Antibody-mediated targeting of NOX2 as a potential therapeutic strategy in cancer

Abstract

NADPH oxidase 2 (NOX2) is a key enzyme in phagocytic microbial killing through its production of superoxide (O2•−), which can subsequently be converted into other reactive oxygen species (ROS). In monocytes and other myeloid cells, NOX2 is localized to endolysosomal and plasma membranes, enabling the generation of both intra- and extracellular ROS. Although ROS are protective in some contexts, excessive extracellular ROS may suppress cancer-targeting lymphocytes, including natural killer (NK) cells, thereby contributing to cancer initiation and progression. In mouse models, both pharmacological and genetic inhibition of NOX2 reduces tumour burden and metastasis, and NOX2 inhibitors have been explored clinically in leukaemia and other cancers. Monoclonal antibodies are powerful therapeutic agents and may represent a promising, yet understudied, strategy for targeting NOX2. This thesis aimed to evaluate the effects of an anti-NOX2 antibody, 7D5, on extracellular ROS production in human monocytes using isoluminol-enhanced chemiluminescence assays. Both 7D5 and a control antibody tended to reduce extracellular ROS, although 7D5 was slightly more effective when ROS production was stimulated by a bacterial peptide. We also examined whether 7D5 could uphold NK cell viability and function in co-cultures of NK cells, monocytes, and the K562 leukemic cell line. Unlike the control antibody, 7D5 significantly protected NK cells from ROS-induced apoptosis. In summary, a monoclonal antibody against NOX2 weakly affected ROS production from human monocytes and yet preserved NK cell viability in co-cultures with ROS-producing monocytes. NOX2 antibodies may thus represent a strategy to improve NK cell function in cancer immunotherapy.