Abstract 543: Monoclonal antibodies against thyimidine kinase 1 for the immunotargeting of lung and breast cancer cells, a preclinical evaluation

This study explores the potential therapeutic use of monoclonal antibodies against the tumor proliferation biomarker TK1 for the immunotargeting of lung and breast cancer cells. Recent clinical trials have led to the approval of monoclonal antibodies for the treatment of several solid tumors including lung and breast tumors. However, a common limitation that antibody-based therapies face is that a significant portion of the current tumor targets are expressed on normal tissues, thus creating off-target tumor effects. TK1 is a tumor proliferation biomarker that is up-regulated in malignant tissues. Recently, we have reported the expression of TK1 on the cell membrane of several cancer cell lines, mononuclear cells (MNC) from patients with leukemia and cells from breast and colon tumors. No membrane expression of TK1 was found on normal cells. To further explore the potential of TK1 as an immunotherapeutic target, we evaluated the capacity of a novel panel of anti TK1 antibodies to target TK1 on the cell membrane of lung and breast cancer cells and to elicit an antibody-dependent cell-mediated-cytotoxicity (ADCC) response in vitro. Antibodies previously developed in our lab were validated to specifically target six different regions of the TK1 molecule. Four different antibodies targeting three different regions in the TK1 molecule were selected for ADCC experiments. Nuclear restricted GFP versions of the NCI-H460 and MDA-MB-231 cell lines were utilized in conjunction with the real-time cell imaging system ImageXpress® Pico to measure the ADCC response. Mono nuclear cells (MNCs) from healthy donors were co-cultured with target cells and 10ug/ml of each anti-TK1 antibody were added to the media. An antibody with the same isotype than the TK1 antibodies, but that doesn't bind to any human surface antigen was utilized as a control. All ADCC responses elicited by the anti-TK1 antibodies were observed between 24-72hrs. The highest ADCC responses were elicited by antibodies 4G10 and 1B12 in both breast and lung cancer cell lines while a minimal response was observed with antibodies 7D1 and 3B2E11. A 50-60% increment in the ADCC response against NCI-H460 cells was observed with antibody 4G10 in comparison with the isotype control (p= 0.001). A 40% increase in the ADCC response against MDA-MB-231 cells was observed using antibody 1B12 (p = 0.003) compared to the its isotype control. This preliminary data suggests that anti TK1 monoclonal antibodies can be used for t