Study of Methylation Pattern of de Novo DNA Methyltransferase Genes and its Correlation with DNA Methylation Pattern of RUNX3 in Individuals with Gastric Cancer from Northern Region of Brazil / Estudio del Estado de Metilación de Novo de Genes Metiltransferasas y su Correlación con el Patrón de Metilación de RUNX3 en Individuos con Cáncer Gástrico de la Región Norte del Brasil

Gastric cancer is the forth malignancy in frequency in the world. In the northern Brazil is the second neoplasia most frequent in males and the third most frequent in females. Genetic and epigenetic alterations are evolved on gastric carcinogenesis and DNA methylation is the epigenetic alteration better studied. We analyzed de novo DNA methyltransferases methylation pattern and its association with RUNX3 gene methylation pattern in Brazilian samples of intestinal-type and diffuse-type of gastric cancer. PCR methylation specific was used to evaluate DNA methylation pattern. Sixty-six samples were studied in this work. Only the gene RUNX3 presented altered methylation pattern, being methylated in 38.5% of gastric cancer intestinal-type samples and in 70% of gastric cancer diffuse-type samples and, by this reason, it should be evolved in the genesis of this neoplasia. There was a statistically significant difference among diffuse-type and intestinal-type samples (p=0.0418) and among normal and tumour tissues (p<0.0001) for RUNX3 gene but not to DNMT3A, DNMT3B e DNMT3 genes on CpG islands analyzed. Alteration of RUNX3 methylation pattern is not associated to de novo alteration of DNA methyltransferases methylation pattern on studied regionsTherefore, it becomes necessary a better comprehension of this phenomenon on gastric carcinogenesis.

El cáncer gástrico es la cuarta patología más frecuente en el mundo. En el norte del Brasil, es la segunda neoplasia más frecuente en hombres y la tercera en mujeres. Alteraciones genéticas y epigenéticas relacionadas con la carcinogénesis gástrica y la metilación del DNA son las alteraciones epigenéticas mejor estudiadas. En este trabajo, analizamos el estado de novo de metilación de genes DNA metiltransferases y su asociación con el estado de metilación del gen RUNX3 en muestras de individuos brasileños con cáncer gástrico de los tipos intestinal y difuso. Fue usada la Reacción en Cadena de la Polimerasa (PCR), metilación específica, para analizar el estado de metilación del DNA. Fueron estudiados 66 tejidos tumorales. Solamente el gen RUNX3 presentó un estado de metilación alterado, estuvo metilado en 38,5% de las muestras de cáncer gástrico tipo intestinal y en 70% de muestras de cáncer gástrico tipo difuso, lo que sugiere que estaría relacionado con la génesis de esta neoplasia. Hubo una diferencia estadística significativa entre muestras de los tipos difuso e intestinal (p=0.0418) y entre tejidos normal y tumoral (p<0.0001)parael gen RUNX3. Esta asociación no fue encontrada para los genes DNMT3A, DNMT3B y DNMT3 en las islas CpG analizadas. Alteraciones del estado de metilación de RUNX3 no están asociadas con alteraciones de novo de genes DNA metiltransferases. De esta forma se hace necesaria una mejor comprensión de este fenómeno en la carcinogénesis gástrica.

Epigenetic alterations in human brain tumors in a Brazilian population

Aberrant methylation of CpG islands located in promoter regions represents one of the major mechanisms for silencing cancer-related genes in tumor cells. We determined the frequency of aberrant CpG island methylation for several tumor-associated genes: DAPK, MGMT, p14ARF, p16INK4a, TP73, RB1 and TIMP-3 in 55 brain tumors, consisting of 26 neuroepithelial tumors, 6 peripheral nerve tumors, 13 meningeal tumors and 10 metastatic brain tumors. Aberrant methylation of at least one of the seven genes studied was detected in 83.6 percent of the cases. The frequencies of aberrant methylation were: 40 percent for p14ARF, 38.2 percent for MGMT, 30.9 percent for, p16INK4a, 14.6 percent for TP73 and for TIMP-3, 12.7 percent for DAPK and 1.8 percent for RB1. These data suggest that the hypermethylation observed in the genes p14ARF, MGMT and p16INK4a is a very important event in the formation or progression of brain tumors, since the inactivation of these genes directly interferes with the cell cycle or DNA repair. The altered methylation rate of the other genes has already been reported to be related to tumorigenesis, but the low methylation rate of RB1 found in tumors in our sample is different from that so far reported in the literature, suggesting that perhaps hypermethylation of the promoter is not the main event in the inactivation of this gene. Our results suggest that hypermethylation of the promoter region is a very common event in nervous system tumors.

Distinct nonrandom patterns of chromosomal deletions in giant-cell lesions of bone

Cytogenetic analyses were performed on a bone giant cell reparative granuloma (GCRG) and on three bone giant cell tumors (GCT). The present GCRG case is the second to be described cytogenetically. A modal chromosome number of 46 was observed in all samples. Clonal chromosome abnormalities were detected in all cases. The numerical alterations most frequently observed involved the loss of chromosomes 17 and 18. Among the structural anomalies observed, there was preferential involvement of chromosomes 6 and 10. Three GCT cases presented del(10)(p13) and two cases presented del(6)(q25) (1 GCRG and 1 GCT). These breakpoints mapped on 10p and 6q may harbour genes of importance in the development of bone giant cell tumors

Investigation of single strand conformational alterations of the TP53 gene in epithelial hyperplasias of the breast

Generally, benign breast lesions behave as innocuous and limited proliferations, but sometimes they can represent pre-cancerous diseases. The practical importance of epithelial hyperplasias studies is related to their potential for malignant transformation. The TP53 tumor supressor gene suffers the greatest number of mutations in human cancer Using single strand conformational polymorphism, we did a mutation screening in exons 5 to 8 of the TP53 gene in the tumoral tissues of five patients with epithelial hyperplasias of the breast. The obtained results do not show any polymorphism that indicates mutation. The lack of mutation indicates that this gene is not involved in the initial process of malignization, strengthening the hypothesis that mutations on TP53 gene are a late event in the breast carcinogenesis.

Karyotypic and histopathologic findings in an accessory breast

Accessory breasts are a clearly hereditary anomaly. They enlarge during pregnancy and lactation as a consequence of high blood levels of estrogen and prolactin, and are subject to all the diseases that occur in normal breasts. Cytogenetic analysis was performed on one accessory breast. The monossomy of chromosome 16 was the main alteration found in this materal. Nonscheduled cell proliferations may produce chromosome alterations, most of them with no clinical meaning. When relevant genes are altered, major proliferations or progression to malignancy may occur.

Chromosome fragility in hematologic disease presumably induced by environmental pollutants

Chromosome instability consists of chromosome abnoprmalities as multiple breaks in in metaphase chromosomes in syndromes of chromosaome instability such as fanconi's anemia (FA) which is mainly characaterized by bone marrow aplasia; some cases progress to acute leukemia. FA is a hereditary disease with recessive and monogenic transmission. This pair of mutated genes is related to chromosome fragility and therefore is responsible for the inefficiency of DNA repair. In normal individuals, these genes are assumed to be expressed normally, but their products ara insufficient to perform DNA repair when the intensity of the polluting agent lelads to exposure above basal levels. In the present study, the bone marrow of four patients with different hematologic diseases was submitted to cytogenetic analysis. Two had aplastic anemia, and one bad lymphoblastic leukemia. These patients were from towns unb the Amazon Region where the mercuri used for gold prospecting and the substances used and/or released in aluminium mining have been introduced into the environment. The last patient had fanconi's anemia and was used as a model in the discussion of the results. The cytogenetic findings were similar for all patients, the major ones being chromosome fragmentation and pulverization. In view of these findings, we believe that chromosome fragility, observed in the first three patients, presumably was induced by environmental pllutants

Chromosome analysis of benign expansive processes in the adrenal cortex

A análise cromossômica foi realizada em uma hiperplasia e em um adenoma da supra-renal. A aberraçäo cromossômica mais freqüentemente observada foi a monossomia do cromossomo 14 (hiperplasia), 5 e 8 (adenoma). Esses achados cariotípicos foram comparados aos já descritos em tumores da supra-renal.

Cytogenetic investigation of four low grade gliomas

Four low-grade gliomas - two oligodendrogliomas and two astrocytomas - were analyzed cytogenetically. All cases exhibited monosomies of chromosomes 10 and 11. The astrocytomas shared monosoniies of chromosomes 8, 9, 1O, 11, 12, 18 and 20. Losses of chromosomes 3, 5, 6, 10 and I I were present in both oligodendrogliomas, and except for monosomy of chromosome 6, were also identified in the pilocytic astrocytoma.

Cancer and cytogenetics

Alguns aspectos da citogenética do câncer säo discutidos aqui. Rearranjos cromossômicos säo agrupados em três categorias, baseadas no mecanismo pelo qual elas promovem o desenvolvimento do tumor: a) translocaçöes, inversöes e inserçöes; b) deleçöes e monossomias cromossômicas; c) amplificaçöes. "Imprinting" genômico, tumores benignos e metástases säo também discutidos

Cytogenetic analysis of human meningiomas

Quatro meningiomas primários humanos foram colocados em cultura e tiveram suas células analisadas citogenéticamente: 1 me meningioma transicional com número modal de 46 cromossomos (I), 2 meningiomas fibroblásticos ambos com número modal de 45 cromossomos (II e III) e 1 meningioma meningoendoteliomatoso com uma classe modal correspondente a 78 - 82 cromossomos (IV). A alteraçäo mais consistente encontrada em todos os tumores foi a monossomia total ou parcial do cromossomo 22 (I - 30%; II - 25%; III - 69% e IV - 30%). O tumor I apresentou também perda do cromossomo Y (80% das célulkas), além de outros marcadores nao identificados. O tumor II apresentou a deleçäo 12p12 - 12pter (65% das células) e del (19) (qter - p13:) (50% das células). O tumor III apresentou 3 marcadores recorrentes, näo identificados. O tumor IV apresentou um marcador acrocêntrico grande, näo identificado. Monossomias, trissomias e tetrassomias esporádicas também foram encontradas nesses tumores. Os pontos de quebra recorrentes foram comparados com os locais de sítios frágeis, pontos específicos de quebras neoplásicas, genes muito ativos de células diferenciadas e oncogenes, já descritos na literatura

A specific recurrent chromosomal break region (2q-24-2q.32) in human gliomas

Doze gliomas humanos foram estudados citogeneticamente e 06 deles apresentaram uma regiäo de quebra cromossômica (2q24 - 2q32), nunca antes descrita em nenhuma neoplasia

Cytogenetic study of a gastric human tumor

Um tumor primário humano de estômago e sete clones dele derivados, foram estudados citogeneticamente e tiveram o tempo de duplicaçäo das populaçöes determinado. A análise do n§ modal revelou números cromossômicos na regiäo peridiplóide. Tanto a linhagem parental como os clones apresentaram "micro-marcadores". O marcador mais característico deste tumor foi um cromossomo submetacêntrico grande envolvendo um rearranjo entre os cromossomos 1 e 8, assim descrito: t(1;8) (1qter-1q12::8p23-8qter), aparecendo em altas freqüências na linhagem parental e em todos os clones. Outros marcadores de origem näo identificada e ocorrendo em freqüências mais baixas foram encontrados: 1 cromossomo submetacêntrico grande, de tamanho semelhante ao cromossomo 3; um cromossomo acrocêntrico grande, maior que os cromossomos do grupo D; um cromossomo semelhante aos cromossomos do grupo B, porém com o braço longo maior e um cromossomo em anel. Além de perdas e ganhos ocasionais, havia em todos os clones e na linhagem parental, uma perda consistente do cromossomo 17