Functionally, co-expression markedly increased orthotopic xenograft tumor growth in mice, and also drastically accentuated activation of both HER2 and HER3 in vitro as well as ligand-independent HER2 homodimerization, and heterodimerization of HER2/HER3 and HER2/EGFR [21]. Here, ERBB2 is linked to neoplasm.