Trastuzumab is a monoclonal antibody that interferes with the HER2/neu receptor. Its main use is to treat certain breast cancers. The HER receptors are proteins that are embedded in the cell membrane and communicate molecular signals from outside the cell (molecules called EGFs) to inside the cell, and turn genes on and off. The HER proteins stimulate cell proliferation. In some cancers, notably certain types of breast cancer, HER2 is over-expressed, and causes cancer cells to reproduce uncontrollably. Trastuzumab is also being studied for the treatment of other cancers. It has been used with some success in women with uterine papillary serous carcinomas that overexpress HER2/neu. Trastuzumab inhibits the effects of overexpression of HER2. If the breast cancer doesn't overexpress HER2, trastuzumab will have no beneficial effect (and may cause harm). Doctors use laboratory tests to discover whether HER2 is overexpressed.
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