DNA topoisomerase II-alpha as a marker of cell proliferation in endocrine and other neoplasms

DNA topoisomerases are enzymes that are able to link and unlink DNA strands. They are classified as type I or type II topoisomerase if they catalyze transient single-strand (topo I) or double-strand (topo II) DNA breaks. Topo II-alpha has been used as a proliferation marker and it can also serve as a molecular target for a variety of anticancer drugs that are used clinically. Topo II-alpha expression is similar to MIB1 immunoreactivity in breast, ovarian, cervix, gastric, endometrial, adrenocortical, and hematological malignancies. In a study of adrenocortical tumors with metastases topo II was significantly higher than in tumors without metastases. Studies of topo II-alpha expression may provide information about the biological behavior of specific tumors a nd may also provide insights into the role that th is enzyme plays in the response of human cancers to topo II-targeted anticancer drugs.