Type II topoisomerases are essential enzymes that play important roles in fundamental nuclear processes such as DNA replication and recombination. The TOP2A gene is approximately 30 kb in size and encodes a 170 kDa protein. The TOP2A protein has been recognized as a proliferation marker and is expressed in proliferating cells and in numerous human malignant tumors, including colon, gastric and breast cancer, lymphomas and others. Type II topoisomerases are the targets for anticancer drugs, such as the topoisomerase II inhibitor therapies like the anthracyclines Doxorubicin and Epirubicin.

The copy number of the TOP2A gene has been shown to influence the sensitivity of the tumor towards topoisomerase II inhibitor therapies.