Alterations in the topoisomerase II alpha gene, messenger RNA, and subcellular protein distribution as well as reduced expression of the DNA topoisomerase II beta enzyme in a mitoxantrone-resistant HL‐60 human leukemia cell line. - Harker,W.G.; Slade,D.L.; Parr,R.L.; Feldhoff,P.W.; Sullivan,D.M.; Holguin,M.H. (Cancer Res, 1995)