reased Survival of Human Breast Cancer Cells Expressing 2/neu on In vitro Incubation with an Anti-HER2/neu

ownload tment of human epidermal growth factor receptor 2 (HER2/neu)-expressing breast cancer patients with oclonal antibody (mAb) directed against HER2/neu improves the outcome of chemotherapy. In cases in remission is observed, antibody-dependent cell-mediated cytotoxicity (ADCC) seems to be one of the echanisms of anti-HER2/neu mAb action, implicating Fcγ receptors (FcγRs) in this tumoricidal activvitro and in vivo studies have revealed that anti-HER2/neu-mediated ADCC is mainly accomplished by orphonuclear granulocytes (PMN). C5a, a cleavage product of the complement component C5, modFcγR expression via upregulation of activating and downregulation of inhibitory FcγRs. C5a also rePMNs to sites of inflammation and increases PMN survival. To enhance the recruitment and activation receptor–bearing cells into the tumor microenvironment, we developed antibody fusion proteins comof a human IgG3 anti-HER2/neu antibody genetically fused to C5a [anti-HER2/neu IgG3-(C5a)] or to ivative, C5adesArg [anti-HER2/neu IgG3-(C5adesArg)]. Both fusion proteins were expressed, properly ased, and secreted by murine myeloma cells, and displayed chemotactic activity on human PMN. Under rable conditions, anti-HER2/neu IgG3-(C5adesArg) increased the survival of PMN more efficiently than ER2/neu IgG3-(C5a) or C5adesArg. Surprisingly, incubation of the fusion proteins with breast cancer hat overexpress HER2/neu (SK-BR-3) induced cell death at a dose at which the anti-HER2/neu IgG3 dy was innocuous. In the presence of human peripheral blood leukocytes as effector cells, both fusion ns induced tumor cell death more efficiently than anti-HER2/neu IgG3. These data suggest that antiprotei HER2/neu IgG3-(C5a) and anti-HER2/neu IgG3-(C5adesArg) fusion proteins possess novel properties that could be useful in cancer immunotherapy. Mol Cancer Ther; 9(8); 2175–85. ©2010 AACR.