Computational models on quantitative prediction of bioactivity of HIV-1 integrase 3' processing inhibitors

In this study, four computational quantitative structure-activity relationship (QSAR) models were built to predict the bioactivity of 3' processing (3'P) inhibitors of HIV-1 integrase. Some 453 inhibitors whose bioactivity values were detected by the radiolabelling method were collected. The molecular structures were represented with MOE descriptors. In total, 21 descriptors were selected for modelling. All inhibitors were divided into a training set and a test set with two methods: (1) by a Kohonen's self-organizing map (SOM); (2) by a random selection. For every training set and test set, a multilinear regression (MLR) analysis and a support vector machine (SVM) were used to establish models, respectively. For the training/test set divided by SOM, the correlation coefficients (r) were over 0.84, and for the training/test set split randomly, the r values were over 0.86. Some molecular properties such as hydrogen bond donor capacity, atomic partial charge properties, molecular refractivity, the number of aromatic bonds and molecular surface area, volume and shape properties played important roles for inhibiting 3' processing step of HIV-1 integrase.

Cholesterol oxidase from Bordetella species promotes irreversible cell apoptosis in lung adenocarcinoma by cholesterol oxidation

Cholesterol oxidase (COD), an enzyme catalyzing the oxidation of cholesterol, has been applied to track the distribution of membrane cholesterol. Little investigations about the effect of COD on tumor cells have been performed. In the present study, we provided evidence that COD from Bordetella species (COD-B), induced apoptosis of lung cancer cells in vitro and in vivo. COD-B treatment inhibited Akt and ERK1/2 phosphorylation in dose- and time-dependent manner, which was not reversed and was even aggravated by cholesterol addition. Further investigation indicated that COD-B treatment promoted the generation of reactive oxygen species (ROS) and that cholesterol addition further elevated ROS levels. Moreover, COD-B treatment resulted in JNK and p38 phosphorylation, downregulation of Bcl-2, upregulation of Bax, activated caspase-3 and cytochrome C release, which likely responded to freshly produced hydrogen peroxide that accompanied cholesterol oxidation. Catalase pretreatment could only partially prevent COD-B-induced events, suggesting that catalase inhibited H₂O₂-induced signal transduction but had little effect on signal pathways involved in cholesterol depletion. Our results demonstrated that COD-B led to irreversible cell apoptosis by decreasing cholesterol content and increasing ROS level. In addition, COD-B may be a promising candidate for a novel anti-tumor therapy.

Molecular basis for the regulation of islet beta cell mass in mice: the role of E-cadherin

AIMS/HYPOTHESIS

In rodents and humans, the rate of beta cell proliferation declines rapidly after birth; formation of the islets of Langerhans begins perinatally and continues after birth. Here, we tested the hypothesis that increasing levels of E-cadherin during islet formation mediate the decline in beta cell proliferation rate by contributing to a reduction of nuclear β-catenin and D-cyclins.

METHODS

We examined E-cadherin, nuclear β-catenin, and D-cyclin levels, as well as cell proliferation during in vitro and in vivo formation of islet cell aggregates, using β-TC6 cells and transgenic mice with green fluorescent protein (GFP)-labelled beta cells, respectively. We tested the role of E-cadherin using antisense-mediated reductions of E-cadherin in β-TC6 cells, and mice segregating for a beta cell-specific E-cadherin knockout (Ecad [also known as Cdh1] βKO).

RESULTS

In vitro, pseudo-islets of β-TC6 cells displayed increased E-cadherin but decreased nuclear β-catenin and cyclin D2, and reduced rates of cell proliferation, compared with monolayers. Antisense knockdown of E-cadherin increased cell proliferation and levels of cyclins D1 and D2. After birth, beta cells showed increased levels of E-cadherin, but decreased levels of D-cyclin, whereas islets of Ecad βKO mice showed increased levels of D-cyclins and nuclear β-catenin, as well as increased beta cell proliferation. These islets were significantly larger than those of control mice and displayed reduced levels of connexin 36. These changes correlated with reduced insulin response to ambient glucose, both in vitro and in vivo.

CONCLUSIONS/INTERPRETATION

The findings support our hypothesis by indicating an important role of E-cadherin in the control of beta cell mass and function.

Insulin receptor and IGF1R are not required for oocyte growth, differentiation, and maturation in mice

In mammals, insulin and insulin-like growth factors (IGFs: IGF1 and IGF2) act through 2 structurally related receptors, the insulin receptor (INSR) and the type 1 IGF receptor (IGF1R), both of which are expressed in developing oocytes. IGF1 plays an important role in female reproduction, and female Igf1 knockout mice fail to ovulate and are infertile. On the other hand, little is known about the in vivo role of the insulin signaling pathway in oocytes during follicular development, although exposure to insulin or IGF1 in vitro improves oocyte maturation. To further address the significance of insulin/IGF signaling, we used conditional mutant mice and ablated the function of the genes encoding INSR, IGF1R, or both receptors specifically in developing mouse oocytes. Our genetic evidence showed unexpectedly that the female reproductive functions are not affected when Insr, Igf1r or both Insr;Igf1r are ablated in oocytes, as the female mice are fertile and exhibit normal estrous cyclicity, oocyte development and maturation, parturition frequency, and litter size. In view of these novel observations indicating that the insulin/IGF signaling is not essential in oocytes, the IGF1-dependent female fertility is re-evaluated and discussed.

BF-1 interferes with transforming growth factor beta signaling by associating with Smad partners

The winged-helix (WH) BF-1 gene, which encodes brain factor 1 (BF-1) (also known as foxg1), is essential for the proliferation of the progenitor cells of the cerebral cortex. Here we show that BF-1-deficient telencephalic progenitor cells are more apt to leave the cell cycle in response to transforming growth factor beta (TGF-beta) and activin. We found that ectopic expression of BF-1 in vitro inhibits TGF-beta mediated growth inhibition and transcriptional activation. Surprisingly, we found that the ability of BF-1 to function as a TGF-beta antagonist does not require its DNA binding activity. Therefore, we investigated whether BF-1 can inhibit Smad-dependent transcriptional responses by interacting with Smads or Smad binding partners. We found that BF-1 does not interact with Smads. Because the identities of the Smad partners mediating growth inhibition by TGF-beta are not clearly established, we examined a model reporter system which is known to be activated by activin and TGF-beta through Smads and the WH factor FAST-2. We demonstrate that BF-1 associates with FAST-2. This interaction is dependent on the same region of protein which mediates its ability to interfere with the antiproliferative activity of TGF-beta and with TGF-beta-dependent transcriptional activation. Furthermore, the interaction of FAST-2 with BF-1 is mediated by the same domain which is required for FAST-2 to interact with Smad2. We propose a model in which BF-1 interferes with transcriptional responses to TGF-beta by interacting with FAST-2 or with other DNA binding proteins which function as Smad2 partners and which have a common mode of interaction with Smad2.

Conditional mutagenesis in mice with heat shock promoter-driven cre transgenes

To explore the potential of a simple and rapid approach for ubiquitous conditional gene disruption, we have generated Cre-producer mouse transgenic lines (Hs-cre1, 6 and 7) expressing a recombinase transgene (cre) from a heat shock gene promoter and tested their performance in Cre-mediated excision of target DNA in crosses with Cre-responder strains carrying loxP-modified alleles of the genes encoding the Huntington's disease gene homolog (Hdh), the epidermal growth factor receptor (Egfr), and the type 1 insulin-like growth factor receptor (Igf1r). Analyses of progeny possessing various transgene/reporter combinations showed that cre expression can occur without heat shock in early embryos, but this constitutive transcription is stochastic and transgene dependent. Thus, Hs-cre1 behaves predominantly as a "deleter" strain, since the majority of progeny (approximately 70-85%) exhibit complete recombination, regardless of reporter locus. Lines Hs-cre6 and Hs-cre7, however, function successfully as "mosaicking" strains because, in addition to two extreme classes of progeny with 0% or 100% recombination, they generate an intermediate class of mosaics exhibiting various degrees of partial DNA excision. Notably, the frequency of offspring in each class varies between reporters, but mosaic embryos are consistently obtained in adequate numbers (approximately 30-60%). The Hs-cre6 transgene is also inducible and can be used to introduce mosaicism into adult tissues at preselected developmental times by heat shock treatment of mice with 0% recombination in tail DNA. By bypassing the lethality resulting from some gene knockouts, mosaic embryos and mice make particular mutational analyses possible and are also very useful for the identification of cell lineage-specific gene functions.

Screening mammography: experience in a health maintenance organization

PURPOSE

To evaluate (a) the relationship between mammogram interpretation and diagnosis of new breast cancer and (b) interprovider variation in mammogram interpretation.

MATERIALS AND METHODS

Interpretations of screening mammograms (133,668 mammograms in 114,899 women) acquired during 21 months in a large health maintenance organization were categorized (categories 1-5) with use of a standard format. During 1 year after mammography, new breast cancer was identified with use of claims data. Interprovider variation in the categories read was evaluated, and percentages of these categories were correlated with breast cancer detection.

RESULTS

Over the 21 months, 1,018 mammograms were followed by a diagnosis of new breast cancer. The category of mammogram interpretation was strongly associated with the diagnosis of new breast cancer; in 47.5% cases of category 5 mammograms, breast cancer was diagnosed. There was substantial interprovider variation in the percentages of category 3, 4, or 5 mammograms read. The percentage of category 4 and 5 mammograms read correlated inversely with the likelihood of cancer detection (Pearson correlation coefficient [r] = -.4778 after log-log transformation, P < .001).

CONCLUSION

A strong correlation existed between a mammographic abnormality suggestive of cancer and its detection; however, substantial interprovider variation in the reading of category 3, 4, and 5 mammograms and their positive predictive values existed. Reduction of interprovider variation should improve quality of care because the number of false-negative and false-positive mammograms should decrease.

Winged helix transcription factor BF-1 is essential for the development of the cerebral hemispheres

We generated mice with a null mutation of the forebrain-restricted transcription factor BF-1 to examine its function in brain development. Heterozygous animals have an apparently normal phenotype. Homozygous null BF-1 mutants die at birth and have a dramatic reduction in the size of the cerebral hemispheres. The development of the ventral telencephalon is more severely affected than that of the dorsal telencephalon. Telencephalic neuroepithelial cells are specified in the BF-1 mutant, but their proliferation is reduced. Dorsal telencephalic neuroepithelial cells also differentiate prematurely, leading to early depletion of the progenitor population. These results suggest that BF-1 controls the morphogenesis of the telencephalon by regulating the rate of neuroepithelial cell proliferation and the timing of neuronal differentiation.

Alteration of immune responses of rabbits infected with bovine immunodeficiency-like virus

Nine 3-month-old rabbits were inoculated with bovine immunodeficiency-like virus (BIV) to study the pathogenesis of BIV and alteration of the immune responses in experimentally infected rabbits. BIV proviral DNA and anti-BIV antibodies were detected from all rabbits inoculated with BIV-infected bovine embryo spleen (BESP) cells. Rabbits inoculated with spleen cells of the BIV-infected rabbit also converted to proviral DNA-positive and BIV-antibody-positive. The blastogenic responses to concanavalin A of peripheral blood mononuclear cells prepared from BIV-infected rabbits were not significantly different from those from uninfected controls at 2 and 4 months post-inoculation (PI). The humoral immune responses against bovine serum albumin (BSA) were depressed in two of four BIV-infected rabbits at 1 to 3 months PI. The antibody responses against sheep red blood cells (SRBCs) were significantly depressed in all BIV-infected rabbits at 2 to 4 months PI. BIV was rescued by cocultivation of spleen cells of infected rabbits with BESP cells. Distinct development of lymphoid follicle was observed in lymph nodes and spleens of uninfected rabbits which received BSA and SRBCs. In contrast, moderate lymphoid cell depletion was observed in BIV-infected rabbits which received the same immunogens.