Novel enhancement of antibody therapy through NOD2 activation

PROJECT SUMMARY Our long-term objective is to understand the expression and function of monocyte/macrophage Fcγ receptors with a goal of improving antibody-based therapies for diseases such as chronic lymphocytic leukemia (CLL). We and others have demonstrated that CD20 antibodies improve outcome of CLL patients receiving both chemoimmunotherapy and recently treatment with a second generation BTK inhibitor acalabrutinib. Monocytes / macrophages play a critical role in antibody-mediated depletion of tumor cells, but they are in a suppressed state within CLL. In particular, macrophages in CLL patients are unusually large in size and play a major role in supporting the survival and proliferation of CLL cells. These macrophages have been called nurse-like cells (NLCs). We have found that activating the intracellular receptor NOD2 in monocytes / NLCs substantially reduces expression of negative regulators such as the inositol phosphatase SHIP1 and the inhibitory receptor CD31. Conversely, we saw upregulation of the activating FcγRI and the associated γ-chain. This led to significant increases in FcγR-mediated cytokine production, including those that activate NK cells. Along with such cytokines, there was upregulation of NK cell activating surface ligands in monocytes / NLCs treated with NOD2 agonists. Indeed, co-culturing of treated monocytes with NK cells enhanced NK-cell maturation and cytotoxicity. Collectively, these results suggest that NOD2 agonists may be an effective adjuvant for the treatment of CLL. Importantly, the NOD2 agonist MTP-PE (mifamurtide/ MePACT) has been the subject of past and current clinical trials for osteosarcoma and was approved by the European Medicine Association (EMA) in combination with intensive chemotherapy for osteosarcoma as an immune adjuvant. Overall, mifamurtide has an acceptable safety profile as well, justifying it as an alternative strategy for clinical development. Based on the above observations, we hypothesize that NOD2 agonists will activate monocytes / NLCs and will also indirectly or directly activate NK cells. To test the predictions of this hypothesis we propose the following three Aims: 1) Interrogate the mechanisms of influence of NOD2 stimulation on monocytes / NLCs and functional outcomes; 2) Examine the mechanisms of influence of NOD2 stimulation on NK cells, including contact- dependent/independent requirements, NK-cell maturation and cytotoxic ability; and 3) Validate the central hypothesis in vivo that NOD2 activation can lead to phenotypic and functional changes in monocytes / NLCs, as well as in NK cells, leading to stronger antitumor activity. At the completion of these studies, we will have established an entirely novel mechanism of activation of monocytes and NK cells in CLL, thus enhancing the efficacy of monoclonal antibody-based therapies.