Critical evaluation of molecular tumour board outcomes following 2 years of clinical practice in a Comprehensive Cancer Centre.

BACKGROUND: Recently, molecular tumour boards (MTBs) have been integrated into the clinical routine. Since their benefit remains debated, we assessed MTB outcomes in the Comprehensive Cancer Center Ostbayern (CCCO) from 2019 to 2021. METHODS AND RESULTS: In total, 251 patients were included. Targeted sequencing was performed with PCR MSI-evaluation and immunohistochemistry for PD-L1, Her2, and mismatch repair enzymes. 125 treatment recommendations were given (49.8%). High-recommendation rates were achieved for intrahepatic cholangiocarcinoma (20/30, 66.7%) and gastric adenocarcinoma (10/16, 62.5%) as opposed to colorectal cancer (9/36, 25.0%) and pancreatic cancer (3/18, 16.7%). MTB therapies were administered in 47 (18.7%) patients, while 53 (21.1%) received alternative treatment regimens. Thus 37.6% of recommended MTB therapies were implemented (47/125 recommendations). The clinical benefit rate (complete + partial + mixed response + stable disease) was 50.0% for MTB and 63.8% for alternative treatments. PFS2/1 ratios were 34.6% and 16.1%, respectively. Significantly improved PFS could be achieved for m1A-tier-evidence-based MTB therapies (median 6.30 months) compared to alternative treatments (median 2.83 months; P = 0.0278). CONCLUSION: The CCCO MTB yielded a considerable recommendation rate, particularly in cholangiocarcinoma patients. The discrepancy between the low-recommendation rates in colorectal and pancreatic cancer suggests the necessity of a weighted prioritisation of entities. High-tier recommendations should be implemented predominantly.

Acute megakaryoblastic leukaemia shows high frequency of chromosome 1q aberrations and dismal outcome.

Acute megakaryoblastic leukaemia (AMKL) is associated with poor prognosis. Limited information is available on its cytogenetics, molecular genetics and clinical outcome. We performed genetic analyses, evaluated prognostic factors and the value of allogeneic haematopoietic stem cell transplantation (allo-HSCT) in a homogenous adult AMKL patient cohort. We retrospectively analysed 38 adult patients with AMKL (median age: 58 years, range: 21-80). Most received intensive treatment in AML Cooperative Group (AMLCG) trials between 2001 and 2016. Cytogenetic data showed an accumulation of adverse risk markers according to ELN 2017 and an unexpected high frequency of structural aberrations on chromosome arm 1q (33%). Most frequently, mutations occurred in TET2 (23%), TP53 (23%), JAK2 (19%), PTPN11 (19%) and RUNX1 (15%). Complete remission rate in 33 patients receiving intensive chemotherapy was 33% and median overall survival (OS) was 33 weeks (95% CI: 21-45). Patients undergoing allo-HSCT (n = 14) had a superior median OS (68 weeks; 95% CI: 11-126) and relapse-free survival (RFS) of 27 weeks (95% CI: 4-50), although cumulative incidence of relapse after allo-HSCT was high (62%). The prognosis of AMKL is determined by adverse genetic risk factors and therapy resistance. So far allo-HSCT is the only potentially curative treatment option in this dismal AML subgroup.

Targeting intracellular WT1 in AML with a novel RMF-peptide-MHC-specific T-cell bispecific antibody.

Antibody-based immunotherapy is a promising strategy for targeting chemoresistant leukemic cells. However, classical antibody-based approaches are restricted to targeting lineage-specific cell surface antigens. By targeting intracellular antigens, a large number of other leukemia-associated targets would become accessible. In this study, we evaluated a novel T-cell bispecific (TCB) antibody, generated by using CrossMAb and knob-into-holes technology, containing a bivalent T-cell receptor-like binding domain that recognizes the RMFPNAPYL peptide derived from the intracellular tumor antigen Wilms tumor protein (WT1) in the context of HLA-A*02. Binding to CD3ε recruits T cells irrespective of their T-cell receptor specificity. WT1-TCB elicited antibody-mediated T-cell cytotoxicity against AML cell lines in a WT1- and HLA-restricted manner. Specific lysis of primary acute myeloid leukemia (AML) cells was mediated in ex vivo long-term cocultures by using allogeneic (mean ± standard error of the mean [SEM] specific lysis, 67 ± 6% after 13-14 days; n = 18) or autologous, patient-derived T cells (mean ± SEM specific lysis, 54 ± 12% after 11-14 days; n = 8). WT1-TCB-treated T cells exhibited higher cytotoxicity against primary AML cells than an HLA-A*02 RMF-specific T-cell clone. Combining WT1-TCB with the immunomodulatory drug lenalidomide further enhanced antibody-mediated T-cell cytotoxicity against primary AML cells (mean ± SEM specific lysis on days 3-4, 45.4 ± 9.0% vs 70.8 ± 8.3%; P = .015; n = 9-10). In vivo, WT1-TCB-treated humanized mice bearing SKM-1 tumors exhibited a significant and dose-dependent reduction in tumor growth. In summary, we show that WT1-TCB facilitates potent in vitro, ex vivo, and in vivo killing of AML cell lines and primary AML cells; these results led to the initiation of a phase 1 trial in patients with relapsed/refractory AML (#NCT04580121).

Spectrum and prognostic relevance of driver gene mutations in acute myeloid leukemia.

The clinical and prognostic relevance of many recently identified driver gene mutations in adult acute myeloid leukemia (AML) is poorly defined. We sequenced the coding regions or hotspot areas of 68 recurrently mutated genes in a cohort of 664 patients aged 18 to 86 years treated on 2 phase 3 trials of the German AML Cooperative Group (AMLCG). The median number of 4 mutations per patient varied according to cytogenetic subgroup, age, and history of previous hematologic disorder or antineoplastic therapy. We found patterns of significantly comutated driver genes suggesting functional synergism. Conversely, we identified 8 virtually nonoverlapping patient subgroups, jointly comprising 78% of AML patients, that are defined by mutually exclusive genetic alterations. These subgroups, likely representing distinct underlying pathways of leukemogenesis, show widely divergent outcomes. Furthermore, we provide detailed information on associations between gene mutations, clinical patient characteristics, and therapeutic outcomes in this large cohort of uniformly treated AML patients. In multivariate analyses including a comprehensive set of molecular and clinical variables, we identified DNMT3A and RUNX1 mutations as important predictors of shorter overall survival (OS) in AML patients <60 years, and particularly in those with intermediate-risk cytogenetics. NPM1 mutations in the absence of FLT3-ITD, mutated TP53, and biallelic CEBPA mutations were identified as important molecular prognosticators of OS irrespective of patient age. In summary, our study provides a comprehensive overview of the spectrum, clinical associations, and prognostic relevance of recurrent driver gene mutations in a large cohort representing a broad spectrum and age range of intensively treated AML patients.

Genetics of acute myeloid leukemia in the elderly: mutation spectrum and clinical impact in intensively treated patients aged 75 years or older.

A cute myeloid leukemia is a disease of the elderly (median age at diagnosis, 65-70 years). The prognosis of older acute myeloid leukemia patients is generally poor. While genetic markers have become important tools for risk stratification and treatment selection in young and middle-aged patients, their applicability in very old patients is less clear. We sought to validate existing genetic risk classification systems and identify additional factors associated with outcomes in intensively treated patients aged ≥75 years. In 151 patients who received induction chemotherapy in the AMLCG-1999 trial, we investigated recurrently mutated genes using a targeted sequencing assay covering 64 genes. The median number of mutated genes per patient was four. The most commonly mutated genes were TET2 (42%), DNMT3A (35%), NPM1 (32%), SRSF2 (25%) and ASXL1 (21%). The complete remission rate was 44% and the 3-year survival was 21% for the entire cohort. While adverse-risk cytogenetics (MRC classification) were associated with shorter overall survival (P=0.001), NPM1 and FLT3-ITD mutations (present in 18%) did not have a significant impact on overall survival. Notably, none of the 13 IDH1-mutated patients (9%) reached complete remission. Consequently, the overall survival of this subgroup was significantly shorter than that of IDH1-wildtype patients (P<0.001). In summary, even among very old, intensively treated, acute myeloid leukemia patients, adverse-risk cytogenetics predict inferior survival. The spectrum and relevance of driver gene mutations in elderly patients differs from that in younger patients. Our data implicate IDH1 mutations as a novel marker for chemorefractory disease and inferior prognosis. (AMLCG-1999 trial: clinicaltrials.gov identifier, NCT00266136).

A 29-gene and cytogenetic score for the prediction of resistance to induction treatment in acute myeloid leukemia.

Primary therapy resistance is a major problem in acute myeloid leukemia treatment. We set out to develop a powerful and robust predictor for therapy resistance for intensively treated adult patients. We used two large gene expression data sets (n=856) to develop a predictor of therapy resistance, which was validated in an independent cohort analyzed by RNA sequencing (n=250). In addition to gene expression markers, standard clinical and laboratory variables as well as the mutation status of 68 genes were considered during construction of the model. The final predictor (PS29MRC) consisted of 29 gene expression markers and a cytogenetic risk classification. A continuous predictor is calculated as a weighted linear sum of the individual variables. In addition, a cut off was defined to divide patients into a high-risk and a low-risk group for resistant disease. PS29MRC was highly significant in the validation set, both as a continuous score (OR=2.39, P=8.63·10-9, AUC=0.76) and as a dichotomous classifier (OR=8.03, P=4.29·10-9); accuracy was 77%. In multivariable models, only TP53 mutation, age and PS29MRC (continuous: OR=1.75, P=0.0011; dichotomous: OR=4.44, P=0.00021) were left as significant variables. PS29MRC dominated all models when compared with currently used predictors, and also predicted overall survival independently of established markers. When integrated into the European LeukemiaNet (ELN) 2017 genetic risk stratification, four groups (median survival of 8, 18, 41 months, and not reached) could be defined (P=4.01·10-10). PS29MRC will make it possible to design trials which stratify induction treatment according to the probability of response, and refines the ELN 2017 classification.

Acute myeloid leukemia with del(9q) is characterized by frequent mutations of NPM1, DNMT3A, WT1 and low expression of TLE4.

Deletions of the long arm of chromosome 9 [del(9q)] are a rare but recurring aberration in acute myeloid leukemia (AML). Del(9q) can be found as the sole abnormality or in combination with other cytogenetic aberrations such as t(8;21) and t(15;17). TLE1 and TLE4 were identified to be critical genes contained in the 9q region. We performed whole exome sequencing of 5 patients with del(9q) as the sole abnormality followed by targeted amplicon sequencing of 137 genes of 26 patients with del(9q) as sole or combined with other aberrations. We detected frequent mutations in NPM1 (10/26; 38%), DNMT3A (8/26; 31%), and WT1 (8/26; 31%) but only few FLT3-ITDs (2/26; 8%). All mutations affecting NPM1 and DNMT3A were exclusively identified in patients with del(9q) as the sole abnormality and were significantly more frequent compared to 111 patients classified as intermediate-II according to the European LeukemiaNet (10/14, 71% vs. 22/111, 20%; P < 0.001, 8/14, 57% vs. 26/111, 23%; P = 0.02). Furthermore, we identified DNMT3B to be rarely but recurrently targeted by truncating mutations in AML. Gene expression analysis of 13 patients with del(9q) and 454 patients with normal karyotype or various cytogenetic aberrations showed significant down regulation of TLE4 in patients with del(9q) (P = 0.02). Interestingly, downregulation of TLE4 was not limited to AML with del(9q), potentially representing a common mechanism in AML pathogenesis. Our comprehensive genetic analysis of the del(9q) subgroup reveals a unique mutational profile with the frequency of DNMT3A mutations in the del(9q) only subset being the highest reported so far in AML, indicating oncogenic cooperativity. © 2016 Wiley Periodicals, Inc.

Adults with Philadelphia chromosome-like acute lymphoblastic leukemia frequently have IGH-CRLF2 and JAK2 mutations, persistence of minimal residual disease and poor prognosis.

Philadelphia-like B-cell precursor acute lymphoblastic leukemia (Ph-like ALL) is characterized by distinct genetic alterations and inferior prognosis in children and younger adults. The purpose of this study was a genetic and clinical characterization of Ph-like ALL in adults. Twenty-six (13%) of 207 adult patients (median age: 42 years) with B-cell precursor ALL (BCP-ALL) were classified as having Ph-like ALL using gene expression profiling. The frequency of Ph-like ALL was 27% among 95 BCP-ALL patients negative for BCR-ABL1 and KMT2A-rearrangements. IGH-CRLF2 rearrangements (6/16; P=0.002) and mutations in JAK2 (7/16; P<0.001) were found exclusively in the Ph-like ALL subgroup. Clinical and outcome analyses were restricted to patients treated in German Multicenter Study Group for Adult ALL (GMALL) trials 06/99 and 07/03 (n=107). The complete remission rate was 100% among both Ph-like ALL patients (n=19) and the "remaining BCP-ALL" cases (n=40), i.e. patients negative for BCR-ABL1 and KMT2A-rearrangements and the Ph-like subtype. Significantly fewer Ph-like ALL patients reached molecular complete remission (33% versus 79%; P=0.02) and had a lower probability of continuous complete remission (26% versus 60%; P=0.03) and overall survival (22% versus 64%; P=0.006) at 5 years compared to the remaining BCP-ALL patients. The profile of genetic lesions in adults with Ph-like ALL, including older adults, resembles that of pediatric Ph-like ALL and differs from the profile in the remaining BCP-ALL. Our study is the first to demonstrate that Ph-like ALL is associated with inferior outcomes in intensively treated older adult patients. Ph-like adult ALL should be recognized as a distinct, high-risk entity and further research on improved diagnostic and therapeutic approaches is needed. (NCT00199056, NCT00198991).

Whole-exome sequencing in adult ETP-ALL reveals a high rate of DNMT3A mutations.

Early T-cell precursor (ETP) acute lymphoblastic leukemia (ALL) is a high-risk subgroup of T-lineage ALL characterized by specific stem cell and myeloid features. In adult ETP-ALL, no comprehensive studies on the genetic background have been performed to elucidate molecular lesions of this distinct subgroup. We performed whole-exome sequencing of 5 paired ETP-ALL samples. In addition to mutations in genes known to be involved in leukemogenesis (ETV6, NOTCH1, JAK1, and NF1), we identified novel recurrent mutations in FAT1 (25%), FAT3 (20%), DNM2 (35%), and genes associated with epigenetic regulation (MLL2, BMI1, and DNMT3A). Importantly, we verified the high rate of DNMT3A mutations (16%) in a larger cohort of adult patients with ETP-ALL (10/68). Mutations in epigenetic regulators support clinical trials, including epigenetic-orientated therapies, for this high-risk subgroup. Interestingly, more than 60% of adult patients with ETP-ALL harbor at least a single genetic lesion in DNMT3A, FLT3, or NOTCH1 that may allow use of targeted therapies.

Exome sequencing identifies recurring FLT3 N676K mutations in core-binding factor leukemia.

The t(8;21) and inv(16)/t(16;16) rearrangements affecting the core-binding factors RUNX1 and CBFB, respectively, are found in 15% to 20% of adult de novo acute myeloid leukemia (AML) cases and are associated with a favorable prognosis. Since the expression of the fusion genes CBFB/MYH11 or RUNX1/RUNX1T1 alone is not sufficient to cause leukemia, we performed exome sequencing of an AML sample with an inv(16) to identify mutations, which may collaborate with the CBFB/MYH11 fusion during leukemogenesis. We discovered an N676K mutation in the adenosine triphosphate (ATP)-binding domain (tyrosine kinase domain 1 [TKD1]) of the fms-related tyrosine kinase 3 (FLT3) gene. In a cohort of 84 de novo AML patients with a CBFB/MYH11 rearrangement and in 36 patients with a RUNX1/RUNX1T1 rearrangement, the FLT3 N676K mutation was identified in 5 and 1 patients, respectively (5 [6%] of 84; 1 [3%] of 36). The FLT3-N676K mutant alone leads to factor-independent growth in Ba/F3 cells and, together with a concurrent FLT3-ITD (internal tandem duplication), confers resistance to the FLT3 protein tyrosine kinase inhibitors (PTKIs) PKC412 and AC220. Gene expression analysis of AML patients with CBFB/MYH11 rearrangement and FLT3 N676K mutation showed a trend toward a specific expression profile. Ours is the first report of recurring FLT3 N676 mutations in core-binding factor (CBF) leukemias and suggests a defined subgroup of CBF leukemias.

GATA2 zinc finger 1 mutations associated with biallelic CEBPA mutations define a unique genetic entity of acute myeloid leukemia.

Cytogenetically normal acute myeloid leukemia (CN-AML) with biallelic CEBPA gene mutations (biCEPBA) represents a distinct disease entity with a favorable clinical outcome. So far, it is not known whether other genetic alterations cooperate with biCEBPA mutations during leukemogenesis. To identify additional mutations, we performed whole exome sequencing of 5 biCEBPA patients and detected somatic GATA2 zinc finger 1 (ZF1) mutations in 2 of 5 cases. Both GATA2 and CEBPA are transcription factors crucial for hematopoietic development. Inherited or acquired mutations in both genes have been associated with leukemogenesis. Further mutational screening detected novel GATA2 ZF1 mutations in 13 of 33 biCEBPA-positive CN-AML patients (13/33, 39.4%). No GATA2 mutations were found in 38 CN-AML patients with a monoallelic CEBPA mutation and in 89 CN-AML patients with wild-type CEBPA status. The presence of additional GATA2 mutations (n=10) did not significantly influence the clinical outcome of 26 biCEBPA-positive patients. In reporter gene assays, all tested GATA2 ZF1 mutants showed reduced capacity to enhance CEBPA-mediated activation of transcription, suggesting that the GATA2 ZF1 mutations may collaborate with biCEPBA mutations to deregulate target genes during malignant transformation. We thus provide evidence for a genetically distinct subgroup of CN-AML. The German AML cooperative group trials 1999 and 2008 are registered with the identifiers NCT00266136 and NCT01382147 at www.clinicaltrials.gov.

RUNX1 mutations in cytogenetically normal acute myeloid leukemia are associated with a poor prognosis and up-regulation of lymphoid genes.

BACKGROUND: The RUNX1 (AML1) gene is a frequent mutational target in myelodysplastic syndromes and acute myeloid leukemia. Previous studies suggested that RUNX1 mutations may have pathological and prognostic implications. DESIGN AND METHODS: We screened 93 patients with cytogenetically normal acute myeloid leukemia for RUNX1 mutations by capillary sequencing of genomic DNA. Mutation status was then correlated with clinical data and gene expression profiles. RESULTS: We found that 15 out of 93 (16.1%) patients with cytogenetically normal acute myeloid leukemia had RUNX1 mutations. Seventy-three patients were enrolled in the AMLCG-99 trial and carried ten RUNX1 mutations (13.7%). Among these 73 patients RUNX1 mutations were significantly associated with older age, male sex, absence of NPM1 mutations and presence of MLL-partial tandem duplications. Moreover, RUNX1-mutated patients had a lower complete remission rate (30% versus 73% P=0.01), lower relapse-free survival rate (3-year relapse-free survival 0% versus 30.4%; P=0.002) and lower overall survival rate (3-year overall survival 0% versus 34.4%; P<0.001) than patients with wild-type RUNX1. RUNX1 mutations remained associated with shorter overall survival in a multivariate model including age and the European Leukemia Net acute myeloid leukemia genetic classification as covariates. Patients with RUNX1 mutations showed a unique gene expression pattern with differential expression of 85 genes. The most prominently up-regulated genes in patients with RUNX1-mutated cytogenetically normal acute myeloid leukemia include lymphoid regulators such as HOP homeobox (HOPX), deoxynucleotidyltransferase (DNTT, terminal) and B-cell linker (BLNK), indicating lineage infidelity. CONCLUSIONS: Our findings firmly establish that RUNX1 mutations are a marker of poor prognosis and provide insights into the pathogenesis of RUNX1 mutation-positive acute myeloid leukemia.

Validation and refinement of the revised 2017 European LeukemiaNet genetic risk stratification of acute myeloid leukemia.

The revised 2017 European LeukemiaNet (ELN) recommendations for genetic risk stratification of acute myeloid leukemia have been widely adopted, but have not yet been validated in large cohorts of AML patients. We studied 1116 newly diagnosed AML patients (age range, 18-86 years) who had received induction chemotherapy. Among 771 patients not selected by genetics, the ELN-2017 classification re-assigned 26.5% of patients into a more favorable or, more commonly, a more adverse-risk group compared with the ELN-2010 recommendations. Forty percent of the cohort, and 51% of patients ≥60 years, were classified as adverse-risk by ELN-2017. In 599 patients <60 years, estimated 5-year overall survival (OS) was 64% for ELN-2017 favorable, 42% for intermediate-risk and 20% for adverse-risk patients. Among 517 patients aged ≥60 years, corresponding 5-year OS rates were 37, 16, and 6%. Patients with biallelic CEBPA mutations or inv(16) had particularly favorable outcomes, while patients with mutated TP53 and a complex karyotype had especially poor prognosis. DNMT3A mutations associated with inferior OS within each ELN-2017 risk group. Our results validate the prognostic significance of the revised ELN-2017 risk classification in AML patients receiving induction chemotherapy across a broad age range. Further refinement of the ELN-2017 risk classification is possible.

Clinical presentation and differential splicing of SRSF2, U2AF1 and SF3B1 mutations in patients with acute myeloid leukemia.

Previous studies demonstrated that splicing factor mutations are recurrent events in hematopoietic malignancies with both clinical and functional implications. However, their aberrant splicing patterns in acute myeloid leukemia remain largely unexplored. In this study, we characterized mutations in SRSF2, U2AF1, and SF3B1, the most commonly mutated splicing factors. In our clinical analysis of 2678 patients, splicing factor mutations showed inferior relapse-free and overall survival, however, these mutations did not represent independent prognostic markers. RNA-sequencing of 246 and independent validation in 177 patients revealed an isoform expression profile which is highly characteristic for each individual mutation, with several isoforms showing a strong dysregulation. By establishing a custom differential splice junction usage pipeline, we accurately detected aberrant splicing in splicing factor mutated samples. A large proportion of differentially used junctions were novel, including several junctions in leukemia-associated genes. In SRSF2(P95H) mutants, we further explored the possibility of a cascading effect through the dysregulation of the splicing pathway. Furthermore, we observed a validated impact on overall survival for two junctions overused in SRSF2(P95H) mutants. We conclude that splicing factor mutations do not represent independent prognostic markers. However, they do have genome-wide consequences on gene splicing leading to dysregulated isoform expression of several genes.

Toll-like receptor 7/8-matured RNA-transduced dendritic cells as post-remission therapy in acute myeloid leukaemia: results of a phase I trial.

OBJECTIVES: Innovative post-remission therapies are needed to eliminate residual AML cells. DC vaccination is a promising strategy to induce anti-leukaemic immune responses. METHODS: We conducted a first-in-human phase I study using TLR7/8-matured DCs transfected with RNA encoding the two AML-associated antigens WT1 and PRAME as well as CMVpp65. AML patients in CR at high risk of relapse were vaccinated 10× over 26 weeks. RESULTS: Despite heavy pretreatment, DCs of sufficient number and quality were generated from a single leukapheresis in 11/12 cases, and 10 patients were vaccinated. Administration was safe and resulted in local inflammatory responses with dense T-cell infiltration. In peripheral blood, increased antigen-specific CD8+ T cells were seen for WT1 (2/10), PRAME (4/10) and CMVpp65 (9/10). For CMVpp65, increased CD4+ T cells were detected in 4/7 patients, and an antibody response was induced in 3/7 initially seronegative patients. Median OS was not reached after 1057 days; median RFS was 1084 days. A positive correlation was observed between clinical benefit and younger age as well as mounting of antigen-specific immune responses. CONCLUSIONS: Administration of TLR7/8-matured DCs to AML patients in CR at high risk of relapse was feasible and safe and resulted in induction of antigen-specific immune responses. Clinical benefit appeared to occur more likely in patients <65 and in patients mounting an immune response. Our observations need to be validated in a larger patient cohort. We hypothesise that TLR7/8 DC vaccination strategies should be combined with hypomethylating agents or checkpoint inhibition to augment immune responses. TRIAL REGISTRATION: The study was registered at https://clinicaltrials.gov on 17 October 2012 (NCT01734304) and at https://www.clinicaltrialsregister.eu (EudraCT-Number 2010-022446-24) on 10 October 2013.

The clinical mutatome of core binding factor leukemia.

The fusion genes CBFB/MYH11 and RUNX1/RUNX1T1 block differentiation through disruption of the core binding factor (CBF) complex and are found in 10-15% of adult de novo acute myeloid leukemia (AML) cases. This AML subtype is associated with a favorable prognosis; however, nearly half of CBF-rearranged patients cannot be cured with chemotherapy. This divergent outcome might be due to additional mutations, whose spectrum and prognostic relevance remains hardly defined. Here, we identify nonsilent mutations, which may collaborate with CBF-rearrangements during leukemogenesis by targeted sequencing of 129 genes in 292 adult CBF leukemia patients, and thus provide a comprehensive overview of the mutational spectrum ('mutatome') in CBF leukemia. Thereby, we detected fundamental differences between CBFB/MYH11- and RUNX1/RUNX1T1-rearranged patients with ASXL2, JAK2, JAK3, RAD21, TET2, and ZBTB7A being strongly correlated with the latter subgroup. We found prognostic relevance of mutations in genes previously known to be AML-associated such as KIT, SMC1A, and DHX15 and identified novel, recurrent mutations in NFE2 (3%), MN1 (4%), HERC1 (3%), and ZFHX4 (5%). Furthermore, age >60 years, nonprimary AML and loss of the Y-chromosomes are important predictors of survival. These findings are important for refinement of treatment stratification and development of targeted therapy approaches in CBF leukemia.

Allelic Imbalance of Recurrently Mutated Genes in Acute Myeloid Leukaemia.

The patho-mechanism of somatic driver mutations in cancer usually involves transcription, but the proportion of mutations and wild-type alleles transcribed from DNA to RNA is largely unknown. We systematically compared the variant allele frequencies of recurrently mutated genes in DNA and RNA sequencing data of 246 acute myeloid leukaemia (AML) patients. We observed that 95% of all detected variants were transcribed while the rest were not detectable in RNA sequencing with a minimum read-depth cut-off (10x). Our analysis focusing on 11 genes harbouring recurring mutations demonstrated allelic imbalance (AI) in most patients. GATA2, RUNX1, TET2, SRSF2, IDH2, PTPN11, WT1, NPM1 and CEBPA showed significant AIs. While the effect size was small in general, GATA2 exhibited the largest allelic imbalance. By pooling heterogeneous data from three independent AML cohorts with paired DNA and RNA sequencing (N = 253), we could validate the preferential transcription of GATA2-mutated alleles. Differential expression analysis of the genes with significant AI showed no significant differential gene and isoform expression for the mutated genes, between mutated and wild-type patients. In conclusion, our analyses identified AI in nine out of eleven recurrently mutated genes. AI might be a common phenomenon in AML which potentially contributes to leukaemogenesis.

Genetic heterogeneity of cytogenetically normal AML with mutations of CEBPA.

Biallelic mutations of the CCAAT/enhancer binding protein α (CEBPA) gene define a distinct genetic entity of acute myeloid leukemia (AML) with favorable prognosis. The presence of GATA2 and CSF3R mutations that are specifically associated with this subgroup but not mutated in all samples suggests a genetic heterogeneity of biCEBPA-mutated AML. We characterized the mutational landscape of CEBPA-mutated cytogenetically normal AML by targeted amplicon resequencing. We analyzed 48 biallelically mutated CEBPA (biCEBPA), 32 monoallelically mutated CEBPA (moCEBPA), and 287 wild-type CEBPA (wtCEBPA) patient samples from German AML Cooperative Group studies or registry. Targeted sequencing of 42 genes revealed that moCEBPA patients had significantly more additional mutations and additional mutated genes than biCEBPA patients. Within the group of biCEBPA patients, we identified 2 genetic subgroups defined by the presence or absence of mutations in chromatin/DNA modifiers (C), cohesin complex (C), and splicing (S) genes: biCEBPA CCSpos (25/48 [52%]) and biCEBPA CCSneg (23/48 [48%]). Equivalent subgroups were identified in 51 biCEBPA patients from the Cancer Genome Project. Patients in the biCEBPA CCSpos group were significantly older and had poorer overall survival and lower complete remission rates following intensive chemotherapy regimens compared with patients in the biCEBPA CCSneg group. Patients with available remission samples from the biCEBPA CCSpos group cleared the biCEBPA mutations, but most had persisting CCS mutations in complete remission, suggesting the presence of a preleukemic clone. In conclusion, CCS mutations define a distinct biological subgroup of biCEBPA AML that might refine prognostic classification of AML. This trial was registered at www.clinicaltrials.gov as #NCT00266136 and NCT01382147.

Persistence of pre-leukemic clones during first remission and risk of relapse in acute myeloid leukemia.

Some patients with acute myeloid leukemia (AML) who are in complete remission after induction chemotherapy harbor persisting pre-leukemic clones, carrying a subset of leukemia-associated somatic mutations. There is conflicting evidence on the prognostic relevance of these clones for AML relapse. Here, we characterized paired pre-treatment and remission samples from 126 AML patients for mutations in 68 leukemia-associated genes. Fifty patients (40%) retained ≥1 mutation during remission at a VAF of ≥2%. Mutation persistence was most frequent in DNMT3A (65% of patients with mutations at diagnosis), SRSF2 (64%), TET2 (55%), and ASXL1 (46%), and significantly associated with older age (p < 0.0001) and, in multivariate analyses adjusting for age, genetic risk, and allogeneic transplantation, with inferior relapse-free survival (hazard ratio (HR), 2.34; p = 0.0039) and overall survival (HR, 2.14; p = 0.036). Patients with persisting mutations had a higher cumulative incidence of relapse before, but not after allogeneic stem cell transplantation. Our work underlines the relevance of mutation persistence during first remission as a novel risk factor in AML. Persistence of pre-leukemic clones may contribute to the inferior outcome of elderly AML patients. Allogeneic transplantation abrogated the increased relapse risk associated with persisting pre-leukemic clones, suggesting that mutation persistence may guide post-remission treatment.