Novel Humanized and Highly Efficient Bispecific Antibodies Mediate Killing of Prostate Stem Cell Antigen-Expressing Tumor Cells by CD8+ and CD4+ T Cells |
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Authors: | Anja Feldmann Claudia Arndt Katrin Töpfer Slava Stamova Franziska Krone Marc Cartellieri Stefanie Koristka Irene Michalk Dirk Lindemann Marc Schmitz Achim Temme Martin Bornhäuser Gerhard Ehninger Michael Bachmann |
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Institution: | Institute of Immunology, Medical Faculty Carl Gustav Carus, TU Dresden, 01307 Dresden, Germany; |
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Abstract: | Prostate cancer is the most common noncutaneous malignancy in men. The prostate stem cell Ag (PSCA) is a promising target for immunotherapy of advanced disease. Based on a novel mAb directed to PSCA, we established and compared a series of murine and humanized anti-CD3-anti-PSCA single-chain bispecific Abs. Their capability to redirect T cells for killing of tumor cells was analyzed. During these studies, we identified a novel bispecific humanized Ab that efficiently retargets T cells to tumor cells in a strictly Ag-dependent manner and at femtomolar concentrations. T cell activation, cytokine release, and lysis of target cells depend on a cross-linkage of redirected T cells with tumor cells, whereas binding of the anti-CD3 domain alone does not lead to an activation or cytokine release. Interestingly, both CD8(+) and CD4(+) T cells are activated in parallel and can efficiently mediate the lysis of tumor cells. However, the onset of killing via CD4(+) T cells is delayed. Furthermore, redirecting T cells via the novel humanized bispecific Abs results in a delay of tumor growth in xenografted nude mice. |
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