Abstract 218P
Background
Estrogen receptors (ER), ERα and ERβ, might serve as extra-hepatic regulators of CYP enzymes involved in steroid hormone metabolism such as CYP1B1, 1A1, 2B6, and CYP3A4. The aim of this project was, to study the responsiveness of either ERα negative and ERα positive cell lines on estrogen induced steroid metabolizing CYP enzyme expression, and changes in ERα or ERβ expression.
Methods
Two commercially available human breast cancer cell lines, which either expressed ERα or ERβ (T47D cells, ERα positive, and SKBR3 cells, ERα negative) were cultivated for gene expression analysis with different concentrations of 17-β estradiol (E2) in a range of 100 pM to 1000 nM for 24 hours. ERα protein expression (Isoforms 48 kDa and 66 kDa) was semiquantified by western blot analysis. The influence of E2 on CYP1B1, CYP2B6 and CYP3A4 expression on mRNA level was investigated by qPCR analysis using Lightcycler© realtime PCR technology.
Results
In both cell lines, CYP1B1 expression increased at higher E2 concentrations, but the induction was significant only in the ERα positive cell line. In the ERα positive cell line, CYP2B6 expression significantly decreased with increasing E2 concentrations indicating an inhibitory effect by E2. It was also investigated whether ER expression changes during estrogen exposure of the cells. In the ERα positive cell line, T47D, expression of ERβ, but not that of ERα, significantly increased after incubation with increasing E2 concentrations. In the ERα negative cell line, only ERβ was detected, and no changes in expression occurred after E2 treatment.
Conclusions
We detected differential effects of estrogen on CYP enzyme expression in ERα negative versus positive cell lines. While CYP1B1, the most prominent estrogen metabolizing enzyme showed a tendency to induction in both cell lines, CYP2B6 which is known to be induced by ERα, showed deceased expression levels at higher estrogen concentrations indicating a potential controversial effect mediated by ERβ, since expression of ERβ increased in the ERα positive cell line by estrogen incubation.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.