Fig. 5. Concentration and time-dependent inhibition/elimination of MGMT and ER-α proteins in response to fulvestrant in breast cancer cells.

A: Time dependent loss of MGMT activity in ERα-positive MCF7 and T47D tumor cells but not in ERα-negative MDAMB-468 cells after 1 μmol/L Fulvestrant treatment (upper panel). Concentration dependent inhibition of MGMT activity in MCF7 and T47D cells but not in MDA-MB-468 cells after a 72 hours exposure to fulvestrant (lower panel). The data represents the mean of two independent experiments in duplicate and the last time point (72 hours) as assessed by student's t-test was significant at P < 0.05. B: Decreased MGMT and ER-α protein levels in MCF7 cells after 48 hours and 72 hours fulvestrant exposure. ICI is fulvestrant, also called ICI-182,780. C: Decreased MGMT and ER-α protein levels in T47D cells after 48 hours and 72 hours fulvestrant exposure. D: Marginal degradation of MGMT in MCF7 cells treated with toremifene, a SERM. MGMT: O⁶-methylguanine DNA-methyltransferase; C: control.