Clinical implications of neuroendocrine differentiation in prostate cancer.

The cellular signaling pathways of the prostate play a central role in the induction, maintenance, and progression of prostate cancer (CaP). Neuroendocrine (NE) cells demonstrate attributes that suggest they are an integral part of these signaling cascades. We summarize what is known regarding NE cells in CaP focusing on NE cellular transdifferentiation. This significant event in CaP progression appears to be accelerated by androgen deprivation (AD) treatment. We examine biochemical pathways that may impact NE differentiation in a chronological manner focusing on AD therapy (ADT) as a central event in inducing androgen-independent CaP. Our analysis is limited to the common adenocarcinoma pattern of CaP and excludes small-cell and carcinoid prostatic variants. In conclusion, we speculate on the future of treatment and research in this area.

Development of liquid chromatographic method for the analysis of kanamycin residues in varicella vaccine using phenylisocyanate as a derivatization reagent.

A liquid chromatographic method for the determination of the aminoglycoside kanamycin in varicella vaccine is described. Kanamycin sulfate was derived with phenylisocyanate (PIC) and triethylamine for 10 min at 70 degrees C and chromatographed on a alkylamide-bonded column, Suplex pKb-100. A derivative of kanamycin sulfate was attached to four phenylisocynato groups and that molecular mass was confirmed with liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS). The kanamycin-PIC derivative was found to have a retention time of 11.7 min using an eluent composed of 40% acetonitrile in water at 1.2 ml/min column flow-rate. Detection was at a wavelength of 240 nm. Recoveries ranging from 97.5 to 99.8% were found. The correlation coefficient was greater than 0.9998 over the range between 10 and 100 microg/ml. The method precision of within-day assay showed a 0.5 to 4.0% coefficient of variation (n = 5) ranging from 10 to 70 microg/ml of kanamycin concentration levels. Kanamycin-PIC derivative in reaction solution was stable for 24 h at room temperature. A simple and efficient method for the analysis of the kanamycin in varicella vaccine was developed and validated.

Conformational studies of irreversible HIV-1 protease inhibitors containing cis-epoxide as an amide isostere.

We have carried out NMR and molecular modeling studies of peptidomimetic HIV-1 protease inhibitors, LB71116: Qc-Asn-Phepsi[(1R,2S)-cis-epoxide]Gly-NH-CH(isopropyl)2 where Qc stands for quinaldic acid and LB71148: Qc-(SMe)Pen(O)2-Phepsi[(1R,2S)-cis-epoxide]Gly-NH-CH(isoprop yl)2 where (SMe)Pen(O)2 stands for S-methyl-S-dioxo-penicillamine. Through conformational calculations and NMR data analysis, we have obtained preferred conformations of the two inhibitors in solution. To our knowledge, this work is one of the first extensive conformational studies of peptidomimetics containing cis-epoxide amide isostere. The resulting preferred conformations contain extended structures. In these conformations, the psi of Phe(cep) is maintained about 130 degrees and the phi angle of (cep)Gly prefers +/- 150 degrees [where Phe(cep) and (cep)Gly are the residues generated by the replacement of the Phe-Gly peptide bond with cis-epoxide]. Two conformations were commonly observed in the preferred conformations of each inhibitor. Through restrained molecular dynamics simulating the hydrogen bond formation between our inhibitor and a water molecule ('flap water'), one of the conformations is assumed as the conformation which can bind to the enzyme without large conformational changes. Recently, we had the opportunity to compare the selected preferred conformation with the binding conformation of LB71116 observed from the X-ray studies of the complex between LB71116 and HIV-1 protease. These two conformations are surprisingly similar to each other. Thus, we can explain high activity and selectivity of our inhibitors to the HIV-1 protease by the similarity between the preferred conformations in solution and the binding conformation.

NMR and topochemical studies of peptidomimetic HIV-I protease inhibitors containing a cis-epoxide amide isostere.

NMR and topochemical studies of irreversible HIV-1 protease inhibitors containing a cis-epoxide as amide isostere have been carried out to identify conformational preference of the inhibitors in solution. The inhibitors prefer to adopt extended conformations similar to the beta-strand in solution.

Application of carboxypeptidase Y and fast atom bombardment mass spectrometry for C-terminal sequencing of small peptides.

The application of fast atom bombardment (FAB) mass spectrometry to the C-terminal amino acid sequence determination of peptides is reported. FAB mass spectrometric analysis of the peptides formed by carboxypeptidase Y (CPY) digestion conveniently provides information about C-terminal amino acid sequences. In these experiments, we accomplished the determination of C-terminal region amino acid sequence of Bradykinin and Angiotensin II. We describe advantages of the combination experiment of CPY and FAB mass spectrometry for C-terminal region amino acid studies of small peptides. The significant advantages of this method are the ability to study peptides without derivatization and the elimination of the separation step of liberated C-terminal amino acids and peptides. With this method, we could overcome several problems which conventionally happened in C-terminal sequence analysis.