Novel actions of inhibitors of DNA topoisomerase II in drug-resistant tumor cells.

We review herein current work on the cytotoxic and cellular actions of two classes of inhibitors of DNA topoisomerase II: one represented by etoposide and teniposide, which stabilize DNA-protein complexes, and another represented by merbarone and aclarubicin, which do not stabilize such complexes. We discuss current concepts of protooncogene activation and cell cycle perturbations by some of these inhibitors and summarize recent findings of novel actions of the latter compounds in tumor cells that express a mutant topoisomerase II.