Inhibitors of Ras signal transduction as antitumor agents

Anarchic cell proliferation, observed in some leukemia and in breast and ovarian cancers, has been related to dysfunctioning of cytoplasmic or receptor tyrosine kinase activities coupled to p21 Ras. The growth factor receptor-bound protein 2 (Grb2) adaptor when complexed with Sos (Son of sevenless), the exchange factor of Ras, conveys the signal induced by tyrosine kinase-activated receptor to Ras by recruiting Sos to the membrane, allowing activation of Ras. This review shows how it is possible to stop the Ras-deregulated signaling pathway to obtain potential antitumor agents. Grb2 protein is comprised of one SH2 surrounded by two SH3 domains and interacts by means of its Src homology (SH2) domain with phosphotyrosine residues of target proteins such as the epidermal growth factor (EGF) receptor or the Shc adaptor. By means of its SH3 domains, Grb2 recognizes proline-rich sequences of Sos, leading to Ras activation. Inhibitors of SH2 and SH3 domains were designed with the aim of interrupting Grb2 recognition. On the one hand, using structural data and molecular modeling, peptide dimers or "peptidimers", made up of two proline-rich sequences from Sos linked by an optimized spacer, were developed. On the other, using the structure of the Grb2 SH2 domain complexed with a phosphotyrosine (pTyr)-containing peptide and molecular modeling studies, a series of N-protected tripeptides containing two phosphotyrosine or mimetic residues, with one pTyr sterically constrained, were devised. These compounds show very high affinities for Grb2 in vitro. They have been targeted into cells showing selective antiproliferative activity on tumor cells. These results suggest that inhibiting SH2 or SH3 domains of signaling proteins might provide antitumor agents.     

Cell permeable BH3-peptides overcome the cytoprotective effect of Bcl-2 and Bcl-X(L)

Peptides corresponding to the BH3 domains of Bax (BaxBH3) or Bcl-2 (Bcl2BH3) are potent inducers of apoptosis when fused to the Atennapedia plasma membrane translocation domain (Ant). BaxBH3Ant and Bcl2BH3Ant caused a mitochondrial membrane permeabilization (MMP) and apoptosis, via a mechanism that was not inhibited by overexpressed Bcl-2 or Bcl-X(L), yet partially inhibited by cyclosporin A (CsA), an inhibitor of the mitochondrial permeability transition pore. When added to isolated mitochondria, BaxBH3 and Bcl2BH3 induced MMP, which was inhibited by CsA. However, Bcl-2 or Bcl-X(L) failed to inhibit MMP induced by BaxBH3 and Bc2BH3 in vitro, while they efficiently suppressed the induction of MMP by the Vpr protein (from human immunodeficiency virus-1), a ligand of the adenine nucleotide translocator (ANT). BaxBH3 but not Bcl2BH3 was found to interact with ANT, and only BaxBH3 (not Bcl2BH3) permeabilized ANT proteoliposomes and induced ANT to form non-specific channels in electrophysiological experiments. In contrast, both BaxBH3 and Bcl2BH3 were able to stimulate channel formation by recombinant Bax protein. Thus, BaxBH3 might induce MMP via an action on at least two targets, ANT and Bax-like proteins. In contrast, Bcl2BH3 would elicit MMP in an ANT-independent fashion. In purified mitochondria, two ligands of ANT, bongkrekic acid and the protein vMIA from cytomegalovirus, failed to prevent MMP induced by BaxBH3 or Bcl2BH3. In conclusion, BaxBH3 and Bcl2BH3 induce MMP and apoptosis through a mechanism which overcomes cytoprotection by Bcl-2 and Bcl-X(L).     

Preoperative risk prediction and intraoperative events in cardiac surgery.

OBJECTIVE: To examine the relationship between preoperative risk prediction and intraoperative events. METHODS: A total of 3118 patients operated in 1999 and 2000 at our institution were analysed, all of whom had their EuroSCORE collected prospectively. The intraoperative variables studied were consultant or trainee operating, long bypass time, long ischaemic time, return on bypass in theatre and use of intra-aortic balloon pump at the end of the procedure. The outcomes are reported as hospital mortality, prolonged length of stay in the intensive therapy unit (pLOS-ITU, >48 h) and death or pLOS-ITU. Risk models were constructed by logistic regression for predicting these three outcomes. RESULTS: With the exception of prolonged cross-clamp time, all variables analysed were independently predictive of a negative outcome. Trainee operating had an apparent protective effect. All risk models performed well. The area under the receiver operating characteristic (ROC) curve (95% CI) increased from 0.857 (0.81, 0.90) for EuroSCORE to 0.874 (0.83, 0.92) for the risk of death model. Similarly, the area under the ROC curve for the pLOS-ITU model increased from 0.687 (0.642, 0.732) to 0.734 (0.691, 0.777) and for the death or pLOS-ITU model from 0.717 (0.677, 0.756) to 0.757 (0.719, 0.795). CONCLUSIONS: Knowledge of adverse intraoperative events enhances preoperative risk prediction. This type of analysis could be used for identifying "near miss" outcomes in adult cardiac surgery.     

Three-dimensional optical profilometry analysis of surface states obtained after finishing sequences for three composite resins

The operating protocols used for finishing composite resins are numerous and affect the success of filling from a mechanical, biological, and aesthetic point of view. The study determined the most favorable finishing for each of the composites considered. The three-dimensional optical profilometry examination was used to obtain qualitative and quantitative measurements of three hybrid composites. Tungsten carbide burs left irregularities harder to eliminate than those caused by diamond burs. Sof-Lex disks and the Enhance System gave good results for the three materials. Charisma presented a good surface regardless of polishing method used. Finishing Z100 and Prisma TPH required a special operating protocol as specified by the manufacturers. This study demonstrated that the finishing procedure for composite materials must be strictly followed to obtain optimal results. Profilometry proved to be an excellent method to study the surface roughness of samples.     

Lung transplantation with bronchial revascularisation. Surgical anatomy, operative technique and early results.

Ischaemic anastomotic complications are an important cause of mortality and morbidity after lung transplantation. Anatomical studies have demonstrated that the pattern of bronchial arterial supply is relatively constant and therefore amenable to attempts at revascularisation. From May 1990, 10 patients who had a double lung transplantation (tracheal anastomosis) and 1 patient who had a right lung transplantation underwent concomitant bronchial revascularisation. There were two early and one late deaths. There were no anastomotic complications. Regular endoscopic examination showed satisfactory healing in all patients. Early angiography showed patent grafts in 7 of 9 patients. At a mean follow-up of 11 months (range 6-17 months) 8 patients are well and leading a normal life. This report describes the anatomical basis, technical aspects and early results of a promising operative procedure in the field of lung transplantation.