Although androgen receptor (AR)-mediated signaling is central to prostate cancer, the ability to modulate AR signaling states is limited. Here we establish a chemical genomic approach for discovery and target prediction of modulators of cancer phenotypes, as exemplified by AR signaling. We first identify AR activation inhibitors, including a group of structurally related compounds comprising celastrol, gedunin, and derivatives. To develop an in silico approach for target pathway identification, we apply a gene expression-based analysis that classifies HSP90 inhibitors as having similar activity to celastrol and gedunin. Validating this prediction, we demonstrate that celastrol and gedunin inhibit HSP90 activity and HSP90 clients, including AR. Broadly, this work identifies new modes of HSP90 modulation through a gene expression-based strategy.

Vancomycin forms complexes with peptides terminating in d-alanyl-d-alanine that are analogous to the biosynthetic precursors of bacterial mucopeptides. The specificity of complex-formation has been studied by means of many synthetic peptides, prepared by both solid-phase and conventional methods. The following conclusions can be drawn: (a) three amide linkages are required to form a stable complex; (b) the terminal carboxyl group must be free; (c) the carboxyl terminal and subterminal residues must be either glycine or of the d-configuration; (d) the size of the side chain in these residues greatly influences the affinity for vancomycin, a methyl group being the optimum in each case; (e) the nature of the side chain in the third and fourth residues has a smaller effect on complex-formation, but an l-configuration was somewhat better than a d-configuration in the third position. In addition to acyl-d-alanyl-d-alanine, other peptides that occur in bacterial cell walls will combine with vancomycin, although less strongly, e.g. acyl-d-alanyl-d-alpha-amino acid (where the terminal d-residue may form the cross-link in mucopeptide structure) and acyl-l-alanyl-d-glutamylglycine (a sequence found in the mucopeptide of Micrococcus lysodeikticus and related organisms). These results throw some light on the specificity of the uptake of vancomycin by living bacteria.

Even though the idea that amyloid B peptide accumulation is the primary event in the pathogenesis of Alzheimer's disease has become the leading hypothesis, the causal link between aberrant amyloid precursor protein processing and tau alterations in this type of dementia remains controversial. We further investigated the role of B-amyloid production/deposition in tau pathology and neuronal cell death in the mouse brain by crossing Tg2576 and VLW lines expressing human mutant amyloid precursor protein and human mutant tau, respectively. The resulting double transgenic mice showed enhanced amyloid deposition accompanied by neurofibrillary degeneration and overt neuronal loss in selectively vulnerable brain limbic areas. These findings challenge the idea that tau pathology in Alzheimer's disease is merely a downstream effect of amyloid production/deposition and suggest that reciprocal interactions between B-amyloid and tau alterations may take place in vivo. D

Electrometric and spectrophotometric titrations showed vancomycin to contain groups having pK values of about 2.9, 7.2, 8.6, 9.6, 10.5 and 11.7. Of these the four last-named were phenolic. Titration above pH11 and below pH1 was irreversible and antibiotic potency was destroyed. Combination with the specific peptide diacetyl-l-lysyl-d-alanyl-d-alanine hindered the titration of the first three phenolic groups. Spectrophotometric titration of iodovancomycin showed that the phenolic group with pK 9.6 was the one iodinated. The stability of the vancomycin-peptide complex in the range pH1-13 showed that complex-formation occurred only when carboxyl groups were ionized and the phenolic groups were non-ionized. The complex was formed in concentrations of urea up to 8m, of potassium chloride up to 4m, of sodium dodecyl sulphate up to 1%, and at temperatures up to 60 degrees C. From titration curves, organic chlorine and iodine analysis, and combination with peptide, a minimum molecular weight for vancomycin of 1700-1800 was estimated. Optical-rotatory-dispersion and circular-dichroism experiments suggested that vancomycin has only limited conformational flexibility. Both vancomycin and its complexes with peptide exhibited properties suggesting aggregation. Vancomycin and iodovancomycin can be fractionated into a main fraction and at least three minor components. The isolation of these fractions salt-free is described and their antibiotic properties are shown to correlate with their ability to form complexes with peptide.

SummaryApoptosis is now widely recognized as a common form of cell death and represents a mechanism of cell clearance in many physiological situations where deletion of cells is required. Peptide growth factors, initially characterised as stimulators of cell proliferation, have now been shown to inhibit death in many cell types. Deprivation of growth factors leads to the induction of apoptosis, i.e. condensation of chromatin and degradation in oligonucleosomesized fragments, formation of plasma and nuclear membrane blebs and cell fragmentation into apoptotic bodies which can be taken up by neighbouring cells. Here we discuss the mechanism(s) by which growth factors may inhibit apoptosis. Apoptosis: an overviewOften referred to as programmed cell death, apoptosis has been extensively reported in the scientific literature through morphological studies in many tissues where death was taking place as a consequence of a physiological phenomenon (reviewed in ref. 1). In these studies the presence of scattered single cells with highly condensed chromatin has been one of the parameters indicating the presence of apoptotic cell death(2). In a later phase the chromatin appears to be distributed into sub-cellular structures called apoptotic bodied3).However, apoptosis is not only observed in the balanced situation of physiological tissue turnover but also in the elimination of specific cell subsets that occurs in embryogenesis, for instance in the embryonic development of the intestine and nervous system and in the regression of female sexual organs in the male(4). Apoptosis has also been implicated as the mechanism of cell elimination during tissue regression in metamorph~sis(~). Apoptotic cells have also been observed during tumour growth and regression. Thus, for example, apoptotic bodies of epithelial cell origin were described during development of squamous cell carcinoma(6) and kinetics studies have demonstrated waves of apoptosis during sarcoma growth(7). Therefore, during tumour growth some cells, perhaps those deprived of growth factors, undergo apoptosis. When tumours are treated with chemotherapy, apoptosis is responsible for at least some of the cell deaths which ensue(*).There are further experimental modulations of tissues where cell death is induced and apoptosis is observed. Regression of hyperplastic organs such as the liver or kidneys after lead poisoning is accompanied by the appearance of apoptotic celld9). Apoptosis is observed in the rat prostate after repeated withdrawal of testosterone stimulation(10), in rat liver after removal of tumour promoters(l]), in keratinocytes after UV irradiation(12) and in neuronal cells following glutamate treatment(13).Because apoptotic cells are rapidly, and specifically, engulfed in vivo by neighbouring cells(14) in order to keep cell debris to a minimum and to allow shrinkage of a tissue without disruption of its basic architecture, these morphological tissue studies probably greatly underestimate the number of deaths occurring. Indeed, it has been proposed that man...

The Snail genes are implicated in processes that involve cell movement, both during embryonic development and tumour progression. In teleosts, the vertebrate Snail1 gene is represented by two distinct genes, snail1a and snail1b (previously snail1 and snail2). These genes are expressed in complementary mesodermal domains and their combined expression matches that of their mammalian counterpart. By analysing their loss and gain of function, we found that the most-anterior axial mesendodermal cells, the precursors of the polster, move in a cohesive manner directed by the activity of snail1a-and snail1b-expressing cells surrounding these precursors. The cell-autonomous function of Snail1 proteins regulates cell motility and influences the behaviour of Snailnegative neighbouring cells. Snail1a is required by the prechordal plate for it to reach its normal position, whereas Snail1b controls the acquisition of its normal shape. These non-redundant functions of Snail1a and Snail1b in controlling axial mesendoderm migration comply with the duplication-degeneration-complementation model, and indicate that Snail genes not only act as inducers of epithelial-to-mesenchymal transition, but also as more general regulators of cell adhesion and movement.

The affinity of ristocetin B for analogues of the C-terminal tripeptide sequence of bacterial cell wall mucopeptide precursors resembles that of vancomycin. Complex-formation requires a d-configuration in the two amino acid residues of the C-terminal dipeptide, an l-configuration is preferred in the preceding amino acid residue and positive charges on the peptide molecule decrease its affinity. The specificity of ristocetin B, however, differs from that of vancomycin in the requirements for the size of the side chains on the C-terminal dipeptide. These differences may explain the observed differences in antibiotic behaviour of vancomycin and ristocetin with particular micro-organisms. The optical rotatory dispersion and u.v.-absorption characteristics of the ristocetins are very different from those of vancomycin but nearly identical with those of ristomycin A. Aglycones prepared from ristomycin A were antibiotically active and also combined with a specific peptide.

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