A high incidence of somatically acquired point mutations in the AML1/RUNX1 gene has been reported in poorly differentiated acute myeloid leukemia (AML, M0) and in radiation-associated and therapy-related myelodysplastic syndrome (MDS) or AML. The vast majority of AML1 mutations identified in these diseases were localized in the amino (N)-terminal region, especially in the DNA-binding Runt homology domain. In this report, we show that AML1 point mutations were found in 26 (23.6%) of 110 patients with refractory anemia with excess blasts (RAEB), RAEB in transformation (RAEBt), and AML following MDS (defined these 3 disease categories as MDS/AML). Among them, 9 (8.2%) mutations occurred in the carboxy (C)-terminal region, which were exclusively found in MDS/AML and were strongly correlated with sporadic MDS/AML. All patients with MDS/AML with an AML1 mutation expressed wild-type AML1 protein and had a significantly worse prognosis than those without AML1 mutations. Most AML1 mutants lost trans-activation potential, regardless of their DNA binding potential. These data suggested that AML1 point mutation is one of the major driving forces of MDS/AML, and these mutations may represent a distinct clinicopatho-

AML1/RUNX1 mutations have been reported frequently in myelodysplastic syndrome (MDS) patients, especially those diagnosed with refractory anemia with excess blast (RAEB), RAEB in transformation (RAEBt), or AML following MDS (these categories are defined as MDS/AML). Although AML1 mutations are suspected to play a pivotal role in the development of MDS/ AML, acquisition of additional genetic alterations is also necessary. We analyzed gene alterations in MDS/AML patients with AML1 mutations, comparing them to alterations in those without an AML1 mutation. AML1 mutations were significantly associated with À7/7q-, whereas MDS/AML patients without AML1 mutations showed a high frequency of À5/5q-and a complex karyotype. Patients with AML1 mutations showed more mutations of their FLT3, N-RAS, PTPN11, and NF1 genes, resulting in a significantly higher mutation frequency for receptor tyrosine kinase (RTK)-RAS signaling pathways in AML1-mutated MDS/AML patients compared to AML1-wild-type MDS/AML patients (38% versus 6.3%, Po0.0001). Conversely, p53 mutations were detected only in patients without AML1 mutations. Furthermore, blast cells of the AML1-mutated patients expressing surface c-KIT, and SHP-2 mutants contributed to prolonged and enhanced extracellular signalregulated kinase activation following stem cell factor stimulation. Our results suggest that MDS/AML arising from AML1/ RUNX1 mutations has a significant association with À7/7q-alteration, and frequently involves RTK-RAS signaling pathway activation.

BackgroundBortezomib offers a novel approach to the treatment of multiple myeloma producing rapid control. The aim of this study was to investigate the outcomes of bortezomib and dexamethasone-treated patients with multiple myeloma.MethodsWe conducted a retrospective study of 44 consecutively-treated multiple myeloma patients with bortezomib (1.3 mg/m2 on days 1, 4, 8, and 11 of a 21-day cycle or 1.3 mg/m2 intravenously 1, 8, 15, and 22 of every 35-day cycle) and dexamethasone.ResultsThe median time to progression, progression free survival time, and overall survival time in the treatment groups was 14.9, 14.9, and 38.3 months, respectively. The present study also suggests the possibility that the prognosis of patients with high levels of AST and LDH might be worse.ConclusionsOur results indicate that the treatment of multiple myeloma with bortezomib and dexamethasone is feasible.