Fluorescent In Situ Hybridization: Methods and Application in Cancer Diagnosis

Abstract

Fluorescent in situ hybridization (FISH) is a molecular cytogenetic technique developed in the 1980s [1] used for the identification, localization, and determination of the presence or absence of specific nucleotide sequences. The technique takes advantage of the inherent ability of complementary strands of DNA or RNA from different sources to hybridize. In situ hybridization is based on the principle of annealing a labeled nucleic acid probe to complementary sequences within cells or tissue mounted (in situ) on a microscope slide. “Fluorescence” refers to the ability to emit light from a reaction within the emitter that renders the visualization of the probe under the microscope possible. Among its advantages in comparison to conventional cytogenetic techniques that require live mitotic cells is its ability to be applied to all nucleated cells or tissues given that the target nucleic acid is not degraded, can be mounted on a slide, and is accessible to the probe. It is a molecular based assay, and therefore is highly sensitive and specific, with a speedy assay time. FISH on nuclear DNA is a powerful tool in the identification of chromosome aneuploidies, segmental gains or losses of chromosomes, rearrangements, gene fusions, and gene amplifications. It can also be applied for the characterization of the highly rearranged chromosomes often present in karyotypes of cancerous cells.