Publications by authors named "Maxime Tarabichi"

19 Publications

  • Page 1 of 1

Common clonal origin of conventional T cells and induced regulatory T cells in breast cancer patients.

Nat Commun 2021 02 18;12(1):1119. Epub 2021 Feb 18.

RCI Regensburg Centre for Interventional Immunology, University and Department of Hematology/Oncology, University Medical Centre of Regensburg, Regensburg, Germany.

Regulatory CD4 T cells (Treg) prevent tumor clearance by conventional T cells (Tconv) comprising a major obstacle of cancer immune-surveillance. Hitherto, the mechanisms of Treg repertoire formation in human cancers remain largely unclear. Here, we analyze Treg clonal origin in breast cancer patients using T-Cell Receptor and single-cell transcriptome sequencing. While Treg in peripheral blood and breast tumors are clonally distinct, Tconv clones, including tumor-antigen reactive effectors (Teff), are detected in both compartments. Tumor-infiltrating CD4 cells accumulate into distinct transcriptome clusters, including early activated Tconv, uncommitted Teff, Th1 Teff, suppressive Treg and pro-tumorigenic Treg. Trajectory analysis suggests early activated Tconv differentiation either into Th1 Teff or into suppressive and pro-tumorigenic Treg. Importantly, Tconv, activated Tconv and Treg share highly-expanded clones contributing up to 65% of intratumoral Treg. Here we show that Treg in human breast cancer may considerably stem from antigen-experienced Tconv converting into secondary induced Treg through intratumoral activation.
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http://dx.doi.org/10.1038/s41467-021-21297-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7893042PMC
February 2021

A practical guide to cancer subclonal reconstruction from DNA sequencing.

Nat Methods 2021 Feb 4;18(2):144-155. Epub 2021 Jan 4.

Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.

Subclonal reconstruction from bulk tumor DNA sequencing has become a pillar of cancer evolution studies, providing insight into the clonality and relative ordering of mutations and mutational processes. We provide an outline of the complex computational approaches used for subclonal reconstruction from single and multiple tumor samples. We identify the underlying assumptions and uncertainties in each step and suggest best practices for analysis and quality assessment. This guide provides a pragmatic resource for the growing user community of subclonal reconstruction methods.
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http://dx.doi.org/10.1038/s41592-020-01013-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7867630PMC
February 2021

Drivers underpinning the malignant transformation of giant cell tumour of bone.

J Pathol 2020 Dec 6;252(4):433-440. Epub 2020 Oct 6.

Department of Pathology (research), University College London Cancer Institute, London, UK.

The rare benign giant cell tumour of bone (GCTB) is defined by an almost unique mutation in the H3.3 family of histone genes H3-3A or H3-3B; however, the same mutation is occasionally found in primary malignant bone tumours which share many features with the benign variant. Moreover, lung metastases can occur despite the absence of malignant histological features in either the primary or metastatic lesions. Herein we investigated the genetic events of 17 GCTBs including benign and malignant variants and the methylation profiles of 122 bone tumour samples including GCTBs. Benign GCTBs possessed few somatic alterations and no other known drivers besides the H3.3 mutation, whereas all malignant tumours harboured at least one additional driver mutation and exhibited genomic features resembling osteosarcomas, including high mutational burden, additional driver event(s), and a high degree of aneuploidy. The H3.3 mutation was found to predate the development of aneuploidy. In contrast to osteosarcomas, malignant H3.3-mutated tumours were enriched for a variety of alterations involving TERT, other than amplification, suggesting telomere dysfunction in the transformation of benign to malignant GCTB. DNA sequencing of the benign metastasising GCTB revealed no additional driver alterations; polyclonal seeding in the lung was identified, implying that the metastatic lesions represent an embolic event. Unsupervised clustering of DNA methylation profiles revealed that malignant H3.3-mutated tumours are distinct from their benign counterpart, and other bone tumours. Differential methylation analysis identified CCND1, encoding cyclin D1, as a plausible cancer driver gene in these tumours because hypermethylation of the CCND1 promoter was specific for GCTBs. We report here the genomic and methylation patterns underlying the rare clinical phenomena of benign metastasising and malignant transformation of GCTB and show how the combination of genomic and epigenomic findings could potentially distinguish benign from malignant GCTBs, thereby predicting aggressive behaviour in challenging diagnostic cases. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.
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http://dx.doi.org/10.1002/path.5537DOI Listing
December 2020

The evolutionary history of 2,658 cancers.

Nature 2020 02 6;578(7793):122-128. Epub 2020 Feb 6.

The Francis Crick Institute, London, UK.

Cancer develops through a process of somatic evolution. Sequencing data from a single biopsy represent a snapshot of this process that can reveal the timing of specific genomic aberrations and the changing influence of mutational processes. Here, by whole-genome sequencing analysis of 2,658 cancers as part of the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA), we reconstruct the life history and evolution of mutational processes and driver mutation sequences of 38 types of cancer. Early oncogenesis is characterized by mutations in a constrained set of driver genes, and specific copy number gains, such as trisomy 7 in glioblastoma and isochromosome 17q in medulloblastoma. The mutational spectrum changes significantly throughout tumour evolution in 40% of samples. A nearly fourfold diversification of driver genes and increased genomic instability are features of later stages. Copy number alterations often occur in mitotic crises, and lead to simultaneous gains of chromosomal segments. Timing analyses suggest that driver mutations often precede diagnosis by many years, if not decades. Together, these results determine the evolutionary trajectories of cancer, and highlight opportunities for early cancer detection.
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http://dx.doi.org/10.1038/s41586-019-1907-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7054212PMC
February 2020

A community effort to create standards for evaluating tumor subclonal reconstruction.

Nat Biotechnol 2020 01 9;38(1):97-107. Epub 2020 Jan 9.

Department of Medical Biophysics, University of Toronto, Toronto, Canada.

Tumor DNA sequencing data can be interpreted by computational methods that analyze genomic heterogeneity to infer evolutionary dynamics. A growing number of studies have used these approaches to link cancer evolution with clinical progression and response to therapy. Although the inference of tumor phylogenies is rapidly becoming standard practice in cancer genome analyses, standards for evaluating them are lacking. To address this need, we systematically assess methods for reconstructing tumor subclonality. First, we elucidate the main algorithmic problems in subclonal reconstruction and develop quantitative metrics for evaluating them. Then we simulate realistic tumor genomes that harbor all known clonal and subclonal mutation types and processes. Finally, we benchmark 580 tumor reconstructions, varying tumor read depth, tumor type and somatic variant detection. Our analysis provides a baseline for the establishment of gold-standard methods to analyze tumor heterogeneity.
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http://dx.doi.org/10.1038/s41587-019-0364-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6956735PMC
January 2020

Investigation of somatic CNVs in brains of synucleinopathy cases using targeted SNCA analysis and single cell sequencing.

Acta Neuropathol Commun 2019 12 23;7(1):219. Epub 2019 Dec 23.

Department of Clinical and Movement Neurosciences, UCL Queen Square Institute of Neurology, London, UK.

Synucleinopathies are mostly sporadic neurodegenerative disorders of partly unexplained aetiology, and include Parkinson's disease (PD) and multiple system atrophy (MSA). We have further investigated our recent finding of somatic SNCA (α-synuclein) copy number variants (CNVs, specifically gains) in synucleinopathies, using Fluorescent in-situ Hybridisation for SNCA, and single-cell whole genome sequencing for the first time in a synucleinopathy. In the cingulate cortex, mosaicism levels for SNCA gains were higher in MSA and PD than controls in neurons (> 2% in both diseases), and for MSA also in non-neurons. In MSA substantia nigra (SN), we noted SNCA gains in > 3% of dopaminergic (DA) neurons (identified by neuromelanin) and neuromelanin-negative cells, including olig2-positive oligodendroglia. Cells with CNVs were more likely to have α-synuclein inclusions, in a pattern corresponding to cell categories mostly relevant to the disease: DA neurons in Lewy-body cases, and other cells in the striatonigral degeneration-dominant MSA variant (MSA-SND). Higher mosaicism levels in SN neuromelanin-negative cells may correlate with younger onset in typical MSA-SND, and in cingulate neurons with younger death in PD. Larger sample sizes will, however, be required to confirm these putative findings. We obtained genome-wide somatic CNV profiles from 169 cells from the substantia nigra of two MSA cases, and pons and putamen of one. These showed somatic CNVs in ~ 30% of cells, with clonality and origins in segmental duplications for some. CNVs had distinct profiles based on cell type, with neurons having a mix of gains and losses, and other cells having almost exclusively gains, although control data sets will be required to determine possible disease relevance. We propose that somatic SNCA CNVs may contribute to the aetiology and pathogenesis of synucleinopathies, and that genome-wide somatic CNVs in MSA brain merit further study.
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http://dx.doi.org/10.1186/s40478-019-0873-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6929293PMC
December 2019

Undifferentiated Sarcomas Develop through Distinct Evolutionary Pathways.

Cancer Cell 2019 03;35(3):441-456.e8

Research Department of Pathology, Cancer Institute, University College London, London WC1E 6BT, UK; Department of Cellular and Molecular Pathology, Royal National Orthopaedic Hospital NHS Trust, Stanmore, Middlesex HA7 4LP, UK. Electronic address:

Undifferentiated sarcomas (USARCs) of adults are diverse, rare, and aggressive soft tissue cancers. Recent sequencing efforts have confirmed that USARCs exhibit one of the highest burdens of structural aberrations across human cancer. Here, we sought to unravel the molecular basis of the structural complexity in USARCs by integrating DNA sequencing, ploidy analysis, gene expression, and methylation profiling. We identified whole genome duplication as a prevalent and pernicious force in USARC tumorigenesis. Using mathematical deconvolution strategies to unravel the complex copy-number profiles and mutational timing models we infer distinct evolutionary pathways of these rare cancers. In addition, 15% of tumors exhibited raised mutational burdens that correlated with gene expression signatures of immune infiltration, and good prognosis.
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http://dx.doi.org/10.1016/j.ccell.2019.02.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6428691PMC
March 2019

Recurrent rearrangements of FOS and FOSB define osteoblastoma.

Nat Commun 2018 06 1;9(1):2150. Epub 2018 Jun 1.

Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire, CB10 1SA, UK.

The transcription factor FOS has long been implicated in the pathogenesis of bone tumours, following the discovery that the viral homologue, v-fos, caused osteosarcoma in laboratory mice. However, mutations of FOS have not been found in human bone-forming tumours. Here, we report recurrent rearrangement of FOS and its paralogue, FOSB, in the most common benign tumours of bone, osteoblastoma and osteoid osteoma. Combining whole-genome DNA and RNA sequences, we find rearrangement of FOS in five tumours and of FOSB in one tumour. Extending our findings into a cohort of 55 cases, using FISH and immunohistochemistry, provide evidence of ubiquitous mutation of FOS or FOSB in osteoblastoma and osteoid osteoma. Overall, our findings reveal a human bone tumour defined by mutations of FOS and FOSB.
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http://dx.doi.org/10.1038/s41467-018-04530-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5984627PMC
June 2018

Distinctive Desmoplastic 3D Morphology Associated With BRAFV600E in Papillary Thyroid Cancers.

J Clin Endocrinol Metab 2018 03;103(3):1102-1111

Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire Université Libre de Bruxelles, Brussels, Belgium.

Context: Although 60% of papillary thyroid carcinomas are BRAFV600E mutant (PTCV600E), the increased aggressiveness of these cancers is still debated.

Objective: For PTCV600E we aimed to further characterize the extent of the stroma and its activation, the three-dimensional (3D) tumor-stroma interface, and the proliferation rates of tumor and stromal fibroblasts.

Design: We analyzed exomes, transcriptomes, and images of 364 papillary thyroid carcinoma (PTCs) from The Cancer Genome Atlas (TCGA), including 211 PTCV600E; stained 22 independent PTCs for BRAFV600E and Ki67; sequenced the exomes and stained BRAFV600E in 5 primary tumor blocks and 4 nodal metastases from one patient with PTCV600E; and reconstructed the 3D volumes of one tumor and one metastatic block at histological resolution.

Results: In TCGA, BRAFV600E was associated with higher expression of proliferation markers and lower expression of thyroid differentiation markers, independently of tumor purity. Moreover, PTCV600E, in line with their overall lower purity, also had higher expression of fibroblast- and T cell-associated genes and presented more fibrosis. Tumor cells that appeared disconnected on two-dimensional histological slices were revealed to be part of a unique tumor component in the 3D reconstructed microvolumes, and they formed a surprisingly complex connected space, infiltrating a proliferative stroma. Finally, in our PTC set, both stromal fibroblasts and tumor cells presented higher proliferation rates in PTCV600E.

Conclusions: Our results support the increased aggressiveness associated with BRAFV600E in PTC and shed light on the important role of the stroma in tumor expansion. The greater and more active fibrotic component predicts better efficiency of combined targeted treatments, as previously proposed for melanomaV600E.
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http://dx.doi.org/10.1210/jc.2017-02279DOI Listing
March 2018

The human bitter taste receptor T2R38 is broadly tuned for bacterial compounds.

PLoS One 2017 13;12(9):e0181302. Epub 2017 Sep 13.

ChemCom S.A., Brussels, Belgium.

T2R38 has been shown to be a specific bacterial detector implicated in innate immune defense mechanism of human upper airway. Several clinical studies have demonstrated that this receptor is associated with the development of chronic rhinosinusitis (CRS). T2R38 was previously reported to bind to homoserine lactones (HSL), quorum sensing molecules specific of Pseudomonas Aeruginosa and other gram negative species. Nevertheless, these bacteria are not the major pathogens found in CRS. Here we report on the identification of bacterial metabolites acting as new agonists of T2R38 based on a single cell calcium imaging study. Two quorum sensing molecules (Agr D1 thiolactone from Staphylococcus Aureus and CSP-1 from Streptococcus Pneumoniae) and a list of 32 bacterial metabolites from pathogens frequently implicated in CRS were tested. First, we observed that HSL failed to activate T2R38 in our experimental system, but that the dimethylsulfoxide (DMSO), used as a solvent for these lactones may, by itself, account for the agonistic effect previously described. Secondly, we showed that both Agr D1 thiolactone and CSP-1 are inactive but that at least 7 bacterial metabolites (acetone, 2-butanone, 2-pentanone, 2-methylpropanal, dimethyl disulfide, methylmercaptan, γ-butyrolactone) are able to specifically trigger this receptor. T2R38 is thus much more broadly tuned for bacterial compounds than previously thought.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0181302PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5597121PMC
October 2017

A research note regarding "Variation in cancer risk among tissues can be explained by the number of stem cell divisions".

F1000Res 2016 22;5:2044. Epub 2016 Aug 22.

IRIBHM, Université Libre de Bruxelles (ULB), Brussels, B-1070, Belgium.

Tomasetti and Vogelstein argued that 2/3 of human cancers are due to 'bad luck' and that "primary prevention measures [against cancer] are not likely to be very effective". We demonstrate that their calculations for hepatocellular carcinomas overlooked a major subset of these cancers proven to be preventable through vaccination. The problem, which is not limited to hepatocellular carcinoma, arises from the general reliance of their analysis on average incidences in the United States and the omission of incidences in specific risk groups.
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http://dx.doi.org/10.12688/f1000research.9448.2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5089134PMC
August 2016

miRNA expression and function in thyroid carcinomas: a comparative and critical analysis and a model for other cancers.

Oncotarget 2016 08;7(32):52475-52492

Institute of Interdisciplinary Research (IRIBHM), University of Brussels, Brussels, Belgium.

As in many cancer types, miRNA expression profiles and functions have become an important field of research on non-medullary thyroid carcinomas, the most common endocrine cancers. This could lead to the establishment of new diagnostic tests and new cancer therapies. However, different studies showed important variations in their research strategies and results. In addition, the action of miRNAs is poorly considered as a whole because of the use of underlying dogmatic truncated concepts. These lead to discrepancies and limits rarely considered. Recently, this field has been enlarged by new miRNA functional and expression studies. Moreover, studies using next generation sequencing give a new view of general miRNA differential expression profiles of papillary thyroid carcinoma. We analyzed in detail this literature from both physiological and differential expression points of view. Based on explicit examples, we reviewed the progresses but also the discrepancies and limits trying to provide a critical approach of where this literature may lead. We also provide recommendations for future studies. The conclusions of this systematic analysis could be extended to other cancer types.
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http://dx.doi.org/10.18632/oncotarget.9655DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5239568PMC
August 2016

Intratumor heterogeneity and clonal evolution in an aggressive papillary thyroid cancer and matched metastases.

Endocr Relat Cancer 2015 Apr 17;22(2):205-16. Epub 2015 Feb 17.

IRIBHMWELBIOUniversité libre de Bruxelles (ULB), Campus Erasme, 808 Route de Lennik, 1070 Brussels, BelgiumCHU d'AngersBâtiment IRIS, 4 rue Larrey, Angers F-49033, FranceEA 3143Université d'Angers, F-49033 Angers, FranceService d'Anatomie et Cytologie PathologiquesCentre de Biologie Sud - Bâtiment 3D, Centre Hospitalier Lyon Sud, 69495 Pierre Bénite Cedex, FranceHôpital Pitié-SalpêtrièreUniversité Pierre et Marie Curie, 47 Boulevard de l'Hôpital, 75013 Paris, FranceInstitut Jules Bordet121 Boulevard de Waterloo, 1000 Brussels, Belgium IRIBHMWELBIOUniversité libre de Bruxelles (ULB), Campus Erasme, 808 Route de Lennik, 1070 Brussels, BelgiumCHU d'AngersBâtiment IRIS, 4 rue Larrey, Angers F-49033, FranceEA 3143Université d'Angers, F-49033 Angers, FranceService d'Anatomie et Cytologie PathologiquesCentre de Biologie Sud - Bâtiment 3D, Centre Hospitalier Lyon Sud, 69495 Pierre Bénite Cedex, FranceHôpital Pitié-SalpêtrièreUniversité Pierre et Marie Curie, 47 Boulevard de l'Hôpital, 75013 Paris, FranceInstitut Jules Bordet121 Boulevard de Waterloo, 1000 Brussels, Belgium

The contribution of intratumor heterogeneity to thyroid metastatic cancers is still unknown. The clonal relationships between the primary thyroid tumors and lymph nodes (LN) or distant metastases are also poorly understood. The objective of this study was to determine the phylogenetic relationships between matched primary thyroid tumors and metastases. We searched for non-synonymous single-nucleotide variants (nsSNVs), gene fusions, alternative transcripts, and loss of heterozygosity (LOH) by paired-end massively parallel sequencing of cDNA (RNA-Seq) in a patient diagnosed with an aggressive papillary thyroid cancer (PTC). Seven tumor samples from a stage IVc PTC patient were analyzed by RNA-Seq: two areas from the primary tumor, four areas from two LN metastases, and one area from a pleural metastasis (PLM). A large panel of other thyroid tumors was used for Sanger sequencing screening. We identified seven new nsSNVs. Some of these were early events clonally present in both the primary PTC and the three matched metastases. Other nsSNVs were private to the primary tumor, the LN metastases and/or the PLM. Three new gene fusions were identified. A novel cancer-specific KAZN alternative transcript was detected in this aggressive PTC and in dozens of additional thyroid tumors. The PLM harbored an exclusive whole-chromosome 19 LOH. We have presented the first, to our knowledge, deep sequencing study comparing the mutational spectra in a PTC and both LN and distant metastases. This study has yielded novel findings concerning intra-tumor heterogeneity, clonal evolution and metastases dissemination in thyroid cancer.
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http://dx.doi.org/10.1530/ERC-14-0351DOI Listing
April 2015

Profiling of olfactory receptor gene expression in whole human olfactory mucosa.

PLoS One 2014 6;9(5):e96333. Epub 2014 May 6.

ChemCom S.A., Brussels, Belgium.

Olfactory perception is mediated by a large array of olfactory receptor genes. The human genome contains 851 olfactory receptor gene loci. More than 50% of the loci are annotated as nonfunctional due to frame-disrupting mutations. Furthermore haplotypic missense alleles can be nonfunctional resulting from substitution of key amino acids governing protein folding or interactions with signal transduction components. Beyond their role in odor recognition, functional olfactory receptors are also required for a proper targeting of olfactory neuron axons to their corresponding glomeruli in the olfactory bulb. Therefore, we anticipate that profiling of olfactory receptor gene expression in whole human olfactory mucosa and analysis in the human population of their expression should provide an opportunity to select the frequently expressed and potentially functional olfactory receptors in view of a systematic deorphanization. To address this issue, we designed a TaqMan Low Density Array (Applied Biosystems), containing probes for 356 predicted human olfactory receptor loci to investigate their expression in whole human olfactory mucosa tissues from 26 individuals (13 women, 13 men; aged from 39 to 81 years, with an average of 67±11 years for women and 63±12 years for men). Total RNA isolation, DNase treatment, RNA integrity evaluation and reverse transcription were performed for these 26 samples. Then 384 targeted genes (including endogenous control genes and reference genes specifically expressed in olfactory epithelium for normalization purpose) were analyzed using the same real-time reverse transcription PCR platform. On average, the expression of 273 human olfactory receptor genes was observed in the 26 selected whole human olfactory mucosa analyzed, of which 90 were expressed in all 26 individuals. Most of the olfactory receptors deorphanized to date on the basis of sensitivity to known odorant molecules, which are described in the literature, were found in the expressed olfactory receptors gene set.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0096333PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4011832PMC
January 2015

Comparative analysis of the thyrocytes and T cells: responses to H2O2 and radiation reveals an H2O2-induced antioxidant transcriptional program in thyrocytes.

J Clin Endocrinol Metab 2013 Oct 10;98(10):E1645-54. Epub 2013 May 10.

Universite Libre de Bruxelles-Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire, B1070 Brussels, Belgium.

Context: Radiation is an established cause of thyroid cancer, and growing evidence supports a role for hydrogen peroxide (H2O2) in spontaneous thyroid carcinogenesis. Little is known about the molecular programs activated by these agents in thyrocytes.

Objective: The purpose of this study was to compare the responses of thyrocytes and T cells to H2O2 and radiation.

Methods: We profiled the DNA damage and cell death induced by γ-radiation (0.1-5 Gy) and H2O2 (0.0025-0.3 mM) in primary human thyrocytes and T cells. We next prepared thyroid and T-cell primary cultures from 8 donors operated for noncancerous thyroid pathological conditions and profiled their genome-wide transcriptional response 4 hours after (1) exposure to 1-Gy radiation, (2) treatment with H2O2 and (3) no treatment. Two H2O2 concentrations were investigated, calibrated in each cell type to elicit levels of single- and double-strand breaks equivalent to 1-Gy γ-radiation.

Results: Although thyrocytes and T cells had comparable radiation responses, 3- to 10-fold more H2O2 was needed to induce detectable DNA damage in thyrocytes. At H2O2 and radiation doses inducing double-strand breaks, cell death occurred after 24 hours in T cells but not in thyrocytes. The transcriptional responses of thyrocytes and T cells to radiation were similar, involving DNA repair and cell death genes. In addition to this transcriptional program, H2O2 also up-regulated antioxidant genes in thyrocytes, including glutathione peroxidases and heme oxygenase at the double-strand breaks-inducing concentration. In contrast, a transcriptional storm involving thousands of genes was raised in T cells. Finally, we showed that inhibiting glutathione peroxidases activity increased the DNA damaging effect of H2O2 in thyrocytes.

Conclusion: We propose that high H2O2 production in thyrocytes is matched with specific transcriptionally regulated antioxidant protection.
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http://dx.doi.org/10.1210/jc.2013-1266DOI Listing
October 2013

5-aza-2'-deoxycytidine has minor effects on differentiation in human thyroid cancer cell lines, but modulates genes that are involved in adaptation in vitro.

Thyroid 2013 Mar;23(3):317-28

Institute of Interdisciplinary Research (IRIBHM), Université libre de Bruxelles, Brussels, Belgium.

Background: In thyroid cancer, the lack of response to specific treatment, for example, radioactive iodine, can be caused by a loss of differentiation characteristics of tumor cells. It is hypothesized that this loss is due to epigenetic modifications. Therefore, drugs releasing epigenetic repression have been proposed to reverse this silencing.

Methods: We investigated which genes were reinduced in dedifferentiated human thyroid cancer cell lines when treated with the demethylating agent 5-aza-2'-deoxycytidine (5-AzadC) and the histone deacetylase inhibitors trichostatin A (TSA) and suberoylanilide hydroxamic acid, by using reverse transcriptase-polymerase chain reaction and microarrays. These results were compared to the expression patterns in in vitro human differentiated thyrocytes and in in vivo dedifferentiated thyroid cancers. In addition, the effects of 5-AzadC on DNA quantities and cell viability were investigated.

Results: Among the canonical thyroid differentiation markers, most were not, or only to a minor extent, re-expressed by 5-AzadC, whether or not combined with TSA or forskolin, an inducer of differentiation in normal thyrocytes. Furthermore, 5-AzadC-modulated overall mRNA expression profiles showed only few commonly regulated genes compared to differentiated cultured primary thyrocytes. In addition, most of the commonly strongly 5-AzadC-induced genes in cell lines were either not regulated or upregulated in anaplastic thyroid carcinomas. Further analysis of which genes were induced by 5-AzadC showed that they were involved in pathways such as apoptosis, antigen presentation, defense response, and cell migration. A number of these genes had similar expression responses in 5-AzadC-treated nonthyroid cell lines.

Conclusions: Our results suggest that 5-AzadC is not a strong inducer of differentiation in thyroid cancer cell lines. Under the studied conditions and with the model used, 5-AzadC treatment does not appear to be a potential redifferentiation treatment for dedifferentiated thyroid cancer. However, this may reflect primarily the inadequacy of the model rather than that of the treatment. Moreover, the observation that 5-AzadC negatively affected cell viability in cell lines could still suggest a therapeutic opportunity. Some of the genes that were modulated by 5-AzadC were also induced in nonthyroid cancer cell lines, which might be explained by an epigenetic modification resulting in the adaptation of the cell lines to their culture conditions.
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http://dx.doi.org/10.1089/thy.2012.0388DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3593687PMC
March 2013

Piecewise polynomial representations of genomic tracks.

PLoS One 2012 15;7(11):e48941. Epub 2012 Nov 15.

IRIBHM, Université Libre de Bruxelles, Brussels, Belgium.

Genomic data from micro-array and sequencing projects consist of associations of measured values to chromosomal coordinates. These associations can be thought of as functions in one dimension and can thus be stored, analyzed, and interpreted as piecewise-polynomial curves. We present a general framework for building piecewise polynomial representations of genome-scale signals and illustrate some of its applications via examples. We show that piecewise constant segmentation, a typical step in copy-number analyses, can be carried out within this framework for both array and (DNA) sequencing data offering advantages over existing methods in each case. Higher-order polynomial curves can be used, for example, to detect trends and/or discontinuities in transcription levels from RNA-seq data. We give a concrete application of piecewise linear functions to diagnose and quantify alignment quality at exon borders (splice sites). Our software (source and object code) for building piecewise polynomial models is available at http://sourceforge.net/projects/locsmoc/.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0048941PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3499510PMC
May 2013

Thyroid cancer cell lines: an overview.

Front Endocrinol (Lausanne) 2012 16;3:133. Epub 2012 Nov 16.

School of Medicine, IRIBHM, Université Libre de Bruxelles Brussels, Belgium.

Human thyroid cancer cell lines are the most used models for thyroid cancer studies. They must be used with detailed knowledge of their characteristics. These in vitro cell lines originate from differentiated and dedifferentiated in vivo human thyroid tumors. However, it has been shown that mRNA expression profiles of these cell lines were closer to dedifferentiated in vivo thyroid tumors (anaplastic thyroid carcinoma, ATC) than to differentiated ones. Here an overview of the knowledge of these models was made. The mutational status of six human thyroid cancer cell lines (WRO, FTC133, BCPAP, TPC1, K1, and 8505C) was in line with previously reported findings for 10 genes frequently mutated in thyroid cancer. However, the presence of a BRAF mutation (T1799A: V600E) in WRO questions the use of this cell line as a model for follicular thyroid carcinoma (FTC). Next, to investigate the biological meaning of the modulated mRNAs in these cells, a pathway analysis on previously obtained mRNA profiles was performed on five cell lines. In five cell lines, the MHC class II pathway was down-regulated and in four of them, ribosome biosynthesis and translation pathways were up-regulated. mRNA expression profiles of the cell lines were also compared to those of the different types of thyroid cancers. Three datasets originating from different microarray platforms and derived from distinct laboratories were used. This meta-analysis showed a significant higher correlation between the profiles of the thyroid cancer cell lines and ATC, than to differentiated thyroid tumors (i.e., PTC or FTC) specifically for DNA replication. This already observed higher correlation was obtained here with an increased number of in vivo tumors and using different platforms. In summary, this would suggest that some papillary thyroid carcinoma or follicular thyroid carcinoma (PTC or FTC) cell lines (i.e., TPC-1) might have partially lost their original DNA synthesis/replication regulation mechanisms during their in vitro cell adaptation/evolution.
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http://dx.doi.org/10.3389/fendo.2012.00133DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3499787PMC
November 2012