MTOR and neoplasm: The HER2 receptor is a member of the ErbB family of transmembrane tyrosine kinase receptors, and its dimerization catalytically activates its downstream signaling cascades through the MEK/ERK/MAPK and PI3K/AKT/mTOR pathways and mediates tumor angiogenesis by activating the VEGF signaling pathway (Fig. 4).