Abstract: AIM: To investigate the roles that adriamycin (ADR) plays in the expression of dephosphorylated RB protein and inducing apoptosis of human breast cancer cells (MCF-7/S) cultured in vitro. METHODS: MTT colorimetric assay was applied to examine the growth inhibition, and apoptosis rates (AR) were determined by terminal-deoxynucleotidyl transferase mediated d-UTP nick end labeling (TUNEL);the expressive levels of dephosphorylated RB protein were detected with immunocytochemistry. RESULTS: ADR inhibited proliferation of MCF-7 S cells in a dose dependent manner, and the 50 % inhibition concentration (IC50) was 0.128 mg·L^-1.Tumor cell AR in ADR group ($x^{-}$=0.261) was significantly higher than that in control group ($x^{-}$=0.045, P < 0.01).The expressive levels of dephosphorylated RB protein in ADR group (MOD ×area=987 ±207) was significantly higher than that in control group (MOD ×area=132 ±32, P <0.01).The dephosphorylated RB was enhanced by ADR in breast cancer cells.There was significant positive correlation between AR and the expressive levels of dephosphorylated RB protein in ADR group (P <0.05). CONCLUSION: ADR inhibits the growth proliferation and induces apoptosis in MCF-7/S cell line, which is possibly related to enhancing dephosphorylated RB protein expression.

Key words: dephosphorylated RB protein, breast neoplasm, apoptosis, adriamycin