Catumaxomab with Activated T-cells Efficiently Lyses Chemoresistant EpCAM-positive Triple-negative Breast Cancer Cell Lines

Epithelial cell adhesion molecule (EpCAM) is expressed in various types of cancer, including breast cancer, and is correlated with metastasis, invasion, therapeutic resistance and prognosis. Moreover, several cell surface markers, such as CD44 and EpCAM, are molecular targets on cancer stem-like cells of breast cancer. The aim of this study was to investigate whether catumaxomab, a clinical-grade bispecific antibody that binds to both EpCAM on tumor cells and CD3 on T-cells, combined with activated T-cells can eliminate chemoresistant triple-negative breast cancer (TNBC) cells in vitro. First, a cell line (MUK-BC1) was established from human breast carcinoma cells derived from a patient with chemoresistant and disseminated breast cancer. These EpCAM-positive TNBC cells were almost completely resistant to various drug-mediated cytotoxicities up to a concentration of 10 μg/ml. Pre-treatment with catumaxomab and subsequent addition of interleukin-2/OKT3-activated autologous T-cells eliminated EpCAM-positive TNBC cells. Catumaxomab combined with activated T-cells may be a potent therapeutic modality to overcome chemoresistant EpCAM-positive TNBC cells.