|M.Sc Student||Ledersnaider Max|
|Subject||How Does Targeting EMMPRIN/CD147 Alleviate Immune|
Suppression and Change the Tumor Microenvironment?
|Department||Department of Medicine||Supervisor||? Michal Rahat|
|Full Thesis text|
Extracellular matrix metalloproteinase inducer (EMMPRIN/CD147) is a multifunctional protein that is overexpressed on many types of tumor cells and mediates tumor cell-macrophage interactions. We previously developed a specific anti-EMMPRIN polyclonal antibody (designated h161-pAb) that recognizes a novel epitope in the protein that is responsible for the induction of MMP-9 and VEGF and promotes angiogenesis. Here, we show that using the h161-pAb to target this antigen can induce human tumor cell death. We showed that this antibody together with complement proteins induced tumor cell death by complement-dependent cytotoxicity (CDC) that triggered necroptosis - a programmed, pro-inflammatory and pro-immunogenic form of cell death. Necroptosis is characterized by inactivation of caspase-8, phosphorylation of RIPK3 and MLKL and their subsequent localization to the plasma membrane where they permeabilize it to achieve death. We demonstrate that unlike other forms of cell death, such as necrosis triggered by hydrogen peroxide or apoptosis triggered by etoposide, necroptosis that is triggered by h161-pAb and complement proteins together released specific danger signals (DAMPs), in particular, IFNβ and elevated levels of dsRNA. We further demonstrated that these released DAMPs were able to activate and polarize naïve macrophages toward an anti-viral/anti-tumoral mode of activation that was characterized by the macrophage secretion of the death-inducing cytokines IFNβ, IP-10 and TRAIL. This response was dsRNA-dependent, as macrophages exposed to conditioned medium that were pretreated with the dsRNA-selective nuclease RNase III, were unable to secrete these cytokines. Furthermore, these polarized macrophages displayed an increased ability to induce tumor cell death via antibody dependent cell cytotoxicity (ADCC) when co-cultured with fresh tumor cells. Collectively, these results suggest that targeting EMMPRIN with the h161-pAb and complement can alleviate TME immune suppression and facilitate an effective immune response against tumor cells.