Cross-resistance of an amsacrine-resistant human leukemia line to topoisomerase II reactive DNA intercalating agents. Evidence for two topoisomerase II directed drug actions

Abstract

HL-60/AMSA is a human leukemia cell line that is 50-100-fold more resistant than its drug-sensitive HL-60 parent line to the cytotoxic actions of the DNA intercalator amsacrine (m-AMSA). HL-60/AMSA topoisomerase II is also resistant to the inhibitory actions of m-AMSA. HL-60/AMSA cells and topoisomerase II are cross-resistant to anthracycline and ellipticine intercalators but relatively sensitive to the nonintercalating topoisomerase II reactive epipodophyllotoxin etoposide. We now demonstrate that HL-60/AMSA and its topoisomerase II are cross-resistant to the DNA intercalators mitoxantrone and amonafide, thus strongly indicating that HL-60/AMSA and its topoisomerase II are resistant to topoisomerase II reactive intercalators but not to nonintercalators. At high concentrations, mitoxantrone and amonafide were also found to inhibit their own, m-AMSA's, and etoposide's abilities to stabilize topoisomerase II-DNA complexes. This appears to be due to the ability of these concentrations of mitoxantrone and amonafide to inhibit topoisomerase II mediated DNA strand passage at a point in the topoisomerization cycle prior to the acquisition of the enzyme-DNA configuration that yields DNA cleavage and topoisomerase II-DNA cross-links. In addition, amonafide can inhibit the cytotoxic actions of m-AMSA and etoposide. Taken together, these results suggest that the cytotoxicity of m-AMSA and etoposide is initiated primarily by the stabilization of the topoisomerase II-DNA complex. Other topoisomerase II reactive drugs may inhibit the enzyme at other steps in the topoisomerization cycle, particularly at elevated concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

The Antitumor Triazoloacridone C-1305 Is a Topoisomerase II Poison with Unusual Properties

“…The cleavable complex formation was dose-dependent, reaching a maximum in the presence of 2.5 to 10 M C-1305. A similar biphasic dose response has previously been reported for the structurally related anthracenediones and imidazoacridones and is characteristic of compounds that are strong DNA binders (Zwelling et al, 1991;Skladanowski et al, 1996).…”

“…Maximal cleavable complex formation is obtained with concentrations of C-1305 between 2.5 and 10 M. Higher concentrations of C-1305 lead to increasing autoinhibition, and at 50 M, only low levels of cleavable complexes are detected. A similar doseresponse has been described previously for several topoisomerase II inhibitors that are strong DNA intercalators, including doxorubicin, mitoxantrone, imidazoacridones, and ellipticines (Tewey et al, 1984;Monnot et al, 1991;Zwelling et al, 1991;Skladanowski et al, 1996). In clear contrast, we observed no autoinhibition for amsacrine, which is a weak DNA intercalator (Denny and Wakelin, 1986).…”

“…DNA/protein complexes were quantified by the KCl/SDS coprecipitation assay as described previously (Zwelling et al, 1991). DNA and proteins of HT-29 cells (approximately 300,000 cells) were radiolabeled with 0.6 Ci/ml [ 3 H]thymidine and 0.2 Ci/ml [ 14 C]leucine, respectively, for 24 h. Radiolabeled cells were exposed to various drug concentrations at 37°C for the indicated times.…”

A mitotic topoisomerase II checkpoint in budding yeast is required for genome stability but acts independently of Pds1/securin

“…Commonly used drugs such as etoposide bind to Topo II either before or after passage of the T-strand, to form what is known as a "cleavable complex" (Zwelling et al 1991). The topoisomerase II-mediated religation reaction, the last step of decatenation, is prevented and ultimately dsDNA breaks result.…”

Topoisomerase Poisons: Harnessing the Dark Side of Enzyme Mechanism

“…However, based on drug competition studies, it appears that DNA cleavage-enhancing agents share an overlapping site of action, at least on topoisomerase II (56,77). Therefore, differential crossresistance patterns observed for specific topoisomerase II mutations (14,75,76,78) probably reflect differences in the microenvironment of bound drug rather than the existence of separate interaction domains.…”