Gastric cancer is one of the most common malignancies. DNA methylation is implicated in DNA mismatch repair genes deficiency. In the present study, we evaluated the methylation status of MLH1, MSH2, MSH6 and PMS2 in 20 diffuse- and 26 intestinal-type gastric cancer samples and 20 normal gastric mucosal of gastric cancer patients from Northern Brazil. We found that none of the nonneoplastic samples showed methylation of any gene promoter and 50% of gastric cancer samples showed at least one methylated gene promoter. Methylation frequencies of MLH1, MSH2, MSH6 and PMS2 promoter were 21.74%, 17.39%, 0% and 28.26% respectively in gastric cancer samples. MLH1 and PMS2 methylation were associated with neoplastic samples compared to nonneoplastic ones. PMS2 methylation was associated with diffuse-and intestinal-type cancer compared with normal controls. Intestinal-type cancer showed significant association with MLH1 methylation. Diffuse-type cancer was significantly associated with MSH2 methylation. Our findings show differential gene methylation in tumoral tissue, which allows us to conclude that methylation is associated with gastric carcinogenesis. Methylation of mismatch repair genes was associated with gastric carcinogenesis and may be a helpful tool for diagnosis, prognosis and therapies. However, MSH6 does not seem to be regulated by methylation in our samples.

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

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% of the cases. The frequencies of aberrant methylation were: 40% for p14ARF, 38.2% for MGMT, 30.9% for, p16INK4a, 14.6% for TP73 and for TIMP-3, 12.7% for DAPK and 1.8% 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.

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.