The mechanism of action of this steroidal antiestrogen differs significantly from other SERMs with mixed agonist/antagonist properties. In contrast to other SERMs, ICI-182,780 blocks ER transactivation coming from both AF-1 and AF-2 domains. The drug may also impair ER dimerization, but most importantly, ICI-182,780 induces ER degradation, with a marked reduction in the cellular concentration of ER. In the present study, ICI-182,780, evodiamine and ICI-182,780 plus evodiamine were treated to MCF-7 cells for 24 to 96 hrs. As indicated in Figure 5, no significant difference was observed at 24, 48, and 72 hrs following treatments. These results imply that the inhibitory effects of evodiamine on cell proliferation are similar to ICI-182,780 which is demonstrated through antiestrogenic and ER degradation pathway. In our current study, we had also found that ER protein expression as well as mRNA levels were decrease after evodiamine treatment. This phenomenon is similar to ICI-182,780 treatment. Moreover, previous study has found that the expression of ERa plays an important role in IGF-1 signaling AbMole Hexyl Chloroformate pathway, down-regulation of ERa by chemicals or specific siRNA reduces cell proliferation index. Therefore, we suggest that evodiamine could inhibit breast cancer cell proliferation through ER-inhibitory pathway. However, the mechanisms 
of ER degradation and cell apoptosis are still unclear and the accurate mechanism of evodiamine has needed further investigated. The Bcl-2-associated X protein, or BAX gene was the first identified pro-apoptotic member of the Bcl-2 protein family. Bax is a pro-apoptotic Bcl-2 protein containing BH1, BH2 and BH3 domains. In healthy mammalian cells, the majority of Bax is found in the cytosol, but upon initiation of apoptotic signaling, Bax undergoes a conformation shift, and inserts into organelle membranes, primarily the outer mitochondrial membrane. Bax is believed to interact with, and induce the opening of the mitochondrial voltage-dependent anion channel. Alternatively, growing evidence suggests that activated Bax and/or Bak form an oligomeric pore, MAC in the outer membrane. This results in the release of cytochrome c and other pro-apoptotic factors from the mitochondria, often referred to as mitochondrial outer membrane permeabilization, leading to activation of caspases. This defines a direct role for Bax in mitochondrial outer membrane permeabilization, a role common to the Bcl-2 proteins containing the BH1, BH2 and BH3 domains. BCL2-interacting killer, also known as BIK, is a protein known to interact with cellular and viral survival-promoting proteins, such as BCL2 and the Epstein-Barr virus in order to enhance programmed cell death. Because its activity is suppressed in the presence of survival-promoting proteins, this protein is suggested as a likely target for antiapoptotic proteins. This protein shares a critical BH3 domain with other death-promoting proteins, Bax and Bak.