<prompt> Trastuzumab all are true EXCEPT:Shows better response in combination with paclitaxelUsed in metastatic breast cancerCauses upregulation of HER2neuDo not causes bone marrow toxicity  <response>: Causes upregulation of HER2neu REF: Lippincotts pharmacology 6th edition 653, Goodman Gillmans 111 edition page 901, It has been suggested that trastuzumab induces some of its effect by downregulation of HER2neu not upregulation Trastuzumab: Herceptin Trastuzumab is a humanized antibody directed against the HER-2 antigen that is overexpressed on the tumor cell surface in approximately 25 of breast cancer patients. Trastuzumab is approved as intravenous infusion in HER2neu overexpressing metastatic breast cancer in combination with paclitaxel as initial treatment or as monotherapy following chemotherapy relapse. Trastuzumab also is synergistic with other cytotoxic agents, but only in HER2neuoverexpressing cancers. Trastuzumab is a humanized monoclonal antibody that binds to the domain IV of the extracellular segment of the HER2neu receptor It has been suggested that trastuzumab induces some of its effect by downregulation of HER2 neu Herceptinus e is associated withinfusion-relatedhypotension , flushing andbronchoconstriction, and skin rash but no bone marrow toxicity Herceptin appears to sensitize patients to cardiotoxicity, an impoant concern in patients also receiving doxorubicin. 