Extracellular HMGB1 prevents necroptosis in acute myeloid leukemia cells

Changes in the expression and subcellular localization of high mobility group box 1 (HMGB1), a damage-associated molecular pattern (DAMP) molecule, have been implicated in tumorigenesis and tumor cell death in response to cancer therapy. Specifically, HMGB1 release has been shown to occur with a specific form of induced cell death known as necroptosis. In the present study, we examined the role of HMGB1 in the necroptosis of acute myeloid leukemia (AML) cells. In two AML cell lines and primary AML cells from two patients, etoposide induced necroptosis via cIAP1/2 degradation when caspase activity was inhibited by Z-VAD-fmk, but treatment with extracellular HMGB1 prevented this necroptosis. Interestingly, HMGB1 did not prevent the degradation of cIAP1/2, but rather activated the nuclear factor kappa B pathway. The results of the present study provide evidence that extracellular HMGB1 is not only an important DAMP molecule released by cells upon necrosis, but also a regulatory factor that prevents necroptosis in AML cells.