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.
Highlights
The development of cancer is a multistep process that involves genetic changes in multiple genes or chromosomes
There are different methodologies to assess loss of heterozygosity (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
A commonly observed type of genetic alteration in cancer is the loss of heterozygosity (LOH), in which the wild-type allele of a gene is inactivated in a first hit, and the remaining functional allele is deleted in the second hit
Summary
The development of cancer is a multistep process that involves genetic changes in multiple genes or chromosomes. There are three classical molecular genetic markers with clinical importance, namely, the 1p/19q loss, the methylation of the O6-methylguaninedeoxyribonucleic acid (DNA) methyltransferase (MGMT) gene promoter, and the isocitrate dehydrogenase 1 (IDH1)/ isocitrate dehydrogenase 2 (IDH2) mutations. Known as PCR-based microsatellite analysis, this technique is often employed to detect allelic losses It is based on a comparison of microsatellites or short tandem repeat (STR) markers between tumor and normal DNA. Following isolation of genetic material, a molecular technique, named multiplex PCR, is run (Figure 1) This approach is employed for simultaneously amplifying multiple microsatellite regions by one million times or more using several primers, which are located in the lost chromosomal regions. Each cycle doubles the number of copies of the target region and this results in an exponential amplification of the specific gene target[22]
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