Concurrent deletion at 1p/19q is a common signature of oligodendrogliomas, and it may be identified in low-grade tumours (grade II) suggesting it represents an early event in the development of these brain neoplasms. Additional non-random changes primarily involve CDKN2A, PTEN and EGFR. Identification of all of these genetic changes has become an additional parameter in the evaluation of the clinical patients' prognosis, including good response to conventional che motherapy. Multiple ligation-dependent probe amplification (MLPA) analysis is a new methodology that allows an easy identification of the oligodendrogliomas' abnormalities in a single step. No need of the respective constitutional DNA from each patient is another advantage of this method. We used MLPA kits P088 and P105 to determine the molecular characteristics of a series of 40 oligodendrogliomas. Deletions at l p and 19q were identified in 45% and 65% of cases, respectively. Alterations of EGFR, CDKN2A, ERBB2, PTEN and TP53 were also identified in variable frequencies among 7% to 35% of tumours. These findings demonstrate that MLPA is a reliable technique to the detection of molecular genetic changes in oligodendrogliomas.

La alteración genética más frecuente en oligodendro gliomas es la pérdida conjunta de lp/19q. Este evento ya acontece en etapas primarias del desarrollo de estos tumores. Es de gran valor clínico conocer si dichos tumores poseen esta deleción ya que se ha correlacionado con un mejor pronóstico de los pacientes. Además de esta alteración. también se ha observado la deleción de CDKN2A y PTEN y la amplificación de EGFR; estos cambios parecen asociarse a una mayor agresividad tumoral. Mediante la técnica de MLPA en una misma reacción podemos determinar si existe pérdida de lp/19q y deleciones/amplificaciones de los genes anteriormente mencionados en el ADN procedente de muestras tumorales. En este trabajo hemos analizado 40 oligodendrogliomas y el kit MLPA P088 para determinar el estado alélico de lp/19q, así como el kit MLPA P105 para observar la amplificación/ deleción de los genes CDKN2A, PTEN, ERBB2, TP53 y EGFR. Mostraron pérdida de 1p el 45% de los tumores (18/40) y el 65% (26/40) de los oligodendrogliomas presentaron deleción de las sondas que hibridan en las regiones de 19q. Para el kit MLPA P105, mostraron duplicación/deleción de EGFR en el 7,5% (3/41) y 35% (14/40) de las muestras, respectivamente. El 60% de los casos (24/40) mostraron deleción de CDKN2 y ninguna muestra presentó duplicación de las sondas para este gen. El gen ERBB2 se presentó duplicado en el 12,5% de los tumores (5/40) y un único tumor mostró pérdidas de dicho gen. El 30% (12/40) de las muestras presentó deleción para PTEN y el 12,5% (5/40) mostró duplicación de dicho gen y, por último, 12,5% de los casos (5/40) presentaron duplicaciones de TP53. Estos resultados indican que la técnica de MLPA es idónea para la identificación de las alteraciones moleculares características de oligodendrogliomas. Estas alteraciones estarían contribuyendo a la formación del tumor, siendo la anomalía más significativa en oligodendrogliomas la pérdida de 1p/19q.

Gastric cancer is the forth most frequent malignancy and the second most common cause of cancer death worldwide. DNA methylation is the most studied epigenetic alteration, occurring through a methyl radical addition to the cytosine base adjacent to guanine. Many tumor genes are inactivated by DNA methylation in gastric cancer. We evaluated the DNA methylation status of ANAPC1, CDKN2A and TP53 by methylation-specific PCR in 20 diffuse- and 26 intestinal-type gastric cancer samples and 20 normal gastric mucosa in individuals from Northern Brazil. All gastric cancer samples were advanced stage adenocarcinomas. Gastric samples were surgically obtained at the João de Barros Barreto University Hospital, State of Pará, and were stored at -80°C before DNA extraction. Patients had never been submitted to chemotherapy or radiotherapy, nor did they have any other diagnosed cancer. None of the gastric cancer samples presented methylated DNA sequences for ANAPC1 and TP53. CDKN2A methylation was not detected in any normal gastric mucosa; however, the CDKN2A promoter was methylated in 30.4% of gastric cancer samples, with 35% methylation in diffuse-type and 26.9% in intestinal-type cancers. CDKN2A methylation was associated with the carcinogenesis process for ~30% diffuse-type and intestinal-type compared to non-neoplastic samples. Thus, ANAPC1 and TP53 methylation was probably not implicated in gastric carcinogenesis in our samples. CDKN2A can be implicated in the carcinogenesis process of only a subset of gastric neoplasias.

Gastric cancer is the second most frequent type of neoplasia and also the second most important cause of death in the world. Virtually all the established cell lines of gastric neoplasia were developed in Asian countries, and western countries have contributed very little to this area. In the present study we describe the establishment of the cell line ACP01 and characterize it cytogenetically by means of in vitro immortalization. Cells were transformed from an intestinal-type gastric adenocarcinoma (T4N2M0) originating from a 48-year-old male patient. This is the first gastric adenocarcinoma cell line established in Brazil. The most powerful application of the cell line ACP01 is in the assessment of cytotoxicity. Solid tumor cell lines from different origins have been treated with several conventional and investigational anticancer drugs. The ACP01 cell line is triploid, grows as a single, non-organized layer, similar to fibroblasts, with focus formation, heterogeneous division, and a cell cycle of approximately 40 h. Chromosome 8 trisomy, present in 60% of the cells, was the most frequent cytogenetic alteration. These data lead us to propose a multifactorial triggering of gastric cancer which evolves over multiple stages involving progressive genetic changes and clonal expansion.

Twelve breast fibroadenomas were analyzed cytogenetically and only four were found to have clonal alterations. The presence of chromosomal alterations in fibroadenomas must be the consequence of the proliferating process and must not be related to the etiology of this type of lesion. In contrast, the few fibroadenomas that exhibit chromosomal alterations are likely to be those presenting a risk of neoplastic transformation. Clonal numerical alterations involved chromosomes 8, 18, 19, and 21. Of the chromosomal alterations found in the present study, only monosomy of chromosomes 19 and 21 has been reported in breast fibroadenomas. The loss of chromosome 21 was the most frequent alteration found in our sample. The study of benign proliferations and their comparison with chromosome alterations in their malignant counterparts ought to result in a better understanding of the genes acting on cell proliferation alone, and of the genes that cause these cells to exhibit varied behaviors such as recurrences, spontaneous regression and fast growth.

Breast cancer in families with germ line mutations in the TP53 gene has been described in the medical literature. Mutation screening for susceptibility genes should allow effective prophylactic and preventive measures. Using single-strand conformational polymorphism, we screened for mutations in exons 5, 6, 7 and 8 of gene TP53 in the peripheral blood of 8 young non-affected members (17 to 36 years old) of families with a history of breast cancer. Studies of this type on young patients (mean age, 25 years) are very rare in the literature. The identification of these mutations would contribute to genetic counseling of members of families with predisposition to breast cancer. The results obtained did not show any polymorphism indicating mutation. In our sample, the familial tumorigenesis is probably related to other gene etiologies.