A comparative study of cellular and molecular pharmacology of doxorubicin and MEN 10755, a disaccharide analogue11Abbreviations: DOX, doxorubicin; DNA-SSB, single-strand breaks; and DNA-DSB, double-strand breaks

Atomic force microscopy-A tool for structural and translational DNA research

Atomic force microscopy (AFM) is a powerful imaging technique that allows for structural characterization of single biomolecules with nanoscale resolution. AFM has a unique capability to image biological molecules in their native states under physiological conditions without the need for labeling or averaging. DNA has been extensively imaged with AFM from early single-molecule studies of conformational diversity in plasmids, to recent examinations of intramolecular variation between groove depths within an individual DNA molecule. The ability to image dynamic biological interactions in situ has also allowed for the interaction of various proteins and therapeutic ligands with DNA to be evaluated-providing insights into structural assembly, flexibility, and movement. This review provides an overview of how innovation and optimization in AFM imaging have advanced our understanding of DNA structure, mechanics, and interactions. These include studies of the secondary and tertiary structure of DNA, including how these are affected by its interactions with proteins. The broader role of AFM as a tool in translational cancer research is also explored through its use in imaging DNA with key chemotherapeutic ligands, including those currently employed in clinical practice.

Combination of doxorubicin with harmine-loaded liposomes exerting synergistic antitumor efficacy

CONTEXT

Long-circulation (PEGLip), pH-sensitive (PEOzLip), and active targeted liposomes (PEG-TATLip)-loading doxorubicin (DOX) and harmine (HM) were prepared. Their physicochemical properties and antitumor effect were investigated.

OBJECTIVES

The aims of the present study were to evaluate synergistic antitumor efficacy.

MATERIALS AND METHODS

Liposomes were prepared by using thin-film dispersion, active drug-loading and target post-insertion method. Subsequently physiochemical properties including particle size distribution, zeta potential, entrapment efficiency (EE), drug-loading content and in-vitro release were determined. Besides, the in vitro cytotoxicity of free drugs and drug-loaded liposomes was explored by using a Sulforhodamine-B Staining assay and the combination index values (CI Value) were calculated. Finally, the cellular uptake experiments by MCF-7cells were carried out via flow cytometry.

RESULTS AND DISCUSSION

All liposomes enhanced the antitumor effect significantly compared to free drugs. Among liposomes, PEG-TATLip enhanced the antitumor effect significantly compared to others. DOX and HM had moderate synergism with CI Value 0.85 for free drugs, 0.81 for PEGLip, 0.72 for PEOzLip, and 0.84 for PEG-TATLip respectively when the weight ratio of two drugs was 1:2. Moreover, the similarity between DOX and HM such as physicochemical properties, in vitro release modes and in vitro uptake kinetics characteristics when they were in the same formulations proved it possible for them to be delivered together.

CONCLUSION

Active targeting liposomes were the most effective delivery system as compared with pH-sensitive and long circulation liposomes. Additionally, DOX and HM could be co-delivered in liposomes and they could play moderate synergism effect in antitumor efficacy.

Development and validation of a UHPLC-MS/MS method for simultaneous quantitation the plasma concentration of Sabarubicin and its alcohol metabolite M3 in Chinese small cell lung cancer patients

To support a novel anthracycline agent - Sabarubicin's pharmacokinetics study in Chinese small cell lung cancer patients, a rapid, sensitive, and high throughput ultra-performance liquid chromatography tandem mass spectrometry method using Doxorubicin hydrochloride as internal standard (IS) was developed and validated for simultaneously quantifying Sabarubicin and its alcohol metabolite M3 in human plasma. Plasma samples were pre-extracted with n-hexane to remove hydrophobic interferences and the target compounds were extracted into a 1ml mixture of chloroform and isopropanol (1:1, v/v) and separated on an ACQUITY UPLC BEH Shield RP18 (100mm×2.1mm, 1.7μm) column with gradient mobile phase composed of acetonitrile and water containing 0.1% formic acid. Detection was performed by electrospray ionization in the positive ionization mode under multiple reaction monitoring of the transitions at m/z 644→130 for Sabarubicin, m/z 646→333.2 for M3, and m/z 544→360 for IS. For Sabarubicin and M3, calibration curves over 2-400ng/ml and 0.5-100ng/ml could achieve excellent linearity respectively(r>0.99). Intra- and inter-day precisions were 1.5%-9.1% and 2.2%-12.8%, and accuracy were -9.6% to 0.7% and -4.8% to 5.9% for Sabarubicin and M3 respectively at four concentration levels. The mean recovery for Sabarubicin was 62.4%, 71.9% for M3, and 58.8% for IS. This method was completely validated and successfully applied in the pharmacokinetics study of Sabarubicin and M3 in Chinese small cell lung cancer patients.

Sabarubicin

Disaccharide derivatives in the daunorubicin and in the 4-demethoxy (idarubicin) series in whichthe first sugar moiety linked to the aglycone is a non-aminated sugar, namely 2-deoxy-L-rhamnose or 2-deoxy-L-fucose andthe second moiety is daunosamine, have been obtained upon synthesis of the appropriate activated sugarintermediate and glycosylation of the corresponding aglycones. The compounds containing 2-deoxy-L-fucose exhibit superior pharmacological properties with respect to thestereoisomers containing 2-deoxy-L-rhamnose. The doxorubicinanalog 7-O-(α-L-daunosaminyl-α(1-4)-2-deoxy-L-fucosyl)-4-demethoxy-adriamycinone (sabarubicin) was prepared startingfrom 14-acetoxyidarubicinone. Solution properties and molecular interactions are compared with thoseof doxorubicin. Sabarubicin exhibits a superior antitumor efficacy, presumably related to theactivation of p53-independent apoptosis. A number of sabarubicin analogues have also been synthesized.

Atomic force microscopy study of DNA conformation in the presence of drugs

Binding of ligands to DNA gives rise to several relevant biological and biomedical effects. Here, through the use of atomic force microscopy (AFM), we studied the consequences of drug binding on the morphology of single DNA molecules. In particular, we quantitatively analyzed the effects of three different DNA-binding molecules (doxorubicin, ethidium bromide, and netropsin) that exert various pharmacologic and therapeutic effects. The results of this study show the consequences of intercalation and groove molecular binding on DNA conformation. These single-molecule measurements demonstrate morphological features that reflect the specific modes of drug-DNA interaction. This experimental approach may have implications in the design of therapeutically effective agents.

Antitumour effect of combination treatment with Sabarubicin (MEN 10755) and cis-platin (DDP) in human lung tumour xenograft

PURPOSE

Sabarubicin (MEN 10755), a new disaccaride anthracycline, has shown greater efficacy than Doxorubicin in a large panel of preclinical models and now it is in phase II clinical trials. Its promising antitumour activity promoted considerable interest to combine Sabarubicin with other antitumour agents. Thus, the purpose of this study was to evaluate in vitro cytotoxic effects and in vivo antitumour activities produced by the combination of Sabarubicin and cisplatin (DDP).

METHODS

The antitumour effect of Sabarubicin and DDP association was investigated, in vitro and in vivo, in preclinical models of lung cancer i.e.: the non-small cell lung carcinoma (NSCLC) H460 and the small-cell lung carcinoma (SCLC) GLC4 in terms of synergism, additivity or antagonism in order to establish the best schedule for the combined treatment. Further, the correlation between antitumour activity and the pharmacokinetic parameters of the studied combination was also evaluated.

RESULTS

The drug combination in vitro was in general more cytotoxic than the single drug alone, indicating the presence of a synergistic effect in both tumour cell lines. Also, in the xenograft experiments a superior antitumoral effect was observed when Sabarubicin was combined with DDP. The antitumour efficacy of Sabarubicin (6 mg/kg q4d x 5) combined with DDP (6 mg/kg q4d x 3) greatly depended on the schedule of administration. In H460 tumour line, the sequential combination was more effective than the simultaneous administration of the two agents, although the antitumour efficacy was not dependent on the sequence of combination. On the other hand, a strong sequence-dependent effect was observed when Sabarubicin was combined with DDP in SCLC, GLC4. In particular, the highest value of LCK = 6.7 was obtained when administration of DDP followed by 24 h that of Sabarubicin. Pharmacokinetics of Sabarubicin in combination with DDP was evaluated at 6 mg/kg for both drugs with different sequential schedule. The experimental data showed no evidence for pharmacokinetics drug-drug interaction.

CONCLUSION

These preclinical results indicate the potential for a strong antitumour activity in lung tumours of the combination Sabarubicin and DDP. In particular, in SCLC the best response should be given by a sequence with administration of Sabarubicin followed 24 h later by that of DDP. Clinical trials based on these results are ongoing.

Enhanced cellular respiration in cells exposed to doxorubicin

Doxorubicin executes topoisomerase II mediated apoptosis, a process known to result in mitochondrial dysfunction, such as the leakage of cytochrome c and the opening of mitochondrial permeability transition pores (PTP). To further define the effects of doxorubicin on cell metabolism, we measured cellular respiration, cellular ATP, DNA fragmentation, and cytochrome c leakage in Jurkat (supersensitive), human leukemia-60 (HL-60, sensitive), and HL-60/MX2 (resistant) cells following exposure to 1.0 microM doxorubicin for 30 min. The measurements were made after 24 h of exposure to the drug. In Jurkat and HL-60 cells, doxorubicin treatment increased cellular mitochondrial oxygen consumption and ATP content by 2-3-fold. The increment in oxygen consumption was blocked by the pan-caspase inhibitor benzyloxycarbonyl-Val-Ala-dl-Asp-fluoromethylketone (zVAD-fmk) and by the PTP inhibitor cyclosporin A. In HL-60/MX2 cells, which are resistant because of a reduced topoisomerase II activity, doxorubicin treatment was without effect on either respiration or ATP content, suggesting that topoisomerase II was essential for induction of apoptosis and stimulation of respiration and ATP content. The conclusion that both of the latter processes were products of oxidations in the mitochondrial respiratory chain was supported by the further observation that rotenone and sodium cyanide inhibited oxygen consumption and substantially lowered ATP content in the treated and untreated cells. Thus, oxidative phosphorylation is enhanced in cells briefly incubated with doxorubicin for as long as 24 h post drug exposure despite apoptosis-associated mitochondrial insults caused by the drug.

Anthracyclines: molecular advances and pharmacologic developments in antitumor activity and cardiotoxicity

The clinical use of anthracyclines like doxorubicin and daunorubicin can be viewed as a sort of double-edged sword. On the one hand, anthracyclines play an undisputed key role in the treatment of many neoplastic diseases; on the other hand, chronic administration of anthracyclines induces cardiomyopathy and congestive heart failure usually refractory to common medications. Second-generation analogs like epirubicin or idarubicin exhibit improvements in their therapeutic index, but the risk of inducing cardiomyopathy is not abated. It is because of their janus behavior (activity in tumors vis-à-vis toxicity in cardiomyocytes) that anthracyclines continue to attract the interest of preclinical and clinical investigations despite their longer-than-40-year record of longevity. Here we review recent progresses that may serve as a framework for reappraising the activity and toxicity of anthracyclines on basic and clinical pharmacology grounds. We review 1) new aspects of anthracycline-induced DNA damage in cancer cells; 2) the role of iron and free radicals as causative factors of apoptosis or other forms of cardiac damage; 3) molecular mechanisms of cardiotoxic synergism between anthracyclines and other anticancer agents; 4) the pharmacologic rationale and clinical recommendations for using cardioprotectants while not interfering with tumor response; 5) the development of tumor-targeted anthracycline formulations; and 6) the designing of third-generation analogs and their assessment in preclinical or clinical settings. An overview of these issues confirms that anthracyclines remain "evergreen" drugs with broad clinical indications but have still an improvable therapeutic index.

The disaccharide anthracycline MEN 10755 binds human serum albumin to a non-classical drug binding site

The interaction of the novel disaccharide anthracycline MEN 10755 with human serum albumin (HSA) was investigated by visible absorption and fluorescence spectroscopies and by ultrafiltration. Notably, MEN 10755 binds serum albumin far stronger than doxorubicin. Albumin binding results into a drastic quenching of the intrinsic fluorescence of MEN 10755; a binding constant of 1.1 x 10(5) was determined from fluorescence data. To localize the HSA binding site of MEN 10755 competition experiments were carried out with ligands that are selective for the different drug binding sites of the protein. No relevant competition effects were seen in the case of warfarin, diazepam and hemin, known ligands of sites I, II and III, respectively. Modest effects were observed following addition of palmitic acid that targets the several fatty acid binding sites of the protein. In contrast, extensive displacement of the bound anthracycline was achieved upon addition of ethacrinic acid. On the basis of these results, it is proposed that MEN 10755 binds serum albumin tightly to a non-canonical surface binding site for which it competes specifically with ethacrinic acid.