Regulation of tissue factor gene expression in epithelial cells. Induction by serum and phorbol 12-myristate 13-acetate

Cell-specific expression of tissue factor (TF) in vivo is consistent with its primary role in hemostasis. In addition, TF expression is induced in cultured cells by a variety of agents, including serum and growth factors, which define the TF gene as a "primary response" gene. In this study we examined the signaling pathways and cis-acting regulatory elements required for induction of TF gene expression in HeLa cells in response to serum and the tumor promoter, phorbol 12-myristate 13-acetate (PMA). TF activity and mRNA were induced greater than sixfold in quiescent HeLa cells by serum and PMA. TF mRNA induction by both agonists required intracellular Ca2+ mobilization, whereas inhibition of protein kinase C abolished induction of the TF gene by PMA but had no effect on induction by serum. Functional studies demonstrated that a region of the human TF promoter between -96 and +121 bp contained regulatory elements required for serum and PMA induction. These data indicate that different signaling pathways regulate TF gene expression in response to serum and PMA, although the same cis-acting DNA elements may mediate induction.     

Inhibition of the tumor promoting action of 12-O-tetradecanoylphorbol-13-acetate by tubeimoside III isolated from Bolbostemma paniculatum

As tubeimoside I isolated from Bolbostemma paniculatum (Maxim.) Franquet (Cucurbitaceae) has been shown to suppress tumor promoter effects, tubeimoside III from the same plant was tested in vitro and in vivo against the action of the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Tubeimoside III, the natural analog of tubeimoside I, also had an anti-inflammatory effect on mouse ear edema induced by arachidonic acid and TPA and a potent anti-tumor promoting effect on two-stage carcinogenesis of mouse skin after topical application. However, the important difference in bioactivities between tubeimosides I and III is the non-activity of tubeimoside III as an inhibitor of tumor promotion if administered orally. Differences in metabolism connected with different routes of the compound may be one of a number of explanations of the important difference.     

Effect of intravenous infusions of 12-O-tetradecanoylphorbol-13-acetate (TPA) in patients with myelocytic leukemia: preliminary studies on therapeutic efficacy and toxicity

Studies by several investigators have shown that 12-0-tetradecanoylphorbol-13-acetate (TPA) is an extraordinarily potent stimulator of differentiation of cultured human promyelocytic leukemia cells in vitro. In the present study, TPA was administered to humans by i.v. infusion without irreversible toxicity, and it was shown to have pharmacological activity for the treatment of myelocytic leukemia in patients refractory to cytosine arabinoside (Ara C), retinoic acid, and other antileukemic drugs. Marked decreases in bone marrow myeloblasts as well as temporary remission of disease symptoms were observed when TPA was administered alone or in combination with vitamin D3 and Ara C. Additional studies with TPA after the determination of optimum dosing regimens are needed to determine whether long-lasting or permanent remissions of myelocytic leukemia can be achieved. Transient and reversible side effects were observed after a 1-mg i.v. dose of TPA, but these adverse effects became less intense or disappeared when a lower dose of TPA was used. The results of this study indicate a therapeutic effect of TPA in patients with myelocytic leukemia.     

Inhibition of phorbol ester tumor promoter 12-O-tetradecanoylphorbol-13-acetate-caused inflammatory responses in SENCAR mouse skin by black tea polyphenols

Reversed-phase high-performance liquid chromatography (RP-HPLC) fractionation, monitored by liquid chromatography/electrospray mass spectrometry (LC/ESI-MS), led to the isolation of two new bioactive annonaceous acetogenins, rollidecin C (1) and rollidecin D (2), from the bioactive aqueous methanol fraction of the leaves of Rollinia mucosa (Annonaceae). The structures were confirmed by analyses of the 1H and 13C NMR data. In addition, a known adjacent bis-tetrahydrofuran (THF) acetogenin, desacetyluvaricin (3), was isolated from this plant for the first time utilizing the LC/ESI-MS monitoring approach. Compound 1 exhibited selective cytotoxicity toward the colon tumor cell line (HT-29), while 2 showed only borderline cytotoxicity in a panel of six human tumor cell lines.     

Induction of collagenase-3 (MMP-13) expression in human skin fibroblasts by three-dimensional collagen is mediated by p38 mitogen-activated protein kinase

Collagenase-3 (matrix metalloproteinase-13, MMP-13) is a recently identified human MMP with an exceptionally wide substrate specificity and restricted tissue-specific expression. Here we show that MMP-13 expression is induced in normal human skin fibroblasts cultured within three-dimensional collagen gel resulting in production and proteolytic activation of MMP-13. Induction of MMP-13 mRNAs by collagen gel was potently inhibited by blocking antibodies against alpha1 and alpha2 integrin subunits and augmented by activating antibody against beta1 integrin subunit, indicating that both alpha1 beta1 and alpha2 beta1 integrins mediate the MMP-13-inducing cellular signal generated by three-dimensional collagen. Collagen-related induction of MMP-13 expression was dependent on tyrosine kinase activity, as it was abolished by treatment of fibroblasts with tyrosine kinase inhibitors genistein and herbimycin A. Contact of fibroblasts to three-dimensional collagen resulted in simultaneous activation of mitogen-activated protein kinases (MAPKs) in three distinct subgroups: extracellular signal-regulated kinase (ERK)1 and ERK2, Jun N-terminal kinase/stress-activated protein kinase, and p38. Induction of MMP-13 expression was inhibited by treatment of fibroblasts with a specific p38 inhibitor, SB 203580, whereas blocking the ERK1,2 pathway (Raf/MEK1,2/ERK1,2) by PD 98059, a selective inhibitor of MEK1,2 activation potently augmented MMP-13 expression. Furthermore, specific activation of ERK1,2 pathway by 12-O-tetradecanoylphorbol-13-acetate markedly suppressed MMP-13 expression in dermal fibroblasts in collagen gel. These results show that collagen-dependent induction of MMP-13 in dermal fibroblasts requires p38 activity, and is inhibited by activation of ERK1,2. Therefore, the balance between the activity of ERK1,2 and p38 MAPK pathways appears to be crucial in regulation of MMP-13 expression in dermal fibroblasts, suggesting that p38 MAPK may serve as a target for selective inhibition of collagen degradation, e.g. in chronic dermal ulcers.     

Regulation of vascular endothelial growth factor (VEGF) expression is mediated by internal initiation of translation and alternative initiation of transcription

The growing amount of high quality molecular dynamics simulations generated using the latest methodological developments and force fields has led to a sharper understanding of the forces underlying the dynamics of biomolecular systems, as well as to stimulating insights into the structure and catalysis of nucleic acids. It is now clear that inclusion of long-range electrostatic interactions and of the aqueous and ionic environment is necessary for producing realistic and accurate simulations. Yet, many papers hint at a force field and protocol dependence of the results and thus contain the seeds for the future improvements that will be necessary for deepening our understanding of recognition phenomena and folding of nucleic acids.