Antitumor Effects of Sorafenib and Lapatinib Alone and in Combination on MCF-7 Breast Cancer Cells

Breast cancer is the most frequently diagnosed cancer and the leading cause of cancer death in women. Biologic markers, such as hormone receptors including estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2) overexpression, tumor size, histological grade and subgroup status, lymph node involvement have prognostic and/or predictive value and are important factors in selecting appropriate treatment (Izadi et al., 2012; Liu et al., 2012; Macfarlane et al., 2012; Mackey et al., 2012; Zubeda et al., 2013; Cabuk et al., 2014). Estradiol exerts of its effects by direct binding ER. ER is a phosphoprotein and belongs to a nuclear receptor superfamily. ER positive breast cancer cells produce growth factors that may influence the proliferation and responsiveness of breast cancer (Stoica et al., 2003). ER functions as a ligand dependent transcription factor and promotes variety of genes. Many of these gene products directly promote breast cancer cell proliferation, survival and tumor progression (Arpino et al., 2008; Osborne and Schiff, Abstract