WT1 Mutations Research Articles

Genomic Landscape and Prognosis in Pediatric Acute Myeloid Leukemia: A Study on the French ELAM02 Trial

Background. Acute Myeloid Leukemia (AML) is a rare and genetically heterogeneous disease that constitutes 15 to 20% of childhood leukemia. Despite major treatment improvement over the past decades pediatric AML remains a challenging disease with poor outcome compared to acute lymphoid leukemia (ALL). About 50% of these patients relapse after standard intensive chemotherapy. Molecular analysis pointed out the prognostic impact of gene mutation such as FLT3-ITD, NPM1 or CEBPA; and new categories of regulators like epigenetic modifiers. More recently mutational profiling studies revealed distinct molecular subgroups with prognostic significant and stratification in adult AML. Nevertheless cytogenetic and mutational profiles are quite different between adult and pediatric AML. Extensive genomic studies have not been reported to date in pediatric AML. In this context it is of importance to identify additional genetic or molecular abnormalities to better understand leukemogenesis and also to predict outcome and serve as novel therapeutic targets.Methods. We performed a mutational analysis on diagnostic samples from patients enrolled in the French National Multicenter ELAM02 trial. 438 patients with de novo AML (except AML3) were enrolled between march 2005 and December 2011 (median age: 8,22yrs [0-18.61]; median WBC: 15.4G/l [0.4-575]; cytogenetic subgroups: CBF-AML[n=97], NK-AML [n=109], MLL-AML[n=95], MRC2 other[n=77], MRC3 [n=55], failure [n=5]). Diagnostic samples were prospectively collected and 386 of the 438 patients (88%) were studied by next-generation sequencing (Miseq, Illumina with haloplex librairy and ion Proton, thermofischer with ampliseq librairy) including 36 genes frequently reported in myeloid malignancy. Two different technologies of next generation sequencing (NGS) were used, allowing direct validation. FLT3-ITD was detected and quantified by Genescan analysis.Results. We identified 579 driver mutations involving 36 genes or regions in 386 patients (mean 1.5 per case), with at least 1 driver mutation in 291 patients (75%) and 2 or more driver mutations in 44% of samples. The number of mutation identified at diagnosis in cytogenetic subgroup is significantly lower in MLL-AML (0.44 mutation/patient; p<10-4). Mutations involving genes from the tyrosine kinase pathways (i.e RAS, FLT3, KIT, PTPN11, JAK2, MPL, CBL) were the most frequent and represent 56.3% of all aberrations. Among them N-RAS was detected in 26.4% of all cases, followed by FLT3-ITD, KIT and K-RAS in 14.8%, 12.4% and 12.2% respectively. We identified 64 driver mutations in the group of transcription factors (CEBPA, RUNX1, GATA, ETV6), 60 in the combined group of chromatin modifier (ASXL1, EZH2, BCOR) and DNA methylation (DNMT3A, IDH, TET2), 59 in the group of tumor suppressor genes (WT1, PHF6, TP53) 36 mutations in NPM1 gene, and few mutations in cohesion and spliceosome sub-groups. Identified mutations are indicated in the figure according cytogenetic subgroups. Among the 438 patients, 398 (91%) were in complete remission (CR) after two courses (induction and first consolidation), the 5-year overall survival (OS) is 71.5% [65-78] and the 5-year leukemia free survival (LFS) is 56.6% [49.7-63.5]. In univariate analysis, we found that FLT3-ITD, mutations in RUNX1, WT1 and PHF6 were associated with reduced LFS (p=0.0003 for FLT3-ITD, p=0.01 for RUNX1, p=0.02 for WT1 and p=0.025 for PHF6) and reduced OS (p=0.0003 for FLT3-ITD, p=0.0003 for RUNX1, p=0.015 for WT1 and p=0.04 for PHF6). Mutations in NPM1 is associated with an improved 5-yr LFS (p=0.014) and 5-yr OS (p=0.005). Multivariate analysis revealed that FLT3-ITD, RUNX1 and PHF6 were independently associated with an adverse outcome and NPM1 with an improved outcome.Conclusions. We performed an extensive mutational study in de novo pediatric AML enrolled in the ELAM02 trial. We described the genomic landscape of 386 patients and showed the frequency of different mutations according cytogenetics. Interestingly we found mutations in genes involved in constitutional or pre-leukemic disease such as PTPN11, RUNX1, MPL or ETV6. We found that FLT3-ITD, RUNX1 and PHF6 mutations predict poor outcome although NPM1 mutations predict a better outcome. Mutational profiling reveals useful information for risk stratification and therapeutic decisions. [Display omitted] DisclosuresBaruchel:Amgen: Consultancy.

Genetic Profile of Acute Erythroid Leukemia

IntroductionAcute erythroid leukemias (AELs) are infrequent acute leukemias characterized by a predominant erythroid population, dysplasticity and ring sideroblasts. The 2016 revision of the World Health Organization (WHO) Classification re-classified previous AELs as myelodysplastic syndromes (MDS) or acute myeloid leukemia (AML) not otherwise specified (non erythroid subtype, or pure erythroid type), according to blast percentage in all nucleated bone marrow cells. Recent studies have offered the evidence that genetic profiles are associated with pathophysiology and clinical outcomes in myeloid malignancies. However, characteristic mutation profiles of AEL and its genetic differences or similarities with other-types of AML and MDS have not been fully elucidated due to the lack of a sufficient number of samples, although frequent TP53 mutations have been reported (35-43.5%).MethodWe performed a comprehensive genetic study, in which paired tumor/normal DNA from 24 AEL cases were analyzed by whole-exome sequencing (WES). Subsequently, in total 41 cases were screened for mutations in 69 driver genes associated with myeloid malignancies using targeted-capture sequencing. Genome-wide copy number analysis was also performed based on allele frequency of heterozygous single nucleotide polymorphisms and sequencing depth. Frequencies of driver mutations in AEL were compared to those in other-types of AML analyzed by the Cancer Genome Atlas Network (TCGA) (N = 197).ResultsThe mean number of nonsynonymous mutations identified by WES was 10 per sample (range, 0-21), which was similar to that in other-types of AML or MDS. Most frequently mutated genes were STAG2, TP53, RUNX1 and TET2 (17%, respectively), followed by WT1 and BCOR (13%, respectively). All TP53 mutated cases harbored complex karyotypes. Subsequent targeted sequencing identified 3.4 mutations per sample on average (range, 0-9). TP53 was mutated in 8 cases (20%), and lower frequency of TP53 mutations in our cohort was attributed to the relatively lower proportion (21%) of cases with complex karyotype compared to those in the previous reports. Commonly mutated genes in other-types of AML, such as NPM1, FLT3, and DNMT3A, were relatively infrequent in AEL and affected 7 (17%), 4 (9.8%) and 3 (7.3%) cases, respectively. Genes associated with splicing machinery were mutated in 5 cases (12%), including SRSF2 (9.8%) and U2AF1 (2.4%). Of note, mutations in genes implicated in cohesin complex were observed in as many as 32% of cases, including those in STAG2 (24%), SMC1A (4.9%) and RAD21 (2.4%). Mutations in epigenetic regulators were also frequently identified in AEL, including those in WT1 (20%), TET2 (15%) and IDH1/2 (7%). Mutations in TP53 were mutually exclusive with those in cohesin complex (p = 0.04) and epigenetic regulators (p = 0.05). When we compared the frequencies of recurrent mutations in AEL to those in other-types of AML analyzed by TCGA, mutations in STAG2 (p = 6*105), SRSF2 (p = 7*104), WT1 (p = 0.01), GATA2 (p = 0.008), and BCOR (p = 0.02) were significantly more frequent in AEL, whereas those in FLT3 (p = 0.01) and DNMT3A (p = 0.007) were significantly less frequent in AEL. Mutations in cohesin complex and splicing factors were frequently observed both in AEL and MDS, and higher frequency of these genetic lesion in AEL rather than other-types of AML suggested that AEL and MDS are similar disease entities. Recently, genomic subgroups of AML with mutations in cohesin complex, spliceosome and TP53 have been associated with poor prognosis in AML, and poor prognosis of AEL was thought to be due to higher frequency of these genetic lesions.ConclusionWES and follow-up targeted sequencing revealed the genetic landscape of AEL. Frequent mutations in TP53, splicing factors and cohesin complex were characteristic to AEL, and thought to be involved in its pathophysiology. Our data showed the genetic similarities between AEL and MDS, which were compatible with the partial integration of AEL into MDS in the recent revision of WHO classifications. DisclosuresKataoka:Kyowa Hakko Kirin: Honoraria; Yakult: Honoraria; Boehringer Ingelheim: Honoraria. Ogawa:Sumitomo Dainippon Pharma: Research Funding; Takeda Pharmaceuticals: Consultancy, Research Funding; Kan research institute: Consultancy, Research Funding. Heuser:Pfizer: Research Funding; BerGenBio: Research Funding; Novartis: Consultancy, Research Funding; Tetralogic: Research Funding; Celgene: Honoraria; Karyopharm Therapeutics Inc: Research Funding; Bayer Pharma AG: Research Funding.

CSF3R Mutations Are Predominantly Subclonal Events in Intermediate Risk Karyotype AML and Prevalently Occur with CEBPA Mutations

Background: The colony stimulating factor 3 receptor(CSF3R) plays an important role in granulocyte differentiation and acquired mutations have been described in different myeloid malignancies. Besides chronic neutrophilic leukemia (CNL) and severe congenital neutropenia (SCN), mutations in CSF3R (CSF3Rmut) have also been reported in acute myeloid leukemia (AML) at low frequency and recently have been associated with CEBPA mutations (Lavallèe et al., Blood 2016; Maxson et al., Blood 2016) in adult and pediatric AML. First studies suggest sensitivity of CSF3Rmut CNL against JAK kinase inhibitors suggesting the possibility for targeted therapy for a subset of CSF3Rmut AML patients.Aims: The evaluation of CSF3Rmut in AML with intermediate-risk karyotype for frequency and association with other mutations with special focus on CEBPA mutation status.Methods: We analyzed 274 cases with intermediate risk de novo AML for CSF3Rmut by next generation sequencing (Illumina, San Diego, CA) of exon 14 and 17 (sensitivity: 1%), which contain the mutational hotspot regions of CSF3R. As CSF3R mutations were associated with CEBPA mutations in the above-mentioned studies, we analyzed a selected cohort of 179 CEBPA mutated cases in comparison to 95 cases with CEBPA wild type.202 cases (74%) had normal karyotype (CN-AML) and 72 (26%) had intermediate-risk aberrant cytogenetics according to MRC criteria. Female/male ratio was 127/147 and age ranged from 16- 88 y (median: 64 y). Mutation status of the following genes were available in all cases: ASXL1, CEBPA, FLT3-ITD, FLT3-TKD, GATA2, IDH1/2, KRAS, KMT2A-PTD, NPM1, NRAS, RUNX1 and WT1. All mutations with a variant allele frequency (VAF) < 10% were defined as subclonal. 95 cases had wild type CEBPA (CEBPAwt), 92 cases were CEBPA single mutated (CEBPAsm), 81 cases were CEBPA double mutated (CEBPAdm), 6 cases showed CEBPA mutations withloss of heterozygosity (CEBPA LOH).Results: Overall, in 7/274 patients (3%) CSF3Rmut were detected. This is slightly higher than expected in an unselected AML cohort (Sano et al., Br J Haematol 2015). Cytomorphology revealed AML M0 (n=1), AML M1 (n=2), AML M2 (n=3) and AML M4 (n=1). With regard to immunophenotype CSF3Rmut cases did not differ from CSF3Rwt cases which may be due to limited case numbers. All CSF3Rmut cases had CN-AML. The activating transmembrane mutation p.Thr618Ile, which has been identified as common mutation in CNL was the most frequent mutation (4/7). In addition two mutations leading to a truncated receptor (p.Ser715* and p.Gln749*) and a previously not described frame-shift mutation leading to a defecting splice variant (p.Ser783Glnfs*6) were identified. The median CSF3R VAF was 7% (range 2-45%). In 5/7 cases, CSF3Rmut was subclonal (VAF <10%, see figure). CSF3Rmut cases showed a median of 2 concomitant mutations (range 1-4). The most frequent concomitantly mutated gene was CEBPA (5/7 cases; 2 cases CEBPAsm, 1 case CEBPAdm and 2 cases with CEBPA LOH), followed by NRAS (3/7), ASXL1 (2/7) and RUNX1 (2/7). IDH1, TET2 and WT1 were mutated in one case each (see figure). Mutations in NPM1, FLT3, KMT2A or GATA2 were never detected. Interestingly, in CEBPAdm and CEBPA LOH cases, CSF3R was the only concomitantly mutated gene, whereas CEBPAsm cases harbored mutations in at least 1 gene in addition to CSF3R. In 2/7 CSF3Rmut cases we analyzed changes in the patterns of genetic lesions between diagnosis and relapse. Case 1 harbored CEBPAdm and a subclonal CSF3Rmut (VAF: 7%) at diagnosis. At relapse the CEBPAdm persisted, whereas CSF3Rmut was lost. Case 2 harbored two germline CEBPAmut and one somatic CEBPAmut at diagnosis. In addition, mutations in CSF3R and WT1 were identified. At relapse both the somatic CEBPAmut and WT1mut persisted, whereas CSF3Rmut was lost. These results indicate again that the CSF3Rmut was present only in a subclone of CEBPAmut AML in both cases.Due to the limited number of CSF3Rmut cases, we did not perform survival analysis in this study.Summary: 1) CSF3R mutations are rare and predominantly subclonal events in AML and therefore may not be a suitable target for directed therapy.2) CSF3Rmut prevalently occur with CEBPA mutations but are not limited to CEBPAdm. [Display omitted] DisclosuresFasan:MLL Munich Leukemia Laboratory: Employment. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Perglerová:MLL2 s.r.o: Employment. Kern:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Haferlach:MLL Munich Leukemia Laboratory: Other: Part Owner MLL Munich Leukemia Laboratory.

Clono-Specific Evaluation of Minimal Residual Disease in Acute Myeloid Leukemia

Background:The genetic landscape of adult acute myeloid leukemias (AML) has been recently unravelled. This makes achievable the determination of a comprehensive profile of driver lesions for virtually all patients at diagnosis. Recent studies using multi-target minimal residual disease (MRD) strategies with around 1% sensitivity indicate that the clearance of all molecular events after chemotherapy is associated with better survival. To improve the clono-specificity and the sensitivity of this approach, after a precise determination of AML clonal composition, we combined cytogenetic, FISH, and high sensitivity deep sequencing technologies to monitor the MRD in a series of 69 patients.Methods:Forty-five consecutive patients reflecting the genetic diversity of AML were prospectively included and 24 patients were retrospectively studied. All patients received an anthracycline + cytarabine based regimen. The clonal architecture was established at diagnosis based on NGS-targeted resequencing (122 gene panel) and cytogenetic data. Lesions were next investigated in complete remission (CR). Based on the initial clonal composition, targeted resequencing panels were designed to improve the sensitivity by the use of unique molecular barcodes (Haloplex High Sensitivity, or HS-NGS assay). Cytogenetic events were evaluated by FISH.Results:In the 69 patients, a median of 4 genetic or chromosomal events were identified per patient (range 0-10). One patient had no evaluable target allowing MRD evaluation in 68/69 patients.To determine the threshold of detection of the HS NGS assay, we analyzed the frequency of mutant reads in multiple samples expected to be wild type for 31 given SNVs and 2 indels. A consensus threshold of detection was set at a variant allele frequency (VAF) of 0.2% for all lesions.In CR samples, early initiating events frequently persisted after treatment, especially mutations in DNMT3A, TET2, ASXL1, EZH2, IDH1, TP53, SRSF2, and U2AF1. Mutations in FLT3, NRAS, KIT, NPM1, CEBPA, WT1, IDH2 and BCOR were the most frequently cleared events.Seven patients did not reach CR after one course, and two had no available material after one course. In the 59 remaining patients, we tested whether the global response level of all targets was associated with prognosis. We used the median VAF of the first events of all clonal architectures to separate good responder from poor responders (i.e. VAF = 1.66%). At 2 years, there was a trend to lower leukemia free survival (LFS) probability in poor responders (31.7+/-9.9% vs 51.7+/-9.8%, p=0.08) with no translation in overall survival (OS).We next investigated if the persistence of two or more detectable markers was associated with prognosis. The 58 patients with more than one evaluable event were consequently separated in two groups: patients with 0 or 1 marker above the detection threshold after treatment (n=31), and patients with 2 or more detectable lesions (n=27). At 2 years, DFS was 64.9+/-9.3 % in patients with 0 or 1 detectable marker vs 19.8+/-8.7% in patients with 2 or more detectable markers (p=0.001). OS probability was higher in patients with 0 or 1 detectable marker 84+/-6.6% vs 57.1+/-10.5% (p=0.023). When focusing on the 40 patients with intermediate cytogenetics, persistence of 2 or more markers was associated with lower LFS (57+/-11.8% vs 19.4+/-10.5 p=0.0048) and with a trend to lower OS (85+/-8% vs 61+/-11.9% p=0.07). Similar results were observed when restricting the analyses to the 42 prospectively included patients (At 2 years: LFS 73+/-10% vs 24+/-10%, p=0.0026 and OS 90.2+/-6.6% vs 62.8+/-11.5%, p=0.036).In 50 patients with 3 or more identified events, the persistence of 3 or more markers after one course was associated with a very high risk of relapse (DFS 23.5+/-10.3 % vs 75.8 +/-7.5% at one year, p<0.0001; median DFS at 7 months in the non-responder group and not reached after two years in the responder group), and lower OS probability (84.8+/-6.2 vs 45.2+/-13.5% at 2 years, p=0.026)ConclusionOur study shows the high prognostic value of a personalized multi-target clono-specific MRD evaluation that can be used in nearly all AML patients. Detection of two or more events in more than 0.4% cells after one course is associated with lower survival, in particular in intermediate cytogenetic patients. Larger studies are needed to confirm the results and to evaluate if this strategy could be useful to guide treatment decisions. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

The Number of RUNX1 Mutations and the Presence of One Intact RUNX1 Allele Influence Cytogenetic Abnormalities, Additional Molecular Mutations and Prognosis in RUNX1 Mutated AML

Background: According to the revised WHO classification of 2016, AML with mutated RUNX1 constitutes a new provisional entity. We previously reported that the subgroup of RUNX1-mutated AML with RUNX1 wild-type (WT) loss is associated with a distinct pattern of cytogenetic and molecular genetic abnormalities and with an adverse prognosis. However, the impact of multiple RUNX1 mutations is unclear yet.Aims: Evaluation of associated genetic alterations and prognosis in AML with >1 RUNX1 mutation as compared to those with (1) RUNX1 WT loss and (2) one RUNX1 mutation.Patient cohorts and methods: The total cohort comprised 467 AML cases with RUNX1 mutations (mut) (296 male, 171 female). Median age was 72 years (range: 18-91 years). All patients were investigated using chromosome banding analysis (CBA) and amplicon sequencing of RUNX1. The cohort was split into the subgroups with RUNX1 WT loss (UPD or RUNX1 deletion detected by genomic arrays) (n=50), cases with >1 RUNX1mut (n = 94) and cases with 1 RUNX1mut and conservation of the RUNX1 WT allele (n = 323). Of these, 50, 55 and 58 cases, respectively, were selected for further mutation analyses of ASXL1, BCOR, CBL, CEBPA, DNMT3A, ETV6, EZH2, FLT3-ITD, FLT3-TKD, GATA2, IDH1, IDH2, KIT, KRAS, MLL-PTD, NPM, NRAS, SETBP1, SF3B1, SRSF2, TET2, TP53, U2AF1 and WT1. Variants of unknown significance were excluded from statistical analysis.Results: In the total cohort of 467 cases, CBA revealed a normal karyotype (NK) in 53% of patients, 18% harbored trisomies, 3% showed a complex karyotype (>3 abnormalities), 26% other aberrations. The proportion of cases with trisomies was largest in cases with RUNX1 WT loss (26%), followed by >1 RUNX1mut (19%) and 1 RUNX1mut (16%). In more detail, in the total cohort, 56% of cases with trisomies harbored +8, in 30% +13 was found. A similar pattern was observed for 1 RUNX1mut, whereas in cases with WT loss +13 was the most abundant trisomy (+8: 66% in 1 RUNX1mut vs. 31% in WT loss, p=0.022; +13: 15% vs. 62%, p<0.001). Cases with >1 RUNX1mut showed an intermediate distribution (+8: 44%, +13: 50%).Missense mutations were the most abundant mutation type (53%) inWT loss cases, followed by frameshift mutations (28%). By contrast, in cases with 1 RUNX1mut, frameshift mutations were found more frequent (45%, p=0.016), whereas missense mutations were detected at a frequency of 31% (p=0.006). In cases with >1 RUNX1mut, both were observed at similar frequencies (missense: 36%, frameshift: 38%).Mutation analyses of 163 selected cases revealed SRSF2 (39%), ASXL1 (36%), DNMT3A (19%), BCOR (18%), IDH2 (17%), SF3B1 (17%) and TET2 (17%) mutations as most frequently mutated genes in the total cohort. Cases with RUNX1 WT loss showed a higher frequency of ASXL1mut compared to the other cases (50% vs. 29%, p=0.013), while U2AF1mut were absent from this group (0% vs. 15%, p=0.019). Differences between cases with and without RUNX1 WT loss were also detected for DNMT3A, TET2, SF3B1 (more abundant in WT loss) and IDH2, WT1 (less abundant in WT loss), although these were not statistically significant. For many genes, the group of cases with >1 RUNX1mut showed an intermediate abundance pattern, or mutation frequencies similar to cases with 1 RUNX1mut were observed. Mutations in spliceosome genes (SF3B1, SRSF2, U2AF1, ZRSR2) were very abundant in all subgroups but less frequent (although not statistically significant) in cases with 1 RUNX1mut.Median overall survival (OS) in the total cohort was 14 months. WT loss (OS: 5 months) and >1 RUNX1mut (14 months) showed an adverse impact on prognosis compared to 1 RUNX1mut (22 months; p=0.002 and p=0.048, respectively). Mutations in ASXL1 and KRAS showed a negative impact on OS in the total cohort (10 vs. 18 months, p=0.028; 1 vs. 15 months, p<0.001), whereas DNMT3A mutations negatively affected OS in WT loss only (in WT loss: 1 vs. 7 months, p=0.005).Conclusion: 1) RUNX1 mutated AML cases with WT loss show a high frequency of +13, RUNX1 missense mutations and accompanying ASXL1 mutations. 2) They clearly separate from cases with 1 RUNX1mut, which depict a predominance of +8, RUNX1 frameshift mutations and mutations in IDH2 and WT1. 3) Patients with >1 RUNX1mut show a pattern intermediate between the former two subgroups. 4) Loss of RUNX1 WT and > 1 RUNX1mut showed an adverse impact on OS. Thus, not only the presence and number of RUNX1mut but also the conservation of an intact RUNX1 allele is biologically and clinically relevant. DisclosuresStengel:MLL Munich Leukemia Laboratory: Employment. Kern:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Meggendorfer:MLL Munich Leukemia Laboratory: Employment. Perglerová:MLL2 s.r.o.: Employment. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership. Haferlach:MLL Munich Leukemia Laboratory: Employment, Equity Ownership.

Identification of Two Distinct Poor Prognostic Subgroups Related to High Expression of BMP2 or PRDM16 in Pediatric AML

[Background]Pediatric acute myeloid leukemia (AML) remains to be a disease with a poor prognosis, with a long-term survival rate of approximately 60%. We have recently reported that high PRDM16 expression (high-PRDM16) was common in t(5;11)(q35;p15.5)/NUP98-NSD1-positive patients, and that high-PRDM16 was found to be a novel poor prognostic factor in this disease. However, this finding was not observed in FAB-M7. The presence of inv(16)(p13.3q24.3)/CBFA2T3-GLIS2 was postulated to be a reason. This fusion was reported as the most frequent fusion gene associated with a poor prognosis in FAB-M7, and we found that all CBFA2T3-GLIS2-positive patients had a low PRDM16 expression (low-PRDM16). Furthermore, some studies reported that bone morphogenetic protein 2 (BMP2) was frequently and highly expressed in CBFA2T3-GLIS2-positive patients, indicating the importance of BMP2 in pathogenesis in a subset of AML. In this study, we analyzed the expression status of BMP2 and PRDM16 and their relationship to prognosis in pediatric AML.[Patients and Methods]A total of 369 AML patient samples, who were enrolled in the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) AML-05 trial, were analyzed. Expression level of BMP2 and PRDM16 is analyzed by real-time quantitative PCR (Taqman Gene Expression Assay), using ABL1 as a control gene. The cutoff value for high-BMP2 was defined as the lowest expression level among 11 CBFA2T3-GLIS2-positive patients, and that for high-PRDM16 was defined as the lowest expression level among 10 NUP98-NSD1-positive patients. We also screened fusion genes and gene mutations of CBFA2T3-GLIS2, NUP98-JARID1A, RBM15-MKL1, MLL rearrangements, NUP98-NSD1, FUS-ERG, DEK-NUP214, RUNX1-RUNX1T1, CBFB-MYH11, and gene mutations of KIT, NRAS, KRAS, WT1, NPM1, MLL-PTD, and FLT3-ITD.[Results]Out of 369 patients, high-BMP2 and high-PRDM16 were identified in 47 (12.7%) and 44 (11.9%) patients, respectively. Only three (0.8%) of 369 patients had both high-BMP2 and high-PRDM16 (high-BMP2/PRDM16). In 44 high-BMP2 patients and 41 high-PRDM16 patients (3 high-BMP2/PRDM16 patients were excluded), MLL rearrangements were only found in high-BMP2 patients (25.5% vs 0%, p < 0.001), whereas FLT3-ITD was significantly much more frequent in high-PRDM16 patients (4.5% vs 56.1%, p < 0.001). Core-Binding-Factor (CBF)-AML was rare in both groups (4.5% and 0%, p = 0.495). Kaplan|Meier analyses revealed that high-BMP2 patients and high-PRDM16 patients had a low 5-year overall survival (OS) (46.3% and 29.3%, respectively). In molecular subgroup analyses, the prognosis of MLL-rearranged patients, including 12 high-BMP2 patients (21.8%), was not influenced by BMP2 expression (5-year OS: high-BMP2 66.7% vs low-BMP2 64.9%, p = 0.488), suggesting that the prognosis of MLL-rearranged patients might primarily be defined by their fusion partner genes and other gene aberrations as previously reported (e.g., EVI1 expression). Considering this result, further survival analyses of the patients lacking CBF-AML or MLL-rearrangements were performed (n = 174, 5-year OS: 50.5%). In this subgroup, 5-year OS of high-BMP2 patients (n = 30) and high-PRDM16 patients (n = 41) were significantly lower than that of low-BMP2/low-PRDM16 patients (36.7% vs 67.2%, p < 0.001, and 29.3% vs 67.2%, p < 0.001, respectively).[Conclusions]High-BMP2 and high-PRDM16 could identify distinct subgroups with poor prognosis in pediatric AML. Further investigation of molecular-targeted therapy against these genes may contribute to the improvement of clinical outcome in these subgroups. [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Marked Differences in the Genomic Landscape of Pediatric Compared to Adult Acute Myeloid Leukemia: A Report from the Children's Oncology Group and NCI/COG Therapeutically Applicable Research to Generate Effective Treatments (TARGET) Initiative

The age distribution of acute myeloid leukemia is unusual among malignancies, with onset spanning from early infancy until past the 9th decade. Despite similar histology, cytogenetic abnormalities and recent identification of somatic mutations (e.g., DNMT3A mutations) have highlighted differences in the events driving adult compared to childhood de novo AML. However, the full extent of these differences remains unknown and is likely to have relevance to treatment approaches. The TARGET AML initiative is an effort of the Children's Oncology Group (COG) and the National Cancer Institute to comprehensively characterize the molecular abnormalities of pediatric AML. The dataset comprises 1) whole genome sequencing (WGS) of AML and matched remission bone marrow in 197 cases, 2) mRNA transcriptome sequencing of 284 cases, 3) miRNA sequencing of 692 cases, 4) methylation array data on 289 cases, and 5) targeted capture sequencing of 174 candidate genes identified from WGS in 800 diagnostic samples, including 182 with WGS (Figure 1). The majority of patients (93%) studied were uniformly treated on COG study AAML0531 or its pilot safety precursor study, AAML03P1. Relapsed specimen data (not shown) are available for a subset of these cases. All patient samples were obtained by written consent upon enrollment in the clinical trial.Consistent with adult studies, we identified a relatively low mutational burden, with 2206 somatic tier 1 mutations resulting in a coding change in 1682 genes (median 6 per patient) from the WGS discovery data. We successfully verified 70-90% of variant calls by secondary methods. Also as with adult data, there were relatively few recurrently mutated genes, with fewer than 40 genes altered in >2% of samples. However, there were marked differences in somatic mutation frequencies in comparison to adult TCGA data, both by raw frequency and after adjustment for cytogenetic subtypes present among the two cohorts (Figure 2). Mutations in TP53, NPM1, IDH1, IDH2, TET2 and DNMT3A are more frequent in adult compared to pediatric disease; in contrast, mutations in NRAS, KRAS, WT1, FLT3, PTPN11, GATA2, ASXL2, MYC, SETD2, EZH2 and IKZF1 appear more common in pediatric AML. Mutations of several genes, including CEBPA, ASXL2 and KRAS are not only more common in pediatric AML, they show peak prevalence within specific pediatric age groups. In addition, several genes, including FLT3, WT1, and KIT show significant differences in mutational hotspots compared to adults.Pediatric-adult differences in AML were not limited to somatic gene mutations, but extended to focal and chromosomal copy number alterations (CNA), translocations, miRNA expression, and methylation-induced gene silencing. We identified recurrent focal CNAs in multiple regions not reported in adult AML including 15 heterozygous focal deletions impacting ELF1, an ETS-family transcriptional regulator of hematopoiesis and leukemia driver as well as deletions of the splicing regulator MBNL1 in 10 cases, 8 of which co-occurred with focal deletions of the hematopoietic transcriptional regulator, ZEB2. De novo assembly of mRNA sequencing data identified fusion transcripts in 63% of cases compared to 45% of TCGA LAML. In addition to cytogenetically evident fusions with well-described enrichment for MLL translocations in pediatrics, we identified 29 diagnostic samples (10%) with nucleoporin family fusions (NUP98 with NSD1, KDM5A, PHF23, HOXD13, HMGB3, BRWD3, and CLINT; NUP214 with DEK and SET), CBFA2T3-GLIS2 fusions in 5, and rare fusions of ETS transcription factor genes (FUS-FEV, ETV6-INO8D). Comparison of miRNA expression patterns between adult and pediatric specimens similarly showed marked differences in expression of key regulatory miRNAs including let-7 family members. Finally, analysis of mRNA expression and DNA methylation for the identification of epigenetically silenced genes suggested that, although specific events favor silencing in adults or children, an overall pattern of gene silencing was more prevalent in pediatric compared to adult cases.This work extends our understanding of the heterogeneity of AML, demonstrates fundamental differences in the biology of pediatric- and adult-onset disease, and suggests important age-related differences within "pediatric" AML. This rich dataset should provide a foundation for the establishment of biologically-guided treatment in children with AML. [Display omitted] [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

Clinical and Biological Features of Pediatric Acute Myeloid Leukemia with Primary Induction Failure in the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) AML-05 Study

INTRODUCTIONTreatment outcome of pediatric acute myeloid leukemia (AML) patients has improved over the past few decades due to intensive chemotherapy. Primary induction failure (PIF), defined as failure to achieve complete remission after the second induction chemotherapy, occurs in around 10% of children with newly diagnosed AML. Effective treatment strategy for these patients is not established and their poor prognoses have been reported elsewhere. Here we investigated the clinical and biological features of pediatric AML patients with PIF who were registered in the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) AML-05 Study (AML-05). METHODSWe conducted a retrospective survey of patients who were registered in the AML-05. We analyzed probabilities of overall survival (OS) according to gender, age at diagnosis, white blood cell count (WBC) at diagnosis, FAB classification, etc. Genetic analysis of primary leukemic blasts was performed. We screened fusion genes and gene mutations as follows: RUNX1-RUNX1T1, CBFB-MYH11, NUP98-NSD1, DEK-NUP214, MLL-PTD, WT1, NPM1, and MLL-rearrangements, gene mutations of KIT and FLT3-ITD. Furthermore, we evaluated the clinical and biological background of these PIF patients to define their prognostic factors statistically. RESULTS: Among the 443 patients registered in the AML-05 between November 2006 and December 2010, 43 patients (9.7%) had PIF. The observation period from the date of PIF was 5-78 months (median, 20 months). The age at diagnosis was 0.1-17 years (median, 6.1 years). There was no significant difference in gender (28 males vs15 females). The 3-year OS rate was 19.0% (95% confidence interval 1.0%-38.0%). This was extremely poor compared to the patients who achieved complete remission (CR): 66.7% for high-, 73.2% for intermediate-, and 92.6% for low-risk groups, respectively. Disease recurrence is the major cause of death (n=19, 46.3%). The mean WBC at diagnosis of PIF patients was 96 x 109/L: this is significantly higher than that of non-PIF patients (51 x 109/L, P<0.01, Cox regression analysis). Morphologically, FAB classification M7 was more frequently detected in the PIF group compared with non- PIF group, although not statistically significant: 11 patients (25.6%) vs 43 patients (9.1%) (P=0.07). Unfavorable prognostic cytogenetics such as FLT3-ITD (n=16, 37.2%), NUP98-NSD1 (n=6, 15.4%), and complex karyotype (n=9, 20.9%) were detected more frequently in PIF patients, as well as MLL-PTD (n=7, 16.2%), c-KIT mutations (n=6, 14.0%), DEK-NUP214 (n=2, 4.7%), and monosomy 7 (n=6, 14%). There were no cases with WT1 or NPM1 mutations. Only 3 patients had core binding factor leukemia with RUNX1-RUNX1T1 or CBFB-MYH11 in the PIF patients. Thirty-seven PIF patients received stem cell transplantation (SCT). The patients without SCT did not achieve CR, and died of primary disease. The patients who had achieved CR before SCT showed significantly better OS (P=0.03). There was no significant difference in donor source and conditioning regimen. Younger age at diagnosis (<10 years of age, P=0.02) was associated with better outcome. High-dose cytarabine-containing re-induction chemotherapy seemed effective on univariate analysis, which indicates the type of re-induction chemotherapy to be prognostic. Finally, multivariate analysis showed only age at diagnosis (<10 years of age) to be a significant prognostic factor. CONCLUSIONSThe prognosis of pediatric AML patients with PIF was extremely poor. In our survey, unfavorable molecular biological background of leukemia was associated with PIF. It is necessary to explore more effective treatment strategies based on leukemia biology for these patients in the future. DisclosuresNo relevant conflicts of interest to declare.

The World's Youngest Cadaveric Kidney Transplant: Medical, Surgical and Ethical Issues.

BackgroundWe report here the first successful transplant from a preterm cadaveric donor. This was performed in November 1994. The donor, who had been born at about 33 weeks of gestation, was diagnosed as having agenesis of the corpus callosum. The transplant was carried out 10 days after the donor's birth. The recipient was a 17-month-old boy with a diagnosis of Denys-Drash syndrome (WT1 mutation).MethodWe describe and analyze the ethical, social, cultural, medical and surgical issues encountered and how these were addressed. The major issue of determining death in a beating heart, very young donor was dealt with in the absence of worldwide experience and guidelines.ResultsThe transplanted recipient has lived with the grafted pair of kidneys for more then 22 years. He has led a relatively normal life.ConclusionsIt is possible for immature preterm deceased donor kidneys to be transplanted into a 17-month-old recipient and for the grafted kidneys to grow with the recipient and function for 22 years. There were challenges in ethically determining the death of the donor, in surgical techniques to obviate potential surgical complications, and in postoperative care of the recipient, but these were managed successfully.

WT1 and NPHS2 gene mutation analysis and clinical management of steroid-resistant nephrotic syndrome.

Nephrotic syndrome (NS) is a kidney disease predominantly present in children with idiopathic condition; final stage of the disease progresses into end-stage renal disease. Generally, NS is treated using standard steroid therapy, however; most of the children are steroid sensitive and about 15-20% are non-responders (SRNS). Non-responsiveness of these children would be a risk with the possibility of mutational changes in podocyte genes (NPHS1, NPHS2, WT1, PLCE1). The mutation in podocyte genes is associated with SRNS. NPHS1, NPHS2, and WT1 genes are identified/directly linked to SRNS. The present study is a surveillance on the mutation analysis of WT1 (exons 8 and 9) and NPHS2 (exons 1-8) gene in SRNS followed by clinical management. In the present study, we analyzed these two genes in a total of 117 SRNS (73 boys and 44 girls) children. A total of five mutations were detected in six children. First, WT1 mutation was detected at 9th intron-IVS 9+4C>T position in one SRNS female patient. This WT1 mutation was identified in a girl having Frasier Syndrome (FS) with focal segmental glomerulosclerosis and a complete sex reversal found through molecular and karyological screening. In NPHS2, missense mutations of P20L (in two children), P316S, and p.R229Q, and a frame shift mutation of 42delG were detected. Thus, applying molecular investigation helped us to decide on treatment plan of SRNS patients, mainly to avoid unnecessary immunosuppressive treatment.

Immunohistochemical loss of 5-hydroxymethylcytosine expression in acute myeloid leukaemia: relationship to somatic gene mutations affecting epigenetic pathways.

Genes affecting epigenetic pathways are frequently mutated in myeloid malignancies, including acute myeloid leukaemia (AML). The genes encoding TET2, IDH1 and IDH2 are among the most commonly mutated genes, and cause defective conversion of 5-methylcytosine into 5-hydroxymethylcytosine (5hmC), impairing demethylation of DNA, and presumably serving as driver mutations in leukaemogenesis. The aim of this study was to correlate 5hmC immunohistochemical loss with the mutation status of genes involved in epigenetic pathways in AML. Immunohistochemical staining with an anti-5hmC antibody was performed on 41 decalcified, formalin-fixed paraffin-embedded (FFPE) bone marrow biopsies from patients with AML. Archived DNA was subjected to next-generation sequencing for analysis of a panel of genes, including TET2, IDH1, IDH2, WT1 and DNMT3A. TET2, IDH1, IDH2, WT1 and DNMT3A mutations were found in 46% (19/41) of the cases. Ten of 15 cases (67%) with TET2, IDH1, IDH2 or WT1 mutations showed deficient 5hmC staining, whereas nine of 26 cases (35%) without a mutation in these genes showed loss of 5hmC. It is of note that all four cases with TET2 mutations showed deficient 5hmC staining. Overall, somatic mutations in TET2, IDH1, IDH2, WT1 and DNMT3A were common in our cohort of AML cases. Immunohistochemical staining for 5hmC was lost in the majority of cases harbouring mutations in these genes, reflecting the proposed relationship between dysfunctional epigenetic pathways and leukaemogenesis.

Denys-Drash syndrome associated WT1 glutamine 369 mutants have altered sequence-preferences and altered responses to epigenetic modifications.

Mutations in human zinc-finger transcription factor WT1 result in abnormal development of the kidneys and genitalia and an array of pediatric problems including nephropathy, blastoma, gonadal dysgenesis and genital discordance. Several overlapping phenotypes are associated with WT1 mutations, including Wilms tumors, Denys-Drash syndrome (DDS), Frasier syndrome (FS) and WAGR syndrome (Wilms tumor, aniridia, genitourinary malformations, and mental retardation). These conditions vary in severity from individual to individual; they can be fatal in early childhood, or relatively benign into adulthood. DDS mutations cluster predominantly in zinc fingers (ZF) 2 and 3 at the C-terminus of WT1, which together with ZF4 determine the sequence-specificity of DNA binding. We examined three DDS associated mutations in ZF2 of human WT1 where the normal glutamine at position 369 is replaced by arginine (Q369R), lysine (Q369K) or histidine (Q369H). These mutations alter the sequence-specificity of ZF2, we find, changing its affinity for certain bases and certain epigenetic forms of cytosine. X-ray crystallography of the DNA binding domains of normal WT1, Q369R and Q369H in complex with preferred sequences revealed the molecular interactions responsible for these affinity changes. DDS is inherited in an autosomal dominant fashion, implying a gain of function by mutant WT1 proteins. This gain, we speculate, might derive from the ability of the mutant proteins to sequester WT1 into unproductive oligomers, or to erroneously bind to variant target sequences.

Clinical Utility of Next-Generation Sequencing for Oncogenic Mutations in Patients with Acute Myeloid Leukemia Undergoing Allogeneic Stem Cell Transplantation

To determine the association of somatic mutations in acute myeloid leukemia (AML) with risk of relapse after allogeneic hematopoietic stem cell transplantation (alloHSCT), we retrospectively studied pre-transplantation genetic profiles obtained from next-generation sequencing of 26 genes in 112 adult patients with AML who underwent alloHSCT. Univariable and multivariable regression analyses were used to assess the association between the presence of a pathogenic mutation and risk of relapse after alloHSCT. Eighty-six percent (96 of 112) of patients had at least 1 pathogenic mutation. Mutations in TP53, WT1, and FLT3-internal tandem duplication (ITD) were associated with an increased risk of relapse after alloHSCT (adjusted hazard ratio [aHR], 2.90; P = .009; aHR, 2.51; P = .02; and aHR, 1.83; P = .07, respectively). DNMT3A mutation in the absence of FLT3-ITD and NPM1 mutations was associated with a lower relapse risk (aHR, .22; P = .04). Comparison of pre-alloHSCT and post-alloHSCT genetic profiles showed clonal evolution in 6 of 6 patients, including acquisition of actionable mutations in 4 patients. In summary, genetic profiling is useful for assessing relapse risk in patients with AML undergoing alloHSCT and may identify patients in need of strategies to reduce this risk. Clonal evolution is present at post-alloHSCT relapse and repeat genetic profiling may uncover acquired actionable mutations.

Genomic complexity and dynamics of clonal evolution in childhood acute myeloid leukemia studied with whole-exome sequencing

Despite significant improvement in treatment of childhood acute myeloid leukemia (AML), 30% of patients experience disease recurrence, which is still the major cause of treatment failure and death in these patients. To investigate molecular mechanisms underlying relapse, we performed whole-exome sequencing of diagnosis-relapse pairs and matched remission samples from 4 pediatric AML patients without recurrent cytogenetic alterations. Candidate driver mutations were selected for targeted deep sequencing at high coverage, suitable to detect small subclones (0.12%). BiCEBPα mutation was found to be stable and highly penetrant, representing a separate biological and clinical entity, unlike WT1 mutations, which were extremely unstable. Among the mutational patterns underlying relapse, we detected the acquisition of proliferative advantage by signaling activation (PTPN11 and FLT3-TKD mutations) and the increased resistance to apoptosis (hyperactivation of TYK2). We also found a previously undescribed feature of AML, consisting of a hypermutator phenotype caused by SETD2 inactivation. The consequent accumulation of new mutations promotes the adaptability of the leukemia, contributing to clonal selection. We report a novel ASXL3 mutation characterizing a very small subclone (<1%) present at diagnosis and undergoing expansion (60%) at relapse. Taken together, these findings provide molecular clues for designing optimal therapeutic strategies, in terms of target selection, adequate schedule design and reliable response-monitoring techniques.

Abstract 2779: A CpG island methylator phenotype in acute myeloid leukemia independent of IDH mutations and associated with a favorable outcome

Abstract Background: Acute myeloid leukemia (AML) causes the most leukemia-related deaths in the United States, and has frequent epigenetic aberrations, including a CpG island methylator phenotype (CIMP). CIMP defines unique molecular subtypes of other cancers and has been linked to mutations in IDH1/2, however the clinical consequences of CIMP and the role of IDH1/2 mutations in AML remain unclear. Methods: To measure genome-wide CpG methylation we used Digital Restriction Enzyme Analysis of Methylation (DREAM) on AML bone marrow samples and normal peripheral blood controls. For validation we used methylation data from patient samples from The Cancer Genome Atlas (TCGA) on the Illumina Infinium HumanMethylation450 platform. We also used RNA-seq data from TCGA, and microarray data from GEO (GSE6891). Statistical analysis was done using R. Results: Genome-wide analysis of variably methylated CpG sites in 96 AML bone marrow samples using DREAM revealed two distinct CpG island methylator phenotypes by hierarchical clustering: IDH-CIMP (I-CIMP) in which 7/10 cases had oncogenic IDH1/2 mutations, and AML-CIMP (A-CIMP), which lacked any mutations in IDH1/2. At median follow-up of 6.16 years, A-CIMP cases, but not I-CIMP cases were associated with longer overall survival (median OS, years: A-CIMP = Not reached, P = 0.08; I-CIMP = 3.35, P = 0.50; CIMP-negative = 1.17). We validated and extended these findings using TCGA data. In this cohort A-CIMP cases also had significantly longer OS compared to CIMP-negative (median OS, years: A-CIMP = 2.34, P = 0.01; I-CIMP = 1.25, P = 0.89; CIMP-negative = 1.00). Aberrant hypermethylation in A-CIMP occurred preferentially at CpG islands by a factor greater than 3, while I-CIMP cases demonstrated a slight preference for hypermethylation at sites outside CpG islands. Interestingly, A-CIMP was enriched in CEBPA (19%) and WT1 mutations (14%), but inversely correlated with IDH, TET2, and NPM1 mutations. Functional pathway analysis revealed that genes hypermethylated in A-CIMP are associated with pluripotency maintenance - including PAX6, GBX2, and HOXA9 - and RNA-seq data largely, but not entirely, recapitulated methylation-based patterns. There was a strong correlation between promoter CpG island methylation and gene expression for many A-CIMP genes. Finally, the transcriptional program associated with A-CIMP was found to correlate with outcome and genetic backgrounds in both TCGA and additional independent datasets. Conclusions: Taken together, our data suggest that CIMP in AML is complex, multifactorial and cannot be explained solely by coding gene mutations (e.g. IDH1/2, TET2). There is an association between A-CIMP and curability in multiple AML datasets that cannot be recapitulated by mutational data alone and that may be worth validating in prospective studies. Citation Format: Andrew D. Kelly, Heike Kroeger, Jumpei Yamazaki, Rodolphe Taby, Frank Neumann, Sijia Yu, Justin T. Lee, Rong He, Shoudan Liang, Yue Lu, Matteo Cesaroni, Sherry A. Pierce, Steven M. Kornblau, Carlos E. Bueso-Ramos, Farhad Ravandi, Hagop M. Kantarjain, Jaroslav Jelinek, Jean-Pierre J. Issa. A CpG island methylator phenotype in acute myeloid leukemia independent of IDH mutations and associated with a favorable outcome. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2779.

Genotype-phenotype analysis of pediatric patients with WT1 glomerulopathy.

WT1 is one of the genes commonly reported as mutated in children with steroid-resistant nephrotic syndrome (SRNS). We analyzed genotype-phenotype correlations in pediatric SRNS patients with WT1 mutations. From 2001 to 2015, WT1 mutations were detected in 21 out of 354 children with SRNS by genetic screening (5.9%). The patients were grouped into missense (n = 11) and KTS splicing (n = 10) mutation groups. Nine (82%) patients with missense mutations presented with congenital/infantile nephrotic syndrome, while 8 (80%) with KTS splicing mutations presented with childhood-onset SRNS. Progression to end-stage renal disease (ESRD) was noted in all patients with missense mutations (median age, 2.6months; interquartile range [IQR], 0.8months to 1.7years) and in 5 patients with KTS splicing mutations (median, 9.3years; IQR, 3.3-16.5years). Disorders of sexual development (DSDs) were noted in all 12 patients with a 46, XY karyotype and in only 1 of the 8 patients with a 46, XX karyotype. One patient developed a Wilms tumor and another developed gonadoblastoma. Three patients had a diaphragmatic defect or hernia. WT1 mutations manifest as a wide spectrum of renal and extra-renal phenotypes. Genetic diagnosis is essential for overall management and to predict the genotype-specific risk of DSDs and the development of malignancies.

Subtype-specific patterns of molecular mutations in acute myeloid leukemia.

Acute myeloid leukemia (AML) can be grouped into morphologically or genetically defined subtypes. Today, the AML phenotype-genotype associations, that is, FAB/WHO (French-American-British/World Health Organization) definitions and recurrent molecular mutations, are not fully understood. Therefore, we evaluated the impact of molecular mutations on the AML differentiation stage by molecular profiling of 4373 adult de novo AML patients in 7 cytomorphological subtypes. We investigated mutations in 20 genes, including myeloid transcription factors (CEBPA, RUNX1), tumor suppressors (TP53, WT1), DNA modifiers (DNMT3A, IDH1/2, TET2), chromatin modifiers (ASXL1, MLL), signal transduction genes (FLT3, KRAS, NRAS) and NPM1. The most frequently mutated genes per cytomorphological subtype were RUNX1 in M0 (43%), NPM1 in M1 (42%), DNMT3A in M2 (26%), NPM1 in M4 (57%), M5a (49%) and M5b (70%) and TP53 in M6 (36%). Although some gene mutations were frequent in several cytomorphological subtypes, a series of associations of co-occurring mutations with distinct phenotypes were identified for molecularly defined subcohorts. FLT3, NPM1 and WT1 mutations were associated with an immature phenotype in myeloblastic AML, whereas other combinations involving ASXL1, RUNX1, MLL-PTD, CEBPA or KRAS were more frequent in myeloblastic AML with maturation. Within the NPM1 mutated subcohort, ASXL1 mutations were significantly associated with a monoblastic differentiation and DNMT3A mutations with a monocytic phenotype.

Wilms' Tumor: Experience of Regional Children’s Hospital in Serbia

Wilms' tumor-nephroblastoma is the most common malignant tumor of the kidney in children. It belongs to disontogenetic tumors, developing in early embryogenesis. Typical age for diagnosis is between 1st and 3rd year of life but it can be found until 15th year. Wilms' tumor develops more often in children with other congenital anomalies. It is caused by mutations of Wilms' tumor suppressor gene WT1 (11p13) and WT2 (11p15). Clinically it presents most often with enlargement of abdomen and haematuria. Diagnosis is made by the ultrasonography and computerized tomography. Patients are treated according to tumor histology and stage. Aim of the study was to present the prevalence of Wilms tumor in regional childrens hospital and identify factors correlating to bad prognossis. The study was retrospective and presents the period of 16 years, from 1995 to 2010. It was conducted in the Center for Hematology and Oncology in the Institute for Children and Youth Health Care of Vojvodina-Novi Sad, Serbia. Prevalence of Wilms' tumor was 23 children in 16 years with higher incidence in years: 2003, 2005, 2009 and 2010. Children diagnosed in stage I and II had better 2 year disease free and overall survival than children in stage III and IV. Also when diagnosis was made in less than 1 month, 2 year disease free and overall survival was better than in group where the diagnosis was made in a period after 1 month. In management of Wilms' tumor there is still controversy whether the children should receive upfront chemotherapy versus primarily operation.

Genetic alterations and their clinical implications in older patients with acute myeloid leukemia.

A number of patient-specific and leukemia-associated factors are related to the poor outcome in older patients with acute myeloid leukemia (AML). However, comprehensive studies regarding the impact of genetic alterations in this group of patients are limited. In this study, we compared relevant mutations in 21 genes between AML patients aged 60 years or older and those younger and exposed their prognostic implications. Compared with the younger patients, the elderly had significantly higher incidences of PTPN11, NPM1, RUNX1, ASXL1, TET2, DNMT3A and TP53 mutations but a lower frequency of WT1 mutations. The older patients more frequently harbored one or more adverse genetic alterations. Multivariate analysis showed that DNMT3A and TP53 mutations were independent poor prognostic factors among the elderly, while NPM1 mutation in the absence of FLT3/ITD was an independent favorable prognostic factor. Furthermore, the status of mutations could well stratify older patients with intermediate-risk cytogenetics into three risk groups. In conclusion, older AML patients showed distinct genetic alterations from the younger group. Integration of cytogenetics and molecular mutations can better risk-stratify older AML patients. Development of novel therapies is needed to improve the outcome of older patients with poor prognosis under current treatment modalities.

Abstract IA12: Mechanisms of tumorigenesis due to somatic mutations in DICER1 and DROSHA in childhood kidney cancers

Abstract Wilms tumor is the most common pediatric kidney cancer and the fourth most common childhood cancer overall. Wilms tumor is treated with a combination of surgery, chemotherapy, and radiation, and, while most children are cured, patients suffer adverse late effects of therapy and survival remains poor in those with advanced-stage disease. Known driver mutations (in WT1, WTX, and β-catenin) account for only one-third of Wilms tumor cases. To better define the genomic landscape of Wilms tumor, we performed whole-exome sequencing of 44 Wilms tumors to identify somatic mutations. Through this approach, we identified recurrent somatic mutations in MYCN, DROSHA, and DICER1, which were mutually exclusive with known Wilms tumor driver mutations in WT1 and β-catenin. DROSHA and DICER1 somatic hotspot mutations occur at or near critical metal-binding residues in RNase III domains and partially or completely disrupt enzyme activity. Examination of miRNA expression in tumors, in vitro processing assays, and genomic editing in human cells demonstrate that DICER1 and DROSHA mutations influence miRNA processing through distinct mechanisms. While DICER1 RNase IIIB mutations preferentially impair processing of miRNAs that derive from the 5′ arm of pre-miRNA hairpins, DROSHA RNase IIIB mutations globally inhibit miRNA biogenesis through a dominant-negative mechanism. Despite their distinct mechanisms of action, DROSHA and DICER1 mutations result in decreased expression of several common tumor-suppressing miRNAs, including multiple members of the let-7 and miR-15/16 families. We also identified a patient carrying a germline DICER1 loss-of-function allele who subsequently developed multiple malignancies with distinct DICER1 RNase IIIB somatic hotspot mutations, suggesting that DICER1 can act as both a tumor-suppressor and an oncogene depending on the nature of the mutation. These results provide new insights into the mechanisms through which mutations in miRNA biogenesis components reprogram miRNA expression in human cancer and suggest that mutations causing impairment of miRNA processing define a distinct subclass of Wilms tumors. Citation Format: Kenneth S. Chen, Dinesh Rakheja, Yangjian Liu, Abhay A. Shukla, Joshua T. Mendell, James F. Amatruda. Mechanisms of tumorigenesis due to somatic mutations in DICER1 and DROSHA in childhood kidney cancers. [abstract]. In: Proceedings of the AACR Special Conference on Noncoding RNAs and Cancer: Mechanisms to Medicines ; 2015 Dec 4-7; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2016;76(6 Suppl):Abstract nr IA12.