The Role of Estrogen in the Development of Breast Cancer

Breast cancer is a hormone-dependent disease that relies on the mitogenic effect ofestrogen to increase tumorigenesis and tumor growth. Clinically significant levels ofestrogen-α receptor (ERα) expression are seen in 80% of human breast cancers,whereas progesterone receptor is expressed in 55% of human breast cancers. Thesedata are one of the bases for the development of endocrine therapy. Endocrinetherapy is therapy that targets the pathway and synthesis of estrogen, by blocking itvia receptors, reducing circulating levels of estrogen, or suppressing estrogensynthesis in the tissues of women diagnosed with breast cancer.

Evaluation of Cell Proliferation in Rat Mammary Glands Is Not Predictive of the Carcinogenic Potential of Insulin In Vivo

For nonclinical safety-assessment of insulin analogues in vivo, mitogenic effects are compared to that of human insulin. Besides histopathologic evaluation, this usually includes assessment of cell proliferation (CP) in mammary glands. Insulin analogue X10 is recommended as positive control, due to its known carcinogenic effect in rat mammary glands. Here, we discuss the mitogenic effect of insulin in vivo and use of X10 as positive control. We present results from 4 nonclinical rat studies evaluating effects of repeated dosing with insulin detemir (≤26 weeks) or degludec (52 weeks) in mammary glands. Studies included human insulin-dosed groups as comparators, CP, and histopathologic evaluation. One study included an X10-dosed group (26 weeks), another ≤3 weeks of dosing with X10 or human insulin evaluating effects of these comparators. Neither human insulin, insulin detemir, degludec, nor X10 induced mammary tumors or increased CP in the studies. The CP marker proliferating cell nuclear antigen varied within/between studies and was not correlated with the remaining markers or CP fluctuations during estrous cycle, whereas the other CP markers, Ki-67 and 5-bromo-2′-deoxyuridine (BrdU), correlated with estrous cycle changes and each other. In conclusion, we propose that the mitogenic effect of insulin in rat mammary glands is weak in vivo. Cell proliferation evaluation in nonclinical safety assessment studies is not predictive of the carcinogenic potential of insulin, thus, the value of including this end point is debatable. Moreover, X10 is not recommended as positive control, due to lack of proliferative effects. Typical CP markers vary greatly in quality, BrdU seemingly most reliable.

GalNAc-Specific Soybean Lectin Inhibits HIV Infection of Macrophages through Induction of Antiviral Factors

ABSTRACTAlthough it has been shown that some mannose-binding lectins (MBLs) exhibit significant activity against HIV infection, little is known about whetherN-acetylgalactosamine (GalNAc)-binding lectins have the ability to inhibit HIV infection. Here, we demonstrate that a soybean-derived lectin (SBL) with GalNAc-binding affinity could potently suppress HIV infection of macrophages in a dose-dependent fashion. Unlike the MBLs, which block HIV only through binding to the glycosylated envelope proteins (gp120 and gp41) of the virus, SBL inhibited HIV at multiple steps of the virus infection/replication cycle. SBL could activate the beta interferon (IFN-β)–STAT signaling pathway, resulting in the upregulation of a number of antiviral interferon-stimulated genes (ISGs) in macrophages. In addition, SBL treatment of macrophages induced the production of C-C chemokines, which bind to HIV entry coreceptor CCR5. Deglycosylation of cell surface galactosyl moieties or presaturation of GalNAc-binding capacity could compromise SBL-mediated induction of the antiviral factors. Furthermore, SBL exerted its anti-HIV activity in the low nanomolar range with no mitogenic effect on CD4+T cells, a major advantage in the development of SBL as a potential anti-HIV agent compared with MBLs. These data indicate a necessity to further investigate SBL as an alternative and cost-effective anti-HIV natural product.IMPORTANCEMannose-binding lectins (MBLs) can block the attachment of HIV to target cells and have been suggested as anti-HIV microbicides. However, the mitogenic effect of MBLs on CD4+T cells limits this potential in clinical settings. Lectins with galactose (Gal)- orN-acetylgalactosamine (GalNAc)-binding specificity are another important category of carbohydrate-binding proteins (CBP). Compared to high-mannose N-linked glycans, GalNAc-type glycans present much less in HIV gp120 or gp41 glycosylation. Here, we demonstrate that GalNAc-specific soybean lectin (SBL) triggers antiviral signaling via recognition of the cell surface galactosyl group of macrophages, which results in the suppression of HIV at multiple steps. More importantly, SBL has no mitogenic effect on the activation of CD4+T cells, a major advantage in the development of Gal/GalNAc-specific lectins as naturopathic anti-HIV agents.

A Negative Feedback Regulates The Flow Of Signal Through Akt/mTORC1/S6K1 Pathway

Several growth factors, cytokines, hormones activate PI3K/Akt pathway. Akt is a key node in this pathway and activates different downstream paths. One such path is Akt/mTORC1/S6K1 that controls protein synthesis, cell survival, and proliferation. Here we show that a negative feedback controls activation of S6K1 through this pathway. Due to this negative feedback, a sustained phospho-Akt signal generates a transient pulse of phospho-S6K1. We have created a mathematical model for this circuit. Analysis of this model shows that the negative feedback acts as a filter and preferentially allows a signal, with sharp and faster rise of phospho-Akt, to induce pronounced activation of S6K1. It blocks an input with a fast oscillation of phospho-Akt to flow through this path. We show that this negative feedback leads to differential activation of S6K1 by Insulin and Insulin-like Growth Factor 1. Such differential effect may explain the difference in the mitogenic effect of these two molecules.

Lectins of Erythrina poeppigiana and Erythrina steyermarkii (Leguminosae): charaderization and mitogenic effect

Las diferentes especies de Erythrina se encuentran ampliamente distribuidas en Costa Rica y se las conoce popularmente con el nombre de "poró". En el presente estudio, se seleccionaron dos especies: Erythrina poeppigiana y Erythrina steyermarkii. Se prepararon extractos de las semillas en solución tampón salina de fosfatos y se verificó la presencia de lectinas en ellos mediante la técnica de hemaglutinación, utilizando eritrocitos humanos. Se trató de demostrar un efecto selectivo de la hemaglutinación empleando eritrocitos de varias especies de mamíferos, específicamente de carnero, caballo y conejo. Solo los eritrocitos de conejo fueron aglutinados con la lectina de E. steyermarkii. El efecto hemaglutinante de las dos lectinas fue inhibido con los siguientes carbohidratos: D-galactosa, N-D-acetil galactosamina, D-Iactosa y Drafinosa. La lectina de E. steyermarkii también fue inhibida con L-rhamnosa. Las dos lectinas fueron aisladas por filtración en gel y cromatografia de afinidad, usando lactosa como ligando. Las fracciones que resultaron positivas se analizaron mediante la técnica de electroforesis en gel de poliacrilamida y duodecil sulfato de sodio (SDSPAGE). Con la filtración en gel y el SDS-PAGE, se comprobó que las dos lectinas tienen una masa molecular aparente de 50 kDa y. que están formadas por dos subunidades de 25 kDa, aproximadamente. Se buscó un efecto mitogénico en las dos lectÍnas y se encontró que sólo E. steyermarkii lo manifestaba sobre células mononucleares humanas aisladas de sangre periférica. Se determinó la estabilidad de las ¡eetinas en diferentes ámbitos de temperatura (4 a 100°C) y de pH (2 a 12 ). Las dos lectinas se mantuvieron estables en un rango de temperatura de 40 a 70°C y en un pH de 2 a 10.