Topoisomerase II levels and drug sensitivity in adult acute myelogenous leukemia

Abstract

The topoisomerase (topo) II-directed agents etoposide, daunorubicin (DNR), and amsacrine (m-AMSA) are widely used in the treatment of acute myelogenous leukemia (AML). In the present study, multiple aspects of topo II-mediated drug action were examined in marrows from adult AML patients. Colony-forming assays revealed that the dose of etoposide, DNR, or m-AMSA required to diminish leukemic colony formation by 90% (LD90) varied over a greater than 20-fold range between different pretreatment marrows. Measurement of nuclear DNR accumulation in the absence and presence of quinidine revealed evidence of P-glycoprotein (Pgp) function in 8 of 82 samples at diagnosis and 5 of 36 samples at first relapse, but the largest quinidine-induced increment in DNR accumulation (< 2-fold) was too small to explain the variations in drug sensitivity. Restriction enzyme-based assays and sequencing of partial topo II alpha and topo II beta cDNAs from the most highly resistant specimens failed to demonstrate topo II gene mutations that could account for resistance. Western blotting of marrow samples containing greater than 80% blasts revealed that the content of the two topo II isoenzymes varied over a greater than 20-fold range, but did not correlate with drug sensitivity in vitro or in vivo. In addition, levels of topo II alpha and topo II beta in 46 of 47 clinical samples were lower than in human AML cell lines. Immunoperoxidase staining showed that these low topo II levels were accompanied by marked cell-to- cell heterogeneity, with topo II alpha being abundant in some blasts and diminished or absent from others. There was a trend toward increasing percentages of topo II alpha-positive cells in pretreatment marrows that contained more S-phase cells. Consistent with this observation, treatment of patients with granulocyte-macrophage colony- stimulating factor for 3 days before chemotherapy resulted in increases in topo II alpha-positive cells concomitant with increases in the number of cells traversing the cell cycle. These observations have implications for the regulation of topo II in AML, for the use of topo II-directed chemotherapy, and for future attempts to relate drug sensitivity to topo II levels in clinical material.

Etoposide‐induced DNA strand breaks in relation to p‐glycoprotein and topoisomerase II protein expression in leukaemic cells from patients with AML and CLL

“…In our study, topo IIβ ranged from undetectable levels up to 2.5‐fold in AML cells and 1.1‐fold in CLL cells compared with the CCRF‐CEM control cells. It has been reported by Kaufmann et al (1994) that topo II levels varied widely in clinical specimens from AML patients. Western blot analysis of AML marrow samples revealed that the content of topo II varied more than 20‐fold.…”

Prognostic significance of β‐catenin and topoisomerase IIα in de novo acute myeloid leukemia

“…Previous reports have shown discrepant results in cell lines and clini- cal samples regarding the topo IIa expression status and cellular susceptibility to topo IIa poison. Although studies in cell lines have suggested that cells with high amounts of this enzyme are more sensitive to the cytotoxicity of topo II inhibitors [24,25], several subsequent studies have demonstrated that the activity of this enzyme in clinical AML samples does not correlate with drug sensitivity in vivo [26][27][28].…”

“…However, the predictive value of topo IIa activity in clinical behavior of AML patients remains a topic of debate. Although most of the available clinical data indicate that the expression of this enzyme does not correlate with drug sensitivity or survival outcome in AML [26][27][28], some suggest otherwise [29]. The actual prognostic role of topo IIa protein in AML needs to be elucidated.…”

In vitro Antitumor Activity of TAS‐103, a Novel Quinoline Derivative That Targets Topoisomerases I and II

“…These results suggested that the mechanisms of action of TAS-103 involve the inhibition of both Topo I and Topo II, and that TAS-103 can be effective against cell lines with already acquired resistance to an inhibitor of Topo. One may expect TAS-103 to show anti-tumor effects in patients when CPT-11 and VP-16 are no longer effective, since it was reported that the resistance of clinical cancers is correlated with a low expression of either Topo, 39) rather than with a mutation of the Topo gene. 40) One of the possible approaches to overcome drug resistance to either Topo I or Topo II inhibitor is combination therapy with a Topo I inhibitor and a Topo II inhibitor.…”