KIT mutations, and not FLT3 internal tandem duplication, are strongly associated with a poor prognosis in pediatric acute myeloid leukemia with t(8;21): a study of the Japanese Childhood AML Cooperative Study Group

Prognostic Factors of Pediatric Acute Myeloid Leukemia Patients with t(8;21) (q22;q22): A Single-Center Retrospective Study

This retrospective study aimed to analyze the treatment effect and prognostic factors of pediatric acute myeloid leukemia (AML) patients with t(8;21). A total of 268 newly diagnosed pediatric AML (pAML) enrolled from 1 January 2005 to 31 December 2022 were retrospectively reviewed, and 50 (18.7%) patients harbored t(8;21) translocation. CR rate, OS, EFS, and RFS were assessed by multivariate Logistic and Cox regression models in these patients. Of the 50 patients, 2 patients abandoned treatment during the first induction course. Of the remaining 48 patients who received double-induction therapy and were included in the final analyses, CR1 and CR2 were 75.0% (36/48) and 95.8% (46/48), respectively. The overall three-year OS, EFS, and RFS were 68.4% (95% CI, 55.0-85.1), 64.2% (95% CI, 50.7-81.4), and 65.5% (95% CI, 51.9-82.8), respectively. The presence of loss of sex chromosome (LOS) at diagnosis (n = 21) was associated with a better 3-year OS [87.5% (95% CI, 72.7-100) vs. 52.7% (95% CI, 35.1-79.3), p = 0.0089], 3-year EFS [81.6% (95% CI, 64.7-100) vs. 49.7% (95% CI, 32.4-76.4), p = 0.023], and 3-year RFS [81.6% (95% CI, 64.7-100) vs. 51.7% (95% CI, 33.9-78.9), p = 0.036] than those without LOS (n = 27), and it was also an independent good prognostic factor of OS (HR, 0.08 [95% CI, 0.01-0.48], p = 0.005), EFS (HR, 0.22 [95% CI, 0.05-0.85], p = 0.029), and RFS (HR, 0.21 [95% CI, 0.05-0.90], p = 0.035). However, extramedullary leukemia (EML) featured the independent risk factors of inferior OS (HR, 10.99 [95% CI, 2.08-58.12], p = 0.005), EFS (HR, 4.75 [95% CI, 1.10-20.61], p = 0.037), and RFS (HR, 6.55 [95% CI, 1.40-30.63], p = 0.017) in pediatric individuals with t(8;21) AML. Further analysis of combining LOS with EML indicated that the EML+LOS- subgroup had significantly inferior OS (92.9%, [95% CI, 80.3-100]), EFS (86.2%, [95% CI, 70.0-100]), and RFS (86.2%, [95% CI, 80.3-100]) compared to the other three subgroups (all p < 0.001). LOS and EML are independent prognostic factors of OS, EFS, and RFS with t(8;21) pAML patients. LOS combined with EML may help improve risk stratification.

KIT exon 17 mutations are predictive of inferior outcome in pediatric acute myeloid leukemia with RUNX1::RUNX1T1

BACKGROUND

Pediatric core binding factor acute myeloid leukemia (CBF-AML), although considered a favorable risk subtype, exhibits variable outcomes primarily driven by additional genetic abnormalities, such as KIT mutations.

PROCEDURE

In this study, we examined the prognostic impact of KIT mutations in 130 pediatric patients with CBF-AML, treated uniformly at a single center over 4 years (2017-2021). KIT mutations were detected via next-generation sequencing using a myeloid panel comprising 52 genes for most patients.

RESULTS

Our findings revealed that KIT mutations were present in 31% of CBF-AML cases. Exon 17 KIT mutation was most commonly (72%) seen with notable occurrences at the D816 and N822 residue in 48% and 39% of cases, respectively. The 3-year cumulative incidence of relapse (CIR) and overall survival (OS) for patients with exon 17 KIT mutation were 36% and 40%, respectively, and was significantly worse in comparison to other site KIT mutations (3-year CIR: 11%; OS: 64%) and without KIT mutation (3-year CIR: 13%; OS:71%). Notably, the prognostic impact of KIT mutations was prominent in patients with RUNX1::RUNX1T1, but not in those with CBFB::MYH11 fusion. Additionally, a high KIT variant-allele frequency (VAF) (>33%) predicted for a higher disease relapse; 3-year CIR of 40% for VAF greater than 33% versus 7% for VAF less than 33%. When adjusted for site of KIT mutation and end-of-induction measurable residual disease, VAF greater than 33% correlated with poor OS (hazard ratio [HR]: 4.4 [95% CI: 1.2-17.2], p = .034).

CONCLUSION

Exon 17 KIT mutations serve as an important predictor of relapse in RUNX1::RUNX1T1 pediatric AML. In addition, a high KIT VAF may predict poor outcomes in these patients. These results emphasize the need to incorporate KIT mutational analysis into risk stratification for pediatric CBF-AML.

Comprehensive molecular understanding of pediatric acute myeloid leukemia

Pediatric acute myeloid leukemia (AML) is a heterogeneous disease with various genetic abnormalities. Recent advances in genetic analysis have enabled the identification of causative genes in > 90% of pediatric AML cases. Fusion genes such as RUNX1::RUNX1T1, CBFB::MYH11, and KMT2A::MLLT3 are frequently detected in > 70% of pediatric AML cases, whereas FLT3-internal tandem duplication, CEBPA-bZip, and NPM1 mutations are detected in approximately 5-15% of cases, respectively. Conversely, mutations in DNMT3A, TET2, and IDH, which are common in adults, are extremely rare in pediatric AML. The genetic characteristics of pediatric AML are slightly different from those of adult AML. For accurate risk stratification and treatment intensity, genome analysis should be performed in a simple, fast, and inexpensive manner and the results should be returned to patients in real time. As with acute lymphoblastic leukemia, the presence or absence of minimal residual disease is an important factor in determining the success of treatment against AML, and it is important to predict prognosis and formulate treatment strategies considering the genetic abnormalities. For the development and clinical application of new molecularly targeted therapies based on identified genetic abnormalities, it is necessary to explore when and in which combinations drugs will be most effective.

Myeloid neoplasms and clonal hematopoiesis from the RUNX1 perspective

RUNX1 is a critical transcription factor for the emergence of definitive hematopoiesis and the precise regulation of adult hematopoiesis. Dysregulation of its regulatory network causes aberrant hematopoiesis. Recurrent genetic alterations in RUNX1, including chromosomal translocations and mutations, have been identified in both inherited and sporadic diseases. Recent genomic studies have revealed a vast mutational landscape surrounding genetic alterations in RUNX1. Accumulating pieces of evidence also indicate the leukemogenic role of wild-type RUNX1 in certain situations. Based on these efforts, part of the molecular mechanisms of disease development as a consequence of dysregulated RUNX1-regulatory networks have become increasingly evident. This review highlights the recent advances in the field of RUNX1 research and discusses the critical roles of RUNX1 in hematopoiesis and the pathobiological function of its alterations in the context of disease, particularly myeloid neoplasms, and clonal hematopoiesis.

Genome-wide DNA Methylation Analysis in Pediatric Acute Myeloid Leukemia

FLT3-ITD and high PRDM16 expression induced methylation changes at STAT5 and AP-1 binding sites in pediatric AML.

Hypomethylated regions in PRDM16-highly expressed AMLs were correlated with enhanced chromatin accessibilities at multiple genomic regions.

We investigated genome-wide DNA methylation patterns in 64 pediatric patients with acute myeloid leukemia (AML). Based on unsupervised clustering with the 567 most variably methylated cytosine guanine dinucleotide (CpG) sites, patients were categorized into 4 clusters associated with genetic alterations. Clusters 1 and 3 were characterized by the presence of known favorable prognostic factors, such as RUNX1-RUNX1T1 fusion and KMT2A rearrangement with low MECOM expression, and biallelic CEBPA mutations (all 8 patients), respectively. Clusters 2 and 4 comprised patients exhibiting molecular features associated with adverse outcomes, namely internal tandem duplication of FLT3 (FLT3-ITD), partial tandem duplication of KMT2A, and high PRDM16 expression. Depending on the methylation values of the 1243 CpG sites that were significantly different between FLT3-ITD⁺ and FLT3-ITD⁻ AML, patients were categorized into 3 clusters: A, B, and C. The STAT5-binding motif was most frequently found close to the 1243 CpG sites. All 8 patients with FLT3-ITD in cluster A harbored high PRDM16 expression and experienced adverse events, whereas only 1 of 7 patients with FLT3-ITD in the other clusters experienced adverse events. PRDM16 expression levels were also related to DNA methylation patterns, which were drastically changed at the cutoff value of PRDM16/ABL1 = 0.10. The assay for transposase-accessible chromatin sequencing of AMLs supported enhanced chromatin accessibility around genomic regions, such as HOXB cluster genes, SCHIP1, and PRDM16, which were associated with DNA methylation changes in AMLs with FLT3-ITD and high PRDM16 expression. Our results suggest that DNA methylation levels at specific CpG sites are useful to support genetic alterations and gene expression patterns of patients with pediatric AML.

Treatment Failure in Acute Myeloid Leukemia: Focus on the Role of Extracellular Vesicles

Acute myeloblastic leukemia (AML) is one of the most common types of blood malignancies that results in an AML-associated high mortality rate each year. Several causes have been reported as prognostic factors for AML in children and adults, the most important of which are cytogenetic abnormalities and environmental risk factors. Following the discovery of numerous drugs for AML treatment, leukemic cells sought a way to escape from the cytotoxic effects of chemotherapy drugs, leading to treatment failure. Nowadays, comprehensive studies have looked at the role of extracellular vesicles (EVs) secreted by AML blasts and how the microenvironment of the tumor changes in favor of cancer progression and survival to discover the mechanisms of treatment failure to choose the well-advised treatment. Reports show that malignant cells secrete EVs that transmit messages to adjacent cells and the tumor's microenvironment. By secreting EVs, containing immune-inhibiting cytokines, AML cells inactivate the immune system against malignant cells, thus ensuring their survival. Also, increased secretion of EVs in various malignancies indicates an unfavorable prognostic factor and the possibility of drug resistance. In this study, we briefly reviewed the challenges of treating AML with a glance at the EVs' role in this process. It is hoped that with a deeper understanding of EVs, new therapies will be developed to eliminate the relapse of leukemic cells.

Population Pharmacokinetics and Safety of Dasatinib in Chinese Children with Core-Binding Factor Acute Myeloid Leukemia

BACKGROUND

Dasatinib, an orally administered Src-family kinase inhibitor, is combined with the standard chemotherapeutic regimen to enhance antineoplastic activity against core-binding factor acute myeloid leukemia (CBF-AML) in adults; however, limited data are available for use in children. In the present study, we studied the pharmacokinetics and safety of dasatinib in children.

METHODS

Dasatinib (60 or 80 mg/m² once daily) was administered to 20 children with CBF-AML. Blood samples were collected and drug concentrations were quantified by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Population pharmacokinetic analysis and Monte-Carlo simulations were performed using NONMEM software, and safety analyses were assessed according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) version 4.0 (NCT03844360).

RESULTS

Twenty pediatric patients (3.3-14.4 years of age) were included, and a total of 40 dasatinib concentrations were available for population pharmacokinetic analysis. The mean (standard deviation) of the estimated area under the concentration-time curve extrapolated to steady state (AUC_ss) of dasatinib 60 and 80 mg/m² was 366.1 (146.6) ng·h/mL and 425.3 (150.7) ng·h/mL, respectively. The majority of adverse events were grade 1/2 in severity, including thrombocytopenia, rash, and pain in the extremities. The estimated cumulative incidence of complete remission and complete molecular response were 95.0% and 75.5%, respectively.

CONCLUSIONS

The population pharmacokinetics of orally administered dasatinib were evaluated in pediatric CBF-AML patients. The AUC_ss of dasatinib (80 mg/m²) in CBF-AML pediatric patients was similar to those of dasatinib (100 mg) in adult patients. Dasatinib is well-tolerated in pediatric patients with CBF-AML.

Treatment of acute myeloid leukemia in children: A practical perspective

Pediatric acute myeloid leukemia (AML) is a heterogeneous disease that requires a multifaceted treatment approach. Although outcomes for low-risk AML have improved significantly over recent decades, high-risk AML continues to be associated with an adverse prognosis. Recent advances in molecular diagnostics, risk stratification, and supportive care have contributed to improvements in outcomes in pediatric AML. Targeted approaches, for example, the use of tyrosine kinase inhibitors to treat FLT3-ITD AML, offer promise and are currently undergoing clinical investigation in pediatric patients. New approaches to hematopoietic stem cell transplantation, including the use of haploidentical donors, are significantly expanding donor options for patients with high-risk AML. This review provides an overview of recent advances in the treatment of pediatric AML that are likely to have clinical impact and reshape the standard of care.

Molecular Genetics of Pediatric Acute Myeloid Leukemia

The genetic basis for pediatric acute myeloid leukemia (AML) is highly heterogeneous, often involving the cooperative action of characteristic chromosomal rearrangements and somatic mutations in progrowth and antidifferentiation pathways that drive oncogenesis. Although some driver mutations are shared with adult AML, many genetic lesions are unique to pediatric patients, and their appropriate identification is essential for patient care. The increased understanding of these malignancies through broad genomic studies has begun to risk-stratify patients based on their combinations of genomic alterations, a trend that will enable precision medicine in this population.

Droplet digital polymerase chain reaction assay for the detection of the minor clone of KIT D816V in paediatric acute myeloid leukaemia especially showing RUNX1-RUNX1T1 transcripts

KIT D816V mutation within exon 17 has been particularly reported as one of the poor prognostic factors in pediatric acute myeloid leukemia (AML) with RUNX1-RUNX1T1. The exact frequency and the prognostic impact of KIT D816V minor clones at diagnosis were not examined. In this study, the minor clones were examined and the prognostic significance of KIT D816V mutation in pediatric patients was investigated. Consequently, 24 KIT D816V mutations (7.2%) in 335 pediatric patients were identified, and 12 of 24 were only detected via the digital droplet polymerase chain reaction method. All 12 patients were confined in core binding factor (CBF)-AML patients. The 5 year event-free survival of the patients with KIT D816V mutation was significantly inferior to those without KIT D816V mutation (44.1% [95% confidence interval (CI), 16.0%-69.4%] vs. 74.7% [95% CI, 63.0%-83.2%] P-value = 0.02, respectively). The 5 year overall survival was not different between the two groups (92.9% [95% CI, 59.0%-NA vs. 89.7% [95% CI, 69.6%-96.8%] P-value = 0.607, respectively). In this study, KIT D816V minor clones in patients with CBF-AML were confirmed and KIT D816V was considered as a risk factor for relapse in patients with RUNX1-RUNX1T1-positive AML.

The outcomes of relapsed acute myeloid leukemia in children: Results from the Japanese Pediatric Leukemia/Lymphoma Study Group AML-05R study

BACKGROUND

The prognosis of children with acute myeloid leukemia (AML) has improved with the efficacy of hematopoietic cell transplantation (HCT) as a second-line therapy and improvements in supportive care following anthracycline- and cytarabine-based chemotherapy; however, the outcomes of children with relapsed AML still remain unsatisfactory.

PROCEDURE

In order to identify prognostic factors and improve their prognosis, we analyzed 111 patients who relapsed after treatment with the Japanese Pediatric Leukemia/Lymphoma Study Group (JPLSG) AML-05 protocol and who were registered in the retrospective JPLSG AML-05R study.

RESULTS

The 5-year overall survival rate was 36.1%. The major determinant of survival was duration from the diagnosis to relapse. The mean duration in the nonsurviving group (10.1 ± 4.1 months) was shorter than that in the surviving group (16.3 ± 8.3 months) (P < .01). Moreover, achieving a second complete remission (CR2) prior to HCT was associated with a good prognosis (P < .01). Etoposide, cytarabine, and mitoxantrone (ECM)- or fludarabine, cytarabine, and granulocyte colony-stimulating factor (FLAG)-based regimens were therefore recommended for reinduction therapy (P < .01). A genetic analysis also revealed the prognostic significance of FMS-like tyrosine kinase 3 (FLT3)-internal tandem duplication as a poor prognostic marker (P = .04) and core binding factor-AML, t(8;21), and inv(16) as good prognostic markers (P < .01).

CONCLUSIONS

Achieving a CR2 prior to HCT is important in order to improve the prognosis of relapsed pediatric AML. Recent molecular targeted therapies, such as FLT3 inhibitors, may contribute to overcome their prognoses. Larger prospective investigations are necessary to establish individualized treatment strategies for patients with relapsed childhood AML.

Influence of KIT mutations on prognosis of pediatric patients with core-binding factor acute myeloid leukemia: a systematic review and meta-analysis

BACKGROUND

KIT mutations are common in children with core-binding factor (CBF) acute myeloid leukemia (AML). The relationship between KIT mutations and their prognostic value has generated intense attention during the past years. Although studies have evaluated the role of KIT mutations, their prognostic implications remain unclear. To clarify this issue, we conducted this meta-analysis.

METHODS

We electronically searched the PubMed, Embase and Cochrane Library databases. Twelve studies met our selection criteria. These studies involved 1,123 children with CBF-AML including 256 children with KIT mutations. We investigated the effects of KIT mutations on the complete remission (CR), relapse, event-free survival (EFS), disease-free survival (DFS), and overall survival (OS) rates of pediatric CBF-AML patients.

RESULTS

KIT mutations were not associated with CR [relative risk: 1.01, 95% confidence interval (CI): 0.94-1.09, P=0.761], but were associated with higher relapse risk [hazard ratio (HR): 1.69, 95% CI: 1.32-2.16, P=0.000], lower OS (HR: 3.05, 95% CI: 1.23-7.60, P=0.016), lower DFS (HR: 1.65, 95% CI: 1.07-2.54, P=0.024), and lower EFS (HR: 3.08, 95% CI: 1.02-9.32, P=0.046).

CONCLUSIONS

Our analysis suggested that KIT mutations had an adverse prognostic effect in pediatric CBF-AML patients. The initial diagnostic workup for these patients should include tests for the detection of KIT mutations, and the treatment may need to be adjusted when these mutations are found to be present.

The genomics of acute myeloid leukemia in children

Acute myeloid leukemia (AML) is a clinically, morphologically, and genetically heterogeneous disorder. Like many malignancies, the genomic landscape of pediatric AML has been mapped recently through sequencing of large cohorts of patients. Much has been learned about the biology of AML through studies of specific recurrent genetic lesions. Further, genetic lesions have been linked to specific clinical features, response to therapy, and outcome, leading to improvements in risk stratification. Lastly, targeted therapeutic approaches have been developed for the treatment of specific genetic lesions, some of which are already having a positive impact on outcomes. While the advances made based on the discoveries of sequencing studies are significant, much work is left. The biologic, clinical, and prognostic impact of a number of genetic lesions, including several seemingly unique to pediatric patients, remains undefined. While targeted approaches are being explored, for most, the efficacy and tolerability when incorporated into standard therapy is yet to be determined. Furthermore, the challenge of how to study small subpopulations with rare genetic lesions in an already rare disease will have to be considered. In all, while questions and challenges remain, precisely defining the genomic landscape of AML, holds great promise for ultimately leading to improved outcomes for affected patients.

Prognostic Role of Postinduction Minimal Residual Disease and Myeloid Sarcoma Type Extramedullary Involvement in Pediatric RUNX1-RUNX1T1 (+) Acute Myeloid Leukemia

BACKGROUND

Acute myeloid leukemia with the t(8;21)(q22;q22) rearrangement (RUNX1-RUNX1T1 (+) AML) is known to have a favorable prognosis. Our study aimed to determine the most important prognostic variables among an aggregate of clinical, genetic, and treatment response-based factors in pediatric RUNX1-RUNX1T1 (+) AML.

MATERIALS AND METHODS

We analyzed the characteristics and outcome of 40 patients who were diagnosed with and treated for RUNX1-RUNX1T1 (+) AML from April 2008 to December 2016 at our institution.

RESULTS

A<-2.2 log fusion transcript decrement after remission induction, myeloid sarcoma type extramedullary involvement (EMI) at diagnosis, higher initial white blood cell count, and presence of KIT mutation predicted lower event-free survival. Both lower fusion transcript decrement after remission induction and the presence of EMI at diagnosis proved to be significant adverse factors in the multivariate study. The 5-year event-free survival was 70.0±7.2% (28/40); 8 of the 12 relapsed patients survive disease-free, resulting in 5-year overall survival of 89.5±5.0% (36/40).

CONCLUSIONS

Kinetics of response to remission induction chemotherapy, measured in terms of the PCR value for the fusion transcript, and the presence of myeloid sarcoma type EMI at diagnosis may predict the risk of relapse in pediatric RUNX1-RUNX1T1 (+) AML.

[The prognostic value of cloned genetic mutations detected by second-generation sequencing in RUNX1-RUNX1T1 positive acute myeloid leukemia patients receiving intensive consolidation therapy]

Objective: To investigate the prognostic value of clonal gene mutations detected by second-generation sequencing in patients with positive RUNX1-RUNX1T1 acute myeloid leukemia (AML) who received high-dose chemotherapy or autologous transplantation (intensive consolidation therapy) in the first complete remission (CR(1)) state. Methods: 79 AML patients with positive RUNX1-RUNX1T1 who received intensive consolidation therapy in CR(1) state from July 2011 to August 2017 were analyzed retrospectively. Kaplan-Meier curve and Cox regression model were used to figure out the effect of leukocyte counts at onset and gene mutations for prognosis. Results: C-KIT, FLT3, CEBPA and DNMT3A gene mutations were found in 25 (31.6%) , 6 (7.6%) , 7 (8.9%) and 1 (1.3%) patient among the population. Mutations in C-KIT exon17 and C-KIT exon8 were detected in 19 (24.1%) and 5 (6.3%) cases, respectively, and mutations of FLT3-ITD were confirmed in 5 (6.3%) cases. The higher leukocyte counts presented at onset of leukemia, the shorter overall survival (OS) was seen in these patients (P=0.03) . Patients with C-KIT exon17 mutation had significantly shorter OS (P=0.01) and disease free survival (DFS) (P=0.006) compared with those without gene mutations, and patients with FLT3-ITD gene mutation got the inferior OS (P=0.048) and DFS (P=0.071) . Conclusion: In AML patients with positive RUNX1-RUNX1T1 receiving intensive consolidation therapy, the white blood cell counts at onset of leukemia, C-KIT mutations in exon 17, and FLT3-ITD gene mutations suggest poor prognosis, which would contribute to elaborate risk stratification, personalized treatment and predict prognosis for these patients.

Patients aged less than 3 years with acute myeloid leukaemia characterize a molecularly and clinically distinct subgroup

Although infants (age <1 year) with acute myeloid leukaemia (AML) have unique characteristics and are vulnerable to chemotherapy, children aged 1-2 years with AML may have characteristics similar to that of infants. Thus, we analysed 723 paediatric AML patients treated on the Japanese AML99 and AML-05 trials to identify characteristics of younger children. We identified patients aged <3 years (the younger group) as a distinct subgroup. KMT2A-rearrangement (KMT2A-R), CBFA2T3-GLIS2, CBFB-MYH11 and NUP98-KDM5A were frequently found in the younger group. Prognostic analyses revealed poor 5-year overall survival (OS), event-free survival (EFS) and cumulative incidence of relapse (CIR) in patients with CBFA2T3-GLIS2 (42%, 17% and 83%, respectively) and those with NUP98-KDM5A (33%, 17% and 83%, respectively). Additionally, we identified KMT2A-R and CBFB-MYH11 as age-specific prognostic markers. Regarding KMT2A-R, the younger group had significantly better OS, EFS and CIR than the older group (aged 3 to <18 years) (P = 0·023, 0·011 and <0·001, respectively). Conversely, concerning CBFB-MYH11, the younger group had significantly poor EFS and CIR than the older group (each P < 0·001), suggesting that certain molecular markers are linked to different prognoses according to age. Therefore, we characterized patients <3 years as a distinct subgroup of paediatric AML.

Hematological malignancies and molecular targeting therapy

Recent genetic analysis using next-generation sequencing (NGS) vastly improved the understanding of molecular mechanism of hematological malignancies. Many molecular targeting drugs have since been used in the clinic, which is timely as clinical outcomes using conventional chemotherapy and hematopoietic stem cell transplantation (HSCT) reached a plateau. The first memorable success in this field was imatinib, a first-generation tyrosine kinase inhibitor (TKI), which has been applied in chronic myeloid leukemia (CML) since 2001. Imatinib drastically changed CML treatment and many CML patients no longer require HSCT. Recently, the second generation TKIs, dasatinib, nilotinib, and ponatinib, have also been available for CML patients. Acute lymphoblastic leukemia (ALL) is sub-categorized based on cytogenetic or molecular genetic abnormalities. Chemotherapy and HSCT combined with TKI improved the event-free survival rate from 20% to 80% in Philadelphia (Ph) chromosome-positive ALL. Reportedly, another Ph-like ALL subgroup with poor prognosis can also be treated by TKIs; additionally, cell therapies that include bispecific T-cell engagers or chimeric antigen receptor (CAR)-T therapy are emerging. Acute myeloid leukemia (AML) is a heterogenous disease and FMS-like related tyrosine kinase-3 (FLT3)-internal tandem duplication, is the most robust marker for poor prognosis. Several first-generation TKIs have been studied for clinical use. Notably, chemotherapy plus midostaurin improved survival compared with chemotherapy alone. Therefore, midostaurin was approved to treat adult AML patients with FLT3-ITD in 2017. Gemtuzumab ozogamicin, a selective anti-CD33 antibody-calicheamicin conjugate, is approved for clinical practice. Many molecular targeting agents are now being used for hematological malignancies.

Negative CD19 expression is associated with inferior relapse-free survival in children with RUNX1-RUNX1T1-positive acute myeloid leukaemia: results from the Japanese Paediatric Leukaemia/Lymphoma Study Group AML-05 study

We performed a retrospective analysis of leukaemic surface antigen expression and genomic data from a total of 100 RUNX1-RUNX1T1-positive paediatric acute myeloid leukaemia (AML) patients enrolled in the Japanese Paediatric Leukaemia/Lymphoma Study Group (JPLSG) AML-05 protocol to determine risk factors for relapse. In univariate analysis, the KIT exon 17 mutation (n = 21) and CD19 negativity (n = 59) were significant risk factors for relapse (P = 0·01). In multivariate analysis, CD19 negativity was the sole significant risk factor for relapse (hazard ratio, 3·09; 95% confidence interval, 1·26-7·59; P < 0·01), suggesting that biological differences between CD19-positive and CD19-negative RUNX1-RUNX1T1 AML patients should be investigated.

Functional Properties of KIT Mutations Are Associated with Differential Clinical Outcomes and Response to Targeted Therapeutics in CBF Acute Myeloid Leukemia

PURPOSE

KIT mutations (KIT ⁺) are common in core binding factor (CBF) AML and have been associated with varying prognostic significance. We sought to define the functional and clinical significance of distinct KIT mutations in CBF pediatric AML.

EXPERIMENTAL DESIGN

Following transfection of exon 17 (E17) and exon 8 (E8) mutations into HEK293 and Ba/F3 cells, KIT phosphorylation, cytokine-independent growth, and response to tyrosine kinase inhibitors (TKI) were evaluated. Clinical outcomes of patients treated on COG AAML0531 (NCT01407757), a phase III study of gemtuzumab ozogamicin (GO), were analyzed according to mutation status [KIT ⁺ vs. wild-type KIT (KIT ^-)] and mutation location (E8 vs. E17).

RESULTS

KIT mutations were detected in 63 of 205 patients (31%); 22 (35%) involved only E8, 32 (51%) only E17, 6 (10%) both exons, and 3 (5%) alternative exons. Functional studies demonstrated that E17, but not E8, mutations result in aberrant KIT phosphorylation and growth. TKI exposure significantly affected growth of E17, but not E8, transfected cells. Patients with KIT ⁺ CBF AML had overall survival similar to those with KIT ^- (78% vs. 81%, P = 0.905) but higher relapse rates (RR = 43% vs. 21%; P = 0.005). E17 KIT ⁺ outcomes were inferior to KIT ^- patients [disease-free survival (DFS), 51% vs. 73%, P = 0.027; RR = 21% vs. 46%, P = 0.007)], although gemtuzumab ozogamicin abrogated this negative prognostic impact. E8 mutations lacked significant prognostic effect, and GO failed to significantly improve outcome.

CONCLUSIONS

E17 mutations affect prognosis in CBF AML, as well as response to GO and TKIs; thus, clinical trials using both agents should be considered for KIT ⁺ patients.

[Study of clinical outcome and prognosis in pediatric core binding factor-acute myeloid leukemia]

Objective: To analyze the clinical outcome and the prognostic factor in pediatric patients with core binding factor-acute myeloid leukemia (CBF-AML). Methods: A total of 121 newly diagnosed pediatric CBF-AML patients enrolled from Aug. 2005 to Sep. 2017 were retrospectively reviewed. Cumulative incidence of relapse (CIR), event-free survival (EFS) and overall survival (OS) rates were estimated by Kaplan-Meier method and prognostic factors were evaluated by Cox regression with SPSS. Results: Of the 121 patients, 120 patients were assessed for bone marrow remission after induction chemotherapy. 100 cases (83.3%) achieved complete remission (CR) after the first course of chemotherapy. 119 cases (99.2%) achieved CR after the second course of chemotherapy. Of the 121 patients, 13 patients (10.7%) had recurrence with the median interval of recurrence as 13.8 months (3.7 to 58.8 months). 17 patients (14.0%) died. The CIR, EFS and OS at 3 years were 12.7%, 77.5% and 82.8%, respectively. The factors including age at diagnosis, sex, initial WBC count, presence of extramedullary leukemia, C-KIT expression, additional chromosomal abnormalities, and CR after the first course of chemotherapy were analyzed by multivariate regression analysis of Cox. Multivariate analysis identified that additional chromosomal abnormalities was the only independent risk factor affecting OS (HR=4.289, 95%CI 1.070-17.183, P=0.040). Conclusions: Pediatric CBF-AML was a unique setting of prognostic subtypes. Chemotherapy produced good responses. Additional chromosomal abnormalities was the only independent risk factor for OS in pediatric CBF-AML.

Clinical and biological features of paediatric acute myeloid leukaemia (AML) with primary induction failure in the Japanese Paediatric Leukaemia/Lymphoma Study Group AML-05 study

The prognosis of paediatric acute myeloid leukaemia (AML) with primary induction failure (PIF) is extremely poor, and effective treatment strategies have not been established. We investigated the clinical and biological features of paediatric AML patients with PIF registered to the Japanese Paediatric Leukaemia/Lymphoma Study Group AML-05 study. The 3-year overall survival rate of the 41 PIF patients was 19.0%. High leucocyte count, M7 morphology, and unfavourable genetic aberrations, such as FLT3-internal tandem duplication, NUP98-NSD1 and high MECOM or PRDM16 expression, were risk factors for PIF. More effective treatment strategies based on leukaemia biology need to be urgently explored.

Acute Myeloid Leukemia with t(8;21)(q22;q22) and Trisomy 4: A Rare Occurrence in a Female Child

Acute myeloid leukemia (AML) with balanced translocation t (8;21) is one of the most frequent chromosomal abnormalities and carries a favorable clinical outcome. However, according to a literature review, additional chromosomal aberrations can affect the overall disease prognosis. Trisomy 4 is a rare numerical abnormality in AML patients with t (8;21), which can be associated with c-KIT gene involvement. In adults, c-KIT mutation carries an unfavorable clinical outcome; however, its incidence and clinical importance in the pediatric population are still under scrutiny. Here, we report a case of AML with t(8;21) and trisomy 4 in an eight-year-old female child and the clinical course of the disease.

Core-binding factor acute myeloid leukemia with t(8;21): Risk factors and a novel scoring system (I-CBFit)

BACKGROUND

Although the prognosis of core-binding factor (CBF) acute myeloid leukemia (AML) is better than other subtypes of AML, 30% of patients still relapse and may require allogeneic hematopoietic cell transplantation (alloHCT). However, there is no validated widely accepted scoring system to predict patient subsets with higher risk of relapse.

METHODS

Eleven centers in the US and Europe evaluated 247 patients with t(8;21)(q22;q22).

RESULTS

Complete remission (CR) rate was high (92.7%), yet relapse occurred in 27.1% of patients. A total of 24.7% of patients received alloHCT. The median disease-free (DFS) and overall (OS) survival were 20.8 and 31.2 months, respectively. Age, KIT D816V mutated (11.3%) or nontested (36.4%) compared with KIT D816V wild type (52.5%), high white blood cell counts (WBC), and pseudodiploidy compared with hyper- or hypodiploidy were included in a scoring system (named I-CBFit). DFS rate at 2 years was 76% for patients with a low-risk I-CBFit score compared with 36% for those with a high-risk I-CBFit score (P < 0.0001). Low- vs high-risk OS at 2 years was 89% vs 51% (P < 0.0001).

CONCLUSIONS

I-CBFit composed of readily available risk factors can be useful to tailor the therapy of patients, especially for whom alloHCT is not need in CR1 (ie, patients with a low-risk I-CBFit score).

Detection of KIT mutations in core binding factor acute myeloid leukemia

We have investigated the frequency and the effect of KIT mutations on the outcome of patients with CBF-AML. 69 patients (34 pediatrics and 35 adults) with CBF-AML were enrolled in the study. The frequency of KIT mutations was higher in adults compared to pediatrics (22.9% and 14.7%, p = 0.38) respectively. Leukocytosis ≥ 20 × 10⁹ /L was significantly associated with pediatrics compared to adults. t(8;21)(q22;22) was significantly associated with thrombocytopenia in adults. We conclude that no significant difference is found between KIT mutated and unmutated CBF-AML in adults and pediatrics. Children with CBF-AML present with leukocytosis. t(8;21) is associated with thrombocytopenia.

Microarray profiling and co-expression network analysis of the lncRNAs and mRNAs associated with acute leukemia in adults

Acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML) are common types of acute leukemia in adults and cause low survival rate and poor outcome after 5 years despite high rates of complete remission (CR) with modern chemotherapeutic regimens. To understand the distinct mechanisms in leukemogenesis for ALL and AML and to identify markers for diagnosis and treatment, lncRNA and mRNA expression profiles of AML and ALL patients and healthy controls were generated using microarray analysis. For comparison, the differentially expressed mRNA functions were annotated using gene ontology (GO) and pathway analysis. The microarray revealed that 1011 lncRNAs and 2656 mRNAs differed in AML patients and 6069 lncRNAs and 5338 mRNAs differed in ALL patients from those in healthy controls. The GO terms and KEGG pathway annotation data revealed that the olfactory receptor activity, G-protein coupled receptor activity and olfactory transduction-related genes were significantly associated with AML and ALL. Co-expression network analysis indicated that 108 lncRNAs and 85 mRNAs were included in the co-expression network. This study is the first to explore genome-wide lncRNA expression and co-expression with mRNA patterns in AML and ALL using microarray technology and could provide basic information for new biomarkers or treatment targets to alleviate AML and ALL.

Amyloid precursor protein has clinical and prognostic significance in AML1-ETO-positive acute myeloid leukemia

Amyloid precursor protein (APP) has been reported to be highly expressed in acute myeloid leukemia (AML)1-eight-twenty one (ETO)-positive AML. In the present study, the clinical and prognostic significance of APP expression was assessed in 65 patients with AML1-ETO-positive AML using reverse transcription-quantitative polymerase chain reaction. The patients were divided into an APP-high expression (APP-H) group (n=32) and an APP-low expression (APP-L) group (n=33) according to the cut-off value of APP relative expression, which was calculated by receiver operating characteristic curve analysis. It was observed that C-KIT mutations (14/32 vs. 3/33, P=0.009), white blood cell count (median, 23.2×10⁹ vs. 12.4×10⁹ cells/l; P=0.011) and bone marrow cellularity (median, 91.0 vs. 84.0%; P=0.039) and incidence of extramedullary leukemia (11/32 vs. 3/33, P=0.013) were all significantly increased in the APP-H group compared with the APP-L group. Furthermore, significantly lower rate of cumulative two-cycle complete remission (83.9 vs. 100%, P=0.016), major molecular remission following two courses of consolidation (34.5 vs. 71.4%, P=0.005), and poorer relapse-free survival (RFS) (33.5±5.2% vs. 76.3±6.9%, P<0.001) and overall survival (OS) (44.5±7.0% vs. 81.9±5.8%, P=0.002) were associated with APP overexpression. Multivariate analysis revealed that APP overexpression was a significant adverse factor affecting both RFS and OS. Taken together, these data suggest that APP may be correlated with C-KIT mutations and involved in leukemia cell proliferation, and its overexpression has an adverse effect on the prognosis in AML1-ETO-positive AML.

Initial Diagnostic Workup of Acute Leukemia: Guideline From the College of American Pathologists and the American Society of Hematology

CONTEXT

- A complete diagnosis of acute leukemia requires knowledge of clinical information combined with morphologic evaluation, immunophenotyping and karyotype analysis, and often, molecular genetic testing. Although many aspects of the workup for acute leukemia are well accepted, few guidelines have addressed the different aspects of the diagnostic evaluation of samples from patients suspected to have acute leukemia.

OBJECTIVE

- To develop a guideline for treating physicians and pathologists involved in the diagnostic and prognostic evaluation of new acute leukemia samples, including acute lymphoblastic leukemia, acute myeloid leukemia, and acute leukemias of ambiguous lineage.

DESIGN

- The College of American Pathologists and the American Society of Hematology convened a panel of experts in hematology and hematopathology to develop recommendations. A systematic evidence review was conducted to address 6 key questions. Recommendations were derived from strength of evidence, feedback received during the public comment period, and expert panel consensus.

RESULTS

- Twenty-seven guideline statements were established, which ranged from recommendations on what clinical and laboratory information should be available as part of the diagnostic and prognostic evaluation of acute leukemia samples to what types of testing should be performed routinely, with recommendations on where such testing should be performed and how the results should be reported.

CONCLUSIONS

- The guideline provides a framework for the multiple steps, including laboratory testing, in the evaluation of acute leukemia samples. Some aspects of the guideline, especially molecular genetic testing in acute leukemia, are rapidly changing with new supportive literature, which will require on-going updates for the guideline to remain relevant.

Phenotype in combination with genotype improves outcome prediction in acute myeloid leukemia: a report from Children's Oncology Group protocol AAML0531

Diagnostic biomarkers can be used to determine relapse risk in acute myeloid leukemia, and certain genetic aberrancies have prognostic relevance. A diagnostic immunophenotypic expression profile, which quantifies the amounts of distinct gene products, not just their presence or absence, was established in order to improve outcome prediction for patients with acute myeloid leukemia. The immunophenotypic expression profile, which defines each patient’s leukemia as a location in 15-dimensional space, was generated for 769 patients enrolled in the Children’s Oncology Group AAML0531 protocol. Unsupervised hierarchical clustering grouped patients with similar immunophenotypic expression profiles into eleven patient cohorts, demonstrating high associations among phenotype, genotype, morphology, and outcome. Of 95 patients with inv(16), 79% segregated in Cluster A. Of 109 patients with t(8;21), 92% segregated in Clusters A and B. Of 152 patients with 11q23 alterations, 78% segregated in Clusters D, E, F, G, or H. For both inv(16) and 11q23 abnormalities, differential phenotypic expression identified patient groups with different survival characteristics (P<0.05). Clinical outcome analysis revealed that Cluster B (predominantly t(8;21)) was associated with favorable outcome (P<0.001) and Clusters E, G, H, and K were associated with adverse outcomes (P<0.05). Multivariable regression analysis revealed that Clusters E, G, H, and K were independently associated with worse survival (P range <0.001 to 0.008). The Children’s Oncology Group AAML0531 trial: clinicaltrials.gov Identifier: 00372593.

Andrographolide Suppresses MV4-11 Cell Proliferation through the Inhibition of FLT3 Signaling, Fatty Acid Synthesis and Cellular Iron Uptake

Background: Andrographolide (ADR), the main active component of Andrographis paniculata, displays anticancer activity in various cancer cell lines, among which leukemia cell lines exhibit the highest sensitivity to ADR. In particular, ADR was also reported to have reduced drug resistance in multidrug resistant cell lines. However, the mechanism of action (MOA) of ADR’s anticancer and anti-drug-resistance activities remain elusive. Methods: In this study, we used the MV4-11 cell line, a FLT3 positive acute myeloid leukemia (AML) cell line that displays multidrug resistance, as our experimental system. We first evaluated the effect of ADR on MV4-11 cell proliferation. Then, a quantitative proteomics approach was applied to identify differentially expressed proteins in ADR-treated MV4-11 cells. Finally, cellular processes and signal pathways affected by ADR in MV4-11 cell were predicted with proteomic analysis and validated with in vitro assays. Results: ADR inhibits MV4-11 cell proliferation in a dose- and time-dependent manner. With a proteomic approach, we discovered that ADR inhibited fatty acid synthesis, cellular iron uptake and FLT3 signaling pathway in MV4-11 cells. Conclusions: ADR inhibits MV4-11 cell proliferation through inhibition of fatty acid synthesis, iron uptake and protein synthesis. Furthermore, ADR reduces drug resistance by blocking FLT3 signaling.

KIT mutations correlate with adverse survival in children with core-binding factor acute myeloid leukemia

The prevalence and clinical relevance of KIT mutations in childhood core-binding factor (CBF) acute myeloid leukemia (AML) have not been well characterized. In this study, a total of 212 children with de novo AML were enrolled from a Chinese population and 50 (23.5%) of the patients were deemed CBF-AML. KIT mutations were identified in 30% of the CBF-AML cohort. The KIT mutations were clustered in exon 17 and exon 8, and KIT mutations in exons 8 and 17 were correlated with a shorter overall survival (OS) (5-year OS: 30.0 ± 14.5% vs. 73.0 ± 8.5%, p = .007) and event-free survival (EFS) (5-year EFS: 30.0 ± 14.5% vs. 73.0 ± 8.5%, p = .003). Multivariate analysis revealed KIT mutations as an independent risk factor in CBF-AML. Our results suggest that KIT mutations are a molecular marker for an inferior prognosis in pediatric CBF-AML.

High level of miR-196b at newly diagnosed pediatric acute myeloid leukemia predicts a poor outcome

Differential expression of microRNAs (miRNAs) has been implicated in leukemogenesis. We investigate the expression pattern of miR-196b. Using quantitative real-time PCR (qRT-PCR), we detected the expression of miR-196b and its correlated genes (SMC1A/MLH1) in initial pediatric AML. A significant association was observed between overexpression of miR-196b and inferior overall survival of pediatric AML (Log Rank P<0.0001). AML M4/5 subtype, high white blood cell (WBC) count at presentation, MLL rearrangement, or FLT3-ITD mutation at diagnosis and non-remission group after the first induction chemotherapy possessed higher miR-196b expression. Furthermore, a positive relationship was found between the expression of miR-196b and SMC1A/MLH1 (Spearman's r=0.37 and 0.44, P=0.001 and <0.0001, respectively). Taken together, these findings suggest that differentially high expression of miR-196b in diagnostic marrow samples of pediatric AML is associated with unfavorable outcome, and miR-196b potentially can be a novel biomarker for the diagnosis, prognosis and treatment in pediatric AML.

ASXL2 mutations are frequently found in pediatric AML patients with t(8;21)/ RUNX1-RUNX1T1 and associated with a better prognosis

ASXL2 is an epigenetic regulator involved in polycomb repressive complex regulation or recruitment. Clinical features of pediatric acute myeloid leukemia (AML) patients with ASXL2 mutations remain unclear. Thus, we investigated frequencies of ASXL1 and ASXL2 mutations, clinical features of patients with these mutations, correlations of these mutations with other genetic alterations including BCOR/BCORL1 and cohesin complex component genes, and prognostic impact of these mutations in 369 pediatric patients with de novo AML (0-17 years). We identified 9 (2.4%) ASXL1 and 17 (4.6%) ASXL2 mutations in 25 patients. These mutations were more common in patients with t(8;21)(q22;q22)/RUNX1-RUNX1T1 (ASXL1, 6/9, 67%, P = 0.02; ASXL2, 10/17, 59%, P = 0.01). Among these 25 patients, 4 (27%) of 15 patients with t(8;21) and 6 (60%) of 10 patients without t(8;21) relapsed. However, most patients with relapse were rescued using stem cell transplantation irrespective of t(8;21). The overall survival (OS) and event-free survival (EFS) rates showed no differences among pediatric AML patients with t(8;21) and ASXL1 or ASXL2 mutations and ASXL wild-type (5-year OS, 75% vs. 100% vs. 91% and 5-year EFS, 67% vs. 80% vs. 67%). In 106 patients with t(8;21) AML, the coexistence of mutations in tyrosine kinase pathways and chromatin modifiers and/or cohesin complex component genes had no effect on prognosis. These results suggest that ASXL1 and ASXL2 mutations play key roles as cooperating mutations that induce leukemogenesis, particularly in pediatric AML patients with t(8;21), and these mutations might be associated with a better prognosis than that reported previously.

Genomic Profiling of a Large Set of Diverse Pediatric Cancers Identifies Known and Novel Mutations across Tumor Spectra

Pediatric cancers are generally characterized by low mutational burden and few recurrently mutated genes. Recent studies suggest that genomic alterations may help guide treatment decisions and clinical trial selection. Here, we describe genomic profiles from 1,215 pediatric tumors representing sarcomas, extracranial embryonal tumors, brain tumors, hematologic malignancies, carcinomas, and gonadal tumors. Comparable published datasets identified similar frequencies of clinically relevant alterations, validating this dataset as biologically relevant. We identified novel ALK fusions in a neuroblastoma (BEND5-ALK) and an astrocytoma (PPP1CB-ALK), novel BRAF fusions in an astrocytoma (BCAS1-BRAF) and a ganglioglioma (TMEM106B-BRAF), and a novel PAX3-GLI2 fusion in a rhabdomyosarcoma. Previously characterized ALK, NTRK1, and PAX3 fusions were observed in unexpected malignancies, challenging the "disease-specific" alterations paradigm. Finally, we identified recurrent variants of unknown significance in MLL3 and PRSS1 predicted to have functional impact. Data from these 1,215 tumors are publicly available for discovery and validation. Cancer Res; 77(2); 509-19. ©2017 AACR.

Prognostic Importance of C-KIT Mutations in Core Binding Factor Acute Myeloid Leukemia: A Systematic Review

OBJECTIVE/BACKGROUND

Acute myeloid leukemia (AML) is defined as leukemic blast reproduction in bone marrow. Chromosomal abnormalities form different subgroups with joint clinical specifications and results. t(8;21)(q22;q22) and inv(16)(p13;q22) form core binding factor-AML (CBF-AML). c-kit mutation activation occurs in 12.8-46.1% of adults with CBF leukemia. These mutations occur in 20-25% of t(8;21) and 30% of inv(16) cases.

METHODS

In this systematic review, we searched different databases, including PubMed, Scopus, and Embase. Selected articles were measured based on the inclusion criteria of this study and initially compared in terms of titles or abstracts. Finally, articles relevant to the subject of this review were retrieved in full text. Twenty-two articles matched the inclusion criteria and were selected for this review.

RESULTS

In this study, c-kit mutations were associated with poor prognosis in AML patients with t(8;21) and inv(16). In addition, these mutations had better prognostic effects on AML patients with inv(16) compared with those with t(8;21).

CONCLUSION

According to the results of this study, c-kit mutations have intense, harmful effects on the relapse and white blood cell increase in CBF-AML adults. However, these mutations have no significant prognostic effects on patients.

Whole-exome sequencing reveals the spectrum of gene mutations and the clonal evolution patterns in paediatric acute myeloid leukaemia

Acute myeloid leukaemia (AML) is a molecularly and clinically heterogeneous disease. Targeted sequencing efforts have identified several mutations with diagnostic and prognostic values in KIT, NPM1, CEBPA and FLT3 in both adult and paediatric AML. In addition, massively parallel sequencing enabled the discovery of recurrent mutations (i.e. IDH1/2 and DNMT3A) in adult AML. In this study, whole-exome sequencing (WES) of 22 paediatric AML patients revealed mutations in components of the cohesin complex (RAD21 and SMC3), BCORL1 and ASXL2 in addition to previously known gene mutations. We also revealed intratumoural heterogeneities in many patients, implicating multiple clonal evolution events in the development of AML. Furthermore, targeted deep sequencing in 182 paediatric AML patients identified three major categories of recurrently mutated genes: cohesion complex genes [STAG2, RAD21 and SMC3 in 17 patients (8·3%)], epigenetic regulators [ASXL1/ASXL2 in 17 patients (8·3%), BCOR/BCORL1 in 7 patients (3·4%)] and signalling molecules. We also performed WES in four patients with relapsed AML. Relapsed AML evolved from one of the subclones at the initial phase and was accompanied by many additional mutations, including common driver mutations that were absent or existed only with lower allele frequency in the diagnostic samples, indicating a multistep process causing leukaemia recurrence.

Celastrol Induces Cell Apoptosis and Inhibits the Expression of the AML1-ETO/C-KIT Oncoprotein in t(8;21) Leukemia

Resistance to chemotherapy is a major challenge to improving overall survival in Acute Myeloid Leukemia (AML). Therefore, the development of innovative therapies and the identification of more novel agents for AML are urgently needed. Celastrol, a compound extracted from the Chinese herb Tripterygium wilfordii Hook, exerts anticancer activity. We investigated the effect of celastrol in the t(8;21) AML cell lines Kasumi-1 and SKNO-1. We demonstrated that inhibition of cell proliferation activated caspases and disrupted mitochondrial function. In addition, we found that celastrol downregulated the AML1-ETO fusion protein, therefore downregulating C-KIT kinases and inhibiting AKT, STAT3 and Erk1/2. These findings provide clear evidence that celastrol might provide clinical benefits to patients with t(8;21) leukemia.

Acute myeloid leukemia in children: Current status and future directions

Acute myeloid leukemia (AML) accounts for 25% of pediatric leukemia and affects approximately 180 patients annually in Japan. The treatment outcome for pediatric AML has improved through advances in chemotherapy, hematopoietic stem cell transplantation (HSCT), supportive care, and optimal risk stratification. Currently, clinical pediatric AML studies are conducted separately according to the AML subtypes: de novo AML, acute promyelocytic leukemia (APL), and myeloid leukemia with Down syndrome (ML-DS). Children with de novo AML are treated mainly with anthracyclines and cytarabine, in some cases with HSCT, and the overall survival (OS) rate now approaches 70%. Children with APL are treated with an all-trans retinoic acid (ATRA)-combined regimen with an 80-90% OS. Children with ML-DS are treated with a less intensive regimen compared with non-DS patients, and the OS is approximately 80%. HSCT in first remission is restricted to children with high-risk de novo AML only. To further improve outcomes, it will be necessary to combine more accurate risk stratification strategies using molecular genetic analysis with assessment of minimum residual disease, and the introduction of new drugs in international collaborative clinical trials.

Prognostic Significance of KIT Mutations in Core-Binding Factor Acute Myeloid Leukemia: A Systematic Review and Meta-Analysis

The prognostic significance of KIT mutations in core-binding factor acute myeloid leukemia (CBF-AML), including inv(16) and t(8;21) AML, is uncertain. We performed a systematic review and meta-analysis of the effect of KIT mutations on the complete remission (CR) and relapse rates and overall survival (OS) of CBF-AML. PubMed, Embase, Web of Science, and the Cochrane Library were searched and relevant studies were included. Negative effect was indicated on relapse risk of CBF-AML (RR [relative risk], 1.43; 95%CI [confidence interval], 1.20–1.70) and t(8;21) AML (RR, 1.70; 95% CI, 1.31–2.21), not on OS of CBF-AML (RR, 1.09; 95% CI, 0.97–1.23), CR (OR [odds ratio], 0.95; 95% CI, 0.52–1.74), relapse risk (RR, 1.12; 95% CI, 0.90–1.41) or OS (RR, 1.03; 95% CI, 0.90–1.18) of inv(16) AML. Subgroup analysis of t(8,21) AML showed negative effect of KIT mutations on CR (OR, 2.03; 95%CI: 1.02–4.05), relapse risk (RR, 1.89; 95%CI: 1.51–2.37) and OS (RR, 2.26; 95%CI: 1.35–3,78) of non-Caucasians, not on CR (OR, 0.61; 95%CI: 0.19–1.95) or OS (RR, 1.12; 95%CI: 0.90–1.40) of Caucasians. This study indicates KIT mutations in CBF-AML to be included in the initial routine diagnostic workup and stratification system of t(8,21) AML. Prospective large-scale clinical trials are warranted to evaluate these findings.

Clinical Impact of Additional Cytogenetic Aberrations, cKIT and RAS Mutations, and Treatment Elements in Pediatric t(8;21)-AML: Results From an International Retrospective Study by the International Berlin-Frankfurt-Münster Study Group

PURPOSE

This retrospective cohort study aimed to determine the predictive relevance of clinical characteristics, additional cytogenetic aberrations, and cKIT and RAS mutations, as well as to evaluate whether specific treatment elements were associated with outcomes in pediatric t(8;21)-positive patients with acute myeloid leukemia (AML).

PATIENTS AND METHODS

Karyotypes of 916 pediatric patients with t(8;21)-AML were reviewed for the presence of additional cytogenetic aberrations, and 228 samples were screened for presence of cKIT and RAS mutations. Multivariable regression models were used to assess the relevance of anthracyclines, cytarabine, and etoposide during induction and overall treatment. End points were the probability of achieving complete remission, cumulative incidence of relapse (CIR), probability of event-free survival, and probability of overall survival.

RESULTS

Of 838 patients included in final analyses, 92% achieved complete remission. The 5-year overall survival, event-free survival, and CIR were 74%, 58%, and 26%, respectively. cKIT mutations and RAS mutations were not significantly associated with outcome. Patients with deletions of chromosome arm 9q [del(9q); n = 104] had a lower probability of complete remission (P = .01). Gain of chromosome 4 (+4; n = 21) was associated with inferior CIR and survival (P < .01). Anthracycline doses greater than 150 mg/m(2) and etoposide doses greater than 500 mg/m(2) in the first induction course and high-dose cytarabine 3 g/m(2) during induction were associated with better outcomes on various end points. Cumulative doses of cytarabine greater than 30 g/m(2) and etoposide greater than 1,500 mg/m(2) were associated with lower CIR rates and better probability of event-free survival.

CONCLUSION

Pediatric patients with t(8;21)-AML and additional del(9q) or additional +4 might not be considered at good risk. Patients with t(8;21)-AML likely benefit from protocols that have high doses of anthracyclines, etoposide, and cytarabine during induction, as well as from protocols comprising cumulative high doses of cytarabine and etoposide.

Collaborative Efforts Driving Progress in Pediatric Acute Myeloid Leukemia

Diagnosis, treatment, response monitoring, and outcome of pediatric acute myeloid leukemia (AML) have made enormous progress during the past decades. Because AML is a rare type of childhood cancer, with an incidence of approximately seven occurrences per 1 million children annually, national and international collaborative efforts have evolved. This overview describes these efforts and includes a summary of the history and contributions of each of the main collaborative pediatric AML groups worldwide. The focus is on translational and clinical research, which includes past, current, and future clinical trials. Separate sections concern acute promyelocytic leukemia, myeloid leukemia of Down syndrome, and relapsed AML. A plethora of novel antileukemic agents that have emerged, including new classes of drugs, are summarized as well. Finally, an important aspect of the treatment of pediatric AML--supportive care--and late effects are discussed. The future is bright, with a wide range of emerging innovative therapies and with more and more international collaboration that ultimately aim to cure all children with AML, with fewer adverse effects and without late effects.

High expression of c-kit mRNA predicts unfavorable outcome in adult patients with t(8;21) acute myeloid leukemia

The reason that a certain subgroup of acute myeloid leukemia (AML) patients with t(8;21) translocation (generating the AML1/ETO fusion gene) displays a poor survival remains elusive. The proto-oncogene c-kit is expressed in approximately 80% of AML cases. The kinase domain mutation of the c-kit gene, one of the most common gain-of-function mutations associated with t(8;21) AML, predicts higher relapse risk and poor prognosis. However, the role of c-kit high expression in t(8;21) AML remains poorly understood. Here we evaluated the prognostic significance of c-kit expression levels in AML patients. The mRNA expression of c-kit was determined by real-time quantitative reverse transcription PCR in 132 adult AML patients. Patients were grouped into quartiles according to c-kit expression levels (Q1–Q4, each quartile containing 25% of patients) and divided into c-kit high (Q4; n = 33) and c-kit low (Q1–Q3; n = 99). High c-kit expression was associated with AML1/ETO-positive and with c-kit mutation. Of note, 35.8% of the AML1/ETO-positive AML patients carrying wild-type c-kit expressed high levels of c-kit, suggesting that other factors are involved in c-kit overexpression. High c-kit expression was associated with inferior overall and event-free survival in AML1/ETO-positive patients and was independently predictive for overall and event-free survival in multivariate analyses in a c-kit mutation-independent manner. Thus, high c-kit expression serves as a reliable molecular marker for poor prognosis, supporting a pathogenetic role of c-kit signaling in AML1/ETO-positive AML. AML1/ETO-positive patients with high c-kit expression might benefit from early treatment modifications and molecular target therapies.

Prognosis and monitoring of core-binding factor acute myeloid leukemia: current and emerging factors

Core-binding factor acute myeloid leukemia (CBF-AML) - including AML with t(8;21) and AML with inv(16) - accounts for about 15% of adult AML and is associated with a relatively favorable prognosis. Nonetheless, relapse incidence may reach 40% in these patients. In this context, identification of prognostic markers is considered of great interest. Due to similarities between their molecular and prognostic features, t(8;21) and inv(16)-AML are usually grouped and reported together in clinical studies. However, considerable experimental evidences have highlighted that they represent two distinct entities and should be considered separately for further studies. This review summarizes recent laboratory and clinical findings in this particular subset of AML and how they could be used to improve management of patients in routine practice.

Prevalence and prognostic significance of c-KIT mutations in core binding factor acute myeloid leukemia: a comprehensive large-scale study from a single Chinese center

To clarify the prevalence and prognostic significance of c-KIT mutations in patients with core binding factor acute myeloid leukemia (CBF-AML), a total of 351 patients who were categorized as pediatric t(8;21), adult t(8;21), pediatric inv(16), or adult inv(16) were screened at diagnosis for c-KIT mutations in exons 17 and 8 using direct sequencing. A total of 250 patients underwent follow-up. Overall, 36.5% of the patients had a c-KIT mutation. Adult t(8;21) and inv(16) patients had mutations predominantly in exons 17 and 8, respectively. Higher White blood cell (WBC) count, WBC index, and AML1-ETO transcript levels in adult t(8;21) patients were significantly associated with c-KIT mutations and mutations in exon 17 (P≤0.030). c-KIT mutations in adult t(8;21) patients were significantly correlated with a high cumulative incidence of relapse (CIR, P=0.0070) at 2 years and a low 2-year disease-free survival (DFS, P=0.013) and overall survival (OS, P=0.0055). However, no significant difference was revealed in the effect of c-KIT mutations on outcome of adult inv(16) and pediatric t(8;21) patients (all P>0.05). Multivariate analysis revealed that c-KIT mutation is an independent prognostic factor for relapse, DFS, and OS (P≤0.016) in adult t(8;21) AML patients. Therefore, with regard to c-KIT mutation, CBF-AML is a heterogeneous disease. c-KIT mutations have a strong adverse effect on the relapse and survival of adult t(8;21) AML patients.