This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Fritz, G. Articles by Kaina, B. Search for Related Content PubMed PubMed Citation Articles by Fritz, G. Articles by Kaina, B.

High-Dose Selection with Mafosfamide Results in Sensitivity to DNA Cross-Linking Agents: Characterization of Hypersensitive Cell Lines¹

Division of Applied Toxicology [G. F., B. K.], Institute of Toxicology [J. G. H.], University of Mainz, Obere Zahlbacher Str. 67, D-55131 Mainz, Germany

One of the most frequently used alkylating drugs in the therapy of a broad spectrum of tumors is cyclophosphamide. To elucidate the mechanisms by which tumor cells acquire resistance to this agent, Chinese hamster ovary cells (CHO-K1) were treated with a high dose of the cyclophosphamide analogue mafosfamide, and survivors were analyzed as to their cell killing response, chromosomal aberrations, and DNA repair capacity. None of the surviving ciones tested were mafosfamide resistant. Surprisingly, some of the isolated cell lines exhibited a mafosfamide-hypersensitive phenotype. Two of these cell variants (designated as CHO-K1-4 and CHO-K1-12) were analyzed in more detail and proved to be cross-sensitive to other DNA cross-linking antineoplastic drugs such as N-hydroxyethyl-N-chlooethylnitrosourea, treosulfan, melphalan, cisplatin, and mitomycin C. The hypersensitivity to the cytotoxic effect of mafosfamide was accompanied by a 2–3-fold increase in the frequency of chromosomal aberrations. The intracellular levels of glutathione and glutathione S-transferase activity of the hypersensitive variants as well as growth rate were comparable to wild-type cells. Both the variant and the parental cells did not exhibit an increase in the amount of p53 upon UV irradiation. Furthermore, sensitive cells displayed similar UV-induced unscheduled DNA synthesis and showed identical amounts of ERCC1 mRNA as wild-type cells, indicating that the hypersensitive phenotype is not due to a defect in nucleotide excision repair. The induction of DNA single-strand breaks upon mafosfamide treatment was very similar in wild-type and mutants, and the removal of mafosfamide-induced DNA cross-links was not reduced in hypersensitive cells. However, the hypersensitive cell variants exhibited a less severe drug-induced block to DNA replication. From the data obtained, we conclude that hypersensitivity to cross-linking agents upon mafosfamide selection is due to changes in cell cycle progression of drug-treated cells.

¹ This work was supported by Grant SFB 519, B4, from the Deutsche Forschungsge-meinschaft and Grant 8036-38 62 61/170 from Stiftung Rheinland-Pfalz.

² To whom requests for reprints should be addressed, at Institut für Toxikologie, Abteilung für Angewandte Toxikologie, Universität Mainz, Obere Zahlbacher Str. 67, D-55131 Mainz, Germany. Phone: 06131/17-3627; Fax: 06131/17-3421.

Received 8/12/96. Accepted 12/ 4/96.

This article has been cited by other articles:

				A Schmittel, M Schmidt-Hieber, P Martus, N. Bechrakis, R Schuster, J. Siehl, M. Foerster, E Thiel, and U Keilholz A randomized phase II trial of gemcitabine plus treosulfan versus treosulfan alone in patients with metastatic uveal melanoma Ann. Onc., December 1, 2006; 17(12): 1826 - 1829. [Abstract] [Full Text] [PDF]

				J. G. Hengstler, U. Bolm-Audorff, A. Faldum, K. Janssen, M. Reifenrath, W. Gotte, D. Jung, O. Mayer-Popken, J. Fuchs, S. Gebhard, et al. Occupational exposure to heavy metals: DNA damage induction and DNA repair inhibition prove co-exposures to cadmium, cobalt and lead as more dangerous than hitherto expected Carcinogenesis, January 1, 2003; 24(1): 63 - 73. [Abstract] [Full Text] [PDF]

				G. Fritz and B. Kaina Activation of c-Jun N-Terminal Kinase 1 by UV Irradiation Is Inhibited by Wortmannin without Affecting c-jun Expression Mol. Cell. Biol., March 1, 1999; 19(3): 1768 - 1774. [Abstract] [Full Text] [PDF]