Altered cleavage of DNA sequences by bleomycin and its deglycosylated derivative in the presence of actinomycin

Assembly of Bleomycin Saccharide-Decorated Spherical Nucleic Acids

Glyco-decorated spherical nucleic acids (SNAs) may be attractive delivery vehicles, emphasizing the sugar-specific effect on the outer sphere of the construct and at the same time hiding unfavorable distribution properties of the loaded oligonucleotides. As examples of such nanoparticles, tripodal sugar constituents of bleomycin were synthesized and conjugated with a fluorescence-labeled antisense oligonucleotide (AONARV7). Successive copper(I)-catalyzed azide-alkyne and strain-promoted alkyne-nitrone cycloadditions (SPANC) were utilized for the synthesis. Then, the glyco-AONARV7 conjugates were hybridized with complementary strands of a C60-based molecular spherical nucleic acid (i.e., a hybridization-mediated carrier). The formation and stability of these assembled glyco-decorated SNAs were evaluated by polyacrylamide gel electrophoresis (PAGE), UV melting profile analysis, and time-resolved fluorescence spectroscopy. Association constants were extracted from time-resolved fluorescence data. Preliminary cellular uptake experiments of the glyco-AONARV7 conjugates (120 nM solutions) and of the corresponding glyco-decorated SNAs (10 nM solutions) with human prostate cancer cells (PC3) showed an efficient uptake in each case. A marked variation in intracellular distribution was observed.

Shining light on single-strand lesions caused by the chemotherapy drug bleomycin

Quantification of the DNA damage induced by chemotherapy in patient cells may aid in personalization of the dose used. However, assays to evaluate individual patient response to chemotherapy are not available today. Here, we present an assay that quantifies single-stranded lesions caused by the chemotherapeutic drug Bleomycin (BLM) in peripheral blood mononuclear cells (PBMCs) isolated from healthy individuals. We use base excision repair (BER) enzymes to process the DNA damage induced by BLM and then extend the processed sites with fluorescent nucleotides using a DNA polymerase. The fluorescent patches are quantified on single DNA molecules using fluorescence microscopy. Using the assay, we observe a significant variation in the in vitro induced BLM damage and its repair for different individuals. Treatment of the cells with the BER inhibitor CRT0044876 leads to a lower level of repair of BLM-induced damage, indicating the ability of the assay to detect a compromised DNA repair in patients. Overall, the data suggest that our assay could be used to sensitively detect the variation in BLM-induced DNA damage and repair in patients and can potentially be able to aid in personalizing patient doses.

Transarterial embolization for renal angiomyolipomas: A single centre experience in 79 patients

Objective To evaluate the long-term efficacy and safety of selective arterial embolization (SAE) in the treatment of renal angiomyolipomas (AMLs). Methods This was a retrospective review of medical records and imaging findings from patients with renal AMLs who attended our clinic and received SAE between January 2007 and January 2014. Only patents with complete medical records, preoperative computed tomography scans using typical imaging and follow-up data were included. Results A total of 79 patients were enrolled in the study. Technical and clinical success rates were 100% and 91% ( n = 72), respectively. Only two patients experienced major complications. Post-embolization syndrome (i.e. fever, abdominal pain, nausea or vomiting) was reported in 68 (86%) patients, but all symptoms were mild and resolved with conservative measures. Mean radiological and clinical follow-up periods were 16.8 and 35.9 months, respectively. In 75 (95%) patients, tumours decreased in size; mean ± SD tumour size significantly decreased from 8.4 ± 3.5 cm pre-embolization to 6.7 ± 3.0 cm post-embolization . Conclusions This study provides long-term evidence that SAE is a safe and effective method in the treatment of patients with renal AMLs.

The disaccharide moiety of bleomycin facilitates uptake by cancer cells

The disaccharide moiety is responsible for the tumor cell targeting properties of bleomycin (BLM). While the aglycon (deglycobleomycin) mediates DNA cleavage in much the same fashion as bleomycin, it exhibits diminished cytotoxicity in comparison to BLM. These findings suggested that BLM might be modular in nature, composed of tumor-seeking and tumoricidal domains. To explore this possibility, BLM analogues were prepared in which the disaccharide moiety was attached to deglycobleomycin at novel positions, namely, via the threonine moiety or C-terminal substituent. The analogues were compared with BLM and deglycoBLM for DNA cleavage, cancer cell uptake, and cytotoxic activity. BLM is more potent than deglycoBLM in supercoiled plasmid DNA relaxation, while the analogue having the disaccharide on threonine was less active than deglycoBLM and the analogue containing the C-terminal disaccharide was slightly more potent. While having unexceptional DNA cleavage potencies, both glycosylated analogues were more cytotoxic to cultured DU145 prostate cancer cells than deglycoBLM. Dye-labeled conjugates of the cytotoxic BLM aglycons were used in imaging experiments to determine the extent of cell uptake. The rank order of internalization efficiencies was the same as their order of cytotoxicities toward DU145 cells. These findings establish a role for the BLM disaccharide in tumor targeting/uptake and suggest that the disaccharide moiety may be capable of delivering other cytotoxins to cancer cells. While the mechanism responsible for uptake of the BLM disaccharide selectively by tumor cells has not yet been established, data are presented which suggest that the metabolic shift to glycolysis in cancer cells may provide the vehicle for selective internalization.

Substituted thiazoles VII. Synthesis and antitumor activity of certain 2-(substituted amino)-4-phenyl-1,3-thiazole analogs

A novel series of 2-acetamido- or 2-propanamido-4-(4-substituted phenyl)-1,3-thiazoles (11-34) was designed and synthesized. Compounds were subjected to National Cancer Institute (NCI) in vitro assessment for their antitumor activity, at a single dose of 10 μM. Most of the investigated compounds exhibited broad-spectrum antitumor activity. Compounds 19 and 28 believed to be the most active members in this study, with MG-MID GI(50), TGI, and LC(50) values of 2.8, 11.4, 44.7; and 3.3, 13.1, 46.8, respectively. Compounds 19 and 28 proved to be nine and sevenfold more active than the standard antitumor drug 5-FU, respectively.

Frequency and spectrum of lacI mutations in the liver of Big Blue mice following the administration of genotoxic carcinogens singly and in series

Transgenic mouse models offer a unique opportunity to study in vivo mutagenicity in any tissue of interest. In this study, the authors have determined the liver mutant frequency (MF) and mutational spectra (MS) of 12 week-old male Big Blue B6C3F1 transgenic mice exposed to the genotoxic carcinogens benzo[a]pyrene (B[a]P; 250 mg/kg/day), N-nitrosodimethylamine (NDMA; 7 mg/kg/day), or N-ethyl-1-nitrosourea (ENU; 50 mg/kg/day) singly (3 daily oral doses) or in series (B[a]P on day 1, NDMA on day 2, and ENU on day 3). All genotoxic agents, alone or in series, increased MF in the liver (three- to sixfold). MS analyses of liver DNA revealed a high percentage of G:C --> A:T transitions in the control (88%) and the NDMA (64%) groups. In contrast, B[a]P, ENU, and the series treatment induced a high percentage (> or = 50%) of transversions. Significantly, 46% (19 out of 41) of the mutations in the series treatment group occurred at CpG dinucleotides, compared to less than 22% in the other treatment groups. The MS from the series exposure was most similar to B[a]P with a high percentage of transversion mutations occurring at guanine nucleotides (36%). These preliminary data suggest that genotoxic carcinogens, when exposed in series, produce a unique MS profile characterized not only by shifts in mutation class but also sequence context.

Downregulation of transcription factor, Sp1, during cellular senescence

We found that the protein level of Sp1 transcription factor decreases as normal human fibroblasts undergo replicative aging. Sp1 also undergoes a rapid decrease in the protein level and activity in MCF-7 cells that are induced to a state of cellular senescence. In the cells treated with other DNA damaging chemicals such as actinomycin D and H(2)O(2), the Sp1 level decreased progressively as well. Inhibition of ATM/ATR kinases prevented this downregulation, suggesting that DNA damage signaling is involved in the regulation of the Sp1. This decrease in Sp1 protein level is due to the accelerated proteasomal degradation since a proteasome inhibitor, ALLN, blocked this downregulation. Therefore, the global decrease in gene transcription frequently reported in aging cells and tissues could be attributed at least in part to the decrease in Sp1 level.

Fluorescent intercalator displacement analyses of DNA binding by the peptide-derived natural products netropsin, actinomycin, and bleomycin

The response of the high-throughput fluorescent intercalator displacement (HT-FID) assay reported recently by Boger et al. to peptide-based DNA binding intercalators and metal complexes was examined through the study of actinomycin and Co(III).bleomycin-B2. Along with a validation of netropsin that illustrated the good laboratory-to-laboratory reproducibility of the assay, our examination of actinomycin revealed results for a four base pair cassette library of DNA hairpins that paralleled the known DNA site-selectivity of this agent and also indicated the involvement of the flanking sequences of the hairpin oligonucleotide. In addition, for Co(III).bleomycin-B2 the established cleavage site-selectivity for 5'-GT and 5'-GC sites was correlated to drug-DNA association in this binding-only assay; our results also suggest a tetranucleotide site-selectivity for metallobleomycin involving cross-strand, 'back-to-back' 5'-GT and 5'-GC sites such as 5'-ACGT and 5'-ACGC.

A new approach to DNA bending by polyamines and its implication in DNA condensation

Polyamines are known to induce dynamical bending of DNA molecules. This mechanism is very important since many DNA binding proteins (DNAse, transcription factor, etc.) exert their action by their ability to bend DNA. We propose an analytical model which describes the dynamical bending of DNA by polyamine ions in highly diluted DNA solutions. The bending probability depends on the entropy loss of polyamines due to their localization. This localization is facilitated by the electrostatic repulsion between multivalent counterions condensed on DNA, which reduces the entropy loss in counterion localization. Therefore DNA bending by polyamines depends on the competition between monovalent counterions and polyamines. We find that the bending probability is weak for a low binding ratio of polyamines (i.e. number of bound polyamines per base pair), whereas a high bending probability can be reached at large polyamine binding ratio. In addition, we describe a new mechanism of DNA bending. It occurs with the help of thermal agitation, which initiates the bending and favours the polyamine localization. This model provides further insights into DNA bending by polyamines and its implication in DNA condensation. A qualitative estimation of the DNA bending probability is obtained by measuring the cleavage efficiency of DNA by bleomycin versus spermidine concentration. Indeed, a local helix distortion by polyamines results in an amplification of the double-strand cleavage by bleomycin. The measurement of the bleomycin amplification is performed by analysing images of DNA molecules with atomic force microscope. Some features of the dynamical bending indicate that condensation and bending are interrelated.

The circadian E-box: when perfect is not good enough

Life on earth has evolved on a photic carousel, spinning through alternating periods of light and darkness. This playful image belies the fact that only those organisms that learned how to benefit from the recurring features in their environment were allowed to ride on. This selection process has engendered many daily rhythms in our biosphere, most of which rely on the anticipatory power of an endogenously generated marker of phase: the biological clock. The basic mechanisms driving this remarkable device have been really tough to decode but are finally beginning to unravel as chronobiologists probe deeper and wider in and around the recently discovered gears of the clock. Like its chemical predecessors, biological circadian oscillators are characterized by interlaced positive and negative feedback loops, but with constants and variables carefully balanced to achieve an approximately 24h period. The loops at the heart of these biological oscillators are sustained by specific patterns of gene expression and precisely tuned posttranscriptional modifications. It follows that a molecular understanding of the biological clock hinges, in no small measure, on a better understanding of the cis-acting elements that bestow a given gene with its circadian properties. The present review summarizes what is known about these elements and what remains to be elucidated.

Amplification of bleomycin-induced DNA cleavage at cytosine residues 3' to GGG sequences by pyrrole triamide

We investigated the amplification of bleomycin-induced DNA cleavage by synthetic triamides containing N-methylpyrrole (Py) and/or N-methylimidazole (Im), PyPyPy, PyPyIm, PyImPy, and PyImIm, using 32P-labeled DNA fragments obtained from the human c-Ha-ras-1 and p53 genes. Peplomycin, a bleomycin analog, plus Fe(II) caused DNA cleavage at the 5'-GC-3' and 5'-GT-3' sequences (damaged bases are underlined). The addition of PyPyPy dramatically enhanced the cleavage, particularly at cytosine residues 3' to consecutive guanines. Alteration in the site specificity was not observed with other triamides (PyPyIm, PyImPy, and PyImIm). DNase I footprinting revealed that PyPyPy bound to the sites adjacent to the sites where DNA cleavage was enhanced by PyPyPy, and that PyPyPy enhanced DNase I-induced cleavage in GC-rich regions. These findings suggest that binding of PyPyPy to the DNA minor groove changes the DNA conformation to allow peplomycin to cleave DNA more efficiently at GC-rich sequences, resulting in intensive site-specific DNA cleavage particularly at cytosines at the 3'-side of polyguanines. The present study on amplifiers of antitumor drugs would appear to offer a novel approach to the establishment of more effective chemotherapy.