Correlation of MLH1 and MGMT expression and promoter methylation with genomic instability in patients with thyroid carcinoma

Background: Gene silencing of the repair genes MLH1 and MGMT was shown to be a mechanism underlying the development of microsatellite instability (MSI), a phenotype frequently associated with various human malignancies. Recently, aberrant methylation of MLH1, MGMT and MSI were shown to be associated with mutations in genes such as BRAF, RAS and IDH1 in colon and brain tumours. Little is known about the methylation status of MLH1 and MGMT in thyroid tumours and its association with MSI and mutational status.Methods: in a series of 96 thyroid tumours whose mutational profiles of BRAF, IDH1 and NRAS mutations and RET/PTC were previously determined, we investigated MLH1 and MGMT expression and methylation status by qPCR and methylation-specific PCR after bisulphite treatment, respectively. MSI was determined by PCR using seven standard microsatellite markers.Results: Samples with point mutations (BRAF, IDH1 and NRAS) show a decrease in MLH1 expression when compared to negative samples. Additionally, malignant lesions show a higher MSI pattern than benign lesions. the MSI phenotype was also associated with down-regulation of MLH1.Conclusions: the results of this study allow us to conclude that low expression of MLH1 is associated with BRAF V600E mutations, RET/PTC rearrangements and transitions (IDH1 and NRAS) in patients with thyroid carcinoma. in addition, a significant relationship between MSI status and histological subtypes was found.Univ Sao Francisco, Unidade Integrada Farmacol & Gastroenterol, BR-12900000 Braganca Paulista, SP, BrazilUniversidade Federal de São Paulo, Disciplina Genet, Lab Bases Genet Tumores Tiroide, São Paulo, BrazilUniversidade Federal de São Paulo, Disciplina Genet, Lab Bases Genet Tumores Tiroide, São Paulo, BrazilWeb of Scienc

Identification of several novel non-p.R132 IDH1 variants in thyroid carcinomas

Context: Somatic mutations at residue R132 of isocitrate dehydrogenase 1 (IDH1) were recently discovered in gliomas and leukaemia at a high frequency. IDH1 is a metabolic gene, and the R132 mutations create a new enzymatic activity.Objectives: To determine whether IDH1 had somatically acquired mutations in thyroid carcinomas.Design: Exons 4 and 6 of IDH1 were sequenced in a large panel of thyroid tumours (n = 138) and compared with the patients normal DNA (n = 26). We also correlated IDH1 mutations with clinical-pathological data and BRAF and RAS mutational status.Results: We identified four novel and two previously described non-synonymous variants in thyroid carcinomas, which were absent in benign tumours and paired normal thyroid. Although IDH1 variants occurred at higher frequency in follicular thyroid carcinomas, follicular variant of papillary thyroid carcinoma (PTC) and undifferentiated thyroid carcinomas than the observed variants in classical PTC (15/72 vs 3/37), it was not significant (P = 0.1). Sequence alignment across several species shows that all IDH1 genetic alterations occurred at evolutionarily conserved residues located within the active site, and therefore, are likely to affect protein function. Unlike other tumours, IDH1 and BRAF or RAS mutations are not mutually exclusive. There was no association between IDH1 mutational status and clinical characteristics.Conclusion: IDH1-acquired genetic alterations are highly prevalent in thyroid carcinomas (16%). Our findings not only extend our understanding of the molecular mechanism underlying pathogenesis of thyroid tumours, but also emphasize the biological differences between tumour types. Those tumours with IDH1 mutations might benefit from therapies that exploit this alteration.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Universidade Federal de São Paulo, Lab Bases Genet Tumores Tiroide, Disciplina Genet, BR-04039032 São Paulo, BrazilUniversidade Federal de São Paulo, Lab Bases Genet Tumores Tiroide, Disciplina Endocrinol, BR-04039032 São Paulo, BrazilUniversidade Federal de São Paulo, Lab Bases Genet Tumores Tiroide, Disciplina Genet, BR-04039032 São Paulo, BrazilUniversidade Federal de São Paulo, Lab Bases Genet Tumores Tiroide, Disciplina Endocrinol, BR-04039032 São Paulo, BrazilFAPESP: 05/60330-8FAPESP: 09/11257-7Web of Scienc

CBX7 and HMGA1b proteins act in opposite way on the regulation of the SPP1 gene expression

Several recent studies have reported the Polycomb Repressive Complex 1 member CBX7 as a tumor-suppressor gene whose expression progressively decreases in different human carcinomas in relation with tumor grade, malignant stage and poor prognosis. We have previously demonstrated that CBX7 is able to inhibit the expression of the SPP1 gene, encoding the chemokine osteopontin that is over-expressed in cancer and has a critical role in cancer progression.Here, we have analyzed the mechanism by which CBX7 regulates the SPP1 gene expression. We show that the SPP1 transcriptional regulation mechanism involves the CBX7-interacting protein HMGA1b, that acts as a positive regulator of the SPP1 gene. In fact, we demonstrate that, in contrast with the transcriptional activity of CBX7, HMGA1b is able to increase the SPP1 expression by inducing the activity of its promoter. Moreover, we show that CBX7 interferes with HMGA1b on the SPP1 promoter and counteracts the positive transcriptional activity of HMGA1b on the SPP1 expression.Furthermore, since we found that also the NF-kappa B complex resulted involved in the modulation of the SPP1 expression in thyroid cells, we suppose that CBX7/HMGA1b/NF-kappa B could take part in the same transcriptional mechanism that finally leads to the regulation of the SPP1 gene expression.Taken together, our data show the important role played by CBX7 in the negative regulation of the SPP1 gene expression, thus contributing to prevent the acquisition of a malignant phenotype.Associazione Italiana per la Ricerca sul Cancro-AIRCMinistero dell'Istruzione, dell'Universita e della Ricerca MIURP.O.R. Campania FSE Progetto CREMeProgetto di Interesse strategico Invecchiamento (PNR-CNR Aging Program) PNR-CNRProgetto Nuove strategie nanotecnologiche per la messa a punto di farmaci e presidi diagnostici diretti verso cellule cancerose circolantiCNR Epigenomics Flagship Project EPIGENCNR Nanomax Progetto Bandiera DESIREDUniv Naples Federico II, Dipartimento Med Mol & Biotecnol Med DMMBM, CNR, Ist Endocrinol & Oncol Sperimentale IEOS G Salvat, I-80131 Naples, ItalyUniv Fed Sao Paulo UNIFESP, Disciplina Genet, Lab Bases Genet Tumores Tiroide, BR-04039032 Sao Paulo, SP, BrazilInst Nacl Canc INCA, BR-20230130 Rio De Janeiro, RJ, BrazilUniv Fed Sao Paulo UNIFESP, Disciplina Genet, Lab Bases Genet Tumores Tiroide, BR-04039032 Sao Paulo, SP, BrazilAssociazione Italiana per la Ricerca sul Cancro-AIRC: IG 11477Progetto Nuove strategie nanotecnologiche per la messa a punto di farmaci e presidi diagnostici diretti verso cellule cancerose circolanti: PON01-02782Web of Scienc