TOP IIA FISH

Type II topoisomerases are enzymes that assist in the DNA replication and recombination by allowing topographical changes to the double helix and are also necessary for correct chromosome structure and segregation. The gene is located on chromosome 17q21-22 and its amplification and deletion is associated with the Her2 gene due to their close proximity in the genome.





As type II topoisomerases are the target for certain chemotherapeutic agents such as the anthracyclines, the copy number of the gene has been shown to have a bearing on the sensitivity of the tumour to these drugs. As such, demonstration of TOP2A has been shown to be a predictive marker in a variety of malignant tumours e.g. breast, gastric and colonic.





The copy number of the topoisomerase II gene can be assessed using fluorescent in situ hybridisation (FISH).