Evaluation of next-generation sequencing for measurable residual disease monitoring in three major fusion transcript subtypes of B-precursor acute lymphoblastic leukaemia.

The use of next-generation sequencing (NGS) for monitoring measurable residual disease (MRD) in acute lymphoblastic leukaemia (ALL) has been gaining traction. This study aimed to investigate the utility of NGS in MRD monitoring for the three major fusion transcript (FT) subtypes of B-precursor ALL (B-ALL). The MRD results for 104 bone marrow samples from 56 patients were analysed through NGS and real time quantitative reverse transcription PCR (RT-qPCR) for the three major FTs: BCR::ABL1, TCF3::PBX1, and ETV6::RUNX1. To validate the NGS approach, NGS-MRD was initially compared with allele-specific oligonucleotide-qPCR-MRD, and the coefficient of determination was good (R2=0.8158). A subsequent comparison of NGS-MRD with FT-MRD yielded a good coefficient of determination (R2=0.7690), but the coefficient varied by subtype. Specifically, the R2 was excellent for TCF3::PBX1 ALL (R2=0.9157), good for ETV6::RUNX1 ALL (R2=0.8606), and subpar for BCR::ABL1 ALL (R2=0.5763). The overall concordance between the two methods was 83.7%, and an excellent concordance rate of 95.8% was achieved for TCF3::PBX1 ALL. Major discordance, which was defined as a >1 log difference between discordant NGS-MRD and FT-MRD, occurred in 6.7% of the samples, with all but one sample being BCR::ABL1 ALL. Among the four non-transplanted patients with BCR::ABL1-MRD (+)/NGS-MRD (-), three did not relapse after long-term follow-up. Our finding indicates that NGS-MRD has a better prognostic impact than RT-qPCR-MRD in ETV6::RUNX1 and BCR::ABL1 ALL, whereas in TCF3::PBX1 ALL, both methods exhibit comparable efficacy.

Refining risk stratification in paediatric B-acute lymphoblastic leukaemia: Combining IKZF1plus and Day 15 MRD positivity.

This study investigates the potential utility of IKZF1 deletion as an additional high-risk marker for paediatric acute lymphoblastic leukaemia (ALL). The prognostic impact of IKZF1 status, in conjunction with minimal/measurable residual disease (MRD), was evaluated within the MRD-guided TPOG-ALL-2013 protocol using 412 newly diagnosed B-ALL patients aged 1-18. IKZF1 status was determined using multiplex ligation-dependent probe amplification. IKZF1 deletions, when co-occurring with CDKN2A, CDKN2B, PAX5 or PAR1 region deletions in the absence of ERG deletions, were termed IKZF1plus. Both IKZF1 deletion (14.6%) and IKZF1plus (7.8%) independently predicted poorer outcomes in B-ALL. IKZF1plus was observed in 4.1% of Philadelphia-negative ALL, with a significantly lower 5-year event-free survival (53.9%) compared to IKZF1 deletion alone (83.8%) and wild-type IKZF1 (91.3%) (p < 0.0001). Among patients with Day 15 MRD ≥0.01%, provisional high-risk patients with IKZF1plus exhibited the worst outcomes in event-free survival (42.0%), relapse-free survival (48.0%) and overall survival (72.7%) compared to other groups (p < 0.0001). Integration of IKZF1plus and positive Day 15 MRD identified a subgroup of Philadelphia-negative B-ALL with a 50% risk of relapse. This study highlights the importance of assessing IKZF1plus alongside Day 15 MRD positivity to identify patients at increased risk of adverse outcomes, potentially minimizing overtreatment.

Comparison of Clinical and Molecular Features Between Patients With Essential Thrombocythemia and Early/Prefibrotic Primary Myelofibrosis Presenting With Thrombocytosis in Taiwan.

OBJECTIVES: The clinical presentations of essential thrombocythemia (ET) may be quite similar to early/prefibrotic primary myelofibrosis (pre-PMF), especially in pre-PMF presenting with thrombocytosis (pre-PMF-T), but may be associated with a different outcome. It is very important to distinguish these two entities. The aim of this study was to address the clinical and prognostic relevance of distinguishing pre-PMF-T from ET. METHODS: All patients, including 258 with ET and 105 with pre-PMF-T, received JAK2V617F, MPL (exon 10), and CALR (exon 9) mutation analysis and allele burden measurement for JAK2V617F and CALR mutants. RESULTS: Patients with pre-PMF-T had an older age and higher leukocyte and platelet counts but lower hemoglobin levels than patients with ET. Patients with pre-PMF-T had a shorter overall, leukemia-free, and thrombosis-free survival compared with patients with ET. Patients with ET had a higher rate of cerebral ischemic stroke, whereas patients with pre-PMF-T tended to have splanchnic vein thrombosis. The frequencies of JAK2V617F, CALR, and MPL mutations and CALR allele burden were no different, but JAK2V617F allele burden was significantly higher in pre-PMF-T. Patients with pre-PMF-T with the JAK2V617F mutation had an inferior overall survival and thrombosis-free survival, whereas the status of driver gene mutations did not influence the outcomes of patients with ET. CONCLUSIONS: ET and pre-PMF-T were two distinct disease entities and exhibited different clinical phenotype, genotype, and outcomes.

Measurable Residual Disease Monitoring by Locked Nucleic Acid Quantitative Real-Time PCR Assay for IDH1/2 Mutation in Adult AML.

Locked nucleic acid quantitative Real-Time PCR (LNA-qPCR) for IDH1/2 mutations in AML measurable residual disease (MRD) detection is rarely reported. LNA-qPCR was applied to quantify IDH1/2 mutants MRD kinetics in bone marrow from 88 IDH1/2-mutated AML patients, and correlated with NPM1-MRD, clinical characteristics, and outcomes. The median normalized copy number (NCN) of IDH1/2 mutants decreased significantly from 53,228 (range 87−980,686)/ALB × 106 at diagnosis to 773 (range 1.5−103,600)/ALB × 106 at first complete remission (CR). IDH1/2 LNA-qPCR MRD was concordant with remission status or NPM1-MRD in 79.5% (70/88) of patients. Younger patients and patients with FLT3 mutations had higher concordance. The Spearman correlation coefficient (rs) and concordance rate between the log reduction of IDH1/2 LNA-qPCR and NPM1-MRD were 0.68 and 81% (K = 0.63, 95% CI 0.50−0.74), respectively. IDH1/2-MRD > 2 log reduction at first CR predicted significantly better relapse-free survival (3-year RFS rates 52.9% vs. 31.9%, p = 0.007) and cumulative incidence of relapse (3-year CIR rates 44.5% vs. 64.5%, p = 0.012) compared to IDH1/2-MRD ≤ 2 log reduction. IDH1/2-MRD > 2 log reduction during consolidation is also associated with a significantly lower CIR rate than IDH1/2-MRD ≤ 2 log reduction (3-year CIR rates 42.3% vs. 68.8%, p = 0.019). LNA-qPCR for IDH1/2 mutation is a potential MRD technique to predict relapse in IDH1/2-mutated AML patients, especially for those with IDH1/2 MRD > 2 log reduction at first CR or a concurrent FLT3 mutation.

Comparison of Two Quantitative PCR-Based Assays for Detection of Minimal Residual Disease in B-Precursor Acute Lymphoblastic Leukemia Harboring Three Major Fusion Transcripts.

Two quantitative PCR (qPCR)-based methods, for clonal immunoglobulin or T-cell receptor gene (Ig/TCR) rearrangements and for fusion transcripts, are widely used for the measurement of minimal residual disease (MRD) in patients with B-precursor acute lymphoblastic leukemia (ALL). MRD of bone marrow samples from 165 patients carrying the three major fusion transcripts, including 74 BCR-ABL1, 54 ETV6-RUNX1, and 37 TCF3-PBX1, was analyzed by using the two qPCR-based methods. The correlation coefficient of both methods was good for TCF3-PBX1 (R2 = 0.8088) and BCR-ABL1 (R2 = 0.8094) ALL and moderate for ETV6-RUNX1 (R2 = 0.5972). The concordance was perfect for TCF3-PBX1 ALL (97.2%), substantially concordant for ETV6-RUNX1 ALL (87.1%), and only moderate for BCR-ABL1 ALL (70.6%). The discordant MRD, positive for only one method with a difference greater than one log, was found in 4 of 93 samples (4.3%) with ETV6-RUNX1, 31 of 245 samples (12.7%) with BCR-ABL1, and none of TCF3-PBX1 ALL. None of the eight non-transplanted patients with BCR-ABL1-MRD (+)/Ig/TCR-MRD (-) with a median follow-up time of 73.5 months had hematologic relapses. Our study showed an excellent MRD concordance between the two qPCR-based methods in TCF3-PBX1 ALL, whereas qPCR for Ig/TCR is more reliable in BCR-ABL1 ALL.

Clonal evolution and clinical implications of genetic abnormalities in blastic transformation of chronic myeloid leukaemia.

Blast crisis (BC) predicts dismal outcomes in patients with chronic myeloid leukaemia (CML). Although additional genetic alterations play a central role in BC, the landscape and prognostic impact of these alterations remain elusive. Here, we comprehensively investigate genetic abnormalities in 136 BC and 148 chronic phase (CP) samples obtained from 216 CML patients using exome and targeted sequencing. One or more genetic abnormalities are found in 126 (92.6%) out of the 136 BC patients, including the RUNX1-ETS2 fusion and NBEAL2 mutations. The number of genetic alterations increase during the transition from CP to BC, which is markedly suppressed by tyrosine kinase inhibitors (TKIs). The lineage of the BC and prior use of TKIs correlate with distinct molecular profiles. Notably, genetic alterations, rather than clinical variables, contribute to a better prediction of BC prognosis. In conclusion, genetic abnormalities can help predict clinical outcomes and can guide clinical decisions in CML.

RAS pathway mutation is an added-value biomarker in pediatric Philadelphia-negative B-cell acute lymphoblastic leukemia with IKZF1 deletions.

BACKGROUND: IKZF1deletion is an unfavorable factor in Philadelphia negative (Ph -) B-cell acute lymphoblastic leukemia. However, the effects of IKZF1 deletions co-existing genetic alterations in Ph (-) ALL have not been extensively studied. METHODS: Bone marrow samples from 368 children with Ph (-) ALL were analyzed by using multiplex ligation-dependent probe amplification kit for detection of gene deletions and Sanger sequencing for mutational analysis of RAS pathway genes. The outcome was analyzed on 215 patients treated with Taiwan Pediatric Oncology Group-ALL-2002 protocol. RESULTS: IKZF1 deletions were present in 12.8% and IKZF1plus in 6.3% of patients. Mutations of RAS pathway genes were detected in 25.0% of IKZF1-deleted patients. The 10-year event-free survival (EFS) of IKZF1-undeleted patients was significantly better compared with IKZF1-deleted patients (80.0% vs. 47.8%, p = 0.001). Compared with outcome of patients harboring IKZF1 deletion alone, no difference in EFS was observed in patients with IKZF1plus , whereas three patients carried both IKZF1 and ERG deletions had a superior 10-year EFS (100%). The 10-year EFS of patients with any gene mutation of RAS pathway was worse than that of patients with wild-type genes (79.1% vs. 61.6%, p = 0.033). In multivariate analysis, RAS pathway mutations and IKZF1 deletion were independent predictors of inferior EFS. Co-existence of IKZF1 deletion with RAS pathway mutations had a worst 10-year EFS (11.1 ± 10.5%) and 10-year OS (53.3 ± 17.6%). CONCLUSIONS: Our results showed that RAS pathway mutation is an added-value biomarker in pediatric IKZF1-deleted Ph (-) ALL patients.

DNMT3A mutants provide proliferating advantage with augmentation of self-renewal activity in the pathogenesis of AML in KMT2A-PTD-positive leukemic cells.

Acute myeloid leukemia (AML) with partial tandem duplication of histone-lysine N-methyltransferase 2A (KMT2A-PTD) is a subtype of AML and is associated with adverse survival, yet the molecular pathogenesis of KMT2A-PTD is not fully understood. DNA methyltransferase 3A (DNMT3A) is mutated in various myeloid neoplasms including AML, especially at the Arg882. Recently, it has been found that DNMT3A mutations frequently coexisted with KMT2A-PTD and are associated with inferior outcomes. We aimed to understand the biological role of DNMT3A mutation in KMT2A-PTD-positive cells. Herein, we found that overexpression of DNMT3A mutants (MT) in KMT2A-PTD-positive EOL-1 cells augmented cell proliferation and clonogenicity. Serial colony replating assays indicated that DNMT3A-MT increased the self-renewal ability of Kmt2a-PTD-expressing mouse bone marrow cells with immature morphology. At 10 months post bone marrow transplantation, mice with the combined Kmt2a-PTD and DNMT3A-MT showed hepatosplenomegaly and leukocytosis with a shorter latency compared to control and DNMT3A-wild-type. Gene expression microarray analyses of bone marrow samples from human AML with KMT2A-PTD/DNMT3A-MT showed a stem cell signature and myeloid hematopoietic lineage with dysregulation of HOXB gene expression. In addition, human bone marrow AML cells carrying KMT2A-PTD/DNMT3A-MT showed abnormal growth and augmented self-renewal activity in primary cell culture. The present study provides information underlying the pathogenic role of DNMT3A-MT with KMT2A-PTD in proliferating advantage with augmentation of self-renewal activity in human leukemia, which may help to better understand the disease and to design better therapy for AML patients with these mutations.

RUNX1 mutations promote leukemogenesis of myeloid malignancies in ASXL1-mutated leukemia.

BACKGROUND: Additional sex combs-like 1 (ASXL1) mutations have been described in all forms of myeloid neoplasms including chronic myelomonocytic leukemia (CMML) and associated with inferior outcomes, yet the molecular pathogenesis of ASXL1 mutations (ASXL1-MT) remains poorly understood. Transformation of CMML to secondary AML (sAML) is one of the leading causes of death in CMML patients. Previously, we observed that transcription factor RUNX1 mutations (RUNX1-MT) coexisted with ASXL1-MT in CMML and at myeloid blast phase of chronic myeloid leukemia. The contribution of RUNX1 mutations in the pathogenesis of myeloid transformation in ASXL1-mutated leukemia, however, remains unclear. METHODS: To evaluate the leukemogenic role of RUNX1-MT in ASXL1-mutated cells, we co-expressed RUNX1-MT (R135T) and ASXL1-MT (R693X) in different cell lines and performed immunoblot, co-immunoprecipitation, gene expression microarray, quantitative RT-PCR, cell proliferation, differentiation, and clonogenic assays for in vitro functional analyses. The in vivo effect was investigated using the C57BL/6 mouse bone marrow transplantation (BMT) model. RESULTS: Co-expression of two mutant genes increased myeloid stem cells in animal model, suggesting that cooperation of RUNX1 and ASXL1 mutations played a critical role in leukemia transformation. The expression of RUNX1 mutant in ASXL1-mutated myeloid cells augmented proliferation, blocked differentiation, and increased self-renewal activity. At 9 months post-BMT, mice harboring combined RUNX1 and ASXL1 mutations developed disease characterized by marked splenomegaly, hepatomegaly, and leukocytosis with a shorter latency. Mice transduced with both ASXL1 and RUNX1 mutations enhanced inhibitor of DNA binding 1 (ID1) expression in the spleen, liver, and bone marrow cells. Bone marrow samples from CMML showed that ID1 overexpressed in coexisted mutations of RUNX1 and ASXL1 compared to normal control and either RUNX1-MT or ASXL1-MT samples. Moreover, the RUNX1 mutant protein was more stable than WT and increased HIF1-α and its target ID1 gene expression in ASXL1 mutant cells. CONCLUSION: The present study demonstrated the biological and functional evidence for the critical role of RUNX1-MT in ASXL1-mutated leukemia in the pathogenesis of myeloid malignancies.

Distinct immunoglobulin heavy chain variable region gene repertoire and lower frequency of del(11q) in Taiwanese patients with chronic lymphocytic leukaemia.

Chronic lymphocytic leukaemia (CLL) is the most common leukaemia in Western countries but very rare in Asia. Peripheral blood or bone marrow mononuclear cells obtained at initial diagnosis from 194 patients with CLL were analysed to determine the ethnic difference in genetic abnormalities. Mutated IGHV was detected in 71·2% of Taiwanese CLL and IGHV3-23 was the most frequently used gene. Stereotyped BCR was present in 18·3% with subset 8 being the most frequent. All cases with subset 8 belonged to IGHV 4-39 and were exclusively associated with un-mutated IGHV and poor outcome. Mutation frequencies of SF3B1 (9·7%), NOTCH1 (8·6%), BIRC3 (1·1%), ATM (16·9%) or TP53 (8·1%), and frequencies of cytogenetic abnormalities including trisomy 12 (18·6%), del(17p) (10·4%), del(13q) (43·7%) and IGH translocation (10·1%) were comparable to those reported from Western countries, except del(11q) (6·9%) which was lower in our patients. Patients with un-mutated IGHV, subset 8, disrupted TP53, trisomy 12, and SF3B1 mutations had a worse outcome compared to patients without these mutations. In conclusion, IGHV3-23 usage, stereotyped subset 8 and lower frequency of del(11q) show an ethnicity-dependent association in Taiwanese CLL patients.

Ets1 Plays a Critical Role in MLL/EB1-Mediated Leukemic Transformation in a Mouse Bone Marrow Transplantation Model.

Leukemogenic potential of MLL fusion with the coiled-coil domain-containing partner genes and the downstream target genes of this type of MLL fusion have not been clearly investigated. In this study, we demonstrated that the coiled-coil-four-helix bundle structure of EB1 that participated in the MLL/EB1 was required for immortalizing mouse bone marrow (BM) cells and producing myeloid, but not lymphoid, cell lines. Compared to MLL/AF10, MLL/EB1 had low leukemogenic ability. The MLL/EB1 cells grew more slowly owing to increased apoptosis in vitro and induced acute monocytic leukemia with an incomplete penetrance and longer survival in vivo. A comparative analysis of transcriptome profiling between MLL/EB1 and MLL/AF10 cell lines revealed that there was an at least two-fold difference in the induction of 318 genes; overall, 51.3% (163/318) of the genes were known to be bound by MLL, while 15.4% (49/318) were bound by both MLL and MLL/AF9. Analysis of the 318 genes using Gene Ontology-PANTHER overrepresentation test revealed significant differences in several biological processes, including cell differentiation, proliferation/programmed cell death, and cell homing/recruitment. The Ets1 gene, bound by MLL and MLL/AF9, was involved in several biological processes. We demonstrated that Ets1 was selectively upregulated by MLL/EB1. Short hairpin RNA knockdown of Ets1 in MLL/EB1 cells reduced the expression of CD115, apoptosis rate, competitive engraftment to BM and spleen, and incidence of leukemia and prolonged the survival of the diseased mice. Our results demonstrated that MLL/EB1 upregulated Ets1, which controlled the balance of leukemia cells between apoptosis and BM engraftment/clonal expansion. Novelty and impact of this study The leukemogenic potential of MLL fusion with cytoplasmic proteins containing coiled-coil dimerization domains and the downstream target genes of this type of MLL fusion remain largely unknown. Using a retroviral transduction/transplantation mouse model, we demonstrated that MLL fusion with the coiled-coil-four-helix bundle structure of EB1 has low leukemogenic ability; Ets1, which is upregulated by MLL/EB1, plays a critical role in leukemic transformation by balance between apoptosis and BM engraftment/clonal expansion.

Clinical and biological relevance of genetic alterations in pediatric T-cell acute lymphoblastic leukemia in Taiwan.

BACKGROUND: The leukemogenesis of T-cell acute lymphoblastic leukemia (T-ALL) involves multistep processes of genetic alterations. We aimed to determine the genetic alterations including common fusion transcripts, overexpression of T-cell transcription factor oncogenes, and deletion or mutation of targeted genes in pediatric T-ALL in Taiwan as well as their impact on outcomes in those treated with the Taiwan Pediatric Oncology Group-ALL-2002 protocol. PROCEDURE: Between 1995 and 2015, bone marrow samples obtained from 102 children aged <18 years consecutively diagnosed with T-ALL were examined. Thirty-two genetic alterations were examined by reverse transcription polymerase chain reaction (PCR) assays-PCR-based assays-followed by direct sequencing, real time quantitative PCR with TaqMan assays, or multiplex ligase probe amplification. RESULTS: TAL1 overexpression, CDKN2A/2B deletions, and NOTCH1 mutation were the most frequent aberrations while none had NF1, SUZ12 deletion, JAK1 or JAK2 mutations, or NUP214-ABL1 fusion in our cohort. The most frequent cooperating occurrence of genetic alterations included CDKN2A/2B and MTAP, MTAP and CDKN2B, LEF1 and PTPN2, and HOX11L2 and PHF6 mutation/deletion. NOTCH1 mutations conferred a favorable overall survival, whereas SIL-TAL1 fusion, TAL overexpression, LEF1 deletion, and PHF6 deletion/mutation were associated with an inferior outcome. By multivariate analysis, PHF6 mutation/deletion was the only independent predictor for inferior overall survival. CONCLUSIONS: The present study showed that the frequencies of genetic alterations in Taiwanese children with T-ALL differed considerably from those reported in Western countries. PHF6 mutation/deletion was an independently adverse predictor.

Genetic and Epigenetic Perturbations by DNMT3A-R882 Mutants Impaired Apoptosis through Augmentation of PRDX2 in Myeloid Leukemia Cells.

DNA methyltransferase 3A (DNMT3A) is mutated in various myeloid neoplasms including acute myeloid leukemia (AML), especially at the Arg882 and associated with inferior outcomes. Here, we report that the DNMT3A-Arg882His/Cys (R882H/C) mutations led to inactivation of apoptosis through DNA damage signaling following the impairment of differentiation of myeloid leukemia cells. Gene expression profiling analysis revealed aberrant expression of several cell-cycle and apoptosis-related genes, and the DNA methylation assay identified both hypo- and hypermethylation features in different regions throughout the whole genome of DNMT3A mutants-transduced myeloid cells. We found that DNMT3A-R882H/C mutations upregulated the expression of an antioxidant protein, pyroxiredoxin-2 (PRDX2), at the mRNA and protein levels with decreased accumulation of reactive oxygen species (ROS). Augmentation of ROS generation by ROS accumulating agent or by knockdown of PRDX2 from myeloid cells effectively increased drug sensitivity and apoptosis as a consequence of reduced cell proliferation. DNMT3A-R882C/H mutations decreased apoptosis induction in part by increasing the antioxidant capacity of the cell owing to upregulation of PRDX2. Molecularly, both DNMT3A-WT and R882H/C mutants interacted with PRDX2; and R882C/H mutation-induced hypomethylation increased PRDX2 expression which enhanced cell proliferation and growth with impairment of apoptosis, thereby contributing to leukemogenesis.

The clinical and prognostic relevance of driver mutations in 203 Taiwanese patients with primary myelofibrosis.

AIMS: We investigated the clinical and prognostic relevance of the mutational status of driver genes with allele burden and endogenous erythroid colony (EEC) growth in 203 Taiwanese patients with primary myelofibrosis (PMF). METHODS: Pyrosequencing was used to detect JAK2V617F mutational status and measure allele burden, while MPL (exon 10) mutations were analysed by PCR assay and then by direct sequencing. CALR exon 9 mutations were first screened for length changes by GeneScan followed by sequencing. The allele burden of the mutated CALR gene was measured by pyrosequencing. The EEC assay was conducted using a serum-free culture system. RESULTS: The frequencies of the three driver mutations and triple-negative status were similarly distributed between pre-PMF and overt PMF patients, except that pre-PMF patients had a higher incidence of CALR type 2/type-2 like mutations and a lower JAK2V617F allele burden. EEC growth and CALR mutations conferred favourable overall survival (OS). A lower JAK2V617F allele burden and grade 3 bone marrow fibrosis were associated with shorter OS and decreased leukaemia-free survival (LFS). Type 2/type 2-like CAL mutations were associated with better LFS compared with type1/type 1-like mutations. Patients with triple-negative mutation status had significantly worse OS and LFS. The allele burden of CALR mutations remained unchanged, while some JAK2V617F mutations showed clonal expansion in patients during secondary acute myeloid leukaemia transformation. CONCLUSIONS: Our study showed that EEC growth, a higher JAK2V617F allele burden and CALR mutations, especially type 2, were independent predictors for better outcomes in PMF. The allele burden of CALR mutations remained stable, but the allele burden of JAK2V617Fmutations was variable during leukaemia transformation.

Concordance of two approaches in monitoring of minimal residual disease in B-precursor acute lymphoblastic leukemia: Fusion transcripts and leukemia-associated immunophenotypes.

BACKGROUND/PURPOSE: Real-time quantitative polymerase chain reaction (RQ-PCR) for fusion transcripts and flow cytometry for leukemia-specific markers are widely used for minimal residual disease (MRD) detection in acute lymphoblastic leukemia, but the relation between the results of either method is unclear. METHODS: Mononucleated cells from 108 bone marrow samples collected from 55 B-precursor acute lymphoblastic leukemia patients (30 with t(12;21)/ETV6-RUNX1, 16 with t(9;22)/BCR-ABL1 and nine with t(1;19)/TCF3-PBX1) were examined in tandem by RQ-PCR and six-color flow cytometry. RESULTS: MRD results were concordant in 91 of the 108 paired samples (84.2%; K=0.690); 49 samples were MRD-negative while 42 were MRD-positive by both methods, with < 1 log difference in positive MRD estimates in 39 samples (92.9%). Of the 17 discordant samples, 16 were MRD-positive by RQ-PCR but MRD-negative by flow cytometry; the opposite was true in one sample. Kappa value/concordance was 0.690/85.0% (n = 60) for ETV6-RUNX1, 0.842/93.3% (n = 15) for TCF3-PBX1, and 0.535/78.8% (n = 33) for BCR-ABL1. Specific immunophenotypic abnormalities were more prevalent in each genetic subgroup, such as CD38 underexpression, CD58 overexpression, and CD34 overexpression in ETV6-RUNX1, TCF3-PBX1, and BCR-ABL1, respectively. CONCLUSION: In most follow-up samples, MRD estimates by two methods are in agreement, especially in patients with TCF3-PBX1.

Cooperation of MLL/AF10(OM-LZ) with PTPN11 activating mutation induced monocytic leukemia with a shorter latency in a mouse bone marrow transplantation model.

PTPN11 mutation, a RAS signaling pathway mutation, is associated with MLL translocations in acute leukemia. A girl with MLL/AF10 AML was found to carry PTPN11G503A . To study the impact of PTPN11G503A cooperating with MLL/AF10 on leukemogenesis, we established a retroviral transduction/transplantation mouse model. Compared to the MLL/AF10(OM-LZ) leukemia cells harboring PTPN11wt , the cells harboring PTPN11G503A were hypersensitive to GM-CSF and IL3, and more resistant to death upon treatment with daunorubicin but sensitive to cytarabine. The cells harboring PTPN11G503A autonomously differentiated into macrophages (1.8%) in the medium containing IL3. Further studies showed that the cells had an elevated (∼2.9-fold) Csf1 transcription level and secreted more (∼4.5-fold) M-CSF to the medium which can stimulate monocyte/macrophage differentiation of BM cells. Mice transplanted with the cells harboring PTPN11G503A had a higher concentration of M-CSF in plasma. When mixed with the MLL/AF10(OM-LZ) leukemia cells harboring PTPN11wt , the cells harboring PTPN11G503A had an increased competitive engraftment and clonal expansion in the BM and spleen of recipient mice, although no competitive growth advantage was observed in the in vitro co-culturing assays. The mice transplanted with the MLL/AF10(OM-LZ) cells harboring PTPN11wt developed myelomonocytic leukemia, while those transplanted with the cells harboring PTPN11G503A -induced monocytic leukemia in a shorter latency. Our results demonstrated that addition of PTPN11G503A to MLL/AF10 affected cell proliferation, chemo-resistance, differentiation, in vivo BM recruitment/clonal expansion and accelerated disease progression.

PecS regulates the urate-responsive expression of type 1 fimbriae in Klebsiella pneumoniae CG43.

In the Klebsiella pneumoniae CG43 genome, the divergently transcribed genes coding for PecS, the MarR-type transcription factor, and PecM, the drug metabolite transporter, are located between the type 1 and type 3 fimbrial gene clusters. The intergenic sequence pecO between pecS and pecM contains three putative PecS binding sites and a CpxR box. Electrophoretic mobility shift assay revealed that the recombinant PecS and CpxR could specifically bind to the pecO sequence, and the specific interaction of PecS and pecO could be attenuated by urate. The expression of pecS and pecM was negatively regulated by CpxAR and PecS, and was inducible by exogenous urate in the absence of cpxAR. Compared with CG43S3ΔcpxAR, the derived mutants CG43S3ΔcpxARΔpecS and CG43S3ΔcpxARΔpecSΔpecM exerted similar levels of sensitivity to H2O2 or paraquat, but higher levels of mannose-sensitive yeast agglutination activity and FimA production. The promoter activity and transcript levels of fimA in CG43S3ΔcpxAR were also increased by deleting pecS. However, no binding activity between PecS and the fimA promoter could be observed. Nevertheless, PecS deletion could reduce the expression of the global regulator HNS and release the negative effect of HNS on FimA expression. In CG43S3ΔcpxAR, the expression of FimA as well as PecS was inducible by urate, whilst urate-induced FimA expression was inhibited by the deletion of pecS. Taken together, we propose that K. pneumoniae PecS indirectly and negatively regulates the expression of type 1 fimbriae, and the regulation is urate-inducible in the absence of CpxAR.

Biological Activities of RUNX1 Mutants Predict Secondary Acute Leukemia Transformation from Chronic Myelomonocytic Leukemia and Myelodysplastic Syndromes.

PURPOSE: Transcription factor RUNX1 is essential for normal hematopoiesis. High mutation frequencies of RUNX1 gene in chronic myelomonocytic leukemia (CMML) and myelodysplastic syndromes (MDS) have been described, whereas the biologic significances of the mutations were not investigated. Here, we aimed to correlate the biologic activities of the RUNX1 mutants with the clinical outcomes of patients. EXPERIMENTAL DESIGN: We examined the mutational status of RUNX1 in 143 MDS and 84 CMML patients. Then, we studied the DNA and CBFß binding abilities of all the RUNX1 mutants identified by using electrophoretic mobility shift assay and co-immunoprecipitation assay, and also determined their activities on target C-FMS gene induction by Western blotting and luciferase reporter assay. Using luciferase reporter assay, the relative biologic activities of each RUNX1 mutant could be quantified and correlated with the patient outcomes by statistical analyses. RESULTS: We observed that most RUNX1 mutants had reduced abilities in DNA binding, CBFß heterodimerization, and C-FMS gene induction. The relative biologic activities of RUNX1 mutants were grouped into high- and low-activity mutations. Correlation of the activities of RUNX1 mutants with the clinical outcomes revealed that patients harboring lower activities of RUNX1 mutants had a higher risk and shorter time to secondary acute myeloid leukemia transformation in MDS and CMML. In multivariate analysis, low RUNX1 activity remained an independent predictor for secondary acute myeloid leukemia-free survival in MDS patients. CONCLUSIONS: The biologic activity rather than the mutational status of RUNX1 might be an indicator in predicting outcome of patients with MDS and CMML.

FimK regulation on the expression of type 1 fimbriae in Klebsiella pneumoniae CG43S3.

Klebsiella pneumoniae CG43, a heavy encapsulated liver abscess isolate, mainly expresses type 3 fimbriae. Type 1 fimbriae expression was only apparent in CG43S3ΔmrkA (the type 3 fimbriae-deficient strain). The expression of type 1 fimbriae in CG43S3ΔmrkA was reduced by deleting the fimK gene, but was unaffected by removing the 3' end of fimK encoding the C-terminal EIL domain (EILfimK). Quantitative RT-PCR and promoter activity analysis showed that the putative DNA-binding region at the N terminus, but not the C-terminal EIL domain, of FimK positively affects transcription of the type 1 fimbrial major subunit, fimA. An electrophoretic mobility shift assay demonstrated that the recombinant FimK could specifically bind to fimS, which is located upstream of fimA and contains a vegetative promoter for the fim operon, also reflecting possible transcriptional regulation. EILfimK was shown to encode a functional phosphodiesterase (PDE) via enhancing motility in Escherichia coli JM109 and in vitro using PDE activity assays. Moreover, EILfimK exhibited higher PDE activity than FimK, implying that the N-terminal DNA-binding domain may negatively affect the PDE activity of FimK. FimA expression was detected in CG43S3 expressing EILfimK or AILfimK, suggesting that FimA expression is not directly influenced by the c-di-GMP level. In summary, FimK influences type 1 fimbriation by binding to fimS at the N-terminal domain, and thereafter, the altered protein structure may activate C-terminal PDE activity to reduce the intracellular c-di-GMP level.

Involvement of Gpr125 in the myeloid sarcoma formation induced by cooperating MLL/AF10(OM-LZ) and oncogenic KRAS in a mouse bone marrow transplantation model.

Oncogenic N-/KRAS mutations were frequently associated with MLL/AF10 in acute myeloid leukemia with myeloid sarcoma (MS). To study the cooperating leukemogenesis by MLL/AF10 and KRAS mutation, we retrovirally transduced MLL/AF10(OM-LZ) and KRASG12C into mouse bone marrow cells and generated two immortalized cell lines. The cells carrying cooperating MLL/AF10(OM-LZ) and KRASG12C had immature myelomonocytic phenotypes. Compared to a previously established cell line carrying MLL/AF10(OM-LZ) alone, cooperation of MLL/AF10(OM-LZ) with KRASG12C blocked the cells at a more immature myelomonocytic stage with reduced expression of monocyte/macrophage markers. The mice transplanted with the cells carrying cooperating MLL/AF10(OM-LZ) and KRASG12C, liked those transplanted with the cells carrying MLL/AF10(OM-LZ) alone, induced myeloproliferative disease-like myeloid leukemia, but in a shorter latency and formed multiple MS at the adipose tissues of skin, peritoneum and intraperitoneal cavity. Cooperation of MLL/AF10(OM-LZ) with KRASG12C increased cell adhesion via upregulation of an adhesion G-protein-coupled receptor Gpr125. Knockdown of Gpr125 in the cells by short hairpin RNA reduced cell aggregation and diminished MS formation in the transplanted mice. Our results indicated that upregulation of Gpr125 by cooperating MLL/AF10(OM-LZ) and KRASG12C promoted cell adhesion and contributed to the MS formation.