ABSTRACT
The prevalence of pathogenic and likely pathogenic (P/LP) variants in genes associated with cancer predisposition syndromes (CPS) is estimated to be 8-18% for paediatric cancer patients. In more than half of the carriers, the family history is unsuspicious for CPS. Therefore, broad genetic testing could identify germline predisposition in additional children with cancer resulting in important implications for themselves and their families. We thus evaluated clinical trio genome sequencing (TGS) in a cohort of 72 paediatric patients with solid cancers other than retinoblastoma or CNS-tumours. The most prevalent cancer types were sarcoma (n = 26), neuroblastoma (n = 15), and nephroblastoma (n = 10). Overall, P/LP variants in CPS genes were identified in 18.1% of patients (13/72) and P/LP variants in autosomal-dominant CPS genes in 9.7% (7/72). Genetic evaluation would have been recommended for the majority of patients with P/LP variants according to the Jongmans criteria. Four patients (5.6%, 4/72) carried P/LP variants in autosomal-dominant genes known to be associated with their tumour type. With the immediate information on variant inheritance, TGS facilitated the identification of a de novo P/LP in NF1, a gonadosomatic mosaic in WT1 and two pathogenic variants in one patient (DICER1 and PALB2). TGS allows a more detailed characterization of structural variants with base-pair resolution of breakpoints which can be relevant for the interpretation of copy number variants. Altogether, TGS allows comprehensive identification of children with a CPS and supports the individualised clinical management of index patients and high-risk relatives.
Subject(s)
Genetic Predisposition to Disease , Neoplasms , Humans , Child , Germ-Line Mutation , Neoplasms/genetics , Genetic Testing/methods , Genotype , Ribonuclease III/genetics , DEAD-box RNA Helicases/geneticsABSTRACT
It has been well-established that mutations in BRCA1 and BRCA2, compromising functions in DNA double-strand break repair (DSBR), confer hereditary breast and ovarian cancer risk. Importantly, mutations in these genes explain only a minor fraction of the hereditary risk and of the subset of DSBR deficient tumors. Our screening efforts identified two truncating germline mutations in the gene encoding the BRCA1 complex partner ABRAXAS1 in German early-onset breast cancer patients. To unravel the molecular mechanisms triggering carcinogenesis in these carriers of heterozygous mutations, we examined DSBR functions in patient-derived lymphoblastoid cells (LCLs) and in genetically manipulated mammary epithelial cells. By use of these strategies we were able to demonstrate that these truncating ABRAXAS1 mutations exerted dominant effects on BRCA1 functions. Interestingly, we did not observe haploinsufficiency regarding homologous recombination (HR) proficiency (reporter assay, RAD51-foci, PARP-inhibitor sensitivity) in mutation carriers. However, the balance was shifted to use of mutagenic DSBR-pathways. The dominant effect of truncated ABRAXAS1 devoid of the C-terminal BRCA1 binding site can be explained by retention of the N-terminal interaction sites for other BRCA1-A complex partners like RAP80. In this case BRCA1 was channeled from the BRCA1-A to the BRCA1-C complex, which induced single-strand annealing (SSA). Further truncation, additionally deleting the coiled-coil region of ABRAXAS1, unleashed excessive DNA damage responses (DDRs) de-repressing multiple DSBR-pathways including SSA and non-homologous end-joining (NHEJ). Our data reveal de-repression of low-fidelity repair activities as a common feature of cells from patients with heterozygous mutations in genes encoding BRCA1 and its complex partners.
Subject(s)
Breast Neoplasms , Female , Humans , BRCA1 Protein/genetics , BRCA1 Protein/metabolism , BRCA2 Protein/genetics , BRCA2 Protein/metabolism , Breast Neoplasms/pathology , DNA Breaks, Double-Stranded , DNA Repair/genetics , Mutagenesis , MutationABSTRACT
Background: The clinical utility of molecular profiling and targeted therapies for neuro-oncology patients outside of clinical trials is not established. We aimed at investigating feasibility and clinical utility of molecular profiling and targeted therapy in adult patients with advanced tumors in the nervous system within a prospective observational study. Methods: molecular tumor board (MTB)@ZPM (NCT03503149) is a prospective observational precision medicine study for patients with advanced tumors. After inclusion of patients, we performed comprehensive molecular profiling, formulated ranked biomarker-guided therapy recommendations based on consensus by the MTB, and collected prospective clinical outcome data. Results: Here, we present initial data of 661 adult patients with tumors of the nervous system enrolled by December 31, 2021. Of these, 408 patients were presented at the MTB. Molecular-instructed therapy recommendations could be made in 380/408 (93.1%) cases and were prioritized by evidence levels. Therapies were initiated in 86/380 (22.6%) cases until data cutoff. We observed a progression-free survival ratio >1.3 in 31.3% of patients. Conclusions: Our study supports the clinical utility of biomarker-guided therapies for neuro-oncology patients and indicates clinical benefit in a subset of patients. Our data might inform future clinical trials, translational studies, and even clinical care.
ABSTRACT
OBJECTIVES: Germline mutations in the CDH1-gene are identified as the cause of 30-40% of cases of hereditary diffuse gastric cancer, an autosomal-dominant inherited cancer predisposition syndrome. Given this high risk of developing diffuse gastric cancer, carriers of a pathogenic CDH1 germline mutation are advised to undergo prophylactic gastrectomy. For patients preferring conservative management, endoscopic surveillance is recommended. The detection of diffuse gastric cancer using white light endoscopy, however, remains challenging. METHODS: Patients with pathogenic CDH1 mutation underwent (chromo)endoscopic surveillance or endoscopy prior to surgery. Biopsies were taken at suspicious sites identified by chromoendoscopy. In addition, endoscopically normal areas were assessed with mapping biopsies. Detection rates from endoscopic biopsies (mapping vs. targeted) and gastrectomy specimen were then compared. RESULT: Between 11/2015 and 12/2020, ten patients from four families with a known CDH1 germline mutation had a total of n = 24 endoscopies with n = 518 total biopsies being examined. Three patients were diagnosed with GC during the study period. These patients all had suspicious chromoendoscopic lesions (= detection rate 100%). In two of three patients who had suspicious chromoendoscopic lesions, signet cell carcinoma was also detected in mapping biopsies and multiple additional cancer foci were identified in the gastrectomy specimen. CONCLUSION: Chromoendoscopy facilitated detection of gastric carcinoma foci in CDH1 mutation carriers. Chromoendoscopy identified all patients with gastric cancer, but not all cancer foci present in these patients. We conclude that for patients opting against prophylactic total gastrectomy, the addition of chromoendoscopy to white light could be used to enhance diagnostic reliability of endoscopic surveillance.
Subject(s)
Carcinoma, Signet Ring Cell , Stomach Neoplasms , Humans , Stomach Neoplasms/diagnosis , Stomach Neoplasms/genetics , Stomach Neoplasms/surgery , Gastroscopy , Reproducibility of Results , Carcinoma, Signet Ring Cell/pathology , Mutation , Gastrectomy , Biopsy , Germ-Line Mutation , Cadherins/genetics , Genetic Predisposition to Disease , Antigens, CD/geneticsABSTRACT
BACKGROUND: Sequencing of tumour tissue with comprehensive gene panels is increasingly used to guide treatment in precision oncology. Analysis of tumour-normal pairs allows in contrast to tumour-only assessment direct discrimination between somatic and germline alterations, which might have important implications not only for the patients but also their families. METHODS: We performed tumour normal sequencing with a large gene panel in 1048 patients with advanced cancer to support treatment decision. Sequencing results were correlated with clinical and family data. RESULTS: We identified 156 likely pathogenic or pathogenic (LP/P) germline variants in cancer predisposition genes (CPGs) in 144 cases (13.7%). Of all patients, 8.8% had a LP/P variant in autosomal-dominant cancer predisposition genes (AD-CPGs), most of them being genes with high or moderate penetrance (ATM, BRCA2, CHEK2 and BRCA1). In 48 cases, the P/LP variant matched the expected tumour spectrum. A second variant in tumour tissue was found in 31 patients with AD-CPG variants. Low frequency mutations in either TP53, ATM or DNMT3A in the normal sample indicated clonal haematopoiesis in five cases. CONCLUSIONS: Tumour-normal testing for personalised treatment identifies germline LP/P variants in a relevant proportion of patients with cancer. The majority of them would not have been referred to genetic counselling based on family history. Indirect functional readouts of tumour-normal sequencing can provide novel links between CPGs and unexpected cancers. The interpretation of increasingly complex datasets in precision oncology is challenging and concepts of interdisciplinary personalised cancer prevention are needed to support patients and their families.
Subject(s)
Hematologic Neoplasms , Neoplasms , Humans , Neoplasms/diagnosis , Neoplasms/genetics , Neoplasms/therapy , Precision Medicine , Germ-Line Mutation , Mutation , Genes, BRCA2 , Genetic Predisposition to Disease , Genetic Testing/methodsABSTRACT
We present the phenotypes of seven previously unreported patients with Marbach-Schaaf neurodevelopmental syndrome, all carrying the same recurrent heterozygous missense variant c.1003C>T (p.Arg335Trp) in PRKAR1B. Clinical features of this cohort include global developmental delay and reduced sensitivity to pain, as well as behavioral anomalies. Only one of the seven patients reported here was formally diagnosed with autism spectrum disorder (ASD), while ASD-like features were described in others, overall indicating a lower prevalence of ASD in Marbach-Schaaf neurodevelopmental syndrome than previously assumed. The clinical spectrum of the current cohort is similar to that reported in the initial publication, delineating a complex developmental disorder with behavioral and neurologic features. PRKAR1B encodes the regulatory subunit R1ß of the protein kinase A complex (PKA), and is expressed in the adult and embryonal central nervous system in humans. PKA is crucial to a plethora of cellular signaling pathways, and its composition of different regulatory and catalytic subunits is cell-type specific. We discuss potential molecular disease mechanisms underlying the patients' phenotypes with respect to the different known functions of PKA in neurons, and the phenotypes of existing R1ß-deficient animal models.
Subject(s)
Autism Spectrum Disorder , Neurodevelopmental Disorders , Adult , Animals , Autism Spectrum Disorder/genetics , Cohort Studies , Humans , Neurodevelopmental Disorders/genetics , Phenotype , SyndromeABSTRACT
OBJECTIVES: To examine the diagnostic yield of trio exome sequencing in fetuses with multiple structural defects with no pathogenic findings in cytogenetic and microarray analyses. METHODS: We recruited 51 fetuses with two or more defects, non-immune fetal hydrops or fetal akinesia deformation syndrome|or fetal akinesia deformation sequence (FADS). Trio exome sequencing was performed on DNA from chorionic villi samples and parental blood. Detection of genomic variation and prioritization of clinically relevant variants was performed according to in-house standard operating procedures. RESULTS: Median maternal and gestational age was 32.0 years and 21.0 weeks, respectively. Forty-three (84.3%) fetuses had two or more affected organ systems. The remaining fetuses had isolated fetal hydrops or FADS. In total, the exome analysis established the genetic cause for the clinical abnormalities in 22 (43.1%, 95% CI 29.4%-57.8%) pregnancies. CONCLUSIONS: In fetuses with multiple defects, hydrops or FADS and normal standard genetic results, trio exome sequencing has the potential to identify genetic anomalies in more than 40% of cases.
Subject(s)
Exome , Hydrops Fetalis , Adult , Female , Fetus/diagnostic imaging , Humans , Hydrops Fetalis/genetics , Parents , Pregnancy , Prenatal Diagnosis/methods , Ultrasonography, Prenatal , Exome Sequencing/methodsABSTRACT
BACKGROUND: Targeted sequencing approaches such as gene panel or exome sequencing have become standard of care for the diagnosis of rare and common genetic disease. The detection and interpretation of point mutations, small insertions and deletions, and even exon-level copy number variants are well established in clinical genetic testing. Other types of genetic variation such as mobile elements insertions (MEIs) are technically difficult to detect. In addition, their downstream clinical interpretation is more complex compared to point mutations due to a larger genomic footprint that can not only predict a clear loss of protein function but might disturb gene regulation and splicing even when located within the non-coding regions. As a consequence, the contribution of MEIs to disease and tumor development remains largely unexplored in routine diagnostics. METHODS: In this study, we investigated the occurrence of MEIs in 7,693 exome datasets from individuals with rare diseases and healthy relatives as well as 788 cancer patients analyzed by panel sequencing. RESULTS: We present several exemplary cases highlighting the diagnostic value of MEIs and propose a strategy for the detection, prioritization, and clinical interpretation of MEIs in routine clinical diagnostics. CONCLUSION: In this paper, we state that detection and interpretation of MEIs in clinical practice in targeted NGS data can be performed relatively easy despite the fact that MEIs very rarely occur in coding parts of the human genome. Large scale reanalysis of MEIs in existing cohorts may solve otherwise unsolvable cases.
Subject(s)
DNA Transposable Elements , Diagnostic Tests, Routine , Genetic Testing , Mutagenesis, Insertional , Computational Biology/methods , Genetic Predisposition to Disease , Genetics, Medical/methods , Germ-Line Mutation , High-Throughput Nucleotide Sequencing , Humans , Molecular Sequence Annotation , Oncogenes , Rare Diseases/diagnosis , Rare Diseases/genetics , Sequence Analysis, DNA , Exome SequencingABSTRACT
There are only limited treatment options for metastatic NRAS mutant melanoma patients with resistance to immune checkpoint inhibitors. Besides activation of the mitogen-activated protein (MAP) kinase pathway, they often have additional disturbances in cell cycle regulation. However, unlike BRAF mutant melanoma, no targeted therapy has yet been approved for NRAS mutant melanoma so far. Here we present a NRAS mutant melanoma patient with response to combined binimetinib and ribociclib therapy following characterization of the molecular defects of the tumor by panel sequencing. Next generation sequencing (708 cancer genes) of a soft tissue metastasis revealed a homozygous deletion of CDKN2A in addition to the previously known NRAS mutation, as well as amplification of CCNE1 and CDK6. Immunohistochemical staining of the altered cell cycle genes confirmed loss of p16, reduced expression of p21 and high expression of CDK6 and cyclin D1. As the patient had been progressive on combined immunotherapy, targeted therapy with combined MEK and CDK4/6 inhibition was initiated as recommended by the molecular tumor board. Response to treatment was monitored with PET/CT and liquid biopsy, serum LDH, and S100. In addition, a patient-derived xenograft (PDX) was used to prove the efficacy of the two drugs in combination. Furthermore, senescence-associated beta-galactosidase staining showed that more cells were senescent under the combination treatment of binimetinib and ribociclib. Our case demonstrates how an individualized, molecular-based therapeutic approach could be found based on next-generation sequencing results. Furthermore our report highlights the fruitful and efficient collaboration of dermatooncologists, human geneticists, molecular pathologists, biochemists, radiologists, and nuclear physicians. Further studies are urgently needed to expand the very limited therapeutic landscape of NRAS mutated melanoma.
ABSTRACT
PURPOSE: BAY1436032, an inhibitor of mutant isocitrate dehydrogenase 1 (mIDH1), was active against multiple IDH1-R132X solid tumors in preclinical models. This first-in-human study was designed to determine the safety and pharmacokinetics of BAY1436032, and to evaluate its potential pharmacodynamics and antitumor effects. PATIENTS AND METHODS: The study comprised of dose escalation and dose expansion cohorts. BAY1436032 tablets were orally administered twice daily on a continuous basis in subjects with mIDH1 solid tumors. RESULTS: In dose escalation, 29 subjects with various tumor types were administered BAY1436032 across five doses (150-1,500 mg twice daily). BAY1432032 exhibited a relatively short half-life. Most evaluable subjects experienced target inhibition as indicated by a median maximal reduction of plasma R-2-hydroxyglutarate levels of 76%. BAY1436032 was well tolerated and an MTD was not identified. A dose of 1,500 mg twice daily was selected for dose expansion, where 52 subjects were treated in cohorts representing four different tumor types [lower grade glioma (LGG), glioblastoma, intrahepatic cholangiocarcinoma, and a basket cohort of other tumor types]. The best clinical outcomes were in subjects with LGG (n = 35), with an objective response rate of 11% (one complete response and three partial responses) and stable disease in 43%. As of August 2020, four of these subjects were in treatment for >2 years and still ongoing. Objective responses were observed only in LGG. CONCLUSIONS: BAY1436032 was well tolerated and showed evidence of target inhibition and durable objective responses in a small subset of subjects with LGG.
Subject(s)
Aniline Compounds/therapeutic use , Antineoplastic Agents/therapeutic use , Benzimidazoles/therapeutic use , Isocitrate Dehydrogenase/antagonists & inhibitors , Isocitrate Dehydrogenase/genetics , Mutation , Neoplasms/drug therapy , Neoplasms/genetics , Adult , Aged , Aged, 80 and over , Alleles , Aniline Compounds/administration & dosage , Aniline Compounds/adverse effects , Aniline Compounds/pharmacokinetics , Antineoplastic Agents/administration & dosage , Antineoplastic Agents/adverse effects , Antineoplastic Agents/pharmacokinetics , Benzimidazoles/administration & dosage , Benzimidazoles/adverse effects , Benzimidazoles/pharmacokinetics , Biomarkers, Tumor , DNA Mutational Analysis , Disease Management , Disease Susceptibility , Female , Humans , Male , Middle Aged , Neoplasm Grading , Neoplasm Staging , Neoplasms/diagnosis , Neoplasms/mortalityABSTRACT
In squamous cell carcinoma (SCC) of the lung, mutations within the genes of fibroblast growth factor receptors (FGFR) such as K660N/K660E in FGFR2 and R248C/S249C in FGFR3 and FGFR1 gene amplification have been described, but their prognostic relevance still remains unclear. In order to detect the mutation frequencies and to define their prognostic value for associated clinicopathologic features and survival of patients, resected ΔNp63/p40-positive SCC of the lung (n = 101) were screened for FGFR1 gene amplification by fluorescence in situ hybridization performed on formalin-fixed paraffin embedded tissues and for the presumed driver mutations in genes of FGFR2 and FGFR3 by PCR and Sanger sequencing. Twenty-two of 101 SCCs (22%) were positive for amplification based on a FGFR1/centromere (chromosome 8) ratio > 2.0 or higher. In advanced tumor stages (III-IV), the overall survival of patients carrying FGFR1 gene amplification was significantly higher (p = 0.006). Among women, FGFR1 gene amplification was significantly associated with longer overall survival (p = 0.023). The presence of FGFR1 gene amplification was associated with patient age (65 versus 69 years, p = 0.046), but not with gender, tumor stage, histologic subtype, tumor grade, or ΔNp63/p40 immunoreactivity. The S249C mutation in the FGFR3 gene was identified in one out of 101 SCCs (1%); the K600N, K660E, or R248C mutations were not identified. These results suggest that FGFR1 gene amplification is a frequent alteration in SCC of the lung and appears not to be a negative but rather a favorable prognostic marker for women and particularly for patients with advanced SCC of the lung (stage III-IV).
Subject(s)
Biomarkers, Tumor/genetics , Carcinoma, Squamous Cell/genetics , Lung Neoplasms/genetics , Receptor, Fibroblast Growth Factor, Type 1/genetics , Adult , Aged , Biomarkers, Tumor/analysis , Carcinoma, Squamous Cell/mortality , Carcinoma, Squamous Cell/pathology , Female , Gene Amplification , Humans , Lung Neoplasms/mortality , Lung Neoplasms/pathology , Male , Middle Aged , PrognosisABSTRACT
BACKGROUND: The underlying molecular mechanisms of the vasculoprotective effects of physical exercise are incompletely understood. Telomere erosion is a central component of aging, and telomere-associated proteins regulate cellular senescence and survival. This study examines the effects of exercising on vascular telomere biology and endothelial apoptosis in mice and the effects of long-term endurance training on telomere biology in humans. METHODS AND RESULTS: C57/Bl6 mice were randomized to voluntary running or no running wheel conditions for 3 weeks. Exercise upregulated telomerase activity in the thoracic aorta and in circulating mononuclear cells compared with sedentary controls, increased vascular expression of telomere repeat-binding factor 2 and Ku70, and reduced the expression of vascular apoptosis regulators such as cell-cycle-checkpoint kinase 2, p16, and p53. Mice preconditioned by voluntary running exhibited a marked reduction in lipopolysaccharide-induced aortic endothelial apoptosis. Transgenic mouse studies showed that endothelial nitric oxide synthase and telomerase reverse transcriptase synergize to confer endothelial stress resistance after physical activity. To test the significance of these data in humans, telomere biology in circulating leukocytes of young and middle-aged track and field athletes was analyzed. Peripheral blood leukocytes isolated from endurance athletes showed increased telomerase activity, expression of telomere-stabilizing proteins, and downregulation of cell-cycle inhibitors compared with untrained individuals. Long-term endurance training was associated with reduced leukocyte telomere erosion compared with untrained controls. CONCLUSIONS: Physical activity regulates telomere-stabilizing proteins in mice and in humans and thereby protects from stress-induced vascular apoptosis.
Subject(s)
Blood Vessels/cytology , Blood Vessels/physiology , Cellular Senescence/physiology , Exercise/physiology , Leukocytes/cytology , Leukocytes/physiology , Physical Conditioning, Animal , Physical Exertion/physiology , Adolescent , Adult , Animals , Endothelium, Vascular/cytology , Endothelium, Vascular/physiology , Female , Humans , Male , Mice , Mice, Inbred C57BL , Mice, Transgenic , Middle Aged , Physical Conditioning, Animal/methods , Running/physiology , Telomere/enzymology , Telomere/physiology , Young AdultABSTRACT
Hepatocyte growth factor (HGF) is a pleiotropic cytokine promoting proliferation, migration and survival in several cell types. HGF and its cognate receptor c-Met are expressed in cardiac cells during early cardiogenesis, but data concerning its role in cardiac differentiation of embryonic stem cells (ESCs) and the underlying molecular mechanisms involved are limited. In the present study we show that HGF significantly increases the number of beating embryoid bodies of differentiating ESCs without affecting beating frequency. Furthermore, HGF up-regulates the expression of the cardiac-specific transcription factors Nkx 2.5 and GATA-4 and of markers of differentiated cardiomyocytes, i.e. alpha-MHC, beta-MHC, ANF, MLC2v and Troponin T. The HGF-induced increase in Nkx 2.5 expression was inhibited by co-treatment with the PI3 kinase inhibitors Wortmannin and LY294002, but not by its inactive homolog LY303511, suggesting an involvement of the PI3 kinase/Akt pathway in this effect. We conclude that HGF is an important growth factor involved in cardiac differentiation and/or proliferation of ESCs and may therefore be critical for the in vitro generation of pre- or fully differentiated cardiomyocytes as required for clinical use of embryonic stem cells in cardiac diseases.
Subject(s)
Embryonic Stem Cells/physiology , Hepatocyte Growth Factor/pharmacology , Myocardium/cytology , Organogenesis , Phosphatidylinositol 3-Kinases/metabolism , Animals , Cell Differentiation , Cells, Cultured , Dose-Response Relationship, Drug , Embryonic Stem Cells/drug effects , Enzyme Activation , GATA4 Transcription Factor/metabolism , Homeobox Protein Nkx-2.5 , Homeodomain Proteins/metabolism , Mice , Myocardium/metabolism , Myocytes, Cardiac , Transcription Factors/metabolismABSTRACT
We evaluated bone mineral density (BMD) and bone turnover in 22 homozygous prepubertal beta-thalassemic patients treated with desferrioxamine. Ten patients underwent treatment with desferrioxamine for the whole study period, while 12 patients stopped desferrioxamine and were then treated with deferiprone (L1). Lumbar and femoral BMD and bone metabolism markers were examined at baseline and after 1 and 3 years of follow up. All patients were prepubertal at baseline and they all became pubertal over the 3 years of follow up. At baseline, the mean lumbar Z score value was -2.048 SD +/- 0.75; the Z score was less than -2 SD in 13 children, within -1 and -2 SD in 6, and within 0 and -1 SD in only 3 subjects. A significant BMD increase (P < 0.0001) was observed at both the lumbar (+8.466%/year) and the femoral level (average of +3.46%/year at neck and +5.83%/year at the intertrochanteric region) after 3 years, without any significant difference being shown between patients treated with desferrioxamine and those treated with L1. The mean Z score SD values increased to -1.957 +/- 0.975 at 1 year (not significantly different from baseline) and to -1.864 +/- 1.221 at 3 year follow up (P < 0.05 vs baseline); an increase in bone turnover was also observed. These findings show that low BMD, a hallmark of beta-thalassemia, improves significantly when puberty begins; this increase involves different skeletal sites, regardless of pharmacological treatment with different iron-chelating drugs.
Subject(s)
Bone Density/drug effects , Bone and Bones/metabolism , Iron Chelating Agents/pharmacology , Thalassemia/drug therapy , Adolescent , Alkaline Phosphatase/drug effects , Alkaline Phosphatase/metabolism , Amino Acids/drug effects , Amino Acids/metabolism , Amino Acids/urine , Body Weights and Measures , Bone Density/physiology , Bone and Bones/drug effects , Child , Deferiprone , Deferoxamine/pharmacology , Female , Femur/chemistry , Femur/drug effects , Ferritins/blood , Humans , Iron Chelating Agents/therapeutic use , Lumbar Vertebrae/chemistry , Lumbar Vertebrae/drug effects , Male , Prospective Studies , Pyridones/pharmacology , Time FactorsABSTRACT
Expansion of the pool of tumor necrosis factor (TNF)-alpha-producing T cells is instrumental for the bone loss induced by estrogen deficiency, but the responsible mechanism is unknown. Here we show that ovariectomy up-regulates IFN-gamma-induced class II transactivator, a multitarget immune modulator, resulting in increased antigen presentation by macrophages, enhanced T cell activation, and prolonged lifespan of active T cells. Up-regulation of class II transactivator derives from increased production of IFN-gamma by T helper 1 cells, resulting from enhanced secretion of IL-12 and IL-18 by macrophages. The resulting T cell expansion and bone loss are prevented in vivo by both blockade of antigen presenting cell-induced T cell activation, and silencing of IFN-gamma receptor signaling. Thus, increased IFN-gamma-induced class II transactivator expression and the resulting enhanced T cell proliferation and lifespan are critical to the bone wasting effect of estrogen deficiency.
Subject(s)
Estrogens/deficiency , Interferon-gamma/physiology , Lymphocyte Activation , Nuclear Proteins , Osteoporosis/etiology , T-Lymphocytes/immunology , Trans-Activators/biosynthesis , Animals , Antigen-Presenting Cells/physiology , Mice , Mice, Inbred BALB C , Mice, Inbred C57BL , Ovariectomy , Receptors, Interferon/physiology , Interferon gamma ReceptorABSTRACT
IL-7, a powerful lymphopoietic cytokine, is elevated in rheumatoid arthritis (RA) and known to induce bone loss when administered in vivo. IL-7 has been suggested to induce bone loss, in part, by stimulating the proliferation of B220(+) cells, a population capable of acting as early osteoclast (OC) precursors. However, the mechanism by which IL-7 leads to differentiation of precursors into mature OCs remains unknown. We previously reported that, in vitro, IL-7 up-regulated T cell cytokines including receptor activator of nuclear factor kappaB ligand (RANKL). To demonstrate the importance of T cells to the bone-wasting effect of IL-7 in vivo, we have now examined IL-7-induced bone loss in T cell-deficient nude mice. We show that T cell-replete mice undergo significant osteoclastic bone loss after IL-7 administration, concurrent with induction of RANKL and tumor necrosis factor alpha (TNF-alpha) secretion by splenic T cells. In contrast, nude mice were resistant to IL-7-induced bone loss and showed no detectable increase in either RANKL or TNF-alpha, despite an up-regulation of B220(+) cells. Importantly, T cell adoptive transfer into nude mice restored IL-7-induced bone loss, and RANKL and TNF-alpha secretion, demonstrating that T cells are essential mediators of IL-7-induced bone loss in vivo.
Subject(s)
Bone Resorption/chemically induced , Interleukin-7/pharmacology , NF-kappa B/metabolism , T-Lymphocytes/immunology , Tumor Necrosis Factor-alpha/immunology , Adoptive Transfer , Animals , Bone Resorption/immunology , Bone Resorption/pathology , Carrier Proteins/metabolism , Cells, Cultured , Glycoproteins/metabolism , Lymphocyte Transfusion , Membrane Glycoproteins/metabolism , Mice , Mice, Nude , Osteoclasts/immunology , Osteoprotegerin , RANK Ligand , Receptor Activator of Nuclear Factor-kappa B , Receptors, Cytoplasmic and Nuclear/metabolism , Receptors, Tumor Necrosis Factor/metabolism , T-Lymphocytes/pathologyABSTRACT
Postmenopausal bone loss stems from the inability of osteoblastic activity to match the increase in osteoclastic bone resorption induced by estrogen deficiency. However, the mechanism that uncouples osteoblast from osteoclast activities remains unexplained. We show that ovariectomy enhances the production of the osteoclastogenic cytokine IL-7, and that its neutralization in vivo prevents ovariectomy-induced bone loss. Surprisingly, serum osteocalcin levels, a biochemical marker of bone formation, suggested that the bone-sparing effects of IL-7 neutralization were due not only to inhibition of bone resorption, but also to stimulation of bone formation. Consistent with these data, addition of IL-7 to neonatal calvarial organ cultures blocked new bone formation, and injection of IL-7 into mice in vivo inhibited bone formation as measured by calcein incorporation into long bones. The antianabolic effects of IL-7 were consistent with an observed downregulation of the osteoblast-specific transcription factor core-binding factor alpha1/Runx2. Thus, because it targets both the osteoclast and the osteoblast pathways, IL-7 is central to the altered bone turnover characteristic of estrogen deficiency.