All these data suggest that HER4 could be a potent therapeutic target; a HER4 JM-a type-specific anti-HER4 monoclonal antibody 1479 is available which has been reported to block HER4 cleavage in breast cancer cells and to suppress breast cancer cell growth both in vivo and in vitro [5, 28]. The gene discussed is ERBB4; the disease is breast carcinoma.