ERBB2 and cancer: Furthermore mutations in human cancer often occur in upstream receptor genes such as EGFR, HER2, Flt-2, PDGFR, Fms, as well as chromosomal translocations (e.g., BCR-ABL, TEL-PDGFR) that serve to activate the Ras/Raf/MEK/ERK and Ras/PI3K/PTEN/Akt/mTOR pathways which have been discussed as playing critical roles in cellular proliferation in this review.