Bispecific monoclonal antibodies (bsAbs) are a promising immunotherapeutic option for treatment of
cancer, especially in situations of
minimal residual disease. The combination of an anti-CD3 and anti-
tumor-associated
antigen antibody redirects cytotoxic T-lymphocytes towards malignant cells. Using a trifunctional bispecific antibody against
EpCAM x CD3, that additionally activates Fc gamma R(+) accessory cells via its Fc region, we investigated the interaction between three
EpCAM(+) prostate
carcinoma cell lines and peripheral blood mononuclear cells (PBMCs) of healthy donors and patients with prostate
carcinoma (PC). Visualization was performed by double immunocytochemical methods and computerized sequential video microscopy.
Tumor cells and PBMCs supplemented with alpha
EpCAM x alpha CD3 in 16-well chamber slides resulted in lysis of
tumor cells within 1--3 days without any differences between patient and healthy donor PBMCs. The characteristic necrotic way of
tumor cell killing (rounding, swelling, disrupting) could be observed in computerized sequences of video frames. Simultaneously, we could not reveal any form of apoptotic signal using three different apoptotic markers (TUNEL, M30 cyto death, anti-active
caspase 3). Within the first 48 hr we observed typical PBMC cluster formation with increasing cell proliferation. PBMCs surrounding the
tumor cells were not dominated by CD4(+), CD8(+), or CD14(+) cells. Lymphocytes with pore-forming
perforin proteins concentrated towards the
tumor target cells. Our combination of double immunocytochemical and computerized video microscopic techniques may serve as an important improvement of validity of cell-cell interaction experiments using in vitro models. (J Histochem Cytochem 49:911-917, 2001)