High Quality Content by WIKIPEDIA articles! Etoposide phosphate (brand names: Eposin, Etopophos, Vepesid, VP-16) is an anti-cancer agent. It is known in the laboratory as a topoisomerase poison. Etoposide is often incorrectly referred to as a topoisomerase inhibitor in order to avoid using the term "poison" in a clinical setting. Unlike enzyme inhibitors, it exploits the normal mechanism of action of the enzyme topoisomerase II, which aids in DNA unwinding, and by doing so causes DNA strands to break. Cancer cells rely on this enzyme more than healthy cells, since they divide more rapidly. It is used as a form of chemotherapy for cancers such as Ewing`s sarcoma, lung cancer, testicular cancer, lymphoma, non-lymphocytic leukemia, and glioblastoma multiforme. It is often given in combination with other drugs. It is also sometimes used in a conditioning regimen prior to a bone marrow or blood stem cell transplant.