and decreased adiponectin levels. The lack of liver abnormalities in CD1d-null mice together with the enrichment of CD1d-restricted iNKT cells in both mouse and human adipose tissue indicated a specific role fo...
Treatment of paracetamol intoxication consists of administration of N-acetylcysteine, preferably ... more Treatment of paracetamol intoxication consists of administration of N-acetylcysteine, preferably shortly after paracetamol ingestion. In most countries, the decision to treat patients with N-acetylcysteine depends on the paracetamol plasma concentration. In the literature, different arguments are given regarding when to treat paracetamol overdose. Some authors do not recommend treatment with N-acetylcysteine at low paracetamol plasma concentrations since unnecessary adverse effects may be induced. But no treatment with N-acetylcysteine at higher paracetamol plasma concentrations may lead to unnecessary severe morbidity and mortality. In this review, we provide an overview on the severity and prevalence of adverse side effects after N-acetylcysteine administration and the consequences these side effects may have for the treatment of paracetamol intoxication. The final conclusion is to continue using the guidelines of the Dutch National Poisons Information Centre for N-acetylcysteine ...
Large-scale chromatin organization is likely to play an important role in epigenetic control of g... more Large-scale chromatin organization is likely to play an important role in epigenetic control of gene expression. This implies that after mitosis the correct chromatin organization must be re-established in the nuclei of the two daughter cells. Here we analyze the dynamic behavior of chromatin during the transition from late anaphase to G1 in dividing HeLa cells, which express green fluorescent
The orexigenic neuropeptide melanin-concentrating hormone (MCH), a product of Pmch, is an importa... more The orexigenic neuropeptide melanin-concentrating hormone (MCH), a product of Pmch, is an important mediator of energy homeostasis. Pmch-deficient rodents are lean and smaller, characterized by lower food intake, body-, and fat mass. Pmch is expressed in hypothalamic neurons that ultimately are components in the sympathetic nervous system (SNS) drive to white and interscapular brown adipose tissue (WAT, iBAT, respectively). MCH binds to MCH receptor 1 (MCH1R), which is present on adipocytes. Currently it is unknown if Pmch-ablation changes adipocyte differentiation or sympathetic adipose drive. Using Pmch-deficient and wild-type rats on a standard low-fat diet, we analyzed dorsal subcutaneous and perirenal WAT mass and adipocyte morphology (size and number) throughout development, and indices of sympathetic activation in WAT and iBAT during adulthood. Moreover, using an in vitro approach we investigated the ability of MCH to modulate 3T3-L1 adipocyte differentiation. Pmch-deficiency decreased dorsal subcutaneous and perirenal WAT mass by reducing adipocyte size, but not number. In line with this, in vitro 3T3-L1 adipocyte differentiation was unaffected by MCH. Finally, adult Pmch-deficient rats had lower norepinephrine turnover (an index of sympathetic adipose drive) in WAT and iBAT than wild-type rats. Collectively, our data indicate that MCH/MCH1R-pathway does not modify adipocyte differentiation, whereas Pmch-deficiency in laboratory rats lowers adiposity throughout development and sympathetic adipose drive during adulthood.
Background We investigated whether plasma ferritin levels through the pro-inflammatory effects of... more Background We investigated whether plasma ferritin levels through the pro-inflammatory effects of free iron are associated with adipose tissue dysfunction in a relevant population of patients with manifest vascular disease who would potentially benefit the most from further aetiological insights. Materials and methods In a cohort of 355 patients with vascular diseases, the association between plasma ferritin and adiponectin levels was quantified using linear regression analysis. Interleukin-6 and adiponectin levels were measured in medium from pre-adipocytes and adipocytes after incubation with increasing concentrations of Fe(III)-citrate and after co-incubation with iron chelators or radical scavengers. Results Increasing ferritin plasma concentrations were not related to plasma adiponectin levels in patients without (b À0Á13; 95% CI À0Á30 to 0Á04) or with the metabolic syndrome (b À0Á04; 95% CI À0Á17 to 0Á10). Similar results were found in patients who developed a new cardiovascular event in the follow-up period. In vitro, incubation with increasing concentrations of Fe(III)-citrate-induced inflammation in pre-adipocyte cultures as witnessed by increased IL-6 secretion at 30 lM Fe(III)-citrate vs. control (500 AE 98 pg/mL vs. 194 AE 31 pg/mL, P = 0Á03). Co-incubation of pre-adipocytes with iron chelators or radical scavengers prevented this inflammatory response. Incubation of adipocytes with 30 lM Fe(III)-citrate did not influence adiponectin secretion compared with control. Conclusions In patients with vascular disease, there is no association between plasma ferritin and adiponectin levels. In vitro, free iron induces an inflammatory response in pre-adipocytes, but not in adipocytes. This response was blocked by co-incubation with iron chelators or radical scavengers. Adiponectin secretion by adipocytes was not influenced by free iron.
In mammals there are two types of adipocytes with opposing functions. Brown adipocytes are charac... more In mammals there are two types of adipocytes with opposing functions. Brown adipocytes are characterized by a high number of mitochondria and are specialized for heat production (thermogenesis), expressing thermogenic genes such as UCP1 (uncoupling protein 1). White adipocytes, on the other hand, store energy. Although many key regulators in the differentiation of white adipocytes have been established, our current knowledge on the same proteins in brown adipogenesis is lagging behind. One example is Pref-1 (pre-adipocyte factor-1), which maintains white pre-adipocytes in an undifferentiated state, but is only poorly characterized in the brown pre-adipocyte lineage. In this issue of the Biochemical Journal, Armengol et al. now shed new light on the role and regulation of Pref-1 in brown pre-adipocytes. First, Pref-1 specifically inhibits the thermogenic gene programme in brown pre-adipocytes. Secondly, they identified the transcription factor C/EBPδ (CCAAT/enhancer-binding protein δ...
The best studied oncogenic mechanisms are inactivating defects in both alleles of tumor suppresso... more The best studied oncogenic mechanisms are inactivating defects in both alleles of tumor suppressor genes and activating mutations in oncogenes. Chromosomal gains and losses are frequent in human tumors, but for many regions, like 1p36 and 17q in neuroblastoma, no mutated tumor suppressor genes or oncogenes were identified. Amplification of N-myc in neuroblastoma is strongly correlated with loss of 1p36 and gain of 17q. Here we report that N-myc down-regulates the mRNA expression of many genes with a role in cell architecture. One of them is the 1p36 gene Cdc42. Restoring the Cdc42 expression in neuroblastoma cells strongly induced differentiation. N-myc also inhibited Cdc42 functioning at the protein level. This was mediated by nm23-H1 and nm23-H2, which are located in the amplified 17q region. Nm23-H1 and nm23-H2 are strongly up-regulated downstream targets of N-myc. Nm23-H1 was shown to bind Cdc42 and prevented the induction of differentiation. Overexpression of Nm23 due to gain o...
Neuroblastoma and ganglioneuroma are neuroblastic tumors originating from the developing sympathe... more Neuroblastoma and ganglioneuroma are neuroblastic tumors originating from the developing sympathetic peripheral nervous system. Ganglioneuromas are usually benign, while neuroblastomas have a variable prognosis and include very aggressive tumors. Examples exist of neuroblastomas regressing to ganglioneuromas and ganglioneuromas progressing to neuroblastomas. Little is known of the molecular differences between the tumor types. Here we report that Dickkopf-3 (DKK3), a putative extra cellular inhibitor of the Wnt/beta-catenin pathway, showed a strongly differential expression between neuroblastoma and ganglioneuroma. Microarray analyses of 109 neuroblastic tumors revealed that DKK3 is strongly expressed in ganglioneuroma but only weakly in neuroblastoma. Low DKK3 expression in neuroblastoma correlated with a poor prognosis. The expression of DKK3 in the tumor series and in neuroblastoma cell lines was inversely correlated with the expression of the MYCN oncogene. Analysis of 2 neuroblastoma cell lines with inducible activity of MYCN showed that DKK3 is down-regulated by MYCN. We subsequently generated cell lines with inducible expression of DKK3, which revealed an inhibitory effect of DKK3 on proliferation. High DKK3 expression in the benign ganglioneuromas and down-regulation of DKK3 by MYCN in neuroblastoma might contribute to the strongly different clinical behavior of both neuroblastic tumor types.
The c-Myc and MYCN oncogenes strongly induce cell proliferation. Although a limited series of cel... more The c-Myc and MYCN oncogenes strongly induce cell proliferation. Although a limited series of cell cycle genes were found to be induced by the myc transcription factors, it is still unclear how they mediate the proliferative phenotype. We therefore analysed a neuroblastoma cell line with inducible MYCN expression. We found that all members of the minichromosome maintenance complex (MCM2-7) and MCM8 and MCM10 were up-regulated by MYCN. Expression profiling of 110 neuroblastoma tumours revealed that these genes strongly correlated with MYCN expression in vivo. Extensive chromatin immunoprecipitation experiments were performed to investigate whether the MCM genes were primary MYCN targets. MYCN was bound to the proximal promoters of the MCM2 to-8 genes. These data suggest that MYCN stimulates the expression of not only MCM7, which is a well defined MYCN target gene, but also of the complete minichromosome maintenance complex.
Paracetamol is the drug for which the Dutch Poisons Information Centre (DPIC) receives the most i... more Paracetamol is the drug for which the Dutch Poisons Information Centre (DPIC) receives the most information requests. The protocol for the treatment of single acute oral paracetamol intoxications is clear, however, ambiguity exists concerning the treatment of intoxications with repeated supratherapeutic doses of paracetamol. Paracetamol intoxications with liquid preparations, extendedrelease tablets, exposure routes other than oral, and repeated supratherapeutic ingestions require a tailored approach. An increased risk of liver damage due to paracetamol intoxication has to be taken into account for patients who consume excessive levels of alcohol, are malnourished or have a preexisting liver condition. The decision tree of the DPIC is a helpful tool to swiftly attain a risk assessment and treatment plan for most types of paracetamol intoxication. Conflict of interest and financial support: none declared.
Abstract Introduction The synthesis of clandestine drugs is a widespread worldwide phenomenon, wi... more Abstract Introduction The synthesis of clandestine drugs is a widespread worldwide phenomenon, with clandestine drug laboratories occurring both in rural and urban areas. There is considerable unfamiliarity among medical professionals about the health risks that are associated with chemicals used in clandestine drug laboratories. Objective To evaluate the adverse health effects resulting from exposure to chemicals involved in the production of clandestine drugs. Methods The US National Library of Medicine PubMed database and the Excerpta Medica database (EMBASE) were searched from their date of inception to October 26, 2021 using combinations of relevant search terms. This yielded 1,558 unique articles, which were subjected to two eligibility criteria: (i) exposure to clandestine drug laboratory chemicals resulting in adverse health effects; (ii) subjects were human. A total of 22 unique articles were retrieved, consisting of 10 reviews, eight case reports/series and four retrospective studies. Further searches among the references cited in these publications yielded another seven case reports/series and six retrospective studies. Results Inhalation: Surveillance studies reported respiratory symptoms (including cough, throat irritation, nasal irritation, and dyspnea) in 59% (n = 1,657 of 2,803) of those exposed. The case reports/series described respiratory symptoms in 43% of the cases (n = 36 of 84). Lung edema was reported occasionally (n = 2). Eye exposure : Surveillance studies reported eye irritation and burns in 23% (n = 647 of 2,803) of those exposed. The case reports/series described ocular adverse events in 36% of the cases (n = 30 of 84). More severe ocular effects, such as corneal damage and conjunctival necrosis, were reported after direct eye contact with caustic fluids. Skin exposure : Surveillance studies reported dermal effects, ranging from skin irritation to severe burns, in 6% of those exposed (n = 174 of 2,803). The case reports/series described dermal effects in 30% of the cases (n = 25 of 84). Ingestion : Gastrointestinal burns were observed after ingestion of caustic substances in 5% of the patients reported in the case reports/series (n = 4 of 84). Systemic effects : Surveillance studies reported headache and dizziness in 31% (n = 882 of 2,803) and 7% (n = 187 of 2,803) of those exposed, respectively. The case reports/series described sympathomimetic effects, including mydriasis, hypertension, tachycardia, in 4% of the cases (n = 3 of 84). Fatalities : Surveillance studies reported death in 1% of those exposed (n = 29 of 2803). Ten percent of the people reported in the cases report/series died (n = 8 of 84). Death was reported after inhalation of phosphine (n = 5), hydrogen sulfide (n = 1), methanol (n = 1), and after ingestion of sulfuric acid (n = 1). Conclusions Exposure to chemicals involved in the production of clandestine drugs mostly resulted in mild to moderate respiratory, ocular or dermal effects, usually caused by caustic chemicals or solvents. Systemic effects were generally mild, but severe symptoms and eight deaths were reported after exposure to phosphine, hydrogen sulfide, methanol and sulfuric acid.
Lipid overload and adipocyte dysfunction are key to the development of insulin resistance and can... more Lipid overload and adipocyte dysfunction are key to the development of insulin resistance and can be induced by a high-fat diet. CD1d-restricted invariant natural killer T (iNKT) cells have been proposed as mediators between lipid overload and insulin resistance, but recent studies found decreased iNKT cell numbers and marginal effects of iNKT cell depletion on insulin resistance under high-fat diet conditions. Here, we focused on the role of iNKT cells under normal conditions. We showed that iNKT cell–deficient mice on a low-fat diet, considered a normal diet for mice, displayed a distinctive insulin resistance phenotype without overt adipose tissue inflammation. Insulin resistance was characterized by adipocyte dysfunction, including adipocyte hypertrophy, increased leptin, and decreased adiponectin levels. The lack of liver abnormalities in CD1d-null mice together with the enrichment of CD1d-restricted iNKT cells in both mouse and human adipose tissue indicated a specific role fo...
Treatment of paracetamol intoxication consists of administration of N-acetylcysteine, preferably ... more Treatment of paracetamol intoxication consists of administration of N-acetylcysteine, preferably shortly after paracetamol ingestion. In most countries, the decision to treat patients with N-acetylcysteine depends on the paracetamol plasma concentration. In the literature, different arguments are given regarding when to treat paracetamol overdose. Some authors do not recommend treatment with N-acetylcysteine at low paracetamol plasma concentrations since unnecessary adverse effects may be induced. But no treatment with N-acetylcysteine at higher paracetamol plasma concentrations may lead to unnecessary severe morbidity and mortality. In this review, we provide an overview on the severity and prevalence of adverse side effects after N-acetylcysteine administration and the consequences these side effects may have for the treatment of paracetamol intoxication. The final conclusion is to continue using the guidelines of the Dutch National Poisons Information Centre for N-acetylcysteine ...
Large-scale chromatin organization is likely to play an important role in epigenetic control of g... more Large-scale chromatin organization is likely to play an important role in epigenetic control of gene expression. This implies that after mitosis the correct chromatin organization must be re-established in the nuclei of the two daughter cells. Here we analyze the dynamic behavior of chromatin during the transition from late anaphase to G1 in dividing HeLa cells, which express green fluorescent
The orexigenic neuropeptide melanin-concentrating hormone (MCH), a product of Pmch, is an importa... more The orexigenic neuropeptide melanin-concentrating hormone (MCH), a product of Pmch, is an important mediator of energy homeostasis. Pmch-deficient rodents are lean and smaller, characterized by lower food intake, body-, and fat mass. Pmch is expressed in hypothalamic neurons that ultimately are components in the sympathetic nervous system (SNS) drive to white and interscapular brown adipose tissue (WAT, iBAT, respectively). MCH binds to MCH receptor 1 (MCH1R), which is present on adipocytes. Currently it is unknown if Pmch-ablation changes adipocyte differentiation or sympathetic adipose drive. Using Pmch-deficient and wild-type rats on a standard low-fat diet, we analyzed dorsal subcutaneous and perirenal WAT mass and adipocyte morphology (size and number) throughout development, and indices of sympathetic activation in WAT and iBAT during adulthood. Moreover, using an in vitro approach we investigated the ability of MCH to modulate 3T3-L1 adipocyte differentiation. Pmch-deficiency decreased dorsal subcutaneous and perirenal WAT mass by reducing adipocyte size, but not number. In line with this, in vitro 3T3-L1 adipocyte differentiation was unaffected by MCH. Finally, adult Pmch-deficient rats had lower norepinephrine turnover (an index of sympathetic adipose drive) in WAT and iBAT than wild-type rats. Collectively, our data indicate that MCH/MCH1R-pathway does not modify adipocyte differentiation, whereas Pmch-deficiency in laboratory rats lowers adiposity throughout development and sympathetic adipose drive during adulthood.
Background We investigated whether plasma ferritin levels through the pro-inflammatory effects of... more Background We investigated whether plasma ferritin levels through the pro-inflammatory effects of free iron are associated with adipose tissue dysfunction in a relevant population of patients with manifest vascular disease who would potentially benefit the most from further aetiological insights. Materials and methods In a cohort of 355 patients with vascular diseases, the association between plasma ferritin and adiponectin levels was quantified using linear regression analysis. Interleukin-6 and adiponectin levels were measured in medium from pre-adipocytes and adipocytes after incubation with increasing concentrations of Fe(III)-citrate and after co-incubation with iron chelators or radical scavengers. Results Increasing ferritin plasma concentrations were not related to plasma adiponectin levels in patients without (b À0Á13; 95% CI À0Á30 to 0Á04) or with the metabolic syndrome (b À0Á04; 95% CI À0Á17 to 0Á10). Similar results were found in patients who developed a new cardiovascular event in the follow-up period. In vitro, incubation with increasing concentrations of Fe(III)-citrate-induced inflammation in pre-adipocyte cultures as witnessed by increased IL-6 secretion at 30 lM Fe(III)-citrate vs. control (500 AE 98 pg/mL vs. 194 AE 31 pg/mL, P = 0Á03). Co-incubation of pre-adipocytes with iron chelators or radical scavengers prevented this inflammatory response. Incubation of adipocytes with 30 lM Fe(III)-citrate did not influence adiponectin secretion compared with control. Conclusions In patients with vascular disease, there is no association between plasma ferritin and adiponectin levels. In vitro, free iron induces an inflammatory response in pre-adipocytes, but not in adipocytes. This response was blocked by co-incubation with iron chelators or radical scavengers. Adiponectin secretion by adipocytes was not influenced by free iron.
In mammals there are two types of adipocytes with opposing functions. Brown adipocytes are charac... more In mammals there are two types of adipocytes with opposing functions. Brown adipocytes are characterized by a high number of mitochondria and are specialized for heat production (thermogenesis), expressing thermogenic genes such as UCP1 (uncoupling protein 1). White adipocytes, on the other hand, store energy. Although many key regulators in the differentiation of white adipocytes have been established, our current knowledge on the same proteins in brown adipogenesis is lagging behind. One example is Pref-1 (pre-adipocyte factor-1), which maintains white pre-adipocytes in an undifferentiated state, but is only poorly characterized in the brown pre-adipocyte lineage. In this issue of the Biochemical Journal, Armengol et al. now shed new light on the role and regulation of Pref-1 in brown pre-adipocytes. First, Pref-1 specifically inhibits the thermogenic gene programme in brown pre-adipocytes. Secondly, they identified the transcription factor C/EBPδ (CCAAT/enhancer-binding protein δ...
The best studied oncogenic mechanisms are inactivating defects in both alleles of tumor suppresso... more The best studied oncogenic mechanisms are inactivating defects in both alleles of tumor suppressor genes and activating mutations in oncogenes. Chromosomal gains and losses are frequent in human tumors, but for many regions, like 1p36 and 17q in neuroblastoma, no mutated tumor suppressor genes or oncogenes were identified. Amplification of N-myc in neuroblastoma is strongly correlated with loss of 1p36 and gain of 17q. Here we report that N-myc down-regulates the mRNA expression of many genes with a role in cell architecture. One of them is the 1p36 gene Cdc42. Restoring the Cdc42 expression in neuroblastoma cells strongly induced differentiation. N-myc also inhibited Cdc42 functioning at the protein level. This was mediated by nm23-H1 and nm23-H2, which are located in the amplified 17q region. Nm23-H1 and nm23-H2 are strongly up-regulated downstream targets of N-myc. Nm23-H1 was shown to bind Cdc42 and prevented the induction of differentiation. Overexpression of Nm23 due to gain o...
Neuroblastoma and ganglioneuroma are neuroblastic tumors originating from the developing sympathe... more Neuroblastoma and ganglioneuroma are neuroblastic tumors originating from the developing sympathetic peripheral nervous system. Ganglioneuromas are usually benign, while neuroblastomas have a variable prognosis and include very aggressive tumors. Examples exist of neuroblastomas regressing to ganglioneuromas and ganglioneuromas progressing to neuroblastomas. Little is known of the molecular differences between the tumor types. Here we report that Dickkopf-3 (DKK3), a putative extra cellular inhibitor of the Wnt/beta-catenin pathway, showed a strongly differential expression between neuroblastoma and ganglioneuroma. Microarray analyses of 109 neuroblastic tumors revealed that DKK3 is strongly expressed in ganglioneuroma but only weakly in neuroblastoma. Low DKK3 expression in neuroblastoma correlated with a poor prognosis. The expression of DKK3 in the tumor series and in neuroblastoma cell lines was inversely correlated with the expression of the MYCN oncogene. Analysis of 2 neuroblastoma cell lines with inducible activity of MYCN showed that DKK3 is down-regulated by MYCN. We subsequently generated cell lines with inducible expression of DKK3, which revealed an inhibitory effect of DKK3 on proliferation. High DKK3 expression in the benign ganglioneuromas and down-regulation of DKK3 by MYCN in neuroblastoma might contribute to the strongly different clinical behavior of both neuroblastic tumor types.
The c-Myc and MYCN oncogenes strongly induce cell proliferation. Although a limited series of cel... more The c-Myc and MYCN oncogenes strongly induce cell proliferation. Although a limited series of cell cycle genes were found to be induced by the myc transcription factors, it is still unclear how they mediate the proliferative phenotype. We therefore analysed a neuroblastoma cell line with inducible MYCN expression. We found that all members of the minichromosome maintenance complex (MCM2-7) and MCM8 and MCM10 were up-regulated by MYCN. Expression profiling of 110 neuroblastoma tumours revealed that these genes strongly correlated with MYCN expression in vivo. Extensive chromatin immunoprecipitation experiments were performed to investigate whether the MCM genes were primary MYCN targets. MYCN was bound to the proximal promoters of the MCM2 to-8 genes. These data suggest that MYCN stimulates the expression of not only MCM7, which is a well defined MYCN target gene, but also of the complete minichromosome maintenance complex.
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Papers by Arjen Koppen