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The switch of vascular smooth muscle cells (SMCs) from the contractile phenotype to proliferative one can make contributions to atherosclerosis and neointima formation. MiR-21 can prevent the rupture of advanced lesion plaques. We previously reported the protection of DNA topoisomerase II (Topo II) inhibitors against atherosclerosis and vascular calcification. However, it remains unknown if Topo II inhibitors can change SMC phenotypes. Herein, we show that teniposide protected SMC phenotype switching during atherosclerosis by enhancing expression of smooth muscle α-actin (SMA) while reducing osteopontin (OPN) expression in aortic lesion plaques. In vitro, teniposide induced expression of smooth muscle protein 22-α and calponin 1, but inhibited expression of OPN and epiregulin in human aortic SMCs (HASMCs). Moreover, teniposide attenuated platelet derived growth factor-BB-induced HASMC proliferation and migration. Mechanistically, the effect of teniposide on SMC phenotypes was completed, at least in part, by activating miR-21 expression. In addition, teniposide ameliorated ligation-induced carotid artery remodeling in C57BL/6J mice by regulating SMA and OPN expression. Taken together, our study demonstrates that teniposide regulates SMC phenotype switching by upregulating expression of contractile genes in a miR-21-dependent manner, and this function is an important anti-atherogenic mechanism of teniposide., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Chemotherapeutic drug-induced apoptosis of human malignant glioma cells involves the death receptor-independent activation of caspases other than caspases 3 or 8 (Glaser et al., Oncogene 18, 5044-5053, 1999). Here, we report that caspases 1, 2, 3, 7, 8, and 9 are constitutively expressed in most human malignant glioma cell lines. Cytotoxic drug-induced apoptosisinvolves delayed activation of caspases 2, 7, and 9, but not 8 and 3, and is blocked by a broad spectrum caspase inhibitor, zVAD-fmk. Cytochrome c release from mitochondria precedes caspase activation during drug-induced apoptosis and is unaffected by zVAD-fmk or ectopic expression of the viral caspase inhibitor, crm-A. In contrast, ectopic expression of BCL-X(L) prevents drug-induced cytochrome c release, caspase activation and cell death. Thus, cancer chemotherapy targets the mitochondrial, caspase-dependent death pathway in human malignant glioma cells., (Copyright 2001 Academic Press.)

Topoisomerase sites were mapped in the 5'-long terminal repeat of HIV-1 DNA by agarose and sequencing gel electrophoresis. Topoisomerase II sites were observed in the absence and presence of teniposide and amsacrine in the transcription initiation region and the TATA box, consistent with a possible role of topoisomerase II in transcription. The NF-kB and Sp1 regions were poorly cleaved. Topoisomerase I sites were relatively unfrequent even in the presence of camptothecin. They were absent in the core promoter and were concentrated in the TAR and the upstream region near the junction with the host DNA.

We have mapped nuclear matrix attachment regions (MARs), defined by their specific binding to nuclear matrices in vitro, and sites of topoisomerase II reaction, detected by DNA cleavage in vitro in the presence of the inhibitor VM-26, in the vicinity of the replication origin of the chicken alpha-globin gene domain. Two MARs are located close to the downstream end (in the direction of transcription) of a 3 kb fragment which includes the origin. These MARs contain sites for strong topoisomerase II binding and reaction. Our observations on this gene domain support two hypotheses concerning MARs in eukaryotic cells, namely that they are close to DNA replication origins and that they contain multiple topoisomerase II recognition sites.

A type II DNA topoisomerase has been partially purified from calf thymus mitochondria by a combination of differential centrifugation and column chromatography. The mitochondrial enzyme was inhibited by amsacrine (m-AMSA) slightly at 0.5 microM, significantly at 5.0 microM, and completely at 50 microM. A similar profile was obtained with teniposide (VM-26) although the latter drug was not quite as potent an inhibitor as the former. P4 unknotting assays of the purified nuclear type II topoisomerase in the presence of m-AMSA and VM-26 indicated that the mitochondrial and nuclear enzymes behaved similarly, although the mitochondrial enzyme appeared to be inhibited more strongly.

The relationship between gene expression and the patterns of histone methylation in Drosophila cells has been investigated using inhibitors of transcription acting at various levels. Inhibition of ribosomal RNA synthesis and processing by 5-fluorouridine or of general RNA synthesis by camptothecin, an inhibitor of topoisomerase I, does not affect the methylation pattern of core histones. This suggests that the arrest of transcription per se is not involved in the changes in histone methylation such as those encountered in heat-shocked cells. However, ethidium bromide and novobiocin, which are known to disrupt nucleosome structure, and VM-26 (teniposide), a specific inhibitor of topoisomerase II, induce changes in histone methylation patterns which, though less severe, are similar to those observed under cellular stress. These results suggest that chromatin conformation is probably an important factor in the accessibility of histones to methyltransferases.

Several antitumor drugs including DNA intercalative and non intercalative agents induce in vitro and in vivo double-stranded DNA breaks by stabilization of a topoisomerase II-DNA complex. In order to locate cleavage sites in an actively transcribed oncogene, N417 cells, originating from a human small cell lung carcinoma and containing 45-50 copies of c-myc oncogene, were treated with mAMSA, 9 hydroxyellipticine and VM 26. The presence of DNA lesions in c-myc was investigated by Southern blot hybridization with a human c-myc probe. In addition to normal bands, DNA patterns of drug treated-cells revealed the presence of new bands most likely corresponding to topoisomerase II-mediated cleavage as these bands were not found in untreated control DNA and in DNA treated with oAMSA, a biologically inactive stereoisomer of mAMSA. Major cleavage sites induced by drugs in the N417 cell c-myc locus were located in the 5' end of the c-myc exon 1 closely to some DNAse I hypersensitive sites which are assumed to reflect an activity of the gene. Therefore our data suggest that TopoII-mediated drug activity correlates with gene activity.

Studies suggest that the anticancer drugs VP16-213 and VM26 produce cytotoxicity by inducing protein-associated DNA breakage in vivo through interaction with a yet unknown nuclear component. The effects of these drugs and their congeners on topoisomerase activities was investigated. VP16-213, VM26, and congeners active toward inducing DNA breaks also inhibited the catenation activity of eukaryote type II topoisomerase in vitro at very low drug concentrations. A structure-activity relationship was obtained for inhibition of catenation that parallels in vivo DNA breakage and cytotoxic activities. Type I topoisomerase activity was totally unaffected by these drugs.