Various intracellular molecules are responsible for progression and development of breast cancer which are currently being used in diagnosis and treatment of breast cancer. More than sixty percent of total breast cancer cases are ER positive . Estrogen receptor alpha (ER-α) is one of the most commonly used molecular marker for breast cancer targeting. The receptor is the member of nuclear receptor family which controls several biological/physiological processes . Estrogen acts as a ligand for this receptor and activates it under normal physiological response however overexpression of ER-α is responsible for breast cancer development .