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.

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.

Evidence that thyroid growth promoting activity of immunoglobulin preparations is due to contamination with EGF

1987 ◽  
Vol 116 (1_Suppl) ◽  
pp. S256-S259 ◽  
Author(s):  
R. Gärtner ◽  
C. Tsavella ◽  
G. Bechtner ◽  
W. Greil
Keyword(s):  
Growth Factors ◽  
Growth Factor ◽  
Egf Receptor ◽  
Protein A ◽  
Graves Disease ◽  
Thyroid Cell ◽  
Immunoglobulin Preparations ◽  
Receptor Assay ◽  
Epidermal Growth ◽  
Growth Promoting

Abstract. Immunoglobulin (IG) preparations may be contaminated with growth factors. Therefore, we investigated whether the growth promoting activity in IG preparations (thyroid growth stimulating immunoglobulins = TGI) from patients with sporadic goitre may be caused by contaminating EGF (epidermal growth factor). EGF in sera as well as in indifferently prepared IG of patients with recurrent goitre (n = 23), Graves' disease (n = 19) and normals (n = 17) was determined by EGF receptor assay. Comparatively, the ability for stimulating thyroid cell growth was determined in these IG preparations (2 mg/ml). EGF in ammoniumsulphate (AS) precipitates was about 2-fold higher than serum EGF. The growth promoting activity of indifferent IG preparations correlated with the EGF content. After additional purification on protein A-sepharose, neither EGF, nor a growth promoting activity was found in these IG preparations. We therefore conclude, that the growth promoting activity of crude IG preparations may be due to a contamination with EGF.

Post-transcriptional control of the onset of DNA synthesis by an insulin-like growth factor

1984 ◽  
Vol 4 (9) ◽  
pp. 1807-1814
Author(s):  
J Campisi ◽  
A B Pardee
Keyword(s):  
Cell Cycle ◽  
Growth Factors ◽  
Growth Factor ◽  
Dna Synthesis ◽  
Transcriptional Control ◽  
S Phase ◽  
G1 Phase ◽  
Insulin Like Growth Factor ◽  
Igf I ◽  
Translational Inhibition

The control of eucaryotic cell proliferation is governed largely by a series of regulatory events which occur in the G1 phase of the cell cycle. When stimulated to proliferate, quiescent (G0) 3T3 fibroblasts require transcription, rapid translation, and three growth factors for the growth state transition. We examined exponentially growing 3T3 cells to relate the requirements for G1 transit to those necessary for the transition from the G0 to the S phase. Cycling cells in the G1 phase required transcription, rapid translation, and a single growth factor (insulin-like growth factor [IGF] I) to initiate DNA synthesis. IGF I acted post-transcriptionally at a late G1 step. All cells in the G1 phase entered the S phase on schedule if either insulin (hyperphysiological concentration) or IGF I (subnanomolar concentration) was provided as the sole growth factor. In medium lacking all growth factors, only cells within 2 to 3 h of the S phase were able to initiate DNA synthesis. Similarly, cells within 2 to 3 h of the S phase were less dependent on transcription and translation for entry into the S phase. Cells responded very differently to inhibited translation than to growth factor deprivation. Cells in the early and mid-G1 phases did not progress toward the S phase during transcriptional or translational inhibition, and during translational inhibition they actually regressed from the S phase. In the absence of growth factors, however, these cells continued progressing toward the S phase, but still required IGF at a terminal step before initiating DNA synthesis. We conclude that a suboptimal condition causes cells to either progress or regress in the cell cycle rather than freezing them at their initial position. By using synchronized cultures, we also show that in contrast to earlier events, this final, IGF-dependent step did not require new transcription. This result is in contrast to findings that other growth factors induce new transcription. We examined the requirements for G1 transit by using a chemically transformed 3T3 cell line (BPA31 cells) which has lost some but not all ability to regulate its growth. Early- and mid-G1-phase BPA31 cells required transcription and translation to initiate DNA synthesis, although they did not regress from the S phase during translational inhibition. However, these cells did not need IGF for entry into the S phase.

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.

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.

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

Effects of growth hormone on rat renal epidermal growth factor expression

1994 ◽  
Vol 267 (2) ◽  
pp. F208-F214 ◽  
Author(s):  
S. A. Rogers ◽  
J. Rasmussen ◽  
S. B. Miller ◽  
M. R. Hammerman
Keyword(s):  
Growth Hormone ◽  
Growth Factors ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Polypeptide Growth Factors ◽  
Factor Expression ◽  
Igf I ◽  
Hypophysectomized Rats ◽  
Epidermal Growth ◽  
Growth Factor Expression

The kidney is a site of synthesis for several polypeptide growth factors including epidermal growth factor (EGF) and insulin-like growth factor I (IGF-I). Interactions between growth hormone (GH) and growth factors have been described that regulate renal growth factor expression. For example, GH and EGF each enhances the expression of IGF-I in kidney. To further define interrelationships in this renal GH-growth factor axis, we characterized the effect of GH on renal EGF expression in hypophysectomized, pituitary-intact (normal) rats, and hypersomatotropic rats. Levels of extractable immunoreactive mature EGF, levels of a 142-kDa EGF-precursor present in renal membrane fractions, and levels of EGF mRNA were significantly reduced in kidneys from hypophysectomized rats compared with levels in normal rats. Each was increased significantly after the administration of GH to hypophysectomized rats. In contrast, induction of hypersomatotropism in normal rats by injection of GH for 17 days did not affect levels of extractable mature EGF or EGF mRNA measured in kidneys. We conclude that GH enhances the renal synthesis of EGF in hypopituitary, but not in hypersomatotropic states.

Sign in / Sign up

Export Citation Format

Share Document