The CD226-ERK1/2-LAMP1 pathway is an important mechanism for Vγ9Vδ2 T cell cytotoxicity against chemotherapy-resistant acute myeloid leukemia blasts and leukemia stem cells

V gamma 9V delta 2 T cells are attractive effector cells for immunotherapy with potent cytotoxic activity against a variety of malignant cells. However, the effect of V gamma 9V delta 2 T cells on chemotherapy-resistant acute myeloid leukemia (AML) blasts, especially highly refractory leukemia stem cells (LSCs) is still unknown. In this study, we investigated the effect of cytotoxicity of allogeneic V gamma 9V delta 2 T cells on chemotherapy-resistant AML cell lines, as well as on primary AML blasts and LSCs obtained from refractory AML patients. The results indicated that V gamma 9V delta 2 T cells can efficiently kill drug-resistant AML cell lines in vitro and in vivo, and the sensitivity of AML cells to V gamma 9V delta 2 T cell-mediated cytotoxicity is not influenced by the sensitivity of AML cells to chemotherapy. We further found that V gamma 9V delta 2 T cells exhibited a comparable effect of cytotoxicity against LSCs to primary AML blasts. More importantly, we revealed that the CD226-extracellular signal-regulatory kinase1/2 (ERK1/2)-lysosome-associated membrane protein 1 (LAMP1) pathway is an important mechanism for V gamma 9V delta 2 T cell-induced cytotoxicity against AML cells. First, V gamma 9V delta 2 T cells recognized AML cells by receptor-ligand interaction of CD226-Nectin-2, which then induced ERK1/2 phosphorylation in V gamma 9V delta 2 T cells. Finally, triggering the movement of lytic granules toward AML cells induced cytolysis of AML cells. The expression level of Nectin-2 may be used as a novel marker to predict the susceptibility/resistance of AML cells to V gamma 9V delta 2 T cell treatment.