Molecular biology techniques for loss of heterozygosity detection: the glioma example / Técnicas de biologia molecular para avaliação da perda de heterozigosidade: o exemplo em glioma

ABSTRACT In recent years, many oncology institutions have implemented the use of molecular approaches to assess and manage cancer patients. One commonly observed type of genetic alteration in cancer is the loss of heterozygosity (LOH). In the clinical setting, this molecular genetic marker is an important tool for disease prognosis, diagnosis and treatment. For example, the loss of 1p/19q is a classical molecular marker for oligodendroglioma assessment. In addition, this marker is associated with a favorable prognosis and chemosensitivity in oligodendroglial tumors. Interpretation of the clinical significance of molecular markers requires that health professionals and biomedical scientists understand the basic theoretical fundamentals of molecular diagnostic techniques. Although there are different methodologies to assess LOH, including high-performance techniques, this review aims to describe the polymerase chain reaction (PCR)-based LOH assays and fluorescence in situ hybridization (FISH), which are the molecular techniques most used for evaluation of 1p/19q status in pathology laboratories.

RESUMO Nos últimos anos, instituições de oncologia têm implementado o uso de abordagens moleculares para avaliar e conduzir pacientes com câncer. O tipo mais comum de alteração encontrada no câncer é a perda de heterozigosidade (LOH). Na clínica, esse marcador molecular pode ter importância para o prognóstico, o diagnóstico e/ou na decisão do tratamento. Por exemplo, a perda de 1p/19q é um marcador molecular clássico para a avaliação do oligodendroglioma. Além disso, esse marcador está associado ao prognóstico favorável e à quimiossensibilidade em tumores oligodendrogliais. A interpretação do significado clínico dos marcadores moleculares exige que os profissionais da área da saúde entendam os fundamentos básicos teóricos das técnicas de diagnóstico molecular. Embora existam diferentes metodologias para avaliar a LOH, inclusive técnicas de alta performance, esta revisão tem o objetivo de descrever o ensaio de LOH com base na reação da cadeia da polimerase (PCR) e a hibridização in situ fluorescente (FISH), que são as técnicas moleculares mais usadas para avaliação do status 1p/19q em laboratórios de patologia.

Antiproliferative activity of Eremanthus crotonoides extracts and centratherin demonstrated in brain tumor cell lines

The genus Eremanthus is recognized by the predominance of sesquiterpene lactones from the furanoheliangolide type, a class of substances extensively tested against cancer cell lines. Thus, the species E. crotonoides (DC.) Sch. Bip., Asteraceae, obtained on "restinga" vegetation was evaluated against U251 and U87-MG glioma cell lines using the MTT colorimetric assay. Dichloromethane fraction was cytotoxic to both glioblastoma multiforme cell lines. We then conducted UPLC-PDA-ESI-MS/MS analysis of the dichloromethane fraction, which allowed the identification of the sesquiterpene lactones centratherin and goyazensolide. The isolation of centratherin was performed using chromatographic techniques and the identification of this substance was confirmed according to NMR data. Cytotoxic activity of centratherin alone was also evaluated against both U251 and U87-MG cells, which showed IC50 values comparable with those obtained for the commercial anticancer drug doxorubicin. All the tested samples showed cytotoxic activity against glioblastoma multiforme cells which suggests that E. crotonoides extracts may be important sources of antiproliferative substances and that the centratherin may serve as prototype for developing new antiglioblastoma drugs.

Frequencies of GSTM1, GSTT1, and GSTP1 polymorphisms in a Brazilian population

The glutathione S-transferase (GST) family of enzymes has a vital role in phase II of biotransformation of environmental carcinogens, pollutants, drugs and other xenobiotics. GSTs are polymorphic, with the type and frequency of polymorphism being ethnic dependent. Polymorphisms in GST genes have been shown to be associated with susceptibility to disease and disease outcome. We determined the frequencies of GSTM1, GSTT1 and GSTP1 polymorphisms in 591 volunteers who had been residents of Rio de Janeiro for at least six months. Blood was collected and DNA extracted by proteinase K/SDS digestion. Information about social habits and health problems was also recorded. GSTM1 and GSTT1 polymorphisms were analyzed by a PCR-Multiplex procedure, whereas GSTP1 polymorphism was analyzed by PCR-RFLP. We found that 42.1% (48.9% of whites and 34.2% of non-whites) of the individuals had the GSTM1 null genotype, whereas 25.4% (25.1% of whites and 25.7% of non-whites) had the GSTT1 null genotype. The genotypic distribution of GSTP1 was 49.7% I/I, 38.1% I/V, and 12.2% V/V, whereas the allelic frequencies were 0.69 for the Ile allele, and 0.31 for the Val allele. The frequencies of GST polymorphisms in this Brazilian population were found to be different from those observed in other populations, particularly of other South American countries.