In vivo characterization of progestins with reduced non-genomic activity in vitro.

Postmenopausal women that still have an uterus and suffer from hot flushes are treated with combinations of estrogens and progestins. Whereas estrogens are indispensable for treating postmenopausal symptoms, progestins are added to counteract the proliferative activity of estrogens on uterine epithelial cells. However, in the mammary gland, progestins, given together with estrogens, stimulate the proliferation of mammary epithelial cells. Therefore, progestins with reduced proliferative activity in the mammary gland would be of advantage for hormone therapy of postmenopausal women. In order to identify progestins with better tissue-selectivity, we exploited the activation of different signal transduction pathways by the classical progesterone receptor. We demonstrated that progestins with reduced non-genomic versus genomic activity in vitro show a better dissociation of uterine versus mammary gland effects in vivo than medroxyprogesterone acetate (MPA), a synthetic progestin that is widely used in hormone therapy.

Ligand mediated activation of ectopic EGF receptor promotes matrix protein adhesion and lung colonization of rat mammary adenocarcinoma cells.

Increased expression of EGF receptor (EGFR) in metastases of human mammary carcinoma as compared to cells of the primary cancer suggests a contribution of EGFR to mammary carcinoma metastasis. To test for a positive causative link, we investigated 13762NF rat mammary adenocarcinoma cloned tumor cell lines of high (MTLn3) or low (MTC) metastatic potential. While MTC cells expressed barely detectable amounts of EGFR, MTLn3 cells expressed readily detectable levels of functional receptors. A full length cDNA of the human EGFR (HER) was introduced by infection with a retroviral vector into MTC cells. Expression of HER was stable and receptors were functional with respect to surface expression, ligand binding and EGF-stimulated phosphorylation. Independent clones of the transfectants were isolated and characterized. Ligand stimulation of MTC HER cells and derived clones led to enhanced adhesion of cells to extracellular matrix proteins. Implantation of cells intravenously into female nu/nu mice revealed ligand-dependent enhancement of lung colonizing potential of EGFR-expressing cells.

EGF enhances attachment of metastatic rat mammary adenocarcinoma cell clone MTLn3 to fibronectin and collagen.

Attachment of highly metastatic rat mammary adenocarcinoma MTLn3 cells to matrix proteins and its modulation by EGF was examined. Plastic plates were coated with varying amounts of collagen or fibronectin. MTLn3 cells exhibited a dose-dependent adhesion to both matrix proteins, however, they attached more efficiently to collagen than to fibronectin. When EGF or TGF alpha were added at 0.3 to 10 ng/ml for 30 min, a dose-dependent increase in adhesion to both matrix proteins was observed. Maximal stimulation (2-fold) was seen with 10 ng/ml of either growth factor. However, EGF was more potent at lower concentrations (0.3-3 ng/ml) than TGF alpha. The ability of growth factors to stimulate adhesion was also dependent on the amount of matrix the cells were exposed to. While EGF increased rapid attachment of MTLn3 cells to both matrix proteins similarly, subsequent cell spreading and formation of lamellar extensions was faster in cells plated on collagen. These results are suggestive of a functional link between EGF receptor and specific integrin activities.

Muramyl dipeptide inhibits replication of human immunodeficiency virus in vitro.

In the search for compounds capable of inducing endogenous production of colony-stimulating factor (CSF) and possessing activity against human immunodeficiency virus (HIV), an immunomodulator, muramyl dipeptide (MDP), was investigated. MDP can enhance monocyte-macrophage CSF in serum and promote nonspecific resistance against a variety of microbial pathogens. MDP exhibited an inhibitory activity against HIV infection of CD4+ H9 lymphocytes and U937 monocytoid cells. An inhibitor of viral reverse transcriptase, 2', 3'-dideoxyadenosine, produced potent inhibition in cultures which were similarly infected with HIV. MDP could partially reduce antigen production in persistently HIV-infected KE37/1 lymphocyte cultures.

Exacerbation of human immunodeficiency virus infection in promonocytic cells by bacterial immunomodulators.

Common bacterial infections are increasingly being diagnosed in HIV-infected individuals. Cells of the monocyte-macrophage lineage kill invading bacterial pathogens and subsequently release immunoadjuvant components from the degraded cell walls. Since monocytes can be infected with HIV, effects of bacterial immunomodulators on infected promonocytic U937 cells were investigated. Synthetic muramyl peptide, mycobacterial trehalose dimycolate, and detoxified endotoxin exhibited an initial reduction followed by a rapid increase in HIV p24 antigen production. The upregulation of virus expression was correlated with enhanced interleukin-1 beta levels and a decrease in TNF-alpha production.

Modulation of natural killer cytotoxicity by muramyl dipeptide and trehalose dimycolate incorporated in squalane droplets.

The effect on natural killer (NK) cytotoxicity of splenic cells from BALB/c mice pretreated i.v. with squalane-in-water preparations of muramyl dipeptide (MDP), trehalose dimycolate (TDM), or the combination of MDP-plus-TDM was investigated. MDP or TDM augmented the NK cytotoxicity which peaked 48 h after the pretreatment whereas the combination of MDP and TDM induced an inhibition of the NK activity. Infection with influenza virus, a potent stimulator of NK cells, after the pretreatment with biological response modifiers resulted in a markedly enhanced NK activity on day 2 in MDP and control groups. Mice pretreated with TDM or the combination of MDP and TDM showed only moderate NK activity which peaked on day 3 after influenza infection. The NK activity was susceptible to asialo GM1 and complement treatment. The cytotoxicity of MDP-plus-TDM cells could be significantly enhanced after treatment with anti-macrophage monoclonal antibody and complement. NK activity induced by MDP or TDM was reduced by mixing MDP-plus-TDM cells. Addition of adherent cell-depleted MDP-plus-TDM suspension to MDP or TDM cells had a NK restorative effect. Splenic cells from mice pretreated 2 days earlier with MDP or TDM, but not MDP-plus-TDM, generated enhanced levels of luminol-dependent chemiluminescence.

Depressed chemiluminescence response by influenza virus is enhanced after conjugation of viral subunits to muramyl dipeptide.

The effect on respiratory burst of murine spleen cells after in vitro exposure to influenza virus, subunits, or subunits conjugated to muramyl dipeptide (MDP) was studied by luminol-dependent chemiluminescence (CL) in response to stimulation by zymosan. CL induced by infectious influenza A virus was depressed but could be elevated to normal levels when MDP was added together with a low, but not with a high, dose of the virus. Profound depression of CL was induced by high doses of influenza A/Brazil, A/Bangkok, and B/Singapore subunits. The same amounts of viral subunits conjugated to MDP restored or even enhanced the CL responses of spleen cells from BALB/c and C57BL/6 mice. Splenic cells from BALB/c mice generated higher levels of CL than did cells from C57BL/6 mice.