Figure 3.

The enhancement effects of SUL in drug-resistant breast cancer are prevented by 7-OH-DPAT in vitro and in vivo. (A) Colony formation assays were conducted on MCF-7/Adr cells for 8 d after exposure to vehicle, SUL, DEX, SUL+DEX, 7-OH-DPAT or SUL+DEX+7-OH-DPAT for 48 h. The fewest colonies in the SUL+DEX group suggested that SUL enhanced the colony formation inhibition by DEX, and this effect could be prevented by 7-OH-DPAT co-administration. The images of the view field and single colonies are magnified 4× and 20×, respectively. (B) Quantitative analyses of the colony counts of each group. (C) In the MCF-7/Adr xenograft model, mice were given 7-OH-DPAT combined with SUL and DEX for 17 d. 7-OH-DPAT were intratumorally administered once daily. The inhibitory effect on tumor growth produced by SUL+DEX was reversed to nearly the same level as that of DEX alone after the addition of 7-OH-DPAT. The data are presented as the mean±SD (n=5). SUL, sulpiride; DEX, dexamethasone; 7-OH-DPAT is a specific D2DR agonist that exerts opposing actions from SUL; NS, non-significant; ^*P<0.05, ^**P<0.01.