Mutations in genes of the splicing machinery have been described recently in myelodysplastic syndromes (MDS). In the present study, we examined a cohort of 193 MDS patients for mutations in SRSF2, U2AF1 (synonym U2AF35), ZRSR2, and, as described previously, SF3B1, in the context of other molecular markers, including mutations in ASXL1, RUNX1, NRAS, TP53, IDH1, IDH2, NPM1, and DNMT3A. Mutations in SRSF2, U2AF1, ZRSR2, and SF3B1 were found in 24 (12.4%), 14 (7.3%), 6 (3.1%), and 28 (14.5%) patients, respectively, corresponding to a total of 67 of 193 MDS patients (34.7%). SRSF2 mutations were associated with RUNX1 (P < .001) and IDH1 (P ‫؍‬ .013) mutations, whereas U2AF1 mutations were associated with ASXL1 (P ‫؍‬ .005) and DNMT3A (P ‫؍‬ .004) mutations. In univariate analysis, mutated SRSF2 predicted shorter overall survival and more frequent acute myeloid leukemia progression compared with wildtype SRSF2, whereas mutated U2AF1, ZRSR2, and SF3B1 had no impact on patient outcome. In multivariate analysis, SRSF2 remained an independent poor risk marker for overall survival (hazard ratio ‫؍‬ 2.3; 95% confidence interval, 1.28-4.13; P ‫؍‬ .017) and acute myeloid leukemia progression (hazard ratio ‫؍‬ 2.83; 95% confidence interval, 1.31-6.12; P ‫؍‬ .008). These results show a negative prognostic impact of SRSF2 mutations in MDS. SRSF2 mutations may become useful for clinical risk stratification and treatment decisions in the future.

Systematic assessment of minimal residual disease (MRD) in acute myeloid leukemia (AML) patients has been hampered by lack of a reliable, uniform MRD marker applicable to all patients. We evaluated next-generation sequencing (NGS) for MRD assessment in AML patients (n = 80 samples). The ability of NGS technologies to generate thousands of clonal sequences makes it possible to determine the allelic ratio of sequence variants. Using NGS, we were able to determine the allelic ratio of different FLT3-internal tandem duplication (ITD) clones within one patient sample, in addition to resolution of FLT3-ITD insertion site, length, and sequence in a single analysis. Furthermore, NGS allowed us to study emergence of clonal dominance. Parallel assessment of MRD by NGS and quantitative real-time polymerase chain reaction in NPM1 mutated patients was concordant in 95% of analyzed samples (n = 38). The frequency of mutated alleles was linearly quantified by NGS. As NGS sensitivity is scalable depending on sequence coverage, it reflects a highly flexible and reliable tool to assess MRD in leukemia patients.

et al. Induction of WT1 (Wilms' tumor gene)-specific cytotoxic T lymphocytes by WT1 peptide vaccine and the resultant cancer regression.

1402 Over 20 different fusion partner genes of NUP98 have been reported in hematological malignancies with the majority of NUP98 fusions occurring in acute myeloid leukemia (AML). Recently, a specific fusion of NUP98 with Nuclear receptor-binding SET domain protein 1 (NSD1) has been analyzed in a large cohort of pediatric and adult AML patients. In this report, 16.1% of pediatric AML samples and 2.3% of adult cytogentically normal (CN)-AML cases were found to be NUP98/NSD1-positive. NUP98/NSD1-positive patients had an adverse outcome. The aim of our study was to investigate the frequency, clinical features and the prognostic impact of NUP98/NSD1 in another large, uniformily treated adult AML cohort, and in patients with myelodysplastic syndromes, which frequently precede overt leukemia. We studied 504 younger AML patients (<60 years) and 193 MDS patients for the presence of NUP98/NSD1 translocations. Analysis in the AML cohort was also performed for mutations in FLT3-ITD, NPM1, DNMT3A, IDH1, IDH2. Additional mutation analyses were performed in the subgroup of CN-AML for CEBPA, MLL-PTD, WT1 and WT1 SNP rs16754, NRAS. The NUP98/NSD1 fusion was identified by a nested RT-PCR using patient-derived cDNA. cDNA from a patient with proven NUP98-NSD1 fusion was used as a positive control. NUP98/NSD1 fusions were identified in 7 out of 504 younger adult AML patients (1.4%) while the NUP98/NSD1 fusion was not found in any of the 193 MDS patients. In the AML cohort, NUP98/NSD1 positive patients showed a higher number of peripheral blood blasts (P=.002), while other clinical characteristics such as FAB-subtype, type of AML, hemoglobin levels, white cell count or platelet count did not significantly differ between patients with or without the NUP98/NSD1 fusion. The majority of NUP98/NSD1 positive patients (5 out of 7) showed a normal karyotype while one patient was found to have a del(9) and another patient an inv(3)(q21q26) with monosomy 7. We identified an association between FLT3-ITD and NUP98/NSD1 fusion in our cohort (P=.007, 5 patients with NUP98/NSD1 also had a FLT3-ITD). This finding confirms the data by Hollink et al. and suggests a possible functional link between FLT3-ITD and the NUP98/NSD1 fusion in leukemogenesis. NUP98/NSD1 fusions were not associated with other mutations like those suggested in epigenetic regulation (DNMT3A, IDH1 and IDH2). In CN-AML, we also looked for an association between BAALC, ERG, EVI1, MN1, MLL5 and WT1 expression but did not find a significant difference between the expression of these genes and NUP98/NSD1 fusion genes. Due to the low frequency of the aberration outcome analysis was performed for explorative purposes. Considering the whole AML cohort we did not detect a significant difference for OS and for RFS between NUP98/NSD1 positive and negative patients (OS, HR 1.6; 95%CI 0.66–3.88; P=.3; RFS, HR 2.33; 95%CI 0.74–7.30; P=.147). However, NUP98/NSD1 positive patients had significantly lower complete remission (CR) rates (43 vs. 77 percent, P=.037). When considering only patients with CN-AML the NUP98/NSD1 positive patients (n=5) had no significantly different OS and RFS (OS, HR 2.08; 95%CI 0.77–5.64; P=.15; RFS, HR 2.88; 95%CI 0.71–11.71; P=.14). Again, a significantly lower CR rate was observed in the NUP98/NSD1 positive patients compared to NUP98/NSD1 negative patients with CN-AML (40 vs. 80 percent, P=.03). Because of the association between FLT3-ITD and NUP98/NSD1 we also investigated the prognostic impact in the subgroup of CN-AML patients also positive for FLT3-ITD. Again, OS and RFS did not differ between NUP98/NSD1 positive and negative patients (OS, HR 1.31; 95%CI 0.47–3.64; P=.61; RFS, HR 2.04; 95%CI 0.49–8.57; P=.33). For this subgroup a trend towards a lower CR rate was observed for NUP98/NSD1 positive FLT3-ITD positive CN-AML patients (40 vs 75 percent, P=.08). In summary, our analysis confirms the presence but low incidence of the NUP98/NSD1 fusion gene in adult AML patients and the strong association with FLT3-ITD. The specific association of NUP98/NSD1 with FLT3-ITD mutations warrants clinical investigation with FLT3 inhibitors in these patients. Disclosures: No relevant conflicts of interest to declare.