17 β-Estradiol responsiveness of MCF-7 laboratory strains is dependent on a n autocrine signal activating the IGF type I receptor
17β-Estradiol responsiveness of MCF-7 laboratory strains is
dependent on an autocrine signal activating the IGF type I receptor
Irene HL Hamelers, Richard FMA van Schaik, John S Sussenbach and
Paul H Steenbergh*
dependent on an autocrine signal activating the IGF type I receptor
Irene HL Hamelers, Richard FMA van Schaik, John S Sussenbach and
Paul H Steenbergh*
Address: Utrecht Graduate School of Developmental Biology, Department of Physiological Chemistry, University Medical Center Utrecht, P. O.
Box 85060, 3508 AB Utrecht, The Netherlands
Email: Irene HL Hamelers - I.Hamelers@nki.nl; Richard FMA van Schaik - F.M.A.vanSchaik@med.uu.nl;
John S Sussenbach - j.sussenbach@hccnet.nl; Paul H Steenbergh* - P.H.Steenbergh@med.uu.nl
* Corresponding author
Published: 11 July 2003
Cancer Cell International 2003, 3:10
Received: 28 January 2003
Accepted: 11 July 2003
This article is available from: http://www.cancerci.com/content/3/1/10
© 2003 Hamelers et al; licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all
media for any purpose, provided this notice is preserved along with the article's original URL.
Box 85060, 3508 AB Utrecht, The Netherlands
Email: Irene HL Hamelers - I.Hamelers@nki.nl; Richard FMA van Schaik - F.M.A.vanSchaik@med.uu.nl;
John S Sussenbach - j.sussenbach@hccnet.nl; Paul H Steenbergh* - P.H.Steenbergh@med.uu.nl
* Corresponding author
Published: 11 July 2003
Cancer Cell International 2003, 3:10
Received: 28 January 2003
Accepted: 11 July 2003
This article is available from: http://www.cancerci.com/content/3/1/10
© 2003 Hamelers et al; licensee BioMed Central Ltd. This is an Open Access article: verbatim copying and redistribution of this article are permitted in all
media for any purpose, provided this notice is preserved along with the article's original URL.
Summary:
Human MCF-7 cells have been used as a model for breast cancer cell growth. Literature states that the serum-starved MCF-7 cells can be induced to proliferate by only adding 17 β-Estradiol (E2). However, the level of the mitogenic response to E2 fluctuates in different MCF-7 laboratory strains. In this paper, the E2-sensitivity of three different MCF-7 laboratory strains was studied.
With about the same levels and activities of the estrogen receptor (ER), the MCF-7 NKI is most E2-sensitive, the MCF-7 ATCC is intermediate E2-sensitive, while the MCF-7S is non-responsive to E2. Yet, the mitogenic response to E2-treatment in MCF-7 ATCC and MCF-7 NKI cells can be inhibited by both suramin and IGF type I receptor blocking antibodies. Therefore, E2-induced proliferation of all three MCF-7 strains depends on IGF type I receptor activation.
To examine whether E2-induced cell cycle in all three MCF-7 strains is dependent on activation of the IGF type I receptor, two DNA synthesis assays were performed; one with suramin addition and the other with αIR3 antibody addition. As results, IGF-induced incorporation of 3H-TdR is completely inhibited with suramin (Figure 3 in the article) and with αIR3 (Figure 4 in the article).
With about the same levels and activities of the estrogen receptor (ER), the MCF-7 NKI is most E2-sensitive, the MCF-7 ATCC is intermediate E2-sensitive, while the MCF-7S is non-responsive to E2. Yet, the mitogenic response to E2-treatment in MCF-7 ATCC and MCF-7 NKI cells can be inhibited by both suramin and IGF type I receptor blocking antibodies. Therefore, E2-induced proliferation of all three MCF-7 strains depends on IGF type I receptor activation.
To examine whether E2-induced cell cycle in all three MCF-7 strains is dependent on activation of the IGF type I receptor, two DNA synthesis assays were performed; one with suramin addition and the other with αIR3 antibody addition. As results, IGF-induced incorporation of 3H-TdR is completely inhibited with suramin (Figure 3 in the article) and with αIR3 (Figure 4 in the article).
Figure 3 (left column): Effect of suramin on the induction of DNA-synthesis by IGF-I and E2 in the three MCF-7 strains
Figure 4 (right column): Effect of an IGF-RI blocking antibody on the induction of DNA-synthesis by IGF-I and E2 in the three MCF-7 strains
Figure 4 (right column): Effect of an IGF-RI blocking antibody on the induction of DNA-synthesis by IGF-I and E2 in the three MCF-7 strains
Significance:
The results of this article indicate that E2-responsiveness of MCF-7 cells is affected by the secretion of an autocrine factor activating the IGF-IR. The blockage of the IGF-RI-pathway prevents all three MCF-7 strains from responding to E2. Breast cancer therapy is generally targeted at inhibiting estrogen action. This study suggests that the inhibition of IGF-action in combination with anti-estrogen-treatment may provide a more effective way to treat or even prevent breast cancer.
I personally chose this paper because my group decided to examine MCF-7 cells’ VEGF secretion and estradiol as its stimulus. This article provides information of MCF-7 cell culture and Western blotting, which should be useful for our project.
The results of this article indicate that E2-responsiveness of MCF-7 cells is affected by the secretion of an autocrine factor activating the IGF-IR. The blockage of the IGF-RI-pathway prevents all three MCF-7 strains from responding to E2. Breast cancer therapy is generally targeted at inhibiting estrogen action. This study suggests that the inhibition of IGF-action in combination with anti-estrogen-treatment may provide a more effective way to treat or even prevent breast cancer.
I personally chose this paper because my group decided to examine MCF-7 cells’ VEGF secretion and estradiol as its stimulus. This article provides information of MCF-7 cell culture and Western blotting, which should be useful for our project.
4 comments:
Its interesting to learn the connection between E2 and IGF1 receptor. E2 is a steroid endocrine hormone that induces oxytocin and prolactin mainly in pregnant women and many other hormones. IGF1 is as well an endocrine growth hormone and its a protein. I would like to learn more on how a steroid hormone affect a receptor activated by a protein hormone. I would like to know more on how E2 contributes to growth/proliferation.
Tizita:
According to this paper…
E2 does not induce cell proliferation in the MCF-7S cell line under serum-free, steroid hormone-free conditions. However, E2 in synergism with submitogenic concentrations of IGF-I (2 ng/ml)does induce a proliferative response, as good as the response to mitogenic amounts of IGF-I (20 ng/ml). They have found that both E2 and mitogenic amounts of IGF-I strongly induce cyclin D1 expression, whereas submitogenic amounts of IGF-I do not significantly elevate cyclin D1 levels. IGF-I, but not E2, is able to activate PI3-kinase, which leads to inhibition of GSK3β activity. Inhibition of GSK3β triggers nuclear accumulation of the cyclin D1, but only if cyclin D1 levels are strongly induced concurrently, which is effected by E2. After cyclin D1 accumulates in the nucleus, activation of the cyclin D1/CDK4 complex and subsequent cell cycle progression is observed.
So, among three MCF-cell strains, the results of this paper indicate that the E2-responsive strains, MCF-7 ATCC and MCF-7 NKI, autonomously activate their IGF-RI, and that this activation is required for their response to E2. In addition, these E2-sensitive cells secrete an autocrine factor capable of activating the IGF-RI.
I hope this answers your question.
Thanks~~
This seems to be a very interesting area of research that can significanly with current studies on breast cancer. In other papers that I've read regarding MCF-7 cells, research usually involves studies with inhibiting estradiol instead of IFG-receptors. I was wondering if the research also involved any long term studies of blocking IGF receptors. Was any quantitative method used for characterizing cell proliferation rate or only for DNA-induction in these cells?
Kumer:
This paper focuses on the point that E2 stimulates MCF-7 cell proliferation through activated IGF-IR. Three MCF-7 strains were grown in serum-starved media, and were preincubated for 1 hour with suramin or IGF-RI blocking antibody, treated with mitogens for 30 h and harvested. Mitogens here means different amount of IGF-I, E2 and their combination. Therefore, I guess 31 hour blocking of IGF receptors is not long term enough!?
They performed DNA synthesis assay to investigate the inhibitory effect of sumarin and αIR3 antibody on E2-induced cell cycle. They also performed Western blot to analyze, for example, the level of ERα (estrogen receptor, ER, is a member of the nuclear hormone family of intracellular receptors) and cyclin D1 (E2-respinsive gene). And they concluded that the differences in E2 induced growth among MCF-7 strains are not caused by ER expression level or its functionality. This result led them to investigate the dependence of E2-induced proliferation on IGF-I receptor activation. I believe that they did not specify other quantitative method used for characterizing cell proliferation rate in this paper.
Hopefully this answers your question~~
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