Related Experiment Videos
Antisense estrogen receptor RNA expression increases epidermal growth factor receptor gene expression in breast
A deFazio1, Y E Chiew, M McEvoy
1Cancer Research Program, Garvan Institute of Medical Research, St. Vincent's Hospital, Sydney, New South Wales, Australia.
Abstract:
In human breast cancer, progression to a more malignant phenotype is often accompanied by decreased expression of estrogen receptor (ER) and increased expression of epidermal growth factor receptor (EGFR). Higher levels of this receptor tyrosine kinase are found in tumors lacking ER, and a quantitative, inverse relationship exists between the level of ER and EGFR mRNA in human breast cell lines. Antisense ER (ASER) RNA was used to evaluate the consequence of decreased ER expression in breast cancer cells, specifically to determine whether ER is involved in the regulation of EGFR gene expression. ER-positive MCF-7 human breast cancer cells were transfected with ASER, and clones constitutively expressing ASER RNA had decreased ER and up to a 3-fold increase in the expression of EGFR mRNA. To confirm that this observation was a direct consequence of ASER expression, a metal-inducible ASER expression construct was transfected into MCF-7 cells, and transfected clones were isolated and characterized. Northern analysis revealed an induction of ASER RNA within 1 h of the addition of zinc, which was followed by a 4-fold increase in EGFR mRNA levels, maximal at 6-12 h. The basal level of expression of the glucocorticoid receptor is also inversely related to that of ER among breast cancer cell lines, but neither constitutive nor inducible expression of ASER affected the expression of glucocorticoid receptor. These data support the hypothesis that the level of expression of ER specifically influences the expression of EGFR in human breast cancer cells and provides a potential link between loss of steroid sensitivity and the acquisition of autonomous growth.
Insights
Decreased estrogen receptor (ER) expression in breast cancer cells leads to increased epidermal growth factor receptor (EGFR) expression. This suggests ER influences EGFR levels, potentially linking hormone sensitivity loss to autonomous growth in breast cancer.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Breast cancer malignancy progression often correlates with reduced estrogen receptor (ER) and elevated epidermal growth factor receptor (EGFR) expression.
- An inverse relationship between ER and EGFR mRNA levels is observed in human breast cancer cell lines.
Purpose of the Study:
- To investigate the role of ER in regulating EGFR gene expression in breast cancer cells.
- To determine if decreased ER expression directly impacts EGFR levels.
Main Methods:
- Transfection of ER-positive MCF-7 cells with antisense ER (ASER) RNA to reduce ER expression.
- Utilizing a metal-inducible ASER construct to control ASER expression and observe EGFR changes.
- Northern blot analysis to quantify ASER and EGFR mRNA levels.
Main Results:
- Constitutive ASER expression resulted in decreased ER and up to a 3-fold increase in EGFR mRNA.
- Inducible ASER expression led to a 4-fold increase in EGFR mRNA within 6-12 hours of zinc induction.
- ASER expression did not affect glucocorticoid receptor levels, indicating specificity.
Conclusions:
- ER expression level specifically influences EGFR expression in human breast cancer cells.
- This finding provides a molecular link between loss of steroid sensitivity and the development of autonomous growth in breast cancer.