Q482H mutation of procaspase-8 in acute myeloid leukemia abolishes caspase-8-mediated apoptosis by impairing procaspase-8 dimerization.

INTRODUCTION: Certain procaspase-8 mutations are reported to be associated with the progression and prognosis of multiple tumors. However, it remains unclear whether the poor chemotherapy response and frequent relapse after complete remission of patients with acute myeloid leukemia (AML) is also related to procaspase-8 abnormalities.

METHODS: Polymerase chain reaction (PCR) amplification and Sanger sequencing of the procaspase-8 gene (CASP8) were performed. Apoptotic rates were analyzed with Annexin V-FITC staining in cells expressing wild-type (WT) procaspase-8, the Q482H or C360S mutant, or control vector after treatment with or without tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Western blot analysis was performed to detect activation of procaspase-8 and downstream apoptotic signaling pathway components in those cells. The Co-immunoprecipitation (Co-IP) assays were performed to detect interaction between WT and mutant procaspase-8 proteins.

RESULTS: AML patients carrying the Q482H mutation were likely to develop chemotherapy resistance. Similar to C360S, The Q482H mutation abolished caspase-8-mediated apoptotic signaling and inhibited TRAIL-induced apoptosis. The Q482H mutation impaired procaspase-8 dimerization, thus preventing the self-activation of procaspase-8.

CONCLUSION: The procaspase-8 Q482H mutation in AML patients abolishes caspase-8-mediated apoptosis by impairing procaspase-8 dimerization.