ERBB2 and breast cancer: In the evolving field of immunotherapy, therapeutic antibodies against tumor antigens (e.g., Herceptin targeting HER-2/neu on breast cancer) or antibodies inhibiting the proliferation of tumor-supplying vessels, stimulatory cytokines (e.g., interferon α and β), and immune checkpoint inhibition (e.g., PD-1 inhibitors) have shown clinical activity in many different types of cancer.