[Inhibitory effect of carbamazepine on proliferation of estrogen-dependent breast cancer cells].

Background & Objective: Carbamazepine, which has been used as an anti-epileptic drug in clinic for many years, is currently recognized as a histone deacetylase inhibitor (HDI), most of which showed anti-tumor characteristics. This study was to investigate the inhibitory effect of carbamazepine on estrogen dependent breast cancer cell lines with estrogen receptor alpha (ERalpha) expression and further explore the underlying mechanisms.

Methods: Sulforhodamine B viability assay was used to evaluate the viability of various cells treated with different drugs. Western blot and reverse transcription-polymerase chain reaction (RT-PCR) were performed to detect the protein and mRNA expression of ERalpha and Cyclin D1. Immunofluorescence assay was employed to observe HER-2 expression in MCF-7RT cells, which were resistant to tamoxifen. Immunoprecipitation was performed to detect the chaperon function and acetylation level of Hsp90.

Results: Carbamazepine treatment could inhibit the proliferation of MCF-7 and T47D cells stimulated by estradiol (P<0.01). Carbamazepine and 4-hydroxytamoxifen (4-OHT) demonstrated a synergic effect on the inhibition of proliferation of MCF-7 cells stimulated by estradiol (q=1.00). Cabamazepine reversed the proliferation of MCF-7RT cells stimulated by 4-hydroxytamoxifen (P<0.01). Carbamazepine treatment could decrease the expression of ERalpha and Cyclin D1 at protein and mRNA level in ERalpha-positive cells and could reduce HER-2 expression in MCF-7RT cells. The decrease of ERalpha and Cyclin D1 expression was inhibited by MG132, an inhibitor of 26S proteosome. Carbamazepine treatment elevated the acetylation level of Hsp90 and disrupted its chaperon function.

Conclusions: Carbamazepine shows significant anti-proliferation effect in ERalpha-positive breast cancer cell lines and this might be due to the enhancement of proteosome-mediated degradation of ERalpha and Cyclin D1 by carbamazepine. Furthermore, carbamazepine could reverse HER-2 dependent drug resistance to 4-OHT by reducing HER-2 expression.