BRCA1 inhibition of estrogen receptor signaling in transfected cells

Mutations of the breast cancer susceptibility gene BRCA1 confer increased risk for breast, ovarian, and prostatic cancers, but it is not clear why the mutations are associated with these particular tumor types. In transient transfection assays, BRCA1 was found to inhibit signaling by the ligand-activated estrogen receptor (ER-alpha) through the estrogen-responsive enhancer element and to block the transcriptional activation function AF-2 of ER-alpha. These results raise the possibility that wild-type BRCA1 suppresses estrogen-dependent transcriptional pathways related to mammary epithelial cell proliferation and that loss of this ability contributes to tumorigenesis.

Glu-tRNAGln amidotransferase: a novel heterotrimeric enzyme required for correct decoding of glutamine codons during translation

The three genes, gatC, gatA, and gatB, which constitute the transcriptional unit of the Bacillus subtilis glutamyl-tRNAGln amidotransferase have been cloned. Expression of this transcriptional unit results in the production of a heterotrimeric protein that has been purified to homogeneity. The enzyme furnishes a means for formation of correctly charged Gln-tRNAGln through the transamidation of misacylated Glu-tRNAGln, functionally replacing the lack of glutaminyl-tRNA synthetase activity in Gram-positive eubacteria, cyanobacteria, Archaea, and organelles. Disruption of this operon is lethal. This demonstrates that transamidation is the only pathway to Gln-tRNAGln in B. subtilis and that glutamyl-tRNAGln amidotransferase is a novel and essential component of the translational apparatus.

Traditional Chinese medicine: an approach to scientific proof and clinical validation

The classical Chinese pharmacopoeia describes a large number of herbal formulations that are used for the treatment of a wide variety of diseases. This therapeutic approach is ignored by many and considered to be an alternative to conventional medicine by others. The scientific proof and clinical validation of these herbal formulations require a rigorous approach that includes chemical standardization, biological assays, animal models, and clinical trials. Such Western methodologies need to take into consideration the complex mixture of chemicals and how they are to be used in humans. This review examines relevant studies on the use of traditional Chinese medicines for the treatment of such diseases as bronchial asthma, atopic dermatitis, and irritable bowel syndrome. An interdisciplinary approach to traditional Chinese medicine may provide a platform for the discovery of novel therapeutics composed of multiple chemical compounds.

A role for the disintegrin domain of cyritestin, a sperm surface protein belonging to the ADAM family, in mouse sperm-egg plasma membrane adhesion and fusion

Sperm-egg plasma membrane fusion is preceded by sperm adhesion to the egg plasma membrane. Cell-cell adhesion frequently involves multiple adhesion molecules on the adhering cells. One sperm surface protein with a role in sperm-egg plasma membrane adhesion is fertilin, a transmembrane heterodimer (alpha and beta subunits). Fertilin alpha and beta are the first identified members of a new family of membrane proteins that each has the following domains: pro-, metalloprotease, disintegrin, cysteine-rich, EGF-like, transmembrane, and cytoplasmic domain. This protein family has been named ADAM because all members contain a disintegrin and metalloprotease domain. Previous studies indicate that the disintegrin domain of fertilin beta functions in sperm-egg adhesion leading to fusion. Full length cDNA clones have been isolated for five ADAMs expressed in mouse testis: fertilin alpha, fertilin beta, cyritestin, ADAM 4, and ADAM 5. The presence of the disintegrin domain, a known integrin ligand, suggests that like fertilin beta, other testis ADAMs could be involved in sperm adhesion to the egg membrane. We tested peptide mimetics from the predicted binding sites in the disintegrin domains of the five testis-expressed ADAMs in a sperm-egg plasma membrane adhesion and fusion assay. The active site peptide from cyritestin strongly inhibited (80-90%) sperm adhesion and fusion and was a more potent inhibitor than the fertilin beta active site peptide. Antibodies generated against the active site region of either cyritestin or fertilin beta also strongly inhibited (80-90%) both sperm-egg adhesion and fusion. Characterization of these two ADAM family members showed that they are both processed during sperm maturation and present on mature sperm. Indirect immunofluorescence on live, acrosome-reacted sperm using antibodies against either cyritestin or fertilin beta showed staining of the equatorial region, a region of the sperm membrane that participates in the early steps of membrane fusion. Collectively, these data indicate that a second ADAM family member, cyritestin, functions with fertilin beta in sperm-egg plasma membrane adhesion leading to fusion.

Suppression of breast cancer invasion and migration by indole-3-carbinol: associated with up-regulation of BRCA1 and E-cadherin/catenin complexes

Indole-3-carbinol (I3C) is a compound occurring naturally in cruciferous vegetables and has been indicated as a promising agent in preventing breast cancer development and progression. In the present study we have investigated the effect of I3C on the cell migration and invasion behavior in estrogen receptor positive MCF-7 and estrogen receptor negative MDA-MB-468 human breast cancer cell lines. Both MCF-7 and MDA-MB-468 were poorly invasive cell lines and exhibited modest invasion and migration capacity in the presence of fibronectin as the chemoattractant. I3C (50 or 100 microM) elicited a significant inhibition of in vitro cell adhesion, migration, and invasion as well as in vivo lung metastasis formation in both cell lines. I3C also suppressed the 17beta-estradiol stimulated migration and invasion in estrogen-responsive MCF-7 cells. These results indicate that anti-invasion and antimigration activities of I3C occur via estrogen-independent and estrogen-dependent pathways. Moreover, I3C significantly caused a dose-dependent increase in E-cadherin, three major catenins (alpha, beta, and gamma-catenin) and BRCA1 expression. Our current finding is the first demonstration that I3C can activate the function of invasion suppressor molecules associated with the suppression of invasion and migration in breast cancer cells. Thus, clinical application of I3C may contribute to the potential benefit for suppression of breast cancer invasion and metastasis.

DNA translocation by the restriction enzyme from E. coli K

The restriction endonuclease Eco K binds to a host specificity site and then proceeds to cleave the DNA at sites that may to several thousand bases away. It does this by translocating the DNA past the enzyme in an ATP-dependent reaction that results in the formation of highly twisted loop intermediates. DNA cleavage can occur on either side of the host specificity site.

Retinoic acid regulates the development of a gut-homing precursor for intestinal dendritic cells

The vitamin A metabolite retinoic acid (RA) regulates intestinal immune responses through immunomodulatory actions on intestinal dendritic cells (DCs) and lymphocytes. Here, we show that RA also controls the generation of gut-tropic migratory DC precursors, referred to as pre-mucosal DCs (pre-μDCs). Pre-μDCs express the gut trafficking receptor α4β7 and home preferentially to the intestines. They develop in the bone marrow (BM), can differentiate into CCR9⁺ plasmacytoid DCs as well as conventional DCs (cDCs), but preferentially give rise to CD103⁺ intestinal cDCs. Generation of pre-μDCs in vivo in the BM or in vitro is regulated by RA and RA receptor α (RARα) signaling. The frequency of pre-μDCs is reduced in vitamin A-deficient animals and in animals treated with RAR inhibitors. The results define a novel vitamin A-dependent, RA-regulated developmental sequence for DCs and identify a targeted precursor for CD103⁺ cDCs in the gut.

Changes in keratometric astigmatism after suture removal more than one year after penetrating keratoplasty

BACKGROUND/PURPOSE

Selective removal of interrupted sutures and adjustment of a running suture can minimize astigmatism after penetrating keratoplasty, but the long-term effects of early suture manipulations remain largely unknown. The authors tested the hypothesis that the cornea becomes "fixed" more than 1 year after keratoplasty so that desirable refractive results will remain when all sutures are eventually removed.

METHODS

The authors reviewed retrospectively the changes in astigmatism that occurred when all remaining sutures were removed from 162 eyes 1 to 6 years after penetrating keratoplasty. Single-running sutures were used in 130 eyes, double-running sutures in 20 eyes, and a combination of interrupted and running sutures in 12 eyes.

RESULTS

Removal of single-running sutures caused an average decrease in astigmatism of 0.52 diopters (D) from 6.10 +/- 4.41 D to 5.57 +/- 3.14 D. However, the astigmatism in 62% of eyes changed 2 or more D (range, 11.94 to -17.87 D), and the range changed more than 20 degrees in 55% of eyes. The average vectorial change was 6.5 +/- 4.3 D (range, 0.59 to 19.8 D). There was no decrease in the amount of astigmatic change with increasing time between surgery and suture removal. Graft size and diagnosis had no effect on the amount of astigmatic change. Astigmatic errors became stable, with less than 1 D of change between successive examinations within 6 months after suture removal. Similar results were obtained for eyes with double-running and interrupted-running sutures.

CONCLUSIONS

Corneal astigmatism may change unpredictably and by large amounts when all remaining sutures are removed 1 to 6 years after penetrating keratoplasty.

Investigating protein-ligand interactions with a mutant FKBP possessing a designed specificity pocket

Using structure-based design and protein mutagenesis we have remodeled the FKBP12 ligand binding site to include a sizable, hydrophobic specificity pocket. This mutant (F36V-FKBP) is capable of binding, with low or subnanomolar affinities, novel synthetic ligands possessing designed substituents that sterically prevent binding to the wild-type protein. Using binding and structural analysis of bumped compounds, we show here that the pocket is highly promiscuous-capable of binding a range of hydrophobic alkyl and aryl moieties with comparable affinity. Ligand affinity therefore appears largely insensitive to the degree of occupancy or quality of packing of the pocket. NMR spectroscopic analysis indicates that similar ligands can adopt radically different binding modes, thus complicating the interpretation of structure-activity relationships.

Inhibition of the type I restriction-modification enzymes EcoB and EcoK by the gene 0.3 protein of bacteriophage T7

The gene 0.3 protein of bacteriophage T7 is a potent inhibitor of the restriction-modification enzymes EcoB and EcoK, both in vivo and in vitro. We have analyzed the ability of purified 0.3 protein to inhibit different steps in the reactions of EcoB and EcoK with DNA. Most of our experiments were done with EcoK, but selected tests with EcoB indicate that the two enzymes are affected by 0.3 protein in the same way. Purified 0.3 protein binds tightly to free enzyme, apparently to one of the small subunits, and prevents it from binding to DNA. If EcoK is allowed to form specific recognition complexes with unmodified DNA before 0.3 protein is added, relatively low levels of 0.3 protein prevent the nuclease activity that would otherwise appear upon addition of ATP, but considerably higher levels are needed to prevent formation of filter-binding complexes or ATPase activity. This, together with other results, suggests that the binding site for 0.3 protein is protected in recognition complexes and in the early stages of the ATP-stimulated reactions, but that it becomes accessible again before cleavage of the DNA, perhaps after the translocation step. If added after the nuclease reaction is substantially over, 0.3 protein has little effect on ATPase activity, and indeed, the subunit having the binding site for 0.3 protein apparently dissociates from the enzyme-DNA complex. The methylase activity of EcoK on hemi-methylated recognition sites is strongly inhibited by 0.3 protein added at any stage of the reaction.

Antibody-mediated modulation of Cryptococcus neoformans infection is dependent on distinct Fc receptor functions and IgG subclasses

Coupling of an antibody response to effector cells through the Fc region of antibodies is a fundamental objective of effective vaccination. We have explored the role of the Fc receptor system in a murine model of Cryptococcus neoformans protection by infecting mice deleted for the common gamma chain of FcRs. Passive administration of an IgG1 mAb protects FcRgamma+/- mice infected with C. neoformans, but fails to protect FcRgamma-/- mice, indicating that the gamma chain acting through FcgammaRI and/or III is essential for IgG1-mediated protection. In contrast, passive administration of an IgG3 mAb with identical specificity resulted in enhanced pathogenicity in gamma chain-deficient and wild-type mice. In vitro studies with isolated macrophages demonstrate that IgG1-, IgG2a-, and IgG2b-opsonized C. neoformans are not phagocytosed or arrested in their growth in the absence of the FcRgamma chain. In contrast, opsonization of C. neoformans by IgG3 does not require the presence of the gamma chain or of FcRII, and the internalization of IgG3-treated organisms does not arrest fungal growth.

CCAAT/enhancer-binding protein-delta (C/EBP-delta) is induced in growth-arrested mouse mammary epithelial cells

CCAAT/enhancer binding proteins (C/EBPs) are a highly conserved family of DNA-binding proteins that regulate cell growth and differentiation in a highly tissue-specific manner. These experiments investigated the influence of the cell cycle on C/EBP isoform expression in mammary epithelial cells (COMMA D) and fibroblasts (NIH3T3). C/EBP-delta gene expression is induced in COMMA D cells arrested in G0 by serum and growth factor withdrawal or contact inhibition. C/EBP-delta mRNA, nuclear protein content, and DNA binding activity increase during G0 growth arrest and decrease after cell cycle induction in COMMA D cells. Growth arrest is markedly delayed in COMMA D cells expressing a C/EBP-delta antisense construct. C/EBP-beta is induced during G1 of the cell cycle. In contrast to COMMA D cells, C/EBP-beta and C/EBP-delta mRNA levels remain relatively constant in growth-arrested and cell cycle-induced NIH3T3 cells. However, C/EBP homologous protein (CHOP10) mRNA levels markedly increase in growth-arrested NIH3T3 cells. Both COMMA D and NIH3T3 cells express growth arrest-specific (gas1) and JunD during G0. These results demonstrate that COMMA D and NIH3T3 cells achieve a common growth arrest (G0) state by cell-specific strategies that involve the induction of different C/EBP isoforms.

Prediction of the rate of decline in FEV(1) in smokers using quantitative Computed Tomography

BACKGROUND

A study was undertaken to determine if quantitative CT estimates of lung parenchymal overinflation and airway dimensions in smokers with a normal forced expiratory volume in 1 s (FEV(1)) can predict the rapid decline in FEV(1) that leads to chronic obstructive pulmonary disease (COPD).

METHODS

Study participants (n = 143; age 45-72 years; 54% male) were part of a lung cancer screening trial, had a smoking history of >30 pack years and a normal FEV(1) and FEV(1)/forced vital capacity (FVC) at baseline (mean (SD) FEV(1) 99.4 (12.8)%, range 80.2-140.7%; mean (SD) FEV(1)/FVC 77.9 (4.4), range 70.0-88.0%). An inspiratory multislice CT scan was acquired for each subject at baseline. Custom software was used to measure airway lumen and wall dimensions; the percentage of the lung inflated beyond a predicted maximal lung inflation, the low attenuation lung area with an x ray attenuation lower than -950 HU and the size distribution of the overinflated lung areas and the low attenuation area were described using a cluster analysis. Multiple regression analysis was used to test the hypothesis that these CT measurements combined with other baseline characteristics might identify those who would develop an excessive annual decline in FEV(1).

RESULTS

The mean (SD) annual change in FEV(1) was -2.3 (4.7)% predicted (range -23.0% to +8.3%). Multiple regression analysis revealed that the annual change in FEV(1)%predicted was significantly associated with baseline percentage overinflated lung area measured on quantitative CT, FEV(1)% predicted, FEV(1)/FVC and gender.

CONCLUSION

Quantitative CT scan evidence of overinflation of the lung predicts a rapid annual decline in FEV(1) in smokers with normal FEV(1).

FDA evaluations using in vitro metabolism to predict and interpret in vivo metabolic drug-drug interactions: impact on labeling

Recent advances in in vitro metabolism methods have led to an improved ability to predict clinically relevant metabolic drug-drug interactions. To address the relationships of in vitro metabolism data and in vivo metabolism outcomes, the Office of Clinical Pharmacology and Biopharmaceutics in the Center for Drug Evaluation and Research, Food and Drug Administration, evaluated a number of recently approved new drug applications. The goal of these evaluations was to determine the contribution of in vitro metabolism data in (1) predicting in vivo drug-drug interactions, (2) determining the need to conduct an in vivo drug-drug interaction study, and (3) incorporating findings into drug product labeling. Ten cases are presented in this article. They fall into two major groups: (1) in vitro data were predictive of in vivo results, and (2) in vitro data were not predictive of in vivo results. Discussion of these cases highlights factors limiting predictability of in vivo metabolic interactions from in vitro metabolism data. The integration of these findings into drug product labeling is also discussed.

Mutant BRCA1 genes antagonize phenotype of wild-type BRCA1

Unregulated expression of wild-type BRCA1 (wtBRCA1) confers an altered phenotype in cultured human prostate cancer cells, characterized by chemosensitivity, susceptibility to apoptosis, decreased DNA repair activity, and alterations of key cell regulatory proteins. We now report that the expression of truncated or mutant full-length BRCA1 genes can abrogate certain phenotypic characteristics and/or confer the opposite phenotype to the wild-type BRCA1 gene. In particular, several carboxyl-terminal truncated BRCA1 proteins conferred chemoresistance, decreased susceptibility to apoptosis, and decreased ability to suppress in vivo tumor growth. These truncated BRCA1 proteins also blocked the ability of ectopically expressed wtBRCA1 to induce chemosensitivity and to inhibit estrogen receptor transcriptional activity. Studies using epitope-tagged truncated proteins confirmed their expression, nuclear localization, and functionality. On the other hand, in cells with no endogenous wild-type BRCA1 (HCC1937 human breast cancer cells), the wtBRCA1 gene enhanced cellular DNA repair activity and rendered the cells resistant to DNA damage; while truncated BRCA1 proteins blocked the wtBRCA1-induced chemoresistance. Our findings suggest that truncated BRCA1 proteins can inhibit the function of wild-type BRCA1. They raise the possibility that some inherited BRCA1 mutations may actively promote oncogenesis by blocking the function of the remaining wild-type BRCA1 allele, although this hypothesis remains to be proved.

Novel potentiometric immunosensor for hepatitis B surface antigen using a gold nanoparticle-based biomolecular immobilization method

A novel potentiometric immunosensor for the detection of hepatitis B surface antigen has been developed by means of self-assembly to immobilize hepatitis B surface antibody on a platinum disk electrode based on gold nanoparticles, Nafion, and gelatin as matrices in this study. The modification procedure of the immunosensor was further characterized by using cyclic voltammetry and the enzyme-linked immunosorbent assay (ELISA) method. The detection is based on the change in the electric potential before and after the antigen-antibody reaction. In contrast to the commonly applied methods (e.g., the glutaraldehyde crosslinking procedure), this strategy could allow for antibodies immobilized with a higher loading amount and better retained immunoactivity, as demonstrated by the potentiometric measurements. A dynamic concentration range of 4-800 ng ml(-1) and a detection limit of 1.3 ng ml(-1) were observed. Analytical results of several human serum samples obtained using the developing technique are in satisfactory agreement with those given by ELISA. In addition, the technique presents some distinct advantages over the traditional sandwich format in that the analyzing performances are direct, rapid, and simple without multiple separation and labeling steps.

Highly selective iodide poly(vinyl chloride) membrane electrode based on a nickel(II) tetraazaannulene macrocyclic complex

A PVC membrane electrode based on a nickel(II) tetraazaannulene macrocyclic complex as the carrier is described. The electrode exhibits an anti-Hofmeister selectivity sequence with a preference for iodide at pH 3.0-4.0. It has a linear response to iodide from 8.0 x 10(-6) to 1 x 10(-1) mol dm-3 with a slope of -54.7 +/- 0.2 mV per decade (20 degrees C), a satisfactory reproducibility and a rapid response time. The pH dependence of the potential response is discussed. The response mechanism of the electrode was investigated by ac impedance, quartz crystal microbalance and spectroscopic techniques. The electrode can be used for the determination of iodide in drug preparations.

Immunoglobulin G3 blocking antibodies to the fungal pathogen Cryptococcus neoformans

Vaccination and infection can elicit protective and nonprotective antibodies to the fungus Cryptococcus neoformans in mice. The effect of nonprotective antibodies on host defense is unknown. In this study we used mixtures of protective and nonprotective monoclonal antibodies (mAbs) to determine if nonprotective mAbs blocked the activity of the protective mAbs. Antibody isotype and epitope specificity are important in determining the ability to prolong survival in mice given a lethal C. neoformans infection. Three different nonprotective immunoglobulin (Ig) G23 mAbs to cryptococcal capsular polysaccharide were used to study the interaction between the IgG3 isotype and protective IgG1 and IgG2a mAbs in murine cryptococcal infection. One IgG3 mAb reduced the protective efficacy of an IgG1 with identical epitope specificity. A second IgG3 mAb with different epitope specificity also reduced the protection provided by the IgG1 mAb. The protective efficacy of an IgG2a mAb was also dramatically decreased by still another IgG3 mAb. To our knowledge this is the first report of blocking antibodies to a fungal pathogen. The results have important implications for the development of vaccines and passive antibody therapy against C. neoformans.

Effect of chronic renal failure on the disposition of highly hepatically metabolized drugs

OBJECTIVE

The objective of this study was to investigate the effect of renal impairment on the disposition of an extensively metabolized drug, i.e., drug X. Drug X has a hepatic extraction ratio of less than 0.1 and free fraction in plasma of less than 1% in healthy volunteers.

METHODS

Pharmacokinetic (PK) parameters of drug X were obtained from subjects with normal renal function (I, n = 6), as well as in subjects with mild (II, n = 5), moderate (III, n = 7) and severe renal impairment (IV, n = 5). Disease-PK models were developed to describe the changes of PK parameters with respect to renal function measured by creatinine clearance. While experimentally observed data are presented for drug X, additional simulations were performed for other drugs that are extensively metabolized (extensive metabolism is defined as metabolism that accounts for more than 90% of total drug elimination). The simulated scenarios included drugs that have a low extraction ratio (ER) and with high plasma protein binding (PPB), low ER and with low PPB, high ER and with high PPB, or high ER and with low PPB.

RESULTS

Systemic clearance of drug X, a low ER and high PPB drug, in renal patients depended on the simultaneous effects of renal disease on protein binding and intrinsic metabolic clearance. Protein binding of drug X was related to creatinine clearance in an inverse hyperbolic relationship, while the unbound intrinsic metabolic clearance declined linearly with creatinine clearance. Because the disease effects on these two factors offset each other in terms of total systemic clearance, the lowest total systemic clearance was not observed in the severely renal impairment patients, but rather in the moderately impaired group. Additional simulations showed that for low ER drugs that are highly metabolized, the pattern and magnitude of systemic clearance change in renal patients depended on how the disease affected PPB and/or intrinsic metabolic clearance. But the systemic clearance of high ER drugs would not be as susceptible to the effect of renal disease as that of low ER drug.

CONCLUSIONS

Chronic renal disease should not be considered as an isolated event that affects only renally excreted drugs. Uremia may also modify the disposition of a highly metabolized drug by changes in plasma protein binding and/or hepatic metabolism.