Interaction of actinomycin D with promoter element of c-met and its inhibitory effect on the expression of c-Met

Context-dependent activation of p53 target genes and induction of apoptosis by actinomycin D in aerodigestive tract cancers

Actinomycin D (ActD) was the first anticancer antibiotic approved for the management of human cancers. However, the notorious toxicity profile limits its widespread application in cancers, including cancers of the aerodigestive tract. Recent studies show that combining low-dose ActD with existing chemotherapies could potentially protect normal cells from the toxicity of chemotherapy drugs through p53 activation (cyclotherapy). An understanding of ActD's effect on p53 signaling is critical for the meaningful application of ActD in cyclotherapy-based combinations. This study evaluated the anti-tumor efficacy and mechanism of action of ActD in aerodigestive tract cancers. We found that ActD strongly inhibited the growth of a panel of aerodigestive tract cancer cell lines and induced efficient apoptosis, although the sensitivity varies among cell lines. The IC₅₀ values of ActD spanned between 0.021 and 2.96 nM. Mechanistic studies revealed that ActD increased the expression of total and phosphorylated p53 (ser15) in a time- and dose-dependent manner. Moreover, ActD-induced apoptosis is dependent on p53 in cells expressing wild-type p53 and that ActD induced context-dependent differential expression of downstream targets p21 and PUMA without significant effects on p27. In the final analysis, this study revealed that p53-p21 is the predominant pathway activated by low-dose ActD, supporting further development of ActD in cyclotherapy.

Identification and characterization of Streptomyces flavogriseus NJ-4 as a novel producer of actinomycin D and holomycin

This paper is the first public report that Streptomyces flavogriseus can produce both actinomycin D and holomycin. The actinomycete strain NJ-4 isolated from the soil of Nanjing Agricultural University was identified as S. flavogriseus. This S. flavogriseus strain was found for the first time to produce two antimicrobial compounds that were identified as actinomycin D and holomycin. GS medium, CS medium and GSS medium were used for the production experiments. All three media supported the production of actinomycin D, while holomycin was detected only in GS medium and was undetectable by HPLC in the CS and GSS media. The antimicrobial activity against B. pumilus, S. aureus, Escherichia coli, F. moniliforme, F. graminearum and A. niger was tested using the agar well diffusion method. Actinomycin D exhibited strong antagonistic activities against all the indicator strains. Holomycin exhibited strong antagonistic activities against B. pumilus, S. aureus and E. coli and had antifungal activity against F. moniliforme and F. graminearum but had no antifungal activity against A. niger. The cell viability was determined using an MTT assay. Holomycin exhibited cytotoxic activity against A549 lung cancer cells, BGC823 gastric cancer cells and HepG2 hepatocellular carcinoma cells. The yield of actinomycin D from S. flavogriseus NJ-4 was 960 mg/l. S. flavogriseus NJ-4 exhibits a distinct capability and has the industrial potential to produce considerable yields of actinomycin D under unoptimized conditions.

Preferential binding of anticancer drugs to triplex DNA compared to duplex DNA: a spectroscopic and calorimetric study

Binding study of adriamycin and actinomycin to triplex DNA formed on the promoter region of hmgb1 gene using spectroscopic and calorimetric technique.

Molecular aspects on adriamycin interaction with hmga1 regulatory region and its inhibitory effect on HMGA1 expression in human cervical cancer

High mobility group A1 (HMGA1), a non-histone chromosomal protein, is highly expressed in a wide range of human cancers including cervical, breast, and prostate cancers. Therefore, hmga1 gene is considered as an attractive potential target for anticancer drugs. We have chosen 27 bp DNA sequence from a regulatory region of hmga1 promoter and studied its interaction with adriamycin (ADM) and in vitro expression of HMGA1 in the presence of ADM in HeLa cell line. A variety of biophysical techniques were employed to understand the characteristics of [DNA-ADM] complex. Spectrophotometric titration data, DNA denaturation profiles, and quenching of fluorescence of ADM in the presence of DNA demonstrated a strong complexation between DNA and ADM with a high binding affinity (Ka) of 1.3 × 10(6) M(-1) and a stoichiometry of 1:3 (drug:nucleotide). The energetics of binding obtained from isothermal titration calorimetry and differential scanning calorimetry suggest the binding to be exothermic and enthalpy (∆H, -6.7 ± 2.4 kcal M(-1)) and entropy (TΔS, 18.5 ± 6.4 kcal M(-1)) driven (20°C), which is typical of intercalative mode of binding. Further, results on decreased expression (by ~70%) of HMGA1 both at mRNA and protein levels in association with the observed cell death (by ~75%) in HeLa cell line, clearly confirm that ADM does target hmga1; however, the effect of ADM on genes other than hmga1 either directly or via hmga1-mediated pathways cannot be ruled out in the observed cytotoxicity. Therefore, hmga1 in general and particularly the regulatory region is a promising target for therapeutic strategy in combating cancer.

Study on interaction of DNA from calf thymus with 1,10-phenanthrolinehexyldithiocarbamatopalladium(II) nitrate as potential antitumor agent

A novel palladium(II) complex has been synthesized with hexyldithiocarbamate (Hex-dtc) and 1,10-phenanthroline (phen) by the reaction of [Pd(phen)(H(2)O)(2)](NO(3))(2) with sodium salt of hexyldithiocarbamate and a complex of type [Pd(Hex-dtc) (phen)]NO(3) has been obtained. The complex has been characterized by elemental analysis, molar conductance, (1)H NMR, IR and electronic spectroscopic studies. The dithiocarbamate ligand acts in bidentate fashion. This water-soluble complex was screened against chronic myelogenous leukemia cell line, K562, for cytotoxic effects and showed significant antitumor activity much lower than that of cisplatin. The interaction of this complex with calf thymus DNA (ctDNA) was extensively investigated by a variety of spectroscopic techniques. Absorbance titration experiments imply the interaction of 4 Pd(II) complex molecules per 1000 nucleotides on DNA with positive cooperativity in the binding process and the complex denature the DNA at very low concentration (~14.3 µM). Fluorescence titration spectra and fluorescence Scatchard plots suggest that the Pd(II) complex intercalate in DNA. The gel chromatograms obtained from Sephadex G-25 column experiments showed that the binding of metal complex with DNA is so strong that it does not readily break. Furthermore, some thermodynamic and binding parameters found in the process of UV-Visible studies are described. They may provide specificity of the compound with ctDNA.

DNA triplex-mediated inhibition of MET leads to cell death and tumor regression in hepatoma

Mesenchymal epithelial transition factor (MET) is one of the critical cell signaling molecules whose aberrant expression is reported in several human cancers. The aim of the study is to investigate the antigene and antiproliferative effect of short triplex forming oligonucleotides, TFO-1 (part of the positive regulatory element) and TFO-2 (away from the transcription start site) on MET expression. HepG2 cells transfected only with TFO-1 (but not with TFO-2 and non-specific TFO) significantly decreased MET levels, which is accompanied by decrease in antiapoptotic proteins and increase in pro-apoptotic proteins. Phosphoproteome-array analysis of 46 intracellular kinases revealed hypophosphorylation of about 15 kinases including ERK, AKT, Src and MEK, suggesting the growth inhibitory effect of TFO-1. Further, the efficacy of TFO-1 was tested on diethylnitrosamine-induced liver tumors in wistar rats. T2-weighted magnetic resonance imaging showed decrease in liver tumor volume up to 90% after treatment with TFO-1. Decreased MET expression and elevated apoptotic activity further indicate that TFO-1 targeted to c-met leads to cell death and tumor regression in hepatoma. Formation of stable DNA triplex between TFO-1 and targeted gene sequence was confirmed by circular dichroic spectroscopy and gel retardation assay. Therefore, it can be concluded that DNA triplex-based therapeutic approaches hold promise in the treatment of malignancies associated with MET overexpression.