The Influence Of EGF On ERα MRNA Expression In Breast Cancer Cells And Its Mechanism

[Purpose] To study the expressions of epidermal growth factor (EGF) onestrogen receptor (ER) in ER-positive and ER-negative breast cancer cells.Meanwhile its possible mechanism is probed as well.[Methods] Based on the technique of RT-PCR, this research explored theinfluence on ERαmRNA expression in breast cancer cells exerted by EGFpathway and the different expressions of ERαmRNA after the prohibition ofsignal transmission in EGF pathway. We observe the expressions of ERαmRNA in ER-positive and ER-negative breast cacer cell after incubating withEGF,EGF combined with the inhibitor of EGFR(BP1585) and EGF combinedwith the inhibitor of PI3K (LY294002).[Result] 1.It is shown that the expression of ERαmRNA (P＜0.05) declineunder the influence of EGF in ER-positive breast cancer cell MCF-7. Themore concentration of EGF the stronger the inhibition (When 100ng/ml and10ng/ml are compared, P＜0.001). While the inhibition (when 100ng/ml and500ng/ml are compared, P=0.215＞0.05) does not change significantly whenthe density of EGF is increased from 100ng/ml to 500ng/ml. 2. It is indicated inthe experiment that in MCF-7 the amount of ERαmRNA expression dropsdramatically under the influence of EGF. This function varies from time to time. After 6,12 and 18 hours, the respective rate of decline are 50.21%,36.17% and10.78%, which are significantly different from that of the control groups(P＜0.05). After 24 hours, the inhibition of ERαmRNA expression is not soobvious (compared with control groups, P＞0.05).3. It is also demonstrated thatthe inhibition of ERαmRNA expression exerted by EGF can be reducedremarkably via the inhibition of EGFR with BP1585 and the inhibition of PI3Kwith LY294002 to stop the EGF signal transmission. BP 1585 and LY294002 arecombined with EGF respectively to act on MCF-7. After 6 hours, the rates ofdecline in ERαmRNA expression are 14.79% and 11.97% separately. Theamount of ERαmRNA expression is strikingly higher than that of the EGFgroup (P＜0.001). After 12 and 18 hours, the amount of ERαmRNA expressionis still higher than that of the EGF group (P＜0.05). After 24 hours, there is noobvious distinction with EGF group (P＞0.05).4. There is no observablychange of ERαmRNA in ER-negative breast cancer cell MDA-MB-435S.[Conclusion] In ER-positive breast cancer cells, the expression of ERαmRNA can be obviously inhibited by EGF. The inhibition can be accomplishedby EGFR and PKB (or AKt) signal transduction pathways. While inER-negative breast cancer cells, the inhibitive function is not so obvious.