Synthesis and application of functional peptides as cell nucleus-directed molecules in the treatment of malignant diseases

A peptide & peptide nucleic acid synthesis technology for transporter molecules and theranostics--the SPPS

Advances in imaging diagnostics using magnetic resonance tomography (MRT), positron emission tomography (PET) and fluorescence imaging including near infrared (NIR) imaging methods are facilitated by constant improvement of the concepts of peptide synthesis. Feasible patient-specific theranostic platforms in the personalized medicine are particularly dependent on efficient and clinically applicable peptide constructs. The role of peptides in the interrelations between the structure and function of proteins is widely investigated, especially by using computer-assisted methods. Nowadays the solid phase synthesis (SPPS) chemistry emerges as a key technology and is considered as a promising methodology to design peptides for the investigation of molecular pharmacological processes at the transcriptional level. SPPS syntheses could be carried out in core facilities producing peptides for large-scale scientific implementations as presented here.

SPPS resins impact the PNA-syntheses' improvement

The personalized medicine, also documented as "individualized medicine", is an effective and therapeutic approach. It is designed to treat the disease of the individual patient whose precise differential gene expression profile is well known. The trend in the biomedical and biophysical research shows important consequences for the pharmaceutical drug and diagnostics research. It requires a high variability in the design and safety of target-specific pharmacologically active molecules and diagnostic components for imaging of metabolic processes. A key technology which may fulfill the highest demands during synthesis of these individual drugs and diagnostics is the solid phase synthesis which is congenial to automated manufacturing. Additionally the choice of tools like resins and reagents is pivotal to synthesize drugs and diagnostics in high quality and yields. Here we demonstrate the solid phase synthesis effects dependent on the choice of resin and of the deprotection agent.

Transfection of molecular beacons in microchannels for single-cell gene-expression analysis

BACKGROUND

Efficient transfection of molecular beacons has to be performed in the microscale in order to fully utilize the potential of molecular beacons and microfluidics for studying the real-time gene-expression dynamics in living cells. Nevertheless, there has been relatively little study on transfection of molecular beacons in microfluidic channels.

RESULTS

In this work, the differences between transfection in conventional cell culture systems and in microfluidic cell culture systems were investigated systematically with a combination of computational and experimental methods. Comparison between a no-flow microchannel and a 96-well plate revealed that the scale-dependence of reaction-diffusion kinetics contributes to the reduced transfection efficiency in the no-flow microchannel. Study on transfection in the microfluidic system under flow conditions suggested that the fluid flow enhances mass transfer, while the fluid shear stress can reduce the transfection efficiency.

CONCLUSION

The results of this study will provide useful guidelines in optimizing molecular beacon transfection efficiency in microfluidic systems for studying gene-expression dynamics in living cells.

Radioiodinated O(6)-Benzylguanine derivatives containing an azido function

INTRODUCTION

Drug resistance to alkylator chemotherapy has been primarily attributed to the DNA repair protein alkylguanine-DNA alkyltransferase (AGT); thus, personalizing chemotherapy could be facilitated if tumor AGT content could be quantified prior to administering chemotherapy. We have been investigating the use of radiolabeled O(6)-benzylguanine (BG) analogues to label and quantify AGT in vivo. BG derivatives containing an azido function were sought to potentially enhance the targeting of these analogues to AGT, which is primarily present in the cell nucleus, either by conjugating them to nuclear localization sequence (NLS) peptides or by pretargeting via bio-orthogonal approaches.

METHODS

Two O(6)-(3-iodobenzyl)guanine (IBG) derivatives containing an azido moiety-O(6)-(4-azidohexyloxymethyl-3-iodobenzyl)guanine (AHOMIBG) and O(6)-(4-azido-3-iodobenzyl)guanine (AIBG)--and their tin precursors were synthesized in multiple steps and the tin precursors were converted to radioiodinated AHOMIBG and AIBG, respectively. Both unlabeled and radioiodinated AHOMIBG analogues were conjugated to alkyne-derivatized NLS peptide heptynoyl-PK(3)RKV. The ability of these radioiodinated compounds to bind to AGT was determined by a trichloroacetic acid precipitation assay and gel electrophoresis/phosphor imaging. Labeling of an AGT-AIBG conjugate via Staudinger ligation using the (131)I-labeled phosphine ligand, 2-(diphenylphosphino)phenyl 4-[(131)I]iodobenzoate, also was investigated.

RESULTS

[(131)I]AHOMIBG was synthesized in two steps from its tin precursor in 52.2 ± 7.5% (n = 5) radiochemical yield and conjugated to the NLS peptide via click reaction in 50.7 ± 4.9% (n = 6) yield. The protected tin precursor of AIBG was radioiodinated in an average radiochemical yield of 69.6 ± 4.5% (n = 7); deprotection of the intermediate gave [(131)I]AIBG in 17.8 ± 4.2% (n = 9) yield. While both [(131)I]AHOMIBG and its NLS conjugate bound to AGT pure protein, their potency as a substrate for AGT was substantially lower than that of [(125)I]IBG. Uptake of [(131)I]AHOMIBG-NLS conjugate in DAOY medulloblastoma cells was up to eightfold higher than that of [(125)I]IBG; however, the uptake was not changed when the cellular AGT content was first depleted with BG treatment. [(131)I]AIBG was almost equipotent as [(125)I]IBG with respect to binding to pure AGT; however, attempts to radiolabel AGT by treatment with unlabeled AIBG followed by Staudinger ligation using the radiolabeled phosphine ligand, 2-(diphenylphosphino)phenyl 4-[(131)I]iodobenzoate were not successful.

CONCLUSION

Although AHOMIBG, and AIBG were synthesized successfully in both unlabeled and radioiodinated forms, the radioiodinated compounds failed to label AGT either after NLS peptide conjugation or via Staundiger ligation. Currently, other bio-orthogonal approaches are being evaluated for labeling AGT by pretargeting.

Delivery of substances and their target-specific topical activation

Goal in pharmaceutical research is achievement of necessary drug concentrations in the target organ, effective treatment with safe delivery of genetic agents, while sparing normal tissue and minimizing side effects. A new "BioShuttle"-delivery system harbouring a cathepsin B cutting site, a nuclear address sequence and a functional peptide was developed and tumor cells were treated. Transport and subcellular activation were determined by confocal laser scanning microscopy permitting the conclusion: BioShuttle-conjugates prove as efficient tools for genetic interventions by selective and topical activation of therapeutic peptide precursors by enzymatic cleavage. As shown here for glioma cells and the cathepsin B cleavable site, living cells can be treated with high specificity and selectivity for diagnostic and therapeutic purposes.

Delivery of different length poly(L-lysine)-conjugated ODN to HepG2 cells using N-stearyllactobionamide-modified liposomes and their enhanced cellular biological effects

Short (14-20-mer range) synthetic oligodeoxynucleotides (ODNs) allow specific modulation of cellular gene expression at various stages, thus providing a versatile tool for fundamental studies and a rational approach to anticancer chemotherapy. However, several problems, such as metabolic stability, efficient cell internalization of ODNs and their efficient entrapment into liposomes continue to markedly limit this approach. To improve the target specificity and biological activity of ODN, three different length of poly(L-lysine) (PLL) were conjugated to ODN and these conjugates were encapsulated in N-stearyllactobionamide (N-SLBA)-modified liposomes, N-SLBA is a ligand for the asialoglycoprotein receptor. Then, we investigated their effects on cell cycle and survivin protein levels of HepG2 cells. The results showed that the encapsulation efficiency was improved because the polycationic charges of PLL neutralized the polyanionic charges of ODN. Among them, PLL (M(W) 2000 and 10,000)-conjugated ODN encapsulated in N-SLBA liposomes induced apoptosis of HepG2 cells and highly inhibited survivin gene expression.

Nuclear Localization Signal-Targeted Poly(ethylene glycol) Conjugates as Potential Carriers and Nuclear Localizing Agents for Carboplatin Analogues

Carboplatin is a low-molecular-weight anticancer drug that acts by binding to the nuclear DNA of cells. Thus, efficient delivery of the platinum drugs to the nucleus of the cancer cells may enhance the cytotoxicity of the drug. Efficient drug delivery to the nucleus of cancer cells requires three levels of localization: targeting to the cancerous tissue, accumulation in the cancer cells, and intracellular localization in the nucleus. Nuclear localization signals (NLS) are short positively charged basic peptides that actively transport large proteins across the nuclear membrane. We have prepared conjugates in which the NLS is tethered to poly(ethyleneglycol)carboplatin conjugate (NLS-PEG-Pt) and compared their pharmacological properties to those of their untargeted analogues that do not possess the NLS (PEG-Pt). NLS-PEG-Pt conjugates are rapidly internalized into cancer cells and accumulate in the nucleus. Despite their rapid nuclear localization, they form less Pt-DNA adducts than the untargeted analogues, PEG-Pt, and are also less cytotoxic. These results support the hypothesis that carboplatin (unlike cisplatin) may require cytosolic activation prior to its binding to nuclear DNA.