Grb7 is an especially promising cancer target as the encoding gene maps closely to the ErbB2 gene on human chromosome 17q12 and is found co-amplified and overexpressed in a subset of breast, esophageal and gastric cancers (Stein et al, 1994; Kishi et al, 1997; Tanaka et al, 1997; Fiddes et al, 1998; Kauraniemi et al, 2001; Varis et al, 2002; Andrechek et al, 2003; Bieche et al, 2003). Here, ERBB2 is linked to cancer.