List of contributors. Preface. 1. Tumor physiology and resistance to chemotherapy: repopulation and drug penetration A.J. Davis, I.F. Tannock. 2. The role of membrane transporters in cellular resistance to anticancer nucleoside drugs M.L. Clarke, et al. 3. MDR and MRP gene families as cellular determinant factors for resistance to clinical anticancer agents L. Deng, et al. 4. The glutathione system in alkylator resistance D. Hamilton, et al. 5. The role of signal transduction pathways in drug and radiation resistance S. Grant, et al. 6. Mechanisms of repair of interstrand crosslinks in DNA R.J. Legerski, C. Richie. 7. DNA repair in resistance to bifunctional alkylating and platinating agents D. Murray. 8. Leukemic cell insensitivity to cyclophosphamide and other oxazaphosphorines mediated by aldehyde dehydrogenase(s) N.E. Sladek. 9. Mechanisms of resistance against cyclophosphamide and ifosfamide: can they be overcome without sacrificing selectivity? S.M. Ludeman, M.P. Gamcsik. 10. Cellular mechanisms of cyclophosphamide resistance: model studies in human medulloblastoma cell lines H.S. Friedman, et al. 11. Model studies of cyclophosphamide resistance in human myeloid leukemia B.S. Andersson, D. Murray. 12. Mechanisms of drug resistance in AML M. Andreeff, M. Konopleva. 13. Biochemical and molecular mechanisms of cisplatin resistance Z.H. Siddik. 14. Modification of radiosensitivity following chemotherapy exposure: potential implications for combined-modality therapy R.A. Britten. 15. Clinical pharmacology of melphalan and itsimplications for clinical resistance to anticancer agents R.B. Jones. 16. Pharmacological considerations of primary alkylators J.S. McCune, J.T. Slattery. 17. Genomic approaches to clinical drug resistance S. Damaraju, et al. Index.

The in vitro cytotoxic properties of acetaldoifosphamide, a new chemically stable bis-acetate analogue of aldoifosphamide that requires enzymatic activation by cellular carboxylate esterases, has been compared with that of 4-hydroperoxycyclophosphamide (4-HC). On a molar basis, acetaldoifosphamide was 8-10 times more potent than 4-HC against two different human leukemic myeloid cell lines, but only twice as potent as 4-HC against normal bone marrow granulocyte-macrophage colony-forming cells (GM-CFC). Acetaldoifosphamide retained its activity against leukemic cell lines that were highly resistant to the antileukemic drugs doxorubicin and m-AMSA. GM-CFC doubling times after exposure of bone marrow to high concentrations of acetaldoifosphamide in suspension cultures were 6-12 hours. Similar doubling times were obtained after incubation of marrow with 4-HC. Acetaldoifosphamide has a sparing effect on hematopoietic stem cells that is similar to that found for 4-HC; however, it is considerably more potent than 4-HC. Acetaldoifosphamide is different from 4-HC in its chemical stability and its unique requirement for carboxylate esterase activation. We conclude that acetaldoifosphamide may have advantages over 4-HC for in vitro purging of leukemic cells from human bone marrow.

One hundred three relapsed leukemia patients were treated with high-dose cytosine arabinoside (Ara-C); 3 g/m2 intravenously over 2 hours every 6 to 12 hours for a total of nine to 12 doses or 3 g/m2 intravenously over 2 hours for two doses 12 hours apart followed by a continuous infusion of 1.5 g/m2 over 24 hours daily for 3 to 4 days. Thirteen of them developed adult respiratory distress syndrome (ARDS) without having any recognized reason for the development of pulmonary edema. This problem showed no correlation with age or prior chemotherapy. Four of the patients recovered, but in nine this complication was fatal. The authors have reviewed the clinical course of these 13 patients and the postmortem findings of the seven patients who had an autopsy performed. The pulmonary tissue from six patients showed massive edema and one had diffuse alveolar damage. Histologic examination revealed a highly proteinaceous intraalveolar infiltrate without any inflammatory reaction in all cases. Intestinal tissue from all patients revealed changes compatible with cytotoxic damage, and pleura and/or pericardium from six of the seven patients showed an extensive fibrinous exudate suggestive of capillary leakage. The time sequence of the clinical events and the histologic findings indicate that high-dose Ara-C treatment in leukemia may cause a capillary leakage syndrome with ARDS that may progress to fatal respiratory failure.

PreviewInfiltration of the skin by benign or malignant cells (or both) is a consequence of leukemia that may look like a less serious skin lesion on first glance. Infiltrates can have many appearances, as clearly illustrated in this article. The authors list the types of cutaneous infiltrates associated with leukemia, describe their clinical presentation, and discuss the distinguishing histologic features that allow differential diagnosis.

K562 is a Philadelphia (Ph) chromosome-positive chronic myelogenous leukemia (CML) blast crisis cell line representing a pluripotent precursor cell. At the molecular level, K562 cells express high levels of the aberrant bcr-abl product, p210bcr-abl, believed to be critical to the pathogenesis of CML. The authors demonstrate that exposure of K562 cells to hemin causes a state of partial, reversible erythroid maturation, accompanied by a marked decrease in p210bcr-abl. The change in bcr-abl expression may be mediated at the translational level since steady state amounts and enzymatic activity of the bcr-abl protein are reduced whereas bcr-abl mRNA levels are unaltered. The decrease in p210bcr-abl phosphokinase enzymatic activity can be detected within 2 hours after addition of hemin to the culture media, indicating that changes in expression of this oncogene probably occur before or concurrent with differentiation. No change in bcr-abl protein occurred in a CML cell line (KBM-5) which did not undergo differentiation after exposure to hemin, consistent with a direct relationship between altered p210bcr-abl expression and hemin-induced erythroid differentiation. Importantly, the marked diminution in bcr-abl protein was not associated with a disruption in K562 growth rates, indicating that the proliferative capacity of these cells may be independent of the bcr-abl product. In contrast to hemin, cytosine arabinoside (Ara-C) caused terminal erythroid differentiation of K562 cells, characterized by irreversible hemoglobin accumulation and cytostasis; and no change in bcr-abl protein expression was observed. The distinct effects of Ara-C and hemin could reflect the existence of pleiotropic differentiation pathways. Both Ara-C and hemin-exposed cells showed a decrease in c-myc and c-myb transcripts, suggesting that altered levels of these proto-oncogenes may be associated with erythroid maturation, regardless of the rate of cell division. K562 cells provide a useful model for analyzing the interaction between oncogene expression and CML cell growth and differentiation.

Benzisoquinolinedione (nafidimide; NSC 308847) is an investigational drug currently in phase I clinical testing. We have studied the antileukemic activity in vitro, the cellular drug transport, and the molecular mechanism of action with DNA of this new compound. By agarose gel electrophoresis, we verified that nafidimide is an intercalating agent, through its alteration of the electrophoretic migration of DNA products produced by the relaxing action of DNA topoisomerase I. Concentrations of up to 100 microM of nafidimide did not produce topoisomerase I-mediated DNA cleavage. Nafidimide produced DNA single-strand breaks (SSB), double-strand breaks, and DNA-protein cross-links in human myeloid leukemia cells (measured with filter elution). The ratio of SSB/DNA-protein cross-links was 1.32 +/- 0.36, a value similar to that produced by 4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA), suggesting that nafidimide, like m-AMSA, produced protein-associated DNA-strand breaks through a topoisomerase II-mediated reaction. The production of double-strand breaks by nafidimide also suggests the involvement of topoisomerase II in the drug-induced DNA cleavage. The cytotoxic activity of nafidimide was quantified in human myeloid leukemia cell lines differing by a factor of 70 in their cytotoxic sensitivity to m-AMSA. The m-AMSA-resistant line was less than 2-fold resistant to nafidimide. Cellular drug uptake was rapid and reached a steady state level in 30 min at 37 degrees C. At the end of exposure, drug egress was rapid, as was the disappearance of the DNA SSB. Rapid cellular uptake of nafidimide, with low retention at the end of exposure and rapid rejoining of DNA SSB suggest that prolonged cellular exposure may be necessary for optimal antitumor effect. In vitro cloning data suggest that nafidimide may be a therapeutic option for patients with leukemia resistant to m-AMSA.

The calcium channel blocker verapamil has been reported to circumvent acquired resistance to different antitumor agents in tumor cell linesin vitro. We studied its effect onin vitro uptake ofm-AMSA and adriamycin in fresh leukemic cells from 11 leukemia patients. Six previously untreated patients were sensitive tom-AMSA (obtained remission). Four were clinically resistant tom-AMSA, and two of these also to adriamycin. Leukemic cells were incubated in pharmacological doses of14C-adriamycin and14C-m-AMSA for up to 2 h. Samples were supplemented with verapamil (750 ng ml−1) 30 min prior to the addition ofm-AMSA or adriamycin. Drug uptake was measured at 15 min intervals up to 2 h and drug retention was measured during 30 min after the end of incubation, following washing and resuspension in fresh medium without cytotoxic drugs. Adriamycin uptake was the same irrespective of verapamil in all four cell samples, two of which were derived from patients resistant to adriamycin. The cellularm-AMSA uptake was higher in cells from clinically sensitive than from resistant patients (510±155 fg cell−1 vs 275±125 fg cell−1;P<0.01). Retention ofm-AMSA 30 min after incubation was higher in cells from sensitive compared to resistant patients (187±78 vs 25±7;P<0.05). Our data suggest: (1)in vitro uptake ≥350 fg cell−1 and subsequent retention >75 fg cell−1 correlate to clinical sensitivity to the drug; and (2) neitherm-AMSA nor adriamycin uptake could be significantly increased by verapamil.