Late signals are required for the stimulation of DNA synthesis in rat mammary fibroblasts by growth factors

1996 ◽  
Vol 16 (3) ◽  
pp. 249-263 ◽  
Author(s):  
Hai-Lan Chen ◽  
Philip S. Rudland ◽  
John A. Smith ◽  
David G. Fernig
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Dna Synthesis ◽  
Maximal Response ◽  
High Concentration ◽  
Initial Concentration ◽  
Maximal Stimulation ◽  
Epidermal Growth ◽  
Lag Period ◽  
Stimulation Of

Maximal stimulation of DNA synthesis in quiescent rat mammary (Rama) 27 fibroblasts is elicited by epidermal growth factor (EGF) or basic fibroblast growth factor (bFGF) 18 h after the initial addition of the growth factors-the ‘lag’ period. At maximally-stimulating concentrations, EGF and bFGF are interchangeable 9 h after their initial addition. When the initial concentration of growth factor is below that required to elicit a maximal response, it is possible to increase the level of DNA synthesis by increasing the concentration of growth factor 9 h after its initial addition. When the initial concentration of growth factor is high, substitution by a lower concentration of growth factor after 9 h allows a greater proportion of cells to synthesize DNA than would be expected from a continuous low dose of growth factor. Similar results are obtained when both the growth factor and its concentration are changed 9 h after the initial addition of growth factor. However, when EGF at a low concentration is substituted for a high concentration of EGF or bFGF the resulting increase in the levels of DNA synthesis is greater when EGF rather than bFGF is added for a second time. The half-life of the growth-stimulatory signals delivered by EGF and by bFGF 9 h after their initial addition is 1–2 h. These results suggest that to stimulate DNA synthesis: (i) EGF or bFGF must deliver a signal(s) continuously; (ii) the initial signals produced by EGF and bFGF are equivalent; (iii) the signals produced between 9–18 h by EGF may be different to those produced by bFGF.

Stimulation of intestinal epithelial cell proliferation in culture by growth factors in human and ruminant mammary secretions

1987 ◽  
Vol 113 (2) ◽  
pp. 285-290 ◽  
Author(s):  
A. N. Corps ◽  
K. D. Brown
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Intestinal Epithelial ◽  
Epithelial Cell Proliferation ◽  
Factor I ◽  
Maximal Stimulation ◽  
Igf I ◽  
Epidermal Growth ◽  
Dose Dependent ◽  
Stimulation Of

ABSTRACT Samples of human and ruminant mammary secretions stimulated the proliferation of rat intestinal epithelial (RIE-1) cells in culture. The stimulation was dose-dependent, and samples taken prepartum had greater potency than those taken after parturition. When various hormones and growth factors known to be present in milk were tested, only epidermal growth factor (EGF), insulin and insulin-like growth factor I (IGF-I) stimulated the proliferation of RIE-1 cells. IGF-I was effective at lower concentrations than insulin, and the maximal stimulation induced by each of these two polypeptides was greater than that induced by EGF. The maximal stimulation induced by samples of mammary secretions was similar to that induced by insulin or IGF-I. J. Endocr. (1987) 113, 285–290

scholarly journals Insulin Growth Factor-I and Epidermal Growth Factor Receptors Recruit Distinct Upstream Signaling Molecules to Enhance AKT Activation in Mammary Epithelial Cells

Endocrinology ◽  
2006 ◽  
Vol 147 (12) ◽  
pp. 6027-6035 ◽  
Author(s):  
Jodie M. Fleming ◽  
Gwenaëlle Desury ◽  
Tiffany A. Polanco ◽  
Wendie S. Cohick
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Dna Synthesis ◽  
Egf Receptor ◽  
Mammary Epithelial ◽  
Insulin Receptor Substrate ◽  
Phosphatidylinositol 3 Kinase ◽  
Mapk Activation ◽  
Igf I ◽  
Epidermal Growth

IGF-I and epidermal growth factor (EGF) stimulate both normal mammary epithelial cell (MEC) growth and tumorigenesis. Whereas both growth factors increase DNA synthesis in MECs, how they evoke a greater response in combination when they activate similar signaling pathways remains unknown. In the present study, we investigated the signaling pathways by which these mitogens act in concert to increase DNA synthesis. Only EGF activated the MAPK pathway, and no further increase in MAPK activation was observed when both mitogens were added together. Both growth factors activated the phosphatidylinositol-3 kinase pathway, and simultaneous treatment enhanced phosphorylation of both AKT and its downstream target, p70S6K. The enhanced activation of AKT was observed at multiple time points (5 and 15 min) and growth factor concentrations (2.5–100 ng/ml). IGF-I activated AKT via insulin receptor substrate-1 and p85, the regulatory subunit of phosphatidylinositol-3 kinase. Treatment with EGF had no effect on insulin receptor substrate-1; however, it activated the EGF receptor, SHC, and c-Src. EGF treatment caused the association of SHC with Grb2 and Gab2 with phospho-SHC, phospho-Gab1, Grb2, and p85. Interestingly, inhibition of Src activation blocked the ability of EGF, but not IGF-I, to activate AKT. This corresponded with a decrease in phosphorylation of the EGF receptor and its association with phospho-SHC as well as downstream signaling. Unexpectedly, inhibition of Src increased basal MAPK activation. This is the first study to show that EGF and IGF-I use separate upstream components within a given MEC line to enhance AKT phosphorylation, contributing to increased DNA synthesis.

scholarly journals Sustained increase in 1,2-diacylglycerol precedes DNA synthesis in epidermal-growth-factor-stimulated fibroblasts. Evidence for stimulated phosphatidylcholine hydrolysis

1990 ◽  
Vol 267 (2) ◽  
pp. 501-507 ◽  
Author(s):  
T M Wright ◽  
H S Shin ◽  
D M Raben
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Dna Synthesis ◽  
De Novo ◽  
Phospholipid Metabolism ◽  
Intracellular Signals ◽  
Mitogenic Signalling ◽  
Epidermal Growth ◽  
Hydrolysis Of

A property common to many growth factors is that they must be present for several hours before the commitment to DNA synthesis and cell division occurs. The intracellular signals that are relevant during this period are poorly defined. We examined the formation of 1,2-diacylglycerol in IIC9 fibroblasts after stimulation with epidermal growth factor (EGF), and found that the mass of this lipid remained elevated for at least four hours. The concentration-dependence of EGF-stimulated 1,2-diacylglycerol production and [3H]thymidine incorporation were similar. Studies of phospholipid metabolism strongly suggested that phosphatidylcholine was the source of the 1,2-diacylglycerol generated in response to EGF. EGF did not stimulate the hydrolysis of other phospholipids, including the phosphoinositides, nor did it increase synthesis de novo of 1,2-diacylglycerol. This pattern of sustained 1,2-diacylglycerol formation from phosphatidylcholine may be important in the mitogenic signalling of EGF and potentially other growth factors.

Growth factor stimulated cell proliferation is accompanied by an elevated labile intracellular pool of zinc in 3T3 cells

2002 ◽  
Vol 80 (8) ◽  
pp. 790-795 ◽  
Author(s):  
Shirley C Paski ◽  
Zhaoming Xu
Keyword(s):  
Cell Proliferation ◽  
Growth Factors ◽  
Growth Factor ◽  
Dna Synthesis ◽  
Cell Number ◽  
3T3 Cells ◽  
Intracellular Pool ◽  
Igf I ◽  
Epidermal Growth ◽  
Number Counts

Growth factors such as platelet-derived growth factor (PDGF), epidermal growth factor (EGF), and insulin-like growth factor-I (IGF-I) are required for quiescent 3T3 cells to proliferate, but zinc deprivation impairs IGF-I-induced DNA synthesis. We recently showed that labile intracellular pool of zinc is involved in cell proliferation. Our objective was to determine whether the labile intracellular pool of zinc plays a role in growth factor (PDGF, EGF, and IGF-I) - stimulated proliferation of 3T3 cells. Quiescent 3T3 cells were cultured in DMEM with or without growth factors. Labile intracellular pool of zinc, DNA synthesis, and cell proliferation were assessed using fluorescence microscopy, 3H-thymidine incorporation, and total cell number counts, respectively. After 24 h, growth factors stimulated DNA synthesis (24%) but not cell proliferation. After 48 h, growth factors stimulated both DNA synthesis (37%) and cell proliferation (89%). In response to growth factor stimulation, the labile intracellular pool of zinc was also elevated after 24 or 48 h of treatment. In summary, growth factor (PDGF, EGF, and IGF-I) - stimulated increase in DNA synthesis and cell proliferation were accompanied by an elevated labile intracellular pool of zinc in 3T3 cells. Since elevation of the labile intracellular pool of zinc occurred along with increased DNA synthesis, but cell proliferation remained unchanged, the elevation of the labile intracellular pool of zinc likely occurred during the S phase to provide the zinc needed to support DNA synthesis and ultimately cell proliferation.Key words: PDGF, EGF, IGF-I, labile intracellular pool of zinc, cell proliferation, DNA synthesis, 3T3 cells.

scholarly journals Extracellular Na+ and initiation of DNA synthesis: role of intracellular pH and K+.

1984 ◽  
Vol 98 (3) ◽  
pp. 1082-1089 ◽  
Author(s):  
C P Burns ◽  
E Rozengurt
Keyword(s):  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Dna Synthesis ◽  
Cellular Proliferation ◽  
Weak Acid ◽  
Mechanisms Of Action ◽  
Epidermal Growth ◽  
Reversible Time ◽  
Stimulation Of

Initiation of DNA synthesis in confluent quiescent 3T3 cell cultures stimulated by epidermal growth factor (EGF), vasopressin, and insulin was abolished by removing extracellular Na+. The inhibition was reversible, time- and Na+-concentration-dependent, and not due to an effect on binding or internalization of 125I-EGF. Stimulation by combinations of other growth factors with different mechanisms of action was also affected by decreasing extracellular Na+, but with different half-maximal Na+ concentrations. When choline was used as an osmotic substitute for Na+, the decrease in DNA synthesis was correlated with the decrease in intracellular K+. In contrast, when sucrose was used there was stimulation of the Na+-K+ pump and maintenance of intracellular K+ that resulted in a somewhat higher rate of DNA synthesis at lowered extracellular Na+ compared to choline. Mitogenesis induced by epidermal growth factor, vasopressin, and insulin led to cytoplasmic alkalinization as determined by an increase in uptake of the weak acid 5,5-dimethyloxazolidine-2,4-dione. Experimental decrease in extracellular Na+ blocked this cellular alkalinization. Therefore, under some conditions the supply of extracellular Na+ may limit cellular proliferation because of a reduction in the provision of Na+ to the Na+/H+ antiport and resultant failure of alkalinization. We conclude that Na+ flux and its effect on intracellular K and pH has a major role in the complex system that regulates proliferation.

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