Novel monoclonal antibody kills lymphoma cells via LFA-1/ICAM-1 dependent, antibody-mediated cellular cytotoxicity

Background: Diffuse large B-cell lymphoma (DLBCL) is an aggressive form of non-Hodgkin's lymphoma. DLBCL patients undergo a first line immunochemotherapy regimen, termed R-CHOP. Unfortunately, approximately 40% of treated patients eventually relapse, or are non-responsive. Thus, there is an urgent need to devise new treatment options. Recently, a novel monoclonal antibody (Antibody X) has been developed as a potential therapeutic strategy. Methods: CD16 (Fc receptor)-expressing NK92 cells were used as effector cells against target DLCBL cell lines in co-culture assays. A high-content, high-throughput drug screening tool was developed to test the effects of small molecule drugs in combination with immunotherapies. Results: We observed that instead of direct cytotoxicity or complement-dependent cytotoxicity, Antibody X exerted its anti-tumour effect primarily through antibody-dependent cellular cytotoxicity (ADCC). To understand the regulators of Antibody X-mediated killing, we utilised a newly developed high-content, high-throughput drug screening tool to evaluate the effects of over 1000 FDA approved compounds on Antibody X-mediated ADCC of DLBCL cells. We noted that BCR-Abl inhibitors differentially regulated Antibody X-mediated ADCC through their effects on Src kinases. Cellular contact between lymphoma cells and immune effector cells was also disrupted through the blockade of LFA-1/ICAM-1 immunological synapse formation. This ultimately led to an absence of death in lymphoma cells. Conclusion: Overall, findings from this study revealed that Antibody X-mediated ADCC is dependent on Src activity and LFA-1/ICAM-1 immunological synapses. We also demonstrated that the novel high-content, high-throughput ADCC platform can be used for immunotherapy-based combinatorial drug screens and mechanistic evaluation of ADCC. [E.K.C. and A.D.J. are co-corresponding authors for this work.]