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Updated: Sep 24, 2026
Profiling of Estrogen-regulated MicroRNAs in Breast Cancer Cells
Published on: February 21, 2014
Relation between cytochrome P450IA1 expression and estrogen receptor content of human breast cancer cells
P J Vickers1, M J Dufresne, K H Cowan
1Medicine Branch, National Cancer Institute, Bethesda, Maryland 20892.
Abstract:
Multidrug resistance (MDR) in an MCF-7 human breast cancer cell line (MCF7/Adr) is associated with decreased drug accumulation and overexpression of P-glycoprotein as well as alterations in the levels of specific drug-metabolizing enzymes, including decreased activity of the phase I drug-metabolizing enzyme aryl hydrocarbon hydroxylase (AHH) and increased expression of the anionic form of the phase II drug-metabolizing enzyme glutathione S-transferase. Since the development of MDR in this MCF-7 cell line is also associated with a loss of estrogen receptors (ER), we have examined the expression of cytochrome P450IA 1, the gene encoding AHH activity, in other breast cancer cell lines not selected for drug resistance but expressing various levels of ER. These studies show that a relationship exists between 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-inducible AHH activity and the ER content in a series of breast cancer cell lines. In these cell lines expression of AHH activity is regulated, at least in part, at the level of P450IA 1 RNA. While TCDD-specific binding proteins (Ah receptors) were found in each of the breast cancer cell lines, there was no apparent relation between the level of nuclear TCDD-binding proteins and the level of TCDD-inducible P450IA 1 expression. Previous studies from our laboratory have described an inverse relationship between levels of the anionic form of glutathione S-transferase and ER in breast cancer.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Multidrug resistance in breast cancer cells involves altered drug metabolism and estrogen receptor (ER) levels. AHH activity correlates with ER content, suggesting a link between drug resistance and ER status in cancer.
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Research
Background:
- Multidrug resistance (MDR) in MCF-7 breast cancer cells is linked to P-glycoprotein overexpression and altered drug-metabolizing enzymes.
- MDR development in this cell line also correlates with a loss of estrogen receptors (ER).
Purpose of the Study:
- To investigate the relationship between aryl hydrocarbon hydroxylase (AHH) activity, P450IA 1 gene expression, and estrogen receptor (ER) content in breast cancer cell lines.
- To explore the regulation of AHH activity by ER levels in various breast cancer models.
Main Methods:
- Examined aryl hydrocarbon hydroxylase (AHH) activity and P450IA 1 RNA levels in breast cancer cell lines with varying ER expression.
- Assessed TCDD-specific binding proteins (Ah receptors) and their relation to P450IA 1 expression.
Main Results:
- A correlation was observed between 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-inducible AHH activity and ER content across different breast cancer cell lines.
- AHH activity expression is, in part, regulated at the P450IA 1 RNA level.
- No direct relationship was found between nuclear TCDD-binding protein levels and TCDD-inducible P450IA 1 expression.
Conclusions:
- A link exists between ER status and TCDD-inducible AHH activity in breast cancer cell lines.
- ER content influences the expression of the P450IA 1 gene, which encodes AHH activity.
- These findings contribute to understanding drug metabolism alterations in breast cancer and their relation to ER signaling.
