Vol. 295, Issue 2, 474-483, November 2000

The Catalytic DNA Topoisomerase II Inhibitor Dexrazoxane (ICRF-187) Induces Endopolyploidy in Chinese Hamster Ovary Cells¹

Brian B. Hasinoff, Michael E. Abram, Gaik-Lean Chee, Erwin Huebner, Edward H. Byard, Norman Barnabé, Victor J. Ferrans, Zu-Xi Yu and Jack C. Yalowich

Faculty of Pharmacy (B.B.H., M.E.A., G.-L.C., N.B.) and Department of Zoology (E.H.), University of Manitoba, Winnipeg, Manitoba, Canada; Department of Biology, University of Winnipeg, Winnipeg, Manitoba, Canada (E.H.B.); Pathology Section, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland (V.J.F., Z.-X.Y); and Department of Pharmacology, University of Pittsburgh School of Medicine and Cancer Institute, Pittsburgh, Pennsylvania (J.C.Y.)

The bisdioxopiperazines, including dexrazoxane (ICRF-187), are catalytic or noncleavable complex-forming inhibitors of DNA topoisomerase II that do not produce DNA strand breaks. In this study we show that dexrazoxane inhibits the division of Chinese hamster ovary (CHO) cells resulting in marked increases in cell size (up to 80 µm in diameter), volume (up to 150-fold greater), and ploidy (as high as 32N). This last result indicates that the dexrazoxane-induced DNA reduplication was restricted to once per cell cycle. Kinetic analysis of the flow cytometry data indicated that the conversion between successively higher ploidy levels was progressively slowed at longer times of exposure to dexrazoxane. Both the protein and DNA content of dexrazoxane-treated CHO cells increased linearly over time in the same proportion. Light and electron microscopic studies of dexrazoxane-treated cells showed ring-like multilobulated nuclei. Immunohistochemical staining of dexrazoxane-treated cells showed that F-actin and acetylated -tubulin were present in large, highly organized networks. Immunohistochemical staining of the dexrazoxane-treated CHO cells also showed that the topoisomerase II colocalized with the DNA of the multilobulated nuclei. Staining of -tubulin revealed that the dexrazoxane-treated cells contained multiple centrosomes, indicating that dexrazoxane prevents cytokinesis but not centrosome reduplication. It is concluded that dexrazoxane inhibits CHO cytokinesis in cells by virtue of its ability to inhibit topoisomerase II.