It is a monoclonal antibody produced by injecting HER-2 antigen; 'cl' i.e., The protein HER2/NEU is expressed in increased amount by breast cancer cells Cancer cells express ceain antigen on their surface. These antigens can be made the target of chemotherapies. Specific antibodies have been developed against these cell surface receptors. Because the antibodies were produced from one cell that was grown into a clone of identical cells it is called monoclonal antibody. These antibodies were originally developed as mice antibody but because human have immune reactions to mouse proteins, these antibodies are usually chimerized or humanized when used as therapeutic reagents. i.e., the antibodies have both human and mouse component. These antibodies kill the cells by following mechanism :? - Antibody dependent cellular toxicity - Complement dependent cytotoxicity - Diret induction of apoptosis However, the clinically relevant mechanism still remains unceain. Herceptin (Trastuzumab) Herceptin is a humanized antibody and is used in breast cancers which are HER2 positive. (Major poion of it is composed of human component and a small pa is composed of mouse protein). HER2 stands for --4 human epidermal growth factor receptor. HER2 gene produces HER2 protein also called HER2 receptor. The HER2 protein is found on the surface of some normal cells in the body. In normal cells HER2 protein help send growth signals from outside the cell to the inside of the cell. These signals tell the cell to grow and divide. In HER2 (+ve) breast cancer the cancer cells have abnormally high number of HER2 genes per cell when this happens too much HER2 protein appears on the surface of these cancer cells. This is called HER2 protein over expression. Too much HER2 protein is thought to cause cancer cells to grow and divide uncontrollably. Herceptin acts in two ways a) Herceptin attaches to HER2+ cancer cells and stimulates the bodys immune system to target the HER2+ cancer cells b) Herceptin attaches itself to the HER2 receptors on the surface and blocks them from receiving the signals. Herceptin also acts by antibody dependent cell c) mediated cytotoxicity. We are not sure if it is increased antibody response Uses of Herceptin (trastuzumab) Currently transtuzumab is approved for HER2/ neu overexpressing metastatic breast cancer in combination with paclitaxel as initial treatment or as monotherapy following chemotherapy.