【Abstract】 Objective To study the effects of different levels estradiol on inhibitory of tamoxifen on human mammary cancer cells(ER+) in vitro. Methods Estrogen receptor (ER) positive MCF7 human breast cancer cell line was treated by the same level of tamoxifen and different levels of estradiol in vitro. Cell proliferation was evaluated by MTT assay. Results E2 at concentrations between 1 × 10-12 mol/L to 1× 10-7 mol / L significantly stimulated the growth of MCF 7 . TAM (10 μmol/ L) inhabited the growth of MCF7 significantly. E2 at different levels may influence inhibitory of tamoxifen on MCF7 cell lines. E2 (1×10-8 mol/L) makes inhibitory of tamoxifen on MCF7 cell lines valueless.Conclusion E2 is the risk factor of breast cancer, and the concentration around breast cancer cells may influence the effects of TAM.
Objective To study the effects on MCF-7 breast cancer cells with combination of tamoxifen（TAM） and antisense oligonucleotide （ASODN） targeting survivin mRNA. Methods MCF-7 breast cancer cells were treated with a 20 mer ASODN targeting survivin mRNA and TAM, which were divided into three groups: TAM group (treated by TAM only), ASODN group (by ASODN only), and TAM+ASODN combined group (by TAM+ASODN combination). The growth inhibition of MCF-7 cells, the changes of cell cycles and apoptotic rate, the positive rate of survivin mRNA expression, and the activity of caspase-3 were tested by MTT, flow cytometry, hybridization in situ, and spectrophotometric method, respectively.Results The rate of growth inhibition of MCF-7 cells in the TAM+ASODN combined group was (62.26±3.92)%, which was significantly higher than that in the TAM group 〔(42.30±6.63)%〕 or ASODN group 〔(54.77±9.99)%〕, Plt;0.05. The apoptotic rate of MCF-7 cells was (28.08±4.32)% in the TAM+ASODN combined group, which was significantly higher than that in the TAM group 〔(18.94±4.01)%〕 or ASODN group 〔(21.12±3.95)%〕, Plt;0.01. The effect of arresting MCF-7 cells in G0/G1 phase in the TAM+ASODN combined group was ber than that in the TAM or ASODN group (Plt;0.05, Plt;0.01). The positive rate of survivin mRNA in the TAM+ASODN combined group was (13.38±3.45)%, which was significantly lower than that in the TAM group 〔(39.67±7.42)%〕 or ASODN group 〔(27.50±5.80)%〕, Plt;0.01. The activity of caspase-3 in the TAM+ASODN combined group （0.93±0.13） was significantly higher than that in the TAM group (0.50±0.09) or ASODN group (0.64±0.08), Plt;0.01. Conclusion The ASODN targeting survivin mRNA can promote the apoptosis of MCF-7 breast cancer cells, and make MCF-7 cells more sensitive to tamoxifen.