The cell death protease Kex1p is essential for hypochlorite-induced apoptosis in yeast.

Following microbial pathogen invasion, the human immune system of activated phagocytes generates and releases the potent oxidant hypochlorous acid (HOCl), which contributes to the killing of menacing microorganisms. Though tightly controlled, HOCl generation by the myeloperoxidase-hydrogen peroxide-chloride system of neutrophils/monocytes may occur in excess and lead to tissue damage. It is thus of marked importance to delineate the molecular pathways underlying HOCl cytotoxicity in both microbial and human cells. Here, we show that HOCl induces the generation of reactive oxygen species (ROS), apoptotic cell death and the formation of specific HOCl-modified epitopes in the budding yeast Saccharomyces cerevisiae. Interestingly, HOCl cytotoxicity can be prevented by treatment with ROS scavengers, suggesting oxidative stress to mediate the lethal effect. The executing pathway involves the pro-apoptotic protease Kex1p, since its absence diminishes HOCl-induced production of ROS, apoptosis and protein modification. By characterizing HOCl-induced cell death in yeast and identifying a corresponding central executor, these results pave the way for the use of Saccharomyces cerevisiae in HOCl research, not least given that it combines both being a microorganism as well as a model for programmed cell death in higher eukaryotes.

RUNX1 mutations in acute myeloid leukemia: results from a comprehensive genetic and clinical analysis from the AML study group.

PURPOSE: To evaluate frequency, biologic features, and clinical relevance of RUNX1 mutations in acute myeloid leukemia (AML). PATIENTS AND METHODS: Diagnostic samples from 945 patients (age 18 to 60 years) were analyzed for RUNX1 mutations. In a subset of cases (n = 269), microarray gene expression analysis was performed. RESULTS: Fifty-nine RUNX1 mutations were identified in 53 (5.6%) of 945 cases, predominantly in exons 3 (n = 11), 4 (n = 10), and 8 (n = 23). RUNX1 mutations clustered in the intermediate-risk cytogenetic group (46 of 640, 7.2%; cytogenetically normal, 34 of 538, 6.3%), whereas they were less frequent in adverse-risk cytogenetics (five of 109, 4.6%) and absent in core-binding-factor AML (0 of 77) and acute promyelocytic leukemia (0 of 61). RUNX1 mutations were associated with MLL-partial tandem duplications (P = .0007) and IDH1/IDH2 mutations (P = .03), inversely correlated with NPM1 (P < .0001), and in trend with CEBPA (P = .10) mutations. RUNX1 mutations were characterized by a distinct gene expression pattern; this RUNX1 mutation-derived signature was not exclusive for the mutation, but also included mostly adverse-risk AML [eg, 7q-, -7, inv(3), or t(3;3)]. RUNX1 mutations predicted for resistance to chemotherapy (rates of refractory disease 30% and 19%, P = .047, for RUNX1-mutated and wild-type patients, respectively), as well as inferior event-free survival (EFS; P < .0001), relapse-free survival (RFS, P = .022), and overall survival (P = .051). In multivariable analysis, RUNX1 mutations were an independent prognostic marker for shorter EFS (P = .007). Explorative subgroup analysis revealed that allogeneic hematopoietic stem-cell transplantation had a favorable impact on RFS in RUNX1-mutated patients (P < .0001). CONCLUSION: AML with RUNX1 mutations are characterized by distinct genetic properties and are associated with resistance to therapy and inferior outcome.