Characterization of cell death induced by vinflunine, the most recent Vinca alkaloid in clinical development.

Vinflunine, the most recent Vinca alkaloid in clinical development, demonstrated superior antitumour activity to other Vincas in preclinical tumour models. This study aimed to define its molecular mechanisms of cell killing in both parental sensitive and vinflunine-resistant P388 leukaemia cells. Vinflunine treatment of these cells resulted in apoptosis characterized by DNA fragmentation and proteolytic cleavage of poly-(ADP-ribose) polymerase. Apoptosis-inducing concentrations of vinflunine caused c-Jun N-terminal kinase 1 stimulation, as well as caspases-3/7 activation. This activation of caspases and the induction of apoptosis could be inhibited by the caspase inhibitor acetyl-Asp-Glu-Val-Asp-aldehyde. Interestingly, the apoptosis signal triggered by vinflunine in these P388 cells was not mediated through Bcl-2 phosphorylation. In addition, when vinflunine resistance was developed in P388 cells, it was associated with resistance to vinflunine-induced apoptosis, as reflected by a loss of capacity to induce DNA fragmentation and PARP degradation, and characterized by increased levels of Bcl-2 and Bfl-1/A1. Therefore, these data indirectly implicate Bcl-2 and Bfl-1/A1 in vinflunine-induced cell death mechanisms.

Hydroxylation of yohimbine in superacidic media: one-step access to human metabolites 10 and 11-hydroxyyohimbine.

Two major human metabolites of yohimbine (1), 10- and 11-hydroxyyohimbine (2 and 3), were prepared by direct hydroxylation of 1 under superacidic conditions. In this medium, the four positions of the benzene part of yohimbine were hydroxylated and the corresponding monohydroxylated compounds (2-5) were isolated. The structures of 2-5 were elucidated by spectroscopic methods including 1D and 2D NMR techniques.

Vinca alkaloid-induced tubulin spiral formation correlates with cytotoxicity in the leukemic L1210 cell line.

The ability of a class of C-20' modified vinca alkaloid congeners to induce tubulin spiral formation was investigated relative to their ability to inhibit microtubule assembly, their cytotoxicity against a leukemic cell line, L1210, and their measured and calculated partition coefficients. These studies were prompted by the observation that the energetics of vinca alkaloid-induced tubulin spiral polymers, or spiraling potential, is inversely related to their clinical dosage and are aimed at the long-term goal of developing the ability to predict the cytotoxic and antineoplastic properties of antimitotic drugs. We demonstrate here that vinca-induced tubulin-spiraling potential is significantly correlated with cytotoxicity against L1210 cells. This is consistent with the size of spirals formed being proportional to the relaxation time for polymer redistribution, the lifetime of cell retention, and effects on microtubule ends and dynamics. Spiraling potential also correlates with calculated but not measured partition coefficients. Surprisingly, spiraling potential does not correlate with the ability to inhibit microtubule formation with purified tubulin or microtubule protein. For the set of C-20' modified compounds studied, the largest inhibitory effects on spiraling potential and cytotoxicity are caused by multiple sites of halogen (-F, -Cl) substitution with the introduction of increased rigidity in the ring. This suggests the C-20' position interacts with a hydrogen bond acceptor or an electrophilic region on the protein that electrostatically disfavors halogen substitutions. These studies are discussed in terms of the cellular mode of action of antimitotic drugs, particularly the importance of microtubule dynamics during mitosis and the factors that regulate those dynamics.

[Structural analysis of vinorelbine in solution determined by nuclear magnetic resonance spectrometry]. / Analyse structurale de la vinorelbine en solution déterminée par spectrométrie de résonance magnétique nucléaire.

An active partnership between the National Centre for Scientific Research (CNRS) and the laboratories Pierre Fabre is underpinning the development of a new molecule, vinorelbine, whose tartrate received marketing authorization in France in 1989, under the name of Navelbine. This medicine was first recommended for the treatment of bronchial cancer "not small cell", then, in 1991, for the treatment of metastatic breast cancer. In 1994, its registration in United States was granted for the treatment of bronchial cancer "not small cell". Vinorelbine is obtained by hemisynthesis using two antecedent monomeric alkaloids, catharanthine and vindoline, followed by a modification of the catharanthine nucleus, so as to produce the first 5' nor vinca-alkaloid. The chemical structure of vinorelbine has been examined in our laboratory using nuclear magnetic resonance spectrometry. Bearing in mind their complexity, the total attribution of the proton spectrum and the carbon-13 spectrum has required experiments for homonuclear (1H-1H) and heteronuclear (1H-13C and 1H-15N) correlation. These experiments have been carried out using a BRUKER spectrometer operating at the nominal proton frequency of 200 MHz in direct detection mode, then with a 400 MHz spectrometer equipped with the reverse detection mode. The chemical structure has thus been analyzed with no ambiguity. The results of this structural study will be presented in due course. We have also undertaken a comparative conformational study between base vinorelbine in chloroform solution and ditartrate vinorelbine (Navelbine) in methanolic solution. The conformation of the vinorelbine molecule in solution in these different solvents have been studied with NOESY (Nuclear Overhauser Effect Spectroscopy) experiments. The results of these experiments have been confirmed by data stemming from molecular modelization.