<prompt> What enzyme is inhibited by etoposide -Topoisomerase ITopoismerase IIDihydrofolate reductaseDihydro orotate oxidase  <response>: Ans. is b i.e., Topoismerase II Etoposide It is a semisynthetic derivative of podophyllotoxin, a plant glycoside. It is not a mitotic inhibitor, but arrests cells in the G2 phase and causes DNA breaks by affecting DNA topoisomerase-2 function. While the cleaving of double stranded DNA is not interfered, the subsequent resealing of the strand is prevented. Etoposide is used in testicular tumours, lung cancer, Hodgkins and other lymphomas, carcinoma bladder and stomach. Alopecia, leucopenia and g.i.t. disturbances are the main toxicity. Oral bioavailability is 50; oral dose is double than i.v. dose. 