ERBB4 and breast cancer: Lustgarten et al. showed that HRG-IL-2 fusions proteins can redirect non-tumor specific cytotoxic lymphocytes to the tumor site and induce lysis of tumor cells in a non-MHC-restricted manner.[173] The fusion protein of HRG attached to the CD3 zeta-chain causes T lymphocytes to recognize and attack breast cancer cells overexpressing HER3 and HER4.[174, 175]