Protein-associated deoxyribonucleic acid strand breaks in L1210 cells treated with the deoxyribonucleic acid intercalating agents 4'-(9-acridinylamino)methanesulfon-m-anisidide and adriamycin

Abstract

The DNA intercalating agents 4'-(9-acridinyl-amino) methanesulfon-m-anisidide (m-AMSA) and adriamycin were studied by using filter elution methods to measure DNA single-strand breaks (SSB's), DNA-protein cross-links (DPC's), and double-stranded breaks (DSB's) in mouse leukemia L1210 cells. Both compounds produced SSB's and DPC's at nearly 1:1 ratios. The SSB's and DPC's were shown to be localized with respect to each other; this was inferred from the finding that filter assays based on protein adsorption completely prevented the elution of the DNA single-strand segments between SSB's. In the case of m-AMSA, which produces relatively high frequencies of DNA lesions, the possibility that a protein bridges across the SSB was excluded by alkaline sedimentation studies. Both compounds also produced DSB's, but the SSB/DSB ratios differed; the SSB/DSB ratios increase in the following order: ellipticine greater than adriamycin greater than m-AMSA greater than X-ray [results of this paper combined with those of Ross, W. E., & Bradley, M. O. (1981) Biochim. Biophys. Acta (in press)]. The o-AMSA isomer is much less cytotoxic than m-AMSA and did not produce protein-associated strand breaks. The simplest model to explain the results is that a protein becomes covalently bound to either the 3' or the 5' termini of the intercalator-induced strand breaks. At moderately cytotoxic doses, m-AMSA yielded much larger frequencies of protein-associated SSB's than did adriamycin. m-AMSA-induced protein-associated SSB's saturated at approximately 60000 per cell over a concentration range in which m-AMSA uptake by the cells was proportional to the drug concentration. m-AMSA was found to enter and exit from cells very rapidly at 37 degrees C; protein-associated SSB's and DSB's also appeared and disappeared rapidly. At reduced temperature, however, the appearance and disappearance of protein-associated SSB's could be blocked while m-AMSA entry and exit still occurred. The saturation behavior and temperature dependence suggest that the formation and disappearance of protein-associated strand breaks is enzymatic. The simplest hypothesis is that the linked protein is a nuclease, such as a topoisomerase, which becomes bound to one terminus of the strand break it produces. It is proposed that topoisomerases producing SSB's and DSB's are stimulated to different degrees by different intercalators.

DNA damage, cytotoxic effect and cell‐cycle perturbation of Hoechst 33342 on L1210 cells in vitro

“…What is worth noting is that other chemicals DNA SSB produced by HO 33342 alone at concentration such as some anticancer agents (e.g., anthracyclines) of 1.5 pg/ml but not significantly with the concentration cause a comparable number of DNA-SSB at equitoxic of 5 pg/ml. concentrations (27).…”

The anthracycline antibiotics: antitumor drugs that alter chromatin structure

“…Therefore, in closing, we would like to propose that such aggregation, in addition to the chromatin structural changes described above, may contribute in a concerted way to the apoptotic cell death induced by these drugs. (58,59) Chromatin aggregation (23) may facilitate or promote the DNA fragmentation (68,69) by specific apoptotic endonucleases. Indeed, it has been recently shown that chromatin aggregation precedes oligonucleosomal fractionation (70) and that DNA is supercoiled in apoptotic chromatin.…”

Topoisomerase inhibitors can selectively interfere with different stages of simian virus 40 DNA replication.

“…A number of cytotoxic drugs which were found to have antineoplastic properties have recently been shown to be topoisomerase inhibitors (3,12,15,25,26,31,33). These drugs typically interfere with the breakage-reunion cycles of topoisomerases to produce single-and double-strand DNA breaks.…”