摘要:

AbstractEpidermal growth factor (EGF) and transforming growth factor alpha (TGF-α) are ligands for the EGF-receptor and act as mitogens for a variety of tissues. TGF-α, in particular, has been implicated as an autocrine growth factor for several cancer cell lines. Over the last 10 years many groups have examined the structure-function relationships in EGF/TGF-αin attempts to develop antagonists or agonists. In this review the results of these studies are summarised and related to the three-dimensional structure of EGF/TGF-α. The dificulties associated with the purification and characterisation of analogues of EGF/TGF-αand with the biological assays are discussed. It is clear that these difficulties have, in some cases, led to apparently contradicting results. The available binding data indicate that the receptor interaction surface for EGF/TGF-αmight encompass one complete side of the molecule with a few strong binding determinants, in particular Arg41 and Leu47. The arginine at position 41 is the most critical residue and its full hydrogen-bonding capacity is needed for strong binding of EGF/TGF-αto the EGF-receptor. As this side of the molecule consists of residues from both the N- and C-terminal domain, it seems unlikely that agonists or antagonists can be developed on the basis of short peptides taken from the primary sequence. This concept is supported by the available binding and activity data.

ISSN:0897-7194    

DOI:10.3109/08977199409010997

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractMixed purine-pyrimidine oligodeoxynucleotides were designed to form collinear DNA triplexes with pyrimidine-rich elements in the EGFR gene promoter. Their effects as mediators of human epidermal growth factor receptor (EGFR) gene transcription and subsequent gene expression were evaluated using human squamous cell carcinoma (A431) and human glioma cell line (U251MG and U87MG). Gel shift analysis indicated that the oligonucleotide forms a collinear triplex within the duplex Sp-1 binding site. Anin vitroassay system revealed a correlation between triplex formation and the repression of EGFR transcription. We postulate that guanine residues are not always optimum in apposition to G-C pairs to form triple helices in the target. Site-specific oligodeoxynucleotides binding to a DNA duplex may serve as the basis for an alternative program of gene controlin vitro.

ISSN:0897-7194    

DOI:10.3109/08977199409010998

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractLeukaemia inhibitory factor (LIF) is a polyfunctional cytokine active on many cell types. We present here1H NMR studies on the solution properties and stability of MH35, a chimera of murine and human LIF which can be expressed at high levels inEscherichia coli, thus enabling efficient labelling of the protein with the stable isotopes13C and15N. MH35 has 85% sequence identity with human LIF and similar activity in biological assays. The1H chemical shifts of the 12 conserved aromatic residues and the pKavalues of the five conserved histidine residues in MH35 and human LIF are very similar. Temperature dependence studies indicate that both proteins are stable, with significant conformational changes occurring only above 70°C. These results show that these proteins have a similar overall structure and stability and that MH35 is therefore a suitable analogue of human LIF for structural studies in solution.

ISSN:0897-7194    

DOI:10.3109/08977199409010999

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractAngiogenesis is an essential component of endometrial regeneration after menses in preparation for implantation. Vascular endothelial growth factor (VEGF) is a secreted angiogenic peptide with mitogenic activity specific for endothelial and trophoblast cells. VEGF-immunoreactivity was detected in glandular epithelium throughout the menstrual cycle by immunohistochemistry, but, showed cyclic variation in the stroma and the blood vessels. During the early proliferative phase, strong staining was seen in the glandular epithelial cells while staining in the stroma was confined to a subpopulation of stromal cells and endometrial blood vessels appeared negative. In contrast, very intense staining of the endometrial stromal cells was seen in the mid proliferative endometrium possibly due to increased synthesis of VEGF by oestrogen. In the late proliferative endometrium, staining was seen in the endothelial cells and the perivascular stromal cells around the endometrial blood vessels. The greatest degree of immunostaining of stromal cells was observed in the mid to late proliferative endometrium. Throughout the secretory phase no staining was seen around the endometrial blood vessels and staining of endometrial stromal cells was confined to early secretory endometrium. In the late secretory endometrium only the glands were positive to VEGF antibody. The observed increase in the immunostaining of stroma suggests increased production of VEGF from early to mid and late proliferative endometrium which parallels the increase in the oestradiol levels in the proliferative phase of the menstrual cycle. It is proposed that VEGF may serve as a paracrine mediator of the effects of ovarian steroids on endometrial vascular development.

ISSN:0897-7194    

DOI:10.3109/08977199409011000

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractWe reported previously that MATLyLu rat prostate cancer cells engineered to overproduce transforming growth factorβ1 (TGFβ1) produce larger, more metastatic tumorsin vivo. We recognized that this ability of TGFβ1 to act as a positive modulator of prostate tumor behavior might be due to effects of TGFβ1 on the host and/or on the tumor cells. In this study we demonstrated that the cells themselves respond to endogenously produced TGFβ1, and that the adenylyl cyclase (AC)-cAMP pathway is affected. TGFβ1-overproducing cells had lower membrane AC activity, lower intracellular cAMP content, and a lower Gsαprotein level than did control cells. Prostate cancer cells were growth inhibited by 8-bromo-cAMP or forskolin, agents that elevate intracellular cAMP. Thus, TGFβ1 overproduction affects the phenotype of the tumor cells, deliberate activation of endogenously produced latent TGFβ1 is not required (indicating that the cells themselves are capable of activating latent TGFβ1), and TGFβ1 overproduction lowers the cellular concentration of the growth inhibitor cAMP. Therefore, TGFβ1 overproduction could affect tumor behaviorin vivoin part via a direct effect on the tumor cells.

ISSN:0897-7194    

DOI:10.3109/08977199409011001

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractHeparin and heparan sulfate proteoglycans (HSPGs) stabilize FGFs which belong to heparin-binding growth factors (HBGFs) on active conformation. They also strongly potentiate their mitogenic activity on many cell types, and protect them against thermal denaturation and enzymatic degradation. In the present work we have tested two heparin-like substances named mesoglycan and sulodexide obtained from bovine intestinal mucosal extracts. These products are used as heparin, in various of therapeutic fields such as atherosclerosis or antithrombotic therapy. The compositions of mesoglycan and sulodexide are partially known and include chondroitin, dermatan and heparan sulfate. We have shown that mesoglycan and sulodexide potentiated the mitogenic activity of FGF1 and FGF2. The magnitude of this effect was identical with that of heparin used as a control substance but at double concentration. Mesoglycan and sulodexide also exerted stabilizing and protective effects on FGFs for heat denaturation and enzymatic degradation. The suppression of the protective properties after heparinase treatment of mesoglycan and sulodexide indirectly demonstrated the presence of heparan sulfate which was shown to represent about 60% of the commercial products.

ISSN:0897-7194    

DOI:10.3109/08977199409011002

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor

摘要:

AbstractWe recently provided evidence that newborn rat olfactory bulb (OB) could be maintained in serum-free organ culture with combinations of insulin-like growth factor-I (IGF-I) and basic fibroblast growth factor (bFGF), both of which are locally synthesized. Des (1–3), or truncated, IGF-I is a potent analog of IGF-I isolated from rat and human brain. We proposed in this study to examine the effects of des (1–3) IGF-I on cell function, morphology and on neuronal and glial cell differentiation in our cultured OB model, using cell-specific immunostains for neurons (150 kDa neurofilament) and glial cells (glial fibrillary associated protein-GFAP). OB were cultured in Iscove's serum-free medium containing IGF-I or des (1–3) IGF-I both alone or in combination with bFGF. Dose dependent responses of14C amino acid uptake showed des (1–3) IGF-I to be 3–5 fold more potent than IGF-I with a half maximal response at about 20 ng/ml in comparison to 100 ng/ml of IGF-I. The maximum response to IGF-I +/- bFGF was seen at 150 ng/ml; a ten-fold higher dose of insulin +/- bFGF was required to achieve the same response.While morphology was close to fresh 6 day OB following culture with IGF-I (150 ng/ml) and bFGF (25 ng/ml), the substitution of des (1–3) IGF-I at 50 ng/ml markedly improved morphology. Neurons were identified following culture in IGF-I or bFGF alone, but showed greater organisation in the mitral layer following combined IGF-I/bFGF culture. However, in contrast to IGF-I (150 ng/ml), des (1–3) IGF-I (50 ng/ml) supported marked neuronal expression. Furthermore, when des (1–3) IGF-I (50 ng/ml) was substituted for IGF-I, in combination with bFGF, the pattern of enhanced neuronal expression in the mitral layer was very close to that seen in the fresh 6 day bulb, with dendrites projecting to the glomerular layer. In OBs treated with no growth factors, or either IGF-I, des (1–3) IGF-I or bFGF alone, glial expression was widespread and poorly organised, suggesting an injury response. In contrast, following treatment with combinations of bFGF with IGF-I or des (1–3) IGF-I, a more ordered, though enhanced glial response was seen in glomerular and granule cell layers.This study using an OB organ culture system suggests that des (1–3) IGF-I, which may be derived from brain, is a potent supporter of viability and differentiated cell growth and organisation in the newborn rat olfactory bulb.

ISSN:0897-7194    

DOI:10.3109/08977199409011003

出版商:Taylor&Francis    

年代:1994

数据来源: Taylor