Programmed cell death is required for normal development and tissue homeostasis, but can also occur as a
defensive response to pathogen infection. We now understand that cells can undergo distinct forms of
programmed cell death: in addition to apoptosis, necroptosis is a recently-described form of cell suicide that
can be induced by viral infection. Necroptosis involves cellular swelling and rupture, and has been
hypothesized to trigger inflammatory and immune responses when it occurs in vivo, but the determinants of
immune responses to necroptosis are not well understood. We have found that activation of the key
necroptosis-inducing kinase, RIPK3, can trigger transcriptional responses in addition to inducing cell death.
Furthermore, our preliminary data indicate that chemokine expression induced by RIPK3 activation
accompanies RIPK3-induced cell death, and that this transcriptional response is required to render necroptosis
immunogenic. This leads to the central hypothesis of this proposal: That necroptosis represents a uniquely
immunogenic form of cell death, because it couples the production if immune-attractant chemokines
with lytic cell death. An important extension of this idea, which we will test, is that induction of necroptosis
within the tumor microenvironment will promote beneficial tumor immunity. To test this idea, we will
focus on three Aims. First, we will use novel high-content imaging approaches to compare the way the
immune system traffics, presents, and reacts to antigens derived from apoptotic, necroptotic, or necrotic cells.
We will then use flank tumor models, in combination with a newly developed system for the rapid induction of
different forms of cell death in vivo, assess the immune response to the necroptotic death of tumor cells. We
will apply these findings to clinically-relevant tumor models, by testing the ability of the immune signature
created by tumor cell necroptosis to synergize with immune checkpoint inhibitors and to promote immune
clearance of metastatic lesions. Finally, we will create and test a system allowing rapid induction of necroptosis
in unmodified tumor cells in vivo. Together, the experiments proposed here will determine what makes
necroptosis immunogenic, then apply these findings to models of tumor immunotherapy.