Results Activation of ERα by 17-βestradiol (E2) increased

the sensibility of ERα-positive T47D cells to chemotherapeutic agents and fulvestant reversed the PND-1186 cell line effect of E2 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assays were AZD0530 ic50 performed to determine the viability of T47D cells treated with four different chemotherapeutic agents (i.e., paclitaxel, epirubicin, fluorouracil, and vinorelbine) with or without the pretreatment of E2. Three concentrations were tested for each chemotherapeutic agent. As shown in Figure 1A and 1B, the pretreatment of 100 nM E2 for 16 hours or 12 days significantly decreased cell survival after exposure to chemotherapeutic agents (p < 0.05). To determine whether or not the E2-induced chemosensitivity was specifically due to an ERα-mediated mechanism, fulvestrant (an ERα antagonist) was used 12 hours before E2. We found that pretreatment with 2 uM fulvestrant completely reversed E2-induced sensitivity to

chemotherapeutic agents (p < 0.05). Figure 1 Activation of ERα increased the sensibility of T47D cells to chemotherapeutic agents. (A, B) The viability of T47D cells after being Tanespimycin manufacturer exposed to four chemotherapeutic agents was determined by MTT assays. (A) Cells were pretreated with or without E2 for 16 hours before being exposed to chemotherapeutic agents. (B) Cells were pretreated with or without E2 for 12 days. Fulvestrant was added to the medium 12 hours before E2 treatment. The chemotherapeutic agents used in the MTT assays were paclitaxel, epirubicin, fluorouracil, and vinorelbine. Three concentrations were tested for each chemotherapeutic agent. Data are means ± standard deviation (SD) (n = 3). (C, D) Cell death induced by chemotherapeutic agents was determined by PI dye exclusion assays. (C) Cells were pretreated with or without E2 for 16 hours before exposed

to chemotherapeutic agents. (D) Cells were pretreated with or without E2 for 12 days. Fulvestrant was added to the medium 12 why hours before E2 treatment. The chemotherapeutic agents used in the PI dye exclusion assays were paclitaxel, fluorouracil, and vinorelbine. One concentration was tested for each chemotherapeutic agent. Bars correspond to mean ± SD. To confirm the effect of ERα on the chemosensitivity of T47D cells, the occurrence of chemotherapeutic agent-induced cell death was assessed using propidium iodide (PI) dye exclusion tests. The chemotherapeutic agents used in the PI dye exclusion tests were paclitaxel, fluorouracil, and vinorelbine. Epirubicin spontaneously emits red fluorescent light, and the wavelength of fluorescent light is similar to that of PI, which interferes with the detection of dead cells induced by epirubicin. Thus, epirubicin was not used in the PI dye exclusion tests performed for the current work.