chartreusin and Adenocarcinoma

Elsamicin (EM) is a recently discovered antitumour agent that is structurally related to several other compounds displaying anticancer activities, including chartreusin (CT), chrysomycin V (CV) and M (CM), gilvocarcin V (GV) and ravidomycin (RM). The biochemical events resulting in cytotoxicity for most of these compounds have not been clearly elucidated. There is some evidence that GV and CT bind to DNA and that GV is photosensitive, causing DNA damage. Therefore, we investigated the effects of these chemicals on DNA in cells and on pBR322 plasmid DNA. Using alkaline elution techniques, we found that all these compounds induced, to a different extent, DNA breakage in the human lung adenocarcinoma A549 cell line. In addition, all either bound to or intercalated into DNA, as indicated by their ability to alter the electrophoretic migration of DNA in agarose gels. Using the P4 unknotting assay, EM, CT, CV, CM, GV and RM were found to be potent inhibitors of the catalytic activity of topoisomerase II (topo II). Their potencies were compared with the known topo II inhibitors teniposide (VM-26) and doxorubicin (DX). EM was the most potent, with an IC50 of 0.4 mumol/l followed in order by CV, GV, and CT. VM-26 was the least potent with an IC50 of 15 mumol/l. It was concluded from these results that EM, GV, CV, CM and CT are capable of inhibiting topo II and that EM is the most potent inhibitor of topo II yet discovered.

Topics: Adenocarcinoma; Aminoglycosides; Anti-Bacterial Agents; Antibiotics, Antineoplastic; Benzopyrans; Cell Division; Coumarins; DNA Damage; DNA, Neoplasm; Glycosides; Humans; Lung Neoplasms; Topoisomerase II Inhibitors; Tumor Cells, Cultured

The in vitro activity of elsamicin A (ELS) was investigated compared with that of doxorubicin (DX) on two sensitive breast cancer cell lines: one estrogen receptor-positive (ER+, MCF7) and one estrogen receptor-negative (ER-, MDA-MB-231) line, and on a DX-resistant subline (MCF7DX). The activity of the two drugs was also investigated on 19 clinical breast cancer specimens from untreated patients. The drugs were tested at pharamcologically relevant concentrations, as calculated from the area under the curve for a 3 h exposure to the lethal dose producing 10% mortality (LD10) in mice, and at 10- and 100-fold concentrations. In DX-sensitive lines, a greater inhibition of RNA and DNA precursor incorporation, as well as of cell proliferation, was caused by ELS than by DX. Moreover, the antiproliferative effect was 10-fold higher in the ER+ MCF7 than in the ER- MDA-MB-231 cell line (IC50: 0.25 versus 0.21 micrograms/ml). ELS was cross-resistant to DX in the MCF7DX subline. In clinical specimens, effects on DNA precursor incorporation were more often observed for ELS than for DX at the same drug concentrations. The in vitro sensitivity to ELS was more pronounced for ER+ than for ER- tumors: minimal inhibiting concentrations of the drug were 0.1 and 3.5 micrograms/ml, respectively, in the two groups. If confirmed in a larger series of human breast tumors, these in vitro results would indicate a promising role for ELS in clinical treatment, mainly of ER+ breast cancer patients.

Topics: Adenocarcinoma; Aminoglycosides; Animals; Anti-Bacterial Agents; Antibiotics, Antineoplastic; Benzopyrans; Breast Neoplasms; Cell Division; DNA, Neoplasm; Doxorubicin; Drug Resistance; Female; Glycosides; Humans; Mice; Receptors, Estrogen; RNA, Neoplasm; Tumor Cells, Cultured