KIT D816 mutation associates with adverse outcomes in core binding factor acute myeloid leukemia, especially in the subgroup with RUNX1/RUNX1T1 rearrangement

Secondary Mutational and Cytogenetic Alterations in Core Binding Factor - Acute Myeloid Leukemia (CBF-AML): A Systematic Review and Meta-Analysis

BACKGROUND

Acute myeloid leukemia (AML) with core-binding factor alterations (CBF-AML) is a notable subtype characterized by specific genetic alterations and a relatively favorable prognosis. Despite this, a significant proportion of CBF-AML patients experience relapse, indicating the potential prognostic role of other co-present cytogenetic abnormalities and gene mutations.

METHODS

A comprehensive search of PubMed, Embase, Web of Science, and Scopus was conducted until April 2024. Studies evaluating the prognostic impact of secondary cytogenetic abnormalities and gene mutations in CBF-AML were included. Data extraction and quality assessment were independently performed by two reviewers. Statistical analysis was conducted using the "meta" package in R.

RESULTS

59 studies met the inclusion criteria. Mutations in the c-kit gene were significantly associated with decreased overall survival (OS) and disease-free survival (DFS) at 1, 5, and 10-year intervals. Patients with high c-kit expression also showed poorer survival outcomes. The presence of FLT3-ITD mutations was also correlated with lower survival rates. N-RAS mutations were found to have a variable impact on prognosis, with some studies indicating a negative effect on OS and DFS, while others showed no significant impact. Certain secondary cytogenetic abnormalities, such as loss of sex chromosomes and trisomy 8, were found to negatively affect prognosis, while trisomy 22 was found to increase 5-year RFS.

CONCLUSION

Secondary cytogenetic abnormalities and mutations, notably c-KIT and FLT3-ITD, were linked to poorer survival in CBF-AML. Trisomy 8 also worsened prognosis, while N-RAS mutations showed minimal impact. These findings highlight the value of genetic profiling for risk stratification and personalized therapy. Future research should explore targeted treatments for high-risk subgroups to improve outcomes and reduce relapse rates.

Pediatric acute myeloid leukemia with t(8;21) and KIT mutation treatment with avapritinib post-stem cell transplantation: a report of four cases

Acute myeloid leukemia (AML) with t(8;21) (q22;q22), which forms RUNX1::RUNX1T1 fusion gene, is classified as a favorable-risk group. However, the presence of mutations in KIT exon 17 results in an adverse prognosis in this group. Avapritinib, a novel tyrosine kinase inhibitor, was designed to target KIT mutation. We report a retrospective study of four pediatric patients with AML with t(8:21) and KIT exon 17 mutation who were treated with avapritinib, three of them failed to demethylate drugs and donor lymphocyte infusion targeting RUNX1::RUNX1T1-positivity after allogeneic hematopoietic stem cell transplantation (allo-HSCT). So far, all patients with RUNX1::RUNX1T1 positivity had turned negative after 1, 9, 7, 2 months of avapritinib treatment. The common adverse effect of avapritinib is neutropenia, which is well-tolerated. This case series indicates that avapritinib may be effective and safe for preemptive treatment of children with AML with t(8;21) and KIT mutation after allo-HSCT, providing a treatment option for preventing relapse after allo-HSCT.

[Analysis of the therapeutic effect of avatinib bridged allogeneic hematopoietic stem cell transplantation on 7 cases of recurrent/refractory RUNX1-RUNX1T1 positive acute myeloid leukemia with KIT mutations]

Objective: To evaluate the efficacy of avatinib plus allogeneic hematopoietic stem cell transplantation (allo-HSCT) for the treatment of recurrent/refractory RUNX1-RUNX1T1 positive acute myeloid leukemia (AML) with KIT mutations. Method: A retrospective study was conducted on the clinical data of seven relapsed/refractory AML patients containing the RUNX1-RUNX1T1 fusion gene and KIT mutation who received afatinib plus allo-HSCT treatment at the First Affiliated Hospital of Soochow University from June 2019 to June 2023. Results: The seven AML patients included one male and six females with a median age of 37 (18-56) years. All seven patients had KIT mutations (five positive for D816V and two positive for D816Y) . There were two refractory patients and five relapsed patients (all of whom had bone marrow recurrence) . All patients had to complete at least one course of treatment with afatinib before transplantation. Four patients achieved complete remission (CR) after treatment with afatinib, six patients had negative KIT gene mutations, and one had a decreased KIT gene mutational burden. There were three cases of unrelated identical transplantation and four cases of haploidentical transplantation. All patients received the modified Bu/Cy pretreatment regimen. After transplantation, all patients were successfully implanted and a bone marrow examination showed CR and minimal residual disease turned negative. Five patients exhibited negative fusion genes. Two patients died from infection following transplantation. Conclusion: Afatinib plus allo-HSCT may be an effective and safe new treatment strategy for RUNX1-RUNX1T1 positive AML patients with KIT-D816 mutation.

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.

CPX-351 and allogeneic stem cell transplant for a therapy-related acute myeloid leukemia that developed after treatment of acute promyelocytic leukemia: a case report and review of the literature

Therapy-related myeloid neoplasms (t-MNs), which develop after cytotoxic, radiation, or immunosuppressive therapy for an unrelated disease, account for 7%-8% of acute myeloid leukemia (AML). Worse outcomes and consequently shortened survival are associated with t-MNs as compared with de novo AML. Therapy-related MNs are being reported with increasing frequency in successfully treated acute promyelocytic leukemia (APL), in particular, before the introduction of all-trans retinoic acid (ATRA) plus arsenic trioxide (ATO). Considering the high curability of APL, t-MNs represent one of the prognosis-limiting factors in this setting of leukemia. We report our experience with a patient who developed t-AML 15 years after treatment for APL. Treatment included three cycles of chemotherapy with CPX-351 (Vyxeos, Jazz Pharmaceuticals) followed, as in remission, by an allogeneic hematopoietic stem cell transplant. A review of available literature was also included.

Management of Advanced Systemic Mastocytosis and Associated Myeloid Neoplasms

Advanced systemic mastocytosis (AdvSM) is a heterogeneous group of disorders characterized by neoplastic mast cell-related organ damage and frequently associated with a myeloid neoplasm. The 3 clinical entities that comprise AdvSM are aggressive SM (ASM), SM-associated hematologic neoplasm, and mast cell leukemia. A gain-of-function KIT D816 V mutation is the primary oncogenic driver found in about 90% of all patients with AdvSM. Midostaurin, an oral multikinase inhibitor with activity against KIT D816V, and avapritinib, an oral selective KIT D816V inhibitor are approved for AdvSM.

G-quadruplexes in cancer-related gene promoters: from identification to therapeutic targeting

INTRODUCTION

Guanine-rich DNA sequences can fold into four-stranded noncanonical secondary structures called G-quadruplexes (G4s) which are widely distributed in functional regions of the human genome, such as telomeres and gene promoter regions. Compelling evidence suggests their involvement in key genome functions such as gene expression and genome stability. Notably, the abundance of G4-forming sequences near transcription start sites suggests their potential involvement in regulating oncogenes.

AREAS COVERED

This review provides an overview of current knowledge on G4s in human oncogene promoters. The most representative G4-binding ligands have also been documented. The objective of this work is to present a comprehensive overview of the most promising targets for the development of novel and highly specific anticancer drugs capable of selectively impacting the expression of individual or a limited number of genes.

EXPERT OPINION

Modulation of G4 formation by specific ligands has been proposed as a powerful new tool to treat cancer through the control of oncogene expression. Actually, most of G4-binding small molecules seem to simultaneously target a range of gene promoter G4s, potentially influencing several critical driver genes in cancer, thus producing significant therapeutic benefits.

c-Kit Receptors as a Therapeutic Target in Cancer: Current Insights

c-Kit is a type III receptor tyrosine kinase (RTK) that has an essential role in various biological functions including gametogenesis, melanogenesis, hematopoiesis, cell survival, and apoptosis. c-KIT aberrations, either overexpression or loss-of-function mutations, have been implicated in the pathogenesis and development of many cancers, including gastrointestinal stromal tumors, mastocytosis, acute myeloid leukemia, breast, thyroid, and colorectal cancer, making c-KIT an attractive molecular target for the treatment of cancers. Therefore, a lot of effort has been put into investigating the utility of tyrosine kinase inhibitors for the management of c-KIT mutated tumors. This review of the literature illustrates the role of c-KIT mutations in many cancers, aiming to provide insights into the role of TKIs as a therapeutic option for cancer patients with c-KIT aberrations. In conclusion, c-KIT is implicated in different types of cancer, and it could be a successful molecular target; however, proper detection of the underlying mutation type is required before starting the appropriate personalized therapy.

Detection of Hybrid Fusion Transcripts, Aberrant Transcript Expression, and Specific Single Nucleotide Variants in Acute Leukemia and Myeloid Disorders with Recurrent Gene Rearrangements

INTRODUCTION

A variety of gene rearrangements and molecular alterations are key drivers in the pathobiology of acute leukemia and myeloid disorders; current classification systems increasingly incorporate these findings in diagnostic algorithms. Therefore, clinical laboratories require versatile tools, which can detect an increasing number and variety of molecular and cytogenetic alterations of clinical significance.

METHODS

We validated an RNA-based next-generation sequencing (NGS) assay that enables the detection of: (i) numerous hybrid fusion transcripts (including rare/novel gene partners), (ii) aberrantly expressed EVI1 (MECOM) and IKZF1 (Del exons 4-7) transcripts, and (iii) hotspot variants in KIT, ABL1, NPM1 (relevant in the context of gene rearrangement status).

RESULTS

For hybrid fusion transcripts, the assay showed 98-100% concordance for known positive and negative samples, with an analytical sensitivity (i.e., limit of detection) of approximately 0.8% cells. Samples with underlying EVI1 (MECOM) translocations demonstrated increased EVI1 (MECOM) expression. Aberrant IKZF1 (Del exons 4-7) transcripts detectable with the assay were also present on orthogonal reverse transcription PCR. Specific hotspot mutations in KIT, ABL1, and NPM1 detected with the assay showed 100% concordance with orthogonal testing. Lastly, several illustrative samples are included to highlight the assay's clinically relevant contributions to patient workup.

CONCLUSION

Through its ability to simultaneously detect various gene rearrangements, aberrantly expressed transcripts, and hotspot mutations, this RNA-based NGS assay is a valuable tool for clinical laboratories to supplement other molecular and cytogenetic methods used in the diagnostic workup and in clinical research for patients with acute leukemia and myeloid disorders.

Synergistic Targeting of DNA-PK and KIT Signaling Pathways in KIT Mutant Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is the most common and aggressive form of acute leukemia, with a 5-year survival rate of just 24%. Over a third of all AML patients harbor activating mutations in kinases, such as the receptor tyrosine kinases FLT3 (receptor-type tyrosine-protein kinase FLT3) and KIT (mast/stem cell growth factor receptor kit). FLT3 and KIT mutations are associated with poor clinical outcomes and lower remission rates in response to standard-of-care chemotherapy. We have recently identified that the core kinase of the non-homologous end joining DNA repair pathway, DNA-PK (DNA-dependent protein kinase), is activated downstream of FLT3; and targeting DNA-PK sensitized FLT3-mutant AML cells to standard-of-care therapies. Herein, we investigated DNA-PK as a possible therapeutic vulnerability in KIT mutant AML, using isogenic FDC-P1 mouse myeloid progenitor cell lines transduced with oncogenic mutant KIT (V560G and D816V) or vector control. Targeted quantitative phosphoproteomic profiling identified phosphorylation of DNA-PK in the T2599/T2605/S2608/S2610 cluster in KIT mutant cells, indicative of DNA-PK activation. Accordingly, proliferation assays revealed that KIT mutant FDC-P1 cells were more sensitive to the DNA-PK inhibitors M3814 or NU7441, compared with empty vector controls. DNA-PK inhibition combined with inhibition of KIT signaling using the kinase inhibitors dasatinib or ibrutinib, or the protein phosphatase 2A activators FTY720 or AAL(S), led to synergistic cell death. Global phosphoproteomic analysis of KIT-D816V cells revealed that dasatinib and M3814 single-agent treatments inhibited extracellular signal-regulated kinase and AKT (RAC-alpha serine/threonine-protein kinase)/MTOR (serine/threonine-protein kinase mTOR) activity, with greater inhibition of both pathways when used in combination. Combined dasatinib and M3814 treatment also synergistically inhibited phosphorylation of the transcriptional regulators MYC and MYB. This study provides insight into the oncogenic pathways regulated by DNA-PK beyond its canonical role in DNA repair and demonstrates that DNA-PK is a promising therapeutic target for KIT mutant cancers.

Mutated KIT Tyrosine Kinase as a Novel Molecular Target in Acute Myeloid Leukemia

KIT is a type-III receptor tyrosine kinase that contributes to cell signaling in various cells. Since KIT is activated by overexpression or mutation and plays an important role in the development of some cancers, such as gastrointestinal stromal tumors and mast cell disease, molecular therapies targeting KIT mutations are being developed. In acute myeloid leukemia (AML), genome profiling via next-generation sequencing has shown that several genes that are mutated in patients with AML impact patients’ prognosis. Moreover, it was suggested that precision-medicine-based treatment using genomic data will improve treatment outcomes for AML patients. This paper presents (1) previous studies regarding the role of KIT mutations in AML, (2) the data in AML with KIT mutations from the HM-SCREEN-Japan-01 study, a genome profiling study for patients newly diagnosed with AML who are unsuitable for the standard first-line treatment (unfit) or have relapsed/refractory AML, and (3) new therapies targeting KIT mutations, such as tyrosine kinase inhibitors and heat shock protein 90 inhibitors. In this era when genome profiling via next-generation sequencing is becoming more common, KIT mutations are attractive novel molecular targets in AML.

How to Improve Prognostication in Acute Myeloid Leukemia with CBFB-MYH11 Fusion Transcript: Focus on the Role of Molecular Measurable Residual Disease (MRD) Monitoring

Acute myeloid leukemia (AML) carrying inv(16)/t(16;16), resulting in fusion transcript CBFB-MYH11, belongs to the favorable-risk category. However, even if most patients obtain morphological complete remission after induction, approximately 30% of cases eventually relapse. While well-established clinical features and concomitant cytogenetic/molecular lesions have been recognized to be relevant to predict prognosis at disease onset, the independent prognostic impact of measurable residual disease (MRD) monitoring by quantitative real-time reverse transcriptase polymerase chain reaction (qRT-PCR), mainly in predicting relapse, actually supersedes other prognostic factors. Although the ELN Working Party recently indicated that patients affected with CBFB-MYH11 AML should have MRD assessment at informative clinical timepoints, at least after two cycles of intensive chemotherapy and after the end of treatment, several controversies could be raised, especially on the frequency of subsequent serial monitoring, the most significant MRD thresholds (most commonly 0.1%) and on the best source to be analyzed, namely, bone marrow or peripheral blood samples. Moreover, persisting low-level MRD positivity at the end of treatment is relatively common and not predictive of relapse, provided that transcript levels remain stably below specific thresholds. Rising MRD levels suggestive of molecular relapse/progression should thus be confirmed in subsequent samples. Further prospective studies would be required to optimize post-remission monitoring and to define effective MRD-based therapeutic strategies.

Prognostic values of D816V KIT mutation and peri-transplant CBFB-MYH11 MRD monitoring on acute myeloid leukemia with CBFB-MYH11

Given the controversies in the prognostic value of KIT mutations and optimal thresholds and time points of MRD monitoring for AML with CBFB-MYH11, we retrospectively evaluated 88 patients who underwent allogeneic hematopoietic stem cell transplantation (Allo-HSCT, n = 60) or autologous HSCT (Auto-HSCT, n = 28). The D816V KIT mutation was significantly associated with post-transplant relapse, contrasting with other types of mutations in KIT. Pre- and post-transplant (3 months after transplant) CBFB-MYH11 MRD assessments were useful in predicting post-transplant relapse and poor survival. The optimal threshold was determined as a 2 log reduction at both time points. In multivariate analysis, the D816V KIT mutation and CBFB-MYH11 MRD assessments were independently associated with post-transplant relapse and survival. Stratification by D816V KIT and pre-transplant CBFB-MYH11 MRD status further distinguished the risk of relapse and survival. Auto-HSCT was superior to Allo-HSCT in MRD negative patients without D816V KIT, while Allo-HSCT trended to be superior to Auto-HSCT in patients with MRD positivity or the D816V KIT mutation. In conclusion, this study demonstrated the differentiated prognostic value of the D816V KIT mutation in AML with CBFB-MYH11 and clarified optimal time points and thresholds for CBFB-MYH11 MRD monitoring in the setting of HSCT.

Prospective evaluation of prognostic impact of KIT mutations on acute myeloid leukemia with RUNX1-RUNX1T1 and CBFB-MYH11

The prognostic impact of KIT mutation on core-binding factor acute myeloid leukemia (CBF-AML) remains controversial. We registered 199 newly diagnosed de novo CBF-AML patients, aged 16 to 64 years, who achieved complete remission. They received 3 courses of high-dose cytarabine therapy and no further treatment until hematological relapse. Mutations in exons 8, 10-11, and 17 of the KIT gene were analyzed. Furthermore, we analyzed mutations in 56 genes that are frequently identified in myeloid malignancies and evaluated minimal residual disease (MRD). The primary end point was relapse-free survival (RFS) according to KIT mutations. The RFS in KIT-mutated patients was inferior to that in unmutated patients (hazard ratio, 1.92; 95% confidence interval, 1.23-3.00; P = .003). Based on subgroup analysis, KIT mutations had a prognostic impact in patients with RUNX1-RUNX1T1, but not in those with CBFB-MYH11, and only exon 17 mutation had a significant prognostic impact. Multivariate Cox regression analysis with stepwise selection revealed that the KIT exon 17 mutation and the presence of extramedullary tumors in patients with RUNX1-RUNX1T1, and loss of chromosome X or Y and NRAS mutation in patients with CBFB-MYH11 were poor prognostic factors for RFS. MRD was evaluated in 112 patients, and it was associated with a poorer RFS in the patients with CBFB-MYH11, but not in those with RUNX1-RUNX1T1. These results suggested that it is necessary to separately evaluate AML with RUNX1-RUNX1T1 or CBFB-MYH11 according to appropriate prognostic factors. This study was registered at www.umin.ac.jp/ctr/ as #UMIN000003434.

Advances in therapeutic options for newly diagnosed, high-risk AML patients

Acute myeloid leukemia (AML) is an aggressive malignancy characterized by clonal proliferation of neoplastic immature precursor cells. AML impacts older adults and has a poor prognosis. Despite recent advances in treatment, AML is complex, with both genetic and epigenetic aberrations in the malignant clone and elaborate interactions with its microenvironment. We are now able to stratify patients on the basis of specific clinical and molecular features in order to optimize individual treatment strategies. However, our understanding of the complex nature of these molecular abnormalities continues to expand the defining characteristics of high-risk mutations. In this review, we focus on genetic and microenvironmental factors in adverse risk AML that play critical roles in leukemogenesis, including those not described in an European LeukemiaNet adverse risk group, and describe therapies that are currently in the clinical arena, either approved or under development.

Both the subtypes of KIT mutation and minimal residual disease are associated with prognosis in core binding factor acute myeloid leukemia: a retrospective clinical cohort study in single center

Core binding factor acute myeloid leukemia (CBF-AML), including cases with KIT mutation, is currently defined as a low-risk AML. However, some patients have poor response to treatment, and the prognostic significance of KIT mutation is still controversial. This study aimed to explore the prognostic significance of different KIT mutation subtypes and minimal residual disease (MRD) in CBF-AML. We retrospectively evaluated continuous patients diagnosed with CBF-AML in our center between January 2014 and April 2019. Of the 215 patients, 147 (68.4%) and 68 (31.6%) patients were RUNX1-RUNX1T1- and CBFB-MYH11 positive, respectively. KIT mutations were found in 71 (33.0%) patients; of them, 38 (53.5%) had D816/D820 mutations. After excluding 10 patients who died or were lost to follow-up within a half year, 42.0% (n = 86) of the remaining 205 patients received allogeneic hematopoietic stem cell transplantation (allo-HSCT). An MRD > 0.1% at the end of two cycles of consolidation predicted relapse (P < 0.001). Multivariate analysis showed that D816 or D820 mutations and MRD > 0.1% at the end of two cycles of consolidation were independent adverse factors affecting relapse-free survival (RFS) and overall survival (OS). Allo-HSCT could improve RFS (74.4% vs. 34.6%, P < 0.001) and OS (78.1% vs. 52.3%, P = 0.002). In conclusion, high-risk CBF-AML patients must be identified before treatment. D816/D820 mutation, MRD > 0.1% at the end of two cycles of consolidation chemotherapy predicted poor survivals, and allo-HSCT can improve the survival of properly identified patients.

Prognostic Impacts of D816V KIT Mutation and Peri-Transplant RUNX1-RUNX1T1 MRD Monitoring on Acute Myeloid Leukemia with RUNX1-RUNX1T1

The prognostic significance of KIT mutations and optimal thresholds and time points of measurable residual disease (MRD) monitoring for acute myeloid leukemia (AML) with RUNX1-RUNX1T1 remain controversial in the setting of hematopoietic stem cell transplantation (HSCT). We retrospectively evaluated 166 high-risk patients who underwent allogeneic (Allo-HSCT, n = 112) or autologous HSCT (Auto-HSCT, n = 54). D816V KIT mutation, a subtype of exon 17 mutations, was significantly associated with post-transplant relapse and poor survival, while other types of mutations in exons 17 and 8 were not associated with post-transplant relapse. Pre- and post-transplant RUNX1-RUNX1T1 MRD assessments were useful for predicting post-transplant relapse and poor survival with a higher sensitivity at later time points. Survival analysis for each stratified group by D816V KIT mutation and pre-transplant RUNX1-RUNX1T1 MRD status demonstrated that Auto-HSCT was superior to Allo-HSCT in MRD-negative patients without D816V KIT mutation, while Allo-HSCT was superior to Auto-HSCT in MRD-negative patients with D816V KIT mutation. Very poor outcomes of pre-transplant MRD-positive patients with D816V KIT mutation suggested that this group should be treated in clinical trials. Risk stratification by both D816V KIT mutation and RUNX1-RUNX1T1 MRD status will provide a platform for decision-making or risk-adapted therapeutic approaches.

Allogeneic Hematopoietic Stem Cell Transplantation Improved Survival for Adult Core Binding Factor Acute Myelogenous Leukemia Patients with Intermediate- and Adverse-Risk Genetics in the 2017 European LeukemiaNet

The use of allogeneic hematopoietic stem cell transplantation (allo-HSCT) for consolidation therapy in patients with core binding factor (CBF) acute myelogenous leukemia (AML) with intermediate- and adverse-risk genetics remains controversial. We retrospectively analyzed the clinical outcomes of 286 CBF-AML patients with intermediate- and adverse-risk genetics in first complete remission following consolidation with chemotherapy (n = 122), auto-HSCT (n = 27), or allo-HSCT (n = 137) between January 2009 and December 2018 at our center. Patients with allo-HSCT showed superior 5-year overall survival (OS; 74% versus 38% or 49%; P < .001) and progression-free survival (PFS; 74% versus 26% or 49%; P < .001) and lower cumulative incidence of relapse (CIR; 9% versus 69% or 31%; P < .001) compared with chemotherapy alone or auto-HSCT. In the allo-HSCT group, minimal residual disease (MRD) at the second and third months after allo-HSCT could predict relapse in t(8;21) patients (2 months: P_CIR = .002; 3 months: P_CIR < .001) but not in inv(16) patients. Moreover, positive MRD after 2 courses of consolidation chemotherapy before allo-HSCT was an independent risk factor for survival in CBF-AML patients with intermediate- and adverse-risk genetics, whereas haploidentical donor (haplo-) HSCT could overcome the adverse prognosis (5-year OS, 87%; 5-year PFS, 81%; 5-year CIR, 7%). Allo-HSCT could be the optimal first-line consolidation therapy for patients with intermediate- and adverse-risk genetics, and haplo-HSCT could improve survival for patients with positive MRD after 2 courses of consolidation chemotherapy.

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.

Outcome of Core Binding Factor Acute Myeloid Leukemia by Receptor Tyrosine Kinase Mutation

BACKGROUND

Core binding factor acute myeloid leukemia (CBF-AML) encodes 2 recurrent cytogenetic abnormalities, t(8;21) and inv(16), which carries an overall good prognosis. However, some patients will develop a relapse. We sought define the unfavorable group of CBF-AML by analysis of (c-KIT and FLT3-ITD) and to correlate them with treatment outcome.

PATIENTS AND METHODS

We performed a prospective study of 70 patients with CBF-AML diagnosed and managed at the medical oncology department of the (National Cancer Institute), Cairo University, with analysis of c-KIT and FLT3 mutations. All patients had received "3 + 7" induction, followed by 3 to 4 courses of high-dose cytarabine consolidation. The institutional review board approved the present study.

RESULTS

The median patient age was 31 years (range, 18-60 years), with a male/female ratio of 4:3. Of the 70 patients, 42 (60%) had t(8;21) and 28 had inv(16) (40%). c-KIT mutations (exons 8 and 17) were detected in 10 of 52 tested patients, and FLT3-ITD was detected in 3 of 70 patients. Patients with inv(16) experienced more lymphadenopathy and splenomegaly, had a higher median initial leukocyte count. Hepatitis C antibody positivity (8 of 42) was exclusively present in patients with t(8;21). The median overall survival (OS) was 19.5 months, and the median disease-free survival (DFS) was not reached. Patients with inv(16) had near-significant (P = .07) better DFS than patients with t(8;21). c-KIT mutations had no significant effect on OS or DFS. However, reverse tyrosine kinase mutations had a negative effect on DFS but not OS (P = .04).

CONCLUSION

CBF-AML with reverse tyrosine kinase mutation conveys a worse prognosis. Hepatitis C virus antibody positivity might be associated with t(8;21) AML and inv(16) with more extramedullary disease.

Clinical heterogeneity under induction with different dosages of cytarabine in core binding factor acute myeloid leukaemia

Repeated cycles of post-remission high-dose cytarabine (Ara-C) have been suggested to improve survival in core binding factor (CBF) acute myeloid leukaemia (AML). High-dose Ara-C used for induction regimens has also been reported to be associated with increased treatment-related mortality (TRM). Few data are available about intermediate-dose Ara-C serving as induction therapy. The aim of our study was to compare the tolerance and outcomes of standard- and intermediate-dose levels of Ara-C as induction in CBF AML and to analyse the clinical heterogeneity of the two AML entities under these induction settings. We retrospectively investigated the outcomes in adults with CBF AML induced with regimens based on standard-dose Ara-C at 100 to 200 mg/m² or intermediate-dose Ara-C at 1,000 mg/m². In total, 152 patients with t(8; 21) and 54 patients with inv(16) AML were administered an induction regimen containing anthracyclines plus either standard- or intermediate-dose Ara-C. After a single course of induction, the complete remission (CR) rate in the inv(16) cohort was 52/52 (100%), higher than the 127/147 (86.4%) in the t(8; 21) cohort (P = 0.005). Intermediate-dose Ara-C (HR = 9.931 [2.135-46.188], P = 0.003) and negative KITmut (HR = 0.304 [0.106-0.874], P = 0.027) independently produced an increased CR rate in the t(8; 21) cohort. Positive CD19 expression (HR = 0.133 [0.045-0.387], P = 0.000) and sex (male) (HR = 0.238 [0.085-0.667], P = 0.006) were associated with superior leukaemia-free survival (LFS) in the t(8; 21) cohort independently of KITmut status or the induction regimen. We conclude that intermediate-dose Ara-C is superior to standard-dose Ara-C for induction of remission in t(8; 21) AML, and CD19 status and sex independently confer prognostic significance for LFS. The KITmut status alone does not have an independent effect on survival in t(8; 21) AML. More intensive induction therapy is unnecessary in inv(16) AML.

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.

KIT D816 mutated/CBF-negative acute myeloid leukemia: a poor-risk subtype associated with systemic mastocytosis

KIT D816 mutations (KIT D816mut) are strongly associated with systemic mastocytosis (SM) but are also detectable in acute myeloid leukemia (AML), where they represent an adverse prognostic factor in combination with core binding factor (CBF) fusion genes. Here, we evaluated the clinical and molecular features of KIT D816mut/CBF-negative (CBFneg) AML, a previously uncharacterized combination. All KIT D816mut/CBFneg cases (n = 40) had histologically proven SM with associated AML (SM-AML). Molecular analyses revealed at least one additional somatic mutation (median, n = 3) beside KIT D816 (e.g., SRSF2, 38%; ASXL1, 31%; RUNX1, 34%) in 32/32 (100%) patients. Secondary AML evolved in 29/40 (73%) patients from SM ± associated myeloid neoplasm. Longitudinal molecular and cytogenetic analyses revealed the acquisition of new mutations and/or karyotype evolution in 15/16 (94%) patients at the time of SM-AML. Median overall survival (OS) was 5.4 months. A screen of two independent AML databases (AMLdatabases) revealed remarkable similarities between KIT D816mut/CBFneg SM-AML and KIT D816mut/CBFneg AMLdatabases (n = 69) with regard to KIT D816mut variant allele frequency, mutation profile, aberrant karyotype, and OS suggesting underlying SM in a significant proportion of AMLdatabases patients. Bone marrow histology and reclassification as SM-AML has important clinical implications regarding prognosis and potential inclusion of KIT inhibitors in treatment concepts.

The immunophenotypic characteristics and flow cytometric scoring system of acute myeloid leukemia with t(8;21) (q22;q22); RUNX1-RUNX1T1

INTRODUCTION

The translocation t(8;21) is one of the most frequent chromosome translocations in AML. Molecular (cyto)genetics is regarded as the gold standard for diagnosis. However, due to the complicated variety of AML-related genetic abnormalities, comprehensive screening for all of these abnormalities may not be cost-effective. Therefore, a flow cytometric (FC) scoring system was generated in this study for rapid screening and diagnosis of t(8;21)AML.

METHODS

The immunophenotypic characteristics of leukemic cells and neutrophils in cases with t(8;21) AML or other subtypes of AML were analyzed to find a method for the flow diagnosis of t(8;21) AML.

RESULTS

In this study, we picked six FC features pointing to the diagnosis of t(8;21) AML: The blasts show high-intensity expression of CD34; aberrant expression of CD19, cCD79a, and CD56 in myeloblasts; co-expression of CD56 in neutrophils, especially in immature neutrophils; and a maturity disturbance in granulocytes. A six-point score was devised using these features. By ROC analysis, the AUC was 0.952, and the sensitivity, specificity, PPV, and NPV were 0.86, 0.90. 0.91, and 0.84 when the score was ≥3 points. The score was then prospectively validated on an independent cohort, and the AUC of the ROC curve for the validation cohort was 0.975. When the cutoff value was set at 3, the obtained sensitivity and specificity values were 0.91 and 0.94, respectively.

CONCLUSIONS

The FC score described can be used for the identification and rapid screening of t(8;21) AML.

[Impact of KIT D816 mutation on salvage therapy in relapsed acute myeloid leukemia with t(8;21) translocation]

Objective: To evaluate the impact of KIT D816 mutation on the salvage therapy in relapsed acute myeloid leukemia (AML) with t(8;21) translocation. Method: The characteristics of the first relapsed AML with t(8;21) translocation from 10 hospitals were retrospectively collected, complete remission (CR(2)) rate after one course salvage chemotherapy and the relationship between KIT mutation and CR(2) rate was analyzed. Results: 68 cases were enrolled in this study, and 30 cases (44.1%) achieved CR(2). All patients received KIT mutation detection, and KIT D816 mutation was identified in 26 cases. The KIT D816 positive group had significantly lower CR(2) compared with non-KIT D816 group (23.1% vs 57.1%, χ(2)=7.559, P=0.006), and patients with longer CR(1) duration achieved significantly higher CR(2) than those with CR(1) duration less than 12 months (74.1% vs 31.9%, χ(2)=9.192, P=0.002). KIT D816 mutation was tightly related to shorter CR(1) duration. No significant difference of 2 years post relapse survival was observed between KIT D816 mutation and non-KIT D816 mutation group. Conclusion: KIT D816 mutation at diagnosis was an adverse factor on the salvage therapy in relapsed AML with t(8;21) translocation, significantly related to shorter CR1 duration, and can be used for prediction of salvage therapy response. KIT D816 mutation could guide the decision-making of salvage therapy in relapsed AML with t(8;21) translocation.

Monitoring of clonal evolution of double C-KIT exon 17 mutations by Droplet Digital PCR in patients with core-binding factor acute myeloid leukemia

C-KIT gene mutations result in the constitutive activation of tyrosine kinase activity, and greatly affect the pathogenesis and prognosis of core-binding factor acute myeloid leukemia (CBF-AML). C-KIT mutations are often found as single point mutations. However, the rate of double mutations has recently increased in AML patients. In this study, we detected six cases (18.8%) harboring double C-KIT exon17 mutations in 75 patients with CBF-AML. The clone composition and dynamic evolution were analyzed by sequencing and droplet digital PCR (ddPCR). Results revealed that these double mutations can be occurred in either the same or different clones. Different clones of double mutations may result in different sensitivity to the treatment of CBF-AML. The clones with N822 mutation responded better to treatment as compared to those with D816 mutation. Moreover, D816 clone was readily transformed into a predominant clone at relapse. Meanwhile, the predominant clones in the same patient may change during the progression of disease. The emerging mutation can originate from a small quantity of clones at diagnosis or newly acquired during the course of disease. Furthermore, patients with double mutations had better overall survival (OS) and event-free survival (EFS) than those with single mutation, but the differences did not reach statistical significance (P > 0.05). The ddPCR is an effective method for monitoring clonal evolution in patients with CBF-AML.

Mutation profiling of 19 candidate genes in acute myeloid leukemia suggests significance of DNMT3A mutations

We selected 19 significantly-mutated genes in AMLs, including FLT3, DNMT3A, NPM1, TET2, RUNX1, CEBPA, WT1, IDH1, IDH2, NRAS, ASXL1, SETD2, PTPN11, TP53, KIT, JAK2, KRAS, BRAF and CBL, and performed massively parallel sequencing for 114 patients with acute myeloid leukemias, mainly including those with normal karyotypes (CN-AML). More than 80% of patients had at least one mutation in the genes tested. DNMT3A mutation was significantly associated with adverse outcome in addition to conventional risk stratification such as the European LeukemiaNet (ELN) classification. We observed clinical usefulness of mutation testing on multiple target genes and the association with disease subgroups, clinical features and prognosis in AMLs.

D816 mutation of the KIT gene in core binding factor acute myeloid leukemia is associated with poorer prognosis than other KIT gene mutations

The clinical impact of KIT mutations in core binding factor acute myeloid leukemia (CBF-AML) is still unclear. In the present study, we analyzed the prognostic significance of each KIT mutation (D816, N822K, and other mutations) in Japanese patients with CBF-AML. We retrospectively analyzed 136 cases of CBF-AML that had gone into complete remission (CR). KIT mutations were found in 61 (45%) of the patients with CBF-AML. D816, N822K, D816 and N822K, and other mutations of the KIT gene were detected in 29 cases (21%), 20 cases (15%), 7 cases (5%), and 5 cases (4%), respectively. The rate of relapse-free survival (RFS) and overall survival (OS) in patients with D816 and with both D816 and N822K mutations was significantly lower than in patients with other or with no KIT mutations (RFS: p < 0.001, OS: p < 0.001). Moreover, stratified analysis of the chromosomal abnormalities t(8;21)(q22;q22) and inv(16)(p13.1q22), t(16;16)(p13.1;q22) showed that D816 mutation was associated with a significantly worse prognosis. In a further multivariate analysis of RFS and OS, D816 mutation was found to be an independent risk factor for significantly poorer prognosis. In the present study, we were able to establish that, of all KIT mutations, D816 mutation alone is an unfavorable prognostic factor.

The spleen microenvironment influences disease transformation in a mouse model of KITD816V-dependent myeloproliferative neoplasm

Activating mutations leading to ligand-independent signaling of the stem cell factor receptor KIT are associated with several hematopoietic malignancies. One of the most common alterations is the D816V mutation. In this study, we characterized mice, which conditionally express the humanized KIT^D816V receptor in the adult hematopoietic system to determine the pathological consequences of unrestrained KIT signaling during blood cell development. We found that KIT^D816V mutant animals acquired a myeloproliferative neoplasm similar to polycythemia vera, marked by a massive increase in red blood cells and severe splenomegaly caused by excessive extramedullary erythropoiesis. Moreover, we found mobilization of stem cells from bone marrow to the spleen. Splenectomy prior to KIT^D816V induction prevented expansion of red blood cells, but rapidly lead to a state of aplastic anemia and bone marrow fibrosis, reminiscent of post polycythemic myeloid metaplasia, the spent phase of polycythemia vera. Our results show that the extramedullary hematopoietic niche microenvironment significantly influences disease outcome in KIT^D816V mutant mice, turning this model a valuable tool for studying the interplay between functionally abnormal hematopoietic cells and their microenvironment during development of polycythemia vera-like disease and myelofibrosis.

Recurrent Cytogenetic Abnormalities in Acute Myeloid Leukemia

The spectrum of chromosomal abnormality associated with leukemogenesis of acute myeloid leukemia (AML) is broad and heterogeneous when compared to chronic myeloid leukemia and other myeloid neoplasms. Recurrent chromosomal translocations such as t(8;21), t(15;17), and inv(16) are frequently detected, but hundreds of other uncommon chromosomal aberrations from AML also exist. This chapter discusses 22 chromosomal abnormalities that are common structural, numerical aberrations, and other important but infrequent (less than 1 %) translocations emphasized in the WHO classification. Brief morphologic, cytogenetic, and clinical characteristics are summarized, so as to provide a concise reference to cancer cytogenetic laboratories. Morphology based on FAB classification is used together with the current WHO classification due to frequent mentioning in a vast number of reference literatures. Characteristic chromosomal aberrations of other myeloid neoplasms such as myelodysplastic syndrome and myeloproliferative neoplasm will be discussed in separate chapters-except for certain abnormalities such as t(9;22) in de novo AML. Gene mutations detected in normal karyotype AML by cutting edge next generation sequencing technology are also briefly mentioned.

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.

The genomic landscape of testicular germ cell tumours: from susceptibility to treatment

The genomic landscape of testicular germ cell tumour (TGCT) can be summarized using four overarching hypotheses. Firstly, TGCT risk is dominated by inherited genetic factors, which determine nearly half of all disease risk and are highly polygenic in nature. Secondly KIT-KITLG signalling is currently the major pathway that is implicated in TGCT formation, both as a predisposition risk factor and a somatic driver event. Results from genome-wide association studies have also consistently suggested that other closely related pathways involved in male germ cell development and sex determination are associated with TGCT risk. Thirdly, the method of disease formation is unique, with tumours universally stemming from a noninvasive precursor lesion, probably of fetal origin, which lies dormant through childhood into adolescence and then eventually begins malignant growth in early adulthood. Formation of a 12p isochromosome, a hallmark of TGCT observed in nearly all tumours, is likely to be a key triggering event for malignant transformation. Finally, TGCT have been shown to have a distinctive somatic mutational profile, with a low rate of point mutations contrasted with frequent large-scale chromosomal gains. These four hypotheses by no means constitute a complete model that explains TGCT tumorigenesis, but advances in genomic technologies have enabled considerable progress in describing and understanding the disease. Further advancing our understanding of the genomic basis of TGCT offers a clear opportunity for clinical benefit in terms of preventing invasive cancer arising in young men, decreasing the burden of chemotherapy-related survivorship issues and reducing mortality in the minority of patients who have treatment-refractory disease.

Significance of KIT exon 17 mutation depends on mutant level rather than positivity in core-binding factor acute myeloid leukemia

KIT exon 17 mutation is a poor prognostic factor in core-binding factor acute myeloid leukemia. However, the mutation detection method used for risk assessment is not assigned. It is necessary to verify the analytical and clinical performance before applying new methods. Herein, we firstly applied a highly sensitive allele-specific, real-time quantitative PCR (AS-qPCR) assay to analyze KIT mutations, which demonstrated excellent sensitivity and specificity. Much higher incidence of KIT mutations (62.2%, 69/111) and prevalence of multiple mutations (43.5%, 30/69) were observed using AS-qPCR, which meant the existence of multiple KIT mutant subclones. The relative KIT mutant level was variable (median, 0.3 per control allele 100 copies, 0.002–532.7) and was divided into two groups: high (⩾10, n=26) and low (<10) mutant level. Interestingly, rather than mutation positivity, mutant level was found to be associated with clinical outcome. High mutant level showed significantly inferior overall survival (P=0.005) and event-free survival (P=0.03), whereas low level did not influence the prognosis. The follow-up data showed that the mutant level were along with fusion transcripts in the majority (n=29), but moved separately in some cases, including the loss of mutations (n=5) and selective proliferation of minor clones (n=2) at relapse. This study highlighted that the KIT mutation should be analyzed using sensitive and quantitative techniques and set a cutoff level for identifying the risk group.

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.

Class III Receptor Tyrosine Kinases in Acute Leukemia - Biological Functions and Modern Laboratory Analysis

Acute myeloid leukemia (AML) is a complex disease caused by deregulation of multiple signaling pathways. Mutations in class III receptor tyrosine kinases (RTKs) have been implicated in alteration of cell signals concerning the growth and differentiation of leukemic cells. Point mutations, insertions, or deletions of RTKs as well as chromosomal translocations induce constitutive activation of the receptor, leading to uncontrolled proliferation of undifferentiated myeloid blasts. Aberrations can occur in all domains of RTKs causing either the ligand-independent activation or mimicking the activated conformation. The World Health Organization recommended including RTK mutations in the AML classification since their detection in routine laboratory diagnostics is a major factor for prognostic stratification of patients. Polymerase chain reaction (PCR)-based methods are well-validated for the detection of fms-related tyrosine kinase 3 (FLT3) mutations and can easily be applied for other RTKs. However, when methodological limitations are reached, accessory techniques can be applied. For a higher resolution and more quantitative approach compared to agarose gel electrophoresis, PCR fragments can be separated by capillary electrophoresis. Furthermore, high-resolution melting and denaturing high-pressure liquid chromatography are reliable presequencing screening methods that reduce the sample amount for Sanger sequencing. Because traditional DNA sequencing is time-consuming, next-generation sequencing (NGS) is an innovative modern possibility to analyze a high amount of samples simultaneously in a short period of time. At present, standardized procedures for NGS are not established, but when this barrier is resolved, it will provide a new platform for rapid and reliable laboratory diagnostic of RTK mutations in patients with AML. In this article, the biological and physiological role of RTK mutations in AML as well as possible laboratory methods for their detection will be reviewed.

Incidences and Prognostic Impact of c-KIT, WT1, CEBPA, and CBL Mutations, and Mutations Associated With Epigenetic Modification in Core Binding Factor Acute Myeloid Leukemia: A Multicenter Study in a Korean Population

BACKGROUND

To identify potential molecular prognostic markers in core binding factor (CBF) AML, we analyzed incidences and prognostic impacts of mutations in c-KIT, WT1, CEBPA, CBL, and a number of epigenetic genes in CBF AML.

METHODS

Seventy one and 21 AML patients with t(8;21) and inv(16) were enrolled in this study, respectively. NPM1, CEBPA, c-KIT, IDH1/2, DNMT3A, EZH2, WT1, and CBL mutations were analyzed by direct sequencing. Patients were categorized with respect to c-KIT and WT1 mutation status, and both clinical features and prognoses were compared.

RESULTS

The incidences of FLT3 internal tandem duplication (ITD), NPM1, CEBPA, IDH1/2, DNMT3A, EZH2, and CBL mutations were low (≤5%) in CBF AML patients. However, c-KIT and WT1 mutations occurred frequently (10.9% and 13.8%, respectively). t(8;21) patients with c-KIT mutations showed significantly shorter overall survival (OS) and disease free survival (DFS) periods than those without mutations (P<0.001, for both); however, although the limited number of t(8;21) patients were analyzed, WT1 mutation status did not affect prognosis significantly. Relapse or death during follow-up occurred more frequently in t(8;21) patients carrying c-KIT mutations than in those without the mutation, although the difference was significant only in a specific patient subgroup with no WT1 mutations (P=0.014).

CONCLUSIONS

The incidences of mutations in epigenetic genes are very low in CBF AML; however, c-KIT and WT1 mutations occur more frequently than others. The poor prognostic impact of c-KIT mutation in t(8;21) AML patients only applies in a specific patient subgroup without WT1 mutations. The prognostic impact of WT1 mutation in CBF AML is not evident and further investigation is required.

Novel R634W c-kit mutation identified in familial mastocytosis

Familial mastocytosis is a well-documented but rare entity, with fewer than 100 cases reported in the literature. The etiology has most commonly been linked to activating c-kit mutations, with several mutations reported to date. We present a novel familial mastocytosis-associated c-kit mutation (R634W) in three siblings with urticaria pigmentosa. This mutation has been previously described in mucosal melanoma, chronic myelomonocytic leukemia, and acute myeloid leukemia. Because this is a rare mutation, it is unclear whether screening for other disease states associated with the mutation would be of benefit.

The use of molecular genetics to refine prognosis in acute myeloid leukemia

The discovery and application of advanced molecular techniques, such as gene and microRNA expression profiling, whole genome and exome sequencing, proteomic analysis and methylation assays, have allowed for the identification of recurrent molecular abnormalities in acute myeloid leukemia (AML) that have revolutionized our understanding of the genetic landscape of the disease. These modalities have emerged as valuable tools that permit a more comprehensive and detailed molecular characterization of AML. Many of these molecular abnormalities have been shown to predict prognosis, particularly within the context of cytogenetically normal AML. This review will discuss the major techniques and platforms that have been used to identify novel recurrent gene mutations in AML and briefly describe how these discoveries have impacted on outcome prediction.