Topoisomerase IIα expression in acute myeloid leukaemia cells that survive after exposure to daunorubicin or ara-C

Abstract

Abstract. Patients diagnosed with acute myeloid leukaemia are often treated with a combination of daunorubicin and 1-ß-D-arabinofuranosylcytosine (ara-C). Both daunorubicin and ara-C exert their effects in the cell nucleus but by different mechanisms, i.e. daunorubicin causes double stranded DNA breaks by inhibition of the nuclear enzyme, topoisomerase (topo) II·, whereas ara-C is an anti-metabolite that integrates with DNA during DNA synthesis and causes cell cycle arrest. Despite the initial efficacy of these drugs, resistance often develops in the clinical setting. The mechanisms underlying clinical resistance to these drugs are poorly understood, but may be associated with an increase in the proportion of topo II· negative cells. Therefore, the aim of this study was to determine whether daunorubicin treatment results in increased numbers of topo II· negative subpopulations in vitro. Acute myeloid leukaemia cells isolated from 12 consenting patients were treated for 24 h with increasing concentrations of daunorubicin or ara-C and the proportion of topo II·-negative cells in surviving cell populations determined by flow cytometry. Treatment with daunorubicin, but not ara-C, resulted in a significant increase in the proportion of topo II· negative cells (p=0.0023). These results suggest that daunorubicin may act by cell cycle arrest and/or by selection of pre-existing topo II· negative subpopulations. Both of these mechanisms can theoretically contribute to a reduced efficacy of a second dose of daunorubicin. The clinical relevance of these interactions should be further elucidated in experimental and clinical studies. IntroductionA combination of daunorubicin and 1-ß-D-arabinofuranosylcytosine (ara-C) is the standard induction treatment for acute myeloid leukaemia (AML) (1). Daunorubicin exerts its effect in the cell nucleus by interaction with DNA and the enzyme, topoisomerase (topo) II·. Ara-C is a nucleoside analogue that requires phosphorylation to ara-CTP to become an active cytotoxic drug (2). Similarly to daunorubicin, ara-C exerts its effect in the cell nucleus and causes DNA damage by incorporation into the DNA molecule (3). Unfortunately, only 50-60% of patients treated with cytostatic drugs such as daunorubicin and ara-C will enter complete remission, and the long-term survival rate is only 10-20% (1). A major reason for this poor outcome is believed to be a result of intrinsic or acquired resistance to cytostatic drugs.Several cellular mechanisms have been identified that are involved in drug resistance. One mechanism that may play a key role in resistance to daunorubicin is expression of the target molecule, topo II·. Topo II· changes the tertiary structure of DNA and plays an essential role during transcription and duplication of DNA (4). To act as a functional enzyme it requires dimerisation, mainly in the form of homodimerisation. The topo II· dimer causes DNA double-strand breaks that are fixed by disulphide bonds, the so-called cleavable complex. Under ATP hydrolysis the DNA break is religate...

Association of immunophenotype with expression of topoisomerase II α and β in adult acute myeloid leukemia

“…Present results do demonstrate a significant inter-individual variability in topo IIα mRNA levels and failed to show any significant association between topo IIα expression and any disease characteristic in de novo and secondary AML patients. It has been shown that exposure of AML blast cells to the anthracyline daunorubicin promotes expansion of topo IIα negative cells 19 . This ex-vivo observation, on daunorubicin-treatment dependent selection of topo IIα negative cells was however, not linked to clinical outcome.…”

“…Analysis of topo IIα expression have suggested correlations between gene amplification of topo IIα and response to anthracycline chemotherapy in breast cancer 14 . Some reports indicate no significant predictive value of topo IIα expression levels, while others suggest that topo IIα expression can predict treatment failure [15][16][17][18][19] . In contrast to the focus on topo IIα in AML the expression of topo IIβ that is targeted by daunorubicin and idarubicin has not been satisfactorily addressed.…”

The mitochondrial transport protein SLC25A43 affects drug efficacy and drug-induced cell cycle arrest in breast cancer cell lines

“…Analysis of cell cycle phase distribution was performed as previously described (29) on isolated cell nuclei using 100 μg/ml propidium iodide (PI) (Sigma-Aldrich) for DNA-staining.…”

Deciphering molecular mechanisms underlying chemoresistance in relapsed AML patients: towards precision medicine overcoming drug resistance

“…The assignment of changes to specific stages in P1 is only implied, as the relapse specimen was obtained after all of the treatments. Chemotherapeutic drugs that plausibly induced remission are denoted in green either via downregulation of topoisomerase II [48,139], upregulation of P-gp or expanded lysosomes, are likely to be cross-resistant to MX and VP-16, thereby inducing another relapse, since all of these drugs share similar cellular pathways. Similarly, leukemic cells that survived Ara-C cytotoxicity might be cross-resistant to other nucleoside analog prodrugs that share the same cellular uptake and activation routes.…”