Abstract
Natural killer (NK) cells mediate the cytolysis of transformed cells and are currently used as an adoptive cellular therapy to treat cancer. Infection with human cytomegalovirus has been shown to expand a subset of "adaptive" NK cells expressing the activation receptor NKG2C that have preferred functional attributes distinct from conventional NK cells. Because NKG2C delivers a strong activating signal to NK cells, we hypothesized that NKG2C could specifically trigger NK-cell-mediated antitumor responses. To elicit a tumor-directed response from NKG2C+ NK cells, we created an anti-NKG2C/IL-15/anti-CD33 killer engager called NKG2C-KE that directs NKG2C+ cells to target CD33+ cells and tumor-associated antigen expressed by acute myelogenous leukemia cells. The NKG2C-KE induced specific degranulation, interferon-γ production, and proliferation of NKG2C-expressing NK cells from patients who reactivated cytomegalovirus after allogeneic transplantation. The NKG2C-KE was also tested in a more homogeneous system using induced pluripotent stem cell (iPSC)-derived NK (iNK) cells that have been engineered to express NKG2C at high levels. The NKG2C-KE triggered iNK-cell-mediated cytotoxicity against CD33+ cells and primary AML blasts. The NKG2C-KE-specific interaction with adaptive NK and NKG2C+ iNK cells represents a new immunotherapeutic paradigm that uniquely engages highly active NK cells to induce cytotoxicity against AML through redirected targeting.