Reactions of PtII diamine anticancer complexes with trypanothione and octreotide

The nature of peptide interactions with acid end-group PLGAs and facile aqueous-based microencapsulation of therapeutic peptides

An important poorly understood phenomenon in controlled-release depots involves the strong interaction between common cationic peptides and low Mw free acid end-group poly(lactic-co-glycolic acids) (PLGAs) used to achieve continuous peptide release kinetics. The kinetics of peptide sorption to PLGA was examined by incubating peptide solutions of 0.2-4mM octreotide or leuprolide acetate salts in a 0.1M HEPES buffer, pH7.4, with polymer particles or films at 4-37°C for 24h. The extent of absorption/loading of peptides in PLGA particles/films was assayed by two-phase extraction and amino acid analysis. Confocal Raman microspectroscopy, stimulated Raman scattering (SRS) and laser scanning confocal imaging, and microtome sectioning techniques were used to examine peptide penetration into the polymer phase. The release of sorbed peptide from leuprolide-PLGA particles was evaluated both in vitro (PBST+0.02% sodium azide, 37°C) and in vivo (male Sprague-Dawley rats). We found that when the PLGA-COOH chains are sufficiently mobilized, therapeutic peptides not only bind at the surface, a common belief to date, but also can be internalized and distributed throughout the polymer phase at physiological temperature forming a salt with low-molecular weight PLGA-COOH. Importantly, absorption of leuprolide into low MW PLGA-COOH particles yielded ~17 wt.% leuprolide loading in the polymer (i.e., ~70% of PLGA-COOH acids occupied), and the absorbed peptide was released from the polymer for >2 weeks in a controlled fashion in vitro and as indicated by sustained testosterone suppression in male Sprague-Dawley rats. This new approach, which bypasses the traditional encapsulation method and associated production cost, opens up the potential for facile production of low-cost controlled-release injectable depots for leuprolide and related peptides.

Solid-phase synthesis and DNA binding studies of dichloroplatinum(ii) conjugates of dicarba analogues of octreotide as new anticancer drugs

The first dichloroplatinum(ii) conjugates of dicarba analogues of octreotide, which is expected to act as a 'tumour-targeting device', have been efficiently synthesized following a stepwise solid-phase approach; these compounds emulate the mechanism of cisplatin since they form a 1,2-intrastrand cross-link with two consecutive guanines of an oligonucleotide.

Application of flavonoids - quercetin and rutin - as new matrices for matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analysis of Pt(II) and Pd(II) complexes

Attempts are being made to overcome the resistance of tumour cells to platinum (Pt) drugs by the synthesis of new generations of Pt complexes, and it is important to find appropriate and simple methods for the characterization of those novel complexes. The additional applicability of such a method for the analysis of the interactions of metal complexes with biomolecules would be advantageous. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) seems to possess the capability to become this method of choice, since it could be applied to low-mass complexes as well as for the analysis of large biomolecules. In this work the applicability of flavonoids - quercetin and rutin - as matrices for MALDI-TOFMS analysis of dichlorido(ethylendiamine)platinum(II) ([PtCl(2)(en)]), dichlorido(diaminocyclohexane)platinum(II) ([PtCl(2)(dach)]) and chloride (diethylenetriamine) palladium(II) chloride ([PdCl(dien)]Cl) complexes is demonstrated. Spectra of Pt(II) and Pd(II) complexes recorded in the presence of quercetin and rutin are rather simple: Pt(II) complexes generate [M+Na](+) or [M+K](+)ions, whereas the investigated Pd(II) complex gives ions generated by the loss of one Cl(-) or HCl. Flavonoids give a relatively small number of well-defined ions in the low-mass region (at m/z 303.3 for quercetin and m/z 633.5 for rutin). Quercetin and rutin can be applied in much lower concentrations than other common MALDI matrices and require rather low laser intensity. We speculate that flavonoids stabilize the structures of the metal complexes and that they may be useful for the analysis of other biologically active metal complexes, thus implying their broader applicability.

Chiral salicyl diamines: potent anticancer molecules

A set of 12 enantiomeric diamine-based small molecules was synthesized and screened for anticancer activity against five human cancer cell lines: NCI-H460, A549, MCF-7, SK-BR-3, and T-47D. The salicyl diamino compounds (1-6) were found to induce inhibition of the growth of cancer cells at submicromolar concentrations. The lead compound, N,N'-bis-salicyl-(1R,2R)-diaminocyclohexane (1) displayed single-reagent anticancer activity with an IC(50) value equal to or less than 2.0 microM in H460 and A-549 cancer cells. SRB and colony formation assays indicated that compound 1 shows greater cytotoxic activity toward MCF-7 cells than MCF-10A cells. Real-time RT-PCR analysis demonstrated that compound 1, is an extremely efficient regulator of antiapoptotic genes, Bcl-xL, Bcl-2, and the cell cycle related gene, cyclin D1. This study provides a new insight into the development of novel small molecules in the treatment of human breast cancers.