ISSN:
1573-7217
Keywords:
occupied EGF receptor
;
ligand dissociation
;
breast cancer
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary The epidermal growth factor (EGF) is one of several growth factors involved in normal breast epithelial development and tumor proliferation. EGF and EGF-like peptide TGFα bind and activate the same membrane receptor protein. This receptor (EGF-R) has been recently studied in breast tumor biopsies and its detectability reported as a prognostic indicator. However, normal and tumor tissue themselves produce EGF and related peptides in variable amount. This suggests that the standard measurement of EGF-R by binding assay should reflect only the number of non-occupied receptor sites. Based on this observation, the presence of occupied sites (EGF-R2) has been assessed in 216 human mammary tumor biopsies simultaneously with the direct measurement of non occupied EGF receptor sites (EGF-R1) and the results compared to estrogen and progesterone receptor status (ER, PGR). EGF-R1 and EGF-R2 were evaluated by 2 separate (125I) EGF binding assays performed on 2 aliquots of tumor crude membrane fraction, the first one directly, the other after dissociation of the endogenously bound ligand. The validity of the method has been assessed on membrane fractions prepared from human placenta. It is shown that the dissociation does not modify the binding dissociation constant. ER and PGR were measured by the dextran coated charcoal method. Results 〉 10 fmol/mg of membrane or cytosol protein were considered as positive. It is found that EGF-R1 and EGF-R2 are detectable in 54 and 90% of the cases, indicating that EGF-R is masked by endogenous ligand in 36% of the tumors. The mean incidence of EGF-R1 positivity is significantly higher in ER-(66%) than in ER+ tumors (49%) while EGF-R2 is detectable in 90% of tumors regardless of ER status. These data suggest that EGF-like peptides are locally produced in the majority of breast tumors. The positive relation between the presence of ER and the total occupancy of EGF-R sites could be in favor of their control by estrogens.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01834623
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