Prevalence and prognostic significance of FLT3 gene mutations in patients with acute leukaemia: analysis of patients from the Shanghai Leukaemia Co-operative Group

Characteristics of Molecular Genetic Mutations and Their Correlation with Prognosis in Adolescent and Adult Patients with Acute Lymphoblastic Leukemia

INTRODUCTION

The prognosis of acute lymphoblastic leukemia (ALL) in adolescents and adults is poor, and recurrence is an important cause of their death. Changes of genetic information play a vital role in the pathogenesis and recurrence of ALL; however, the impact of molecular genetic mutations on disease diagnosis and prognosis remains unexplored. This study aimed to explore the frequency spectrum of gene mutations and their prognostic significance, along with the minimal residual disease (MRD) level and hematopoietic stem cell transplantation (HSCT), in adolescent and adult patients aged ≥15 years with ALL.

METHODS

The basic characteristics, cytogenetics, molecular genetics, MRD level, treatment regimen, and survival outcome of patients with untreated ALL (≥15 years) were collected, and the correlation and survival analysis were performed using the SPSS 25.0 and R software.

RESULTS

This study included 404 patients, of which 147 were selected for next-generation sequencing (NGS). NGS results revealed that 91.2% of the patients had at least one mutation, and 67.35% had multiple (≥2) mutations. NOTCH1, PHF6, RUNX1, PTEN, JAK3, TET2, and JAK1 were the most common mutations in T-ALL, whereas FAT1, TET2, NARS, KMT2D, FLT3, and RELN were the most common mutations in B-ALL. Correlation analysis revealed the mutation patterns, which were significantly different between T-ALL and B-ALL. In the prognostic analysis of 107 patients with B-ALL, multivariate analysis showed that the number of mutations ≥5 was an independent risk factor for overall survival and the RELN mutation was an independent poor prognostic factor for event-free survival.

DISCUSSION

The distribution of gene mutations and the co-occurrence and repulsion of mutant genes in patients with ALL were closely related to the immunophenotype of the patients. The number of mutations ≥5 and the RELN mutation were significantly associated with poor prognosis in adolescent and adult patients with ALL.

Small Molecule Induced FLT3 Degradation

Target protein degrader is a new paradigm in the small molecule drug discovery field and relates to the term ‘event-driven pharmacology’. Fms-like tyrosine kinase 3 (FLT3) is a significant target for treating acute myeloid leukemia (AML). A few FLT3 kinase inhibitors are currently used in the clinic for AML patients. However, resistance to current FLT3 inhibitors has emerged, and strategies to overcome this resistance are required. Small molecules downregulating FLT3 protein level are reported, exhibiting antileukemic effects against AML cell lines. Small molecules with various mechanisms such as Hsp90 inhibition, proteasome inhibition, RET inhibition, and USP10 inhibition are explained. In addition, reports of FLT3 as a client of Hsp90, current knowledge of the ubiquitin proteasome system for FLT3 degradation, the relationship with FLT3 phosphorylation status and susceptibility of FLT3 degradation are discussed.

Discovery of small molecule FLT3 inhibitors that are able to overcome drug-resistant mutations

Herein we report the discovery of 1-(5-(tert-butyl)isoxazol-3-yl)-3- (3-fluorophenyl)urea derivatives as new FLT3 inhibitors that are able to overcome the drug resistance mutations: the secondary D835Y and F691L mutations on the basis of the internal tandem duplications (ITD) mutation of FLT3 (FLT3-ITD/D835Y and FLT3-ITD/F691L, respectively). The most potent compound corresponds to 1-(5-(tert-butyl)isoxazol-3-yl)-3-(4-((6,7-dimethoxyquinolin-4-yl)oxy)-3- fluorophenyl)urea (4d), which showed IC₅₀s (half maximal inhibitory concentrations) of 0.072 nM, 5.86 nM and 3.48 nM against FLT3-ITD, FLT3-ITD/F691L and FLT3-ITD/D835Y, respectively. Compound 4d also showed good selectivity for FLT3 in a kinase profiling assay. Collectively, 4d could be a good lead compound and deserves further in-depth studies.

Combined Expression of CD34 and FLT3-Internal Tandem Duplication Mutation Predicts Poor Response to Treatment in Acute Myeloid Leukemia

Background

Acute myeloid leukemia (AML) is a common hematological malignancy associated with different cytogenetic and genetic abnormalities.

Methods

FLT3-internal tandem duplication (FLT3/ITD) mutation and CD34 expression levels were assessed in the bone marrow (BM) aspirates of 153 de novo AML patients. Data were correlated with relevant clinic-pathological features of the patients, response to treatment, disease-free survival (DFS), and overall free survival (OS) rates.

Results

FLT3-ITD mutation was detected in 27/153 (17.6%) AML patients (P=0.001), and CD34 was expressed in 83/153 (54.2%) patients (P=0.293) compared to those with wild FLT3 and CD34⁻ expression, respectively. Patients with FLT3-ITD mutation showed increased peripheral blood and BM blast cells, abnormal cytogenetics, poor DFS and OS compared to those with wild FLT3 (P=0.013, P<0.001, P=0.010, P=0.008 and P=0.004, respectively), while there was no significant association with response to treatment (P=0.081). There was no significant association between CD34 expression and response to treatment, DFS, and OS (P>0.05). FLT3-ITD mutation and FAB subtypes were independent prognostic factors for DFS. Older age ≥39 years, HB <7 mg/dL PB blast ≥54%, and FLT3-ITD mutation were independent prognostic factors for poor OS in AML patients. The presence of both FLT3-ITD mutation and CD34 expression associated significantly with resistance to therapy (P=0.024), short DFS and OS rates (P=0.006, P=0.037, respectively).

Conclusion

Combined expression of both FLT3-ITD mutation and CD34 expression is an important prognostic and predictive factor for poor disease outcome in AML patients.

Significance of FLT3-tyrosine kinase domain mutation as a prognostic factor for acute myeloid leukemia

The prognostic significance of FLT3-tyrosine kinase domain (TKD) mutations remains unknown. To investigate the prognostic impact of FLT3-TKD, 676 de novo acute myeloid leukemia (AML), we retrospectively analyzed cases and conducted a review of the literature. Of the 676 de novo AML cases, 34 (5.0%) were FLT3-TKD-positive; both FLT3-TKD and FLT3-ITD were noted in only two cases (0.3%). Although no significant differences in relapse-free survival (RFS) were noted, FLT3-TKD-positive cases showed better prognoses than FLT3-ITD-positive cases (FLT3-TKD versus FLT3-ITD, p = 0.152). For overall survival (OS), although FLT3-TKD-positive cases showed prognoses similar to those for FLT3-WT cases, their prognoses were significantly better than those of FLT3-ITD-positive cases (FLT3-TKD versus FLT3-ITD, p = 0.032). Moreover, the 5-year OS for FLT3-TKD-positive cases was 46.1%, indicating that this as an intermediate prognosis group. Although no reports from Asia have indicated a frequency of FLT3-TKD-positive cases > 10%, several reports from Europe and the United States have indicated frequencies > 10%. This suggests the possibility that FLT3-TKD-positive cases are less common in Asia than in Europe and the United States. We anticipate that in the future, the appearance of targeting agents, such as FLT3 inhibitors, will improve the prognosis of FLT3-TKD-positive AML relative to that of FLT3-WT AML.

How Precision Medicine Is Changing Acute Myeloid Leukemia Therapy

Pretreatment somatic mutations influence acute myeloid leukemia (AML) pathogenesis and responses to chemotherapy. Integration of cytogenetic abnormalities and molecular mutations, co-occurring and in isolation, have resulted in a more refined prognostic assessment. In addition, research performed over the last few years has led to the development of novel therapies and new drug approvals in patients with both newly diagnosed and relapsed/refractory (R/R) AML. Here we discuss the use of these newly approved therapies. Advances in AML have also occurred through development of better tools to assess response to treatment. Both multiparameter flow cytometry and polymerase chain reaction can be used to assess for the presence or absence of measurable residual disease (MRD) and increase the sensitivity of response assessment. The role of MRD assessment is gaining relevance and its integration in clinical trials and treatment decision making will be explored in the second half of this article.

DNMT3A (R882) mutation features and prognostic effect in acute myeloid leukemia in Coexistent with NPM1 and FLT3 mutations

OBJECTIVE/BACKGROUND

In the absence of high-risk cytogenetic, DNMT3A (DNA Methyltransferase 3a) mutation status has an impact on outcome in the presence of FLT3 (FMS-like Tyrosine Kinase3) and/or NPM1 (Nucleophosmin). In this study, we focus on the features and effect of DNMT3A (R882) mutation in acute myeloid leukemia (AML) in the presence or absence of NPM1 and FLT3 mutations.

METHODS

A total of 174 cytogenetically normal (CN)-AML cases were analyzed for NPM1, FLT3, and DNMT3A mutations. For NPM1 mutation detection, we used the pyrosequencing technique; for FLT3 mutations, polymerase chain reaction and RFLP with ECO-RV techniques were used, and for DNMT3A mutation analysis, we used Sanger sequencing and RFLP (Restriction Fragment Length Polymorphism) techniques.

RESULTS

NPM1 mutation was found in 40.80%, DNMT3A in 12.06%, and FLT3 mutation was found in 16.66% of 174 CN-AML patients. We also found seven cases which were (NPM1+, FLT3+), 10 cases which were (NPM1+, DNMT3A+), and two cases were found positive for (DNMT3A+, FLT3+) mutations. Adult patients had significantly higher frequency of NPM1 mutation than children (72.22% vs. 16.66%; p = .020), whereas FLT3/ITD and DNMT3A mutation was associated with higher white blood count (p = .081). Immunophenotypically, NPM1 and DNMT3A mutations were significantly associated with the lack of CD34, whereas FLT3/ITD mutation was positively associated with the expression of CD7. We also assessed the overall survival and progression-free survival of DNMT3A mutation status among patients with CN-AML. Indeed, DNMT3A mutations within the CN-AML subset were associated with significantly shorter overall survival and progression-free survival compared to NPM1 and FLT3 mutated patients (p = .067 and p = .065, respectively).

CONCLUSION

DNMT3A R882 mutation plays an important role in CN-AML patients' prognosis and clinical outcomes in the presence and absence of NPM1 and FLT3 mutations.

Prevalence and Clinical Significance of FLT3 and NPM1 Mutations in Acute Myeloid Leukaemia Patients of Assam, India

Acute Myeloid Leukaemia (AML) is one of the common forms of haematological malignancy in adults. We analysed the prevalence and clinical significance of FMS-like tyrosine kinase 3 (FLT3) and Nucleophosmin 1 (NPM1) mutations in AML patients of North East India. Co-prevalence and clinical significance of three recurrent chromosomal translocations namely t(15; 17), t(8; 21), t(16; 16) and expression of epidermal growth factor receptor (EGFR), flow markers were also documented and co-related with disease progress. We analysed bone marrow aspirates or peripheral blood samples from 165 newly diagnosed AML patients. All clinical samples were analysed by Real Time PCR and DNA sequencing based assays. NPM1 was the most frequently detected mutation in the study population (46/165 = 27.90%, 95% CI 20.75-35.05). FLT3 mutations were detected in 27/165 (16.40%, 95% CI 10.45-22.35) patients with internal tandem duplication (FLT3-ITD) in 24/165 (14.60%, 95% CI 8.91-20.29) and FLT3-D835 in 3/165 (1.80%, 95% CI 0-4.13) patients. NPM1 mutations were associated with a higher complete remission rate and longer overall survival (P < 0.01) compared to FLT3-ITD whereas FLT3-ITD showed adverse impact with poor survival rate (P < 0.01), leukocytosis (P < 0.01) and a packed bone marrow. EGFR expression was more in patients with NPM1 mutation compared to FLT3 mutation (P = 0.09). Patients with FLT3 and NPM1 mutations uniformly expressed CD13 and CD33 whereas CD34 was associated with poor prognosis (P ≤ 0.01) in patients with NPM1 mutation. FLT3-ITD was associated with inferior overall survival. However the clinical significance of FLT3-D835 was not clear due to small number of samples. NPM1 mutation showed better prognosis with increased response to treatment in the absence of FLT3-ITD.

11q23 abnormalities in adult Chinese patients with hematological malignancies

The mixed lineage leukemia (MLL) gene on chromosome region 11q23 is frequently involved in chromosomal translocations associated with various human hematologic malignant neoplasms. The aim of this study was to investigate the profile of 11q23 abnormalities in adult Chinese patients with hematological malignancies. In this study, 11q23 abnormalities were detected by cytogenetic and fluorescence in situ hybridization (FISH) approaches in 77 out of a total of 2,404 adult Chinese patients with leukemia, lymphoma, and myelodysplastic syndrome (MDS). 11q23 abnormalities were found in 5.31 % of the acute myeloid leukemia (AML) cases, 5.71 % of the acute lymphoid leukemia (ALL) cases, 2.94 % of lymphoma cases, and 1.24 % of MDS cases. Of the patients with 11q23 abnormalities, 59.74 % showed rearrangement or deletion of the MLL gene by FISH; a novel 11q23 rearrangement, der(6)t(6;11)(q23;q23), was discovered in one case. Our data showed that t(11;19)(q23;p13.1) was the most frequent translocation in AML patients and t(4;11)(q21;q23) was the most frequent translocation in ALL patients. FLT-ITD mutations were detected in three out of 33 AML patients with 11q23 abnormalities (9.09 %). The Kaplan-Meier survival analysis further showed that the 11q23 aberration was a poor prognostic factor for AML. The median survival times in the 11q23 aberration subgroup, the normal karyotype subgroup, and the subgroup with other abnormalities were 7.4, 11.3, and 16.8 months, respectively (P = 0.0464). Our study found one novel 11q23 rearrangement, der(6)t(6;11)(q23;q23), and demonstrated the profile of 11q23 abnormalities in adult Chinese patients with hematological malignancies.

FLT3 Internal Tandem Duplication and D835 Mutations in Patients with Acute Lymphoblastic Leukemia and its Clinical Significance

The fms-like tyrosine kinase 3 (FLT3) gene is a member of the class III receptor tyrosine kinase family. Mutations of FLT3 were first described in 1997 and account for the most frequent molecular mutations in acute myeloid leukemia.

Currently, there is no published data on FLT3 mutations in Saudi acute lymphoblastic leukemia (ALL) patients.

In this retrospective study, we have examined a cohort of 77 ALL patients to determine the prevalence of FLT3 mutations and the possible prognostic relevance of these mutations in ALL patients. Correlations to other biologic factors such as karyotype, molecular mutations, and leukocyte count were also considered.

FLT3 internal tandem duplication (ITD) mutations and point mutation in tyrosine kinase domain (D835) were analyzed in ALL patients, at diagnosis, by polymerase chain reaction (PCR).

Two cases (2.6%, 2/77) were positive for FLT3 mutations; one was found to have FLT3/ITD and the other FLT3/D835.

Our findings suggest that FLT3 mutations are not common in Saudi ALL and do not affect clinical outcome.

Treatment with FLT3 inhibitor in patients with FLT3-mutated acute myeloid leukemia is associated with development of secondary FLT3-tyrosine kinase domain mutations

BACKGROUND

FLT3-internal tandem duplication (ITD) mutations are found in approximately 30% of patients with acute myeloid leukemia (AML). FLT3 inhibitors have shown clinical activity in AML with FLT3-ITD, but responses are usually short-lived.

METHODS

This study examined 69 FLT3-mutated patients with AML, who were treated with different FLT3 inhibitors to analyze emergence of new mutations.

RESULTS

At baseline, 87% of patients had an ITD mutation, 7% had a D835/I836 mutation, and 6% had combined ITD and D835/I836 mutations. Responses occurred in 32% of patients, all with FLT3-ITD; none of the patients with D835/I836 or ITD+D835/I836 responded. Mutational assessment at the time of FLT3 inhibitor discontinuation showed that 68% of patients were unchanged, 10% had become undetectable, and 22% of patients progressed from a single ITD to have combined ITD+D835/I836 mutations. In those patients with unchanged FLT3 mutation at progression, the median survival was 5 months, whereas in those with undetectable and with combined ITD+D835/I836 mutations, the median survival was 7 months, respectively.

CONCLUSIONS

These data confirm in vitro observations that a secondary tyrosine kinase domain mutation may arise after the use of FLT3 inhibitors in patients with single FLT3-ITD mutated AML, a phenomenon that is associated with resistance and a poor prognosis.

FLT3 inhibitors for acute myeloid leukemia: a review of their efficacy and mechanisms of resistance

Since the Food and Drug Administration approval of imatinib for treatment of chronic myeloid leukemia in 2001, tyrosine kinase inhibitors (TKIs) have become a mainstay in the care of many malignancies. In acute myeloid leukemia (AML), activating mutations in the FMS-like tyrosine kinase 3 (FLT3) gene result in survival and proliferation of leukemic blasts and are associated with adverse prognosis. Therefore, the FLT3 receptor is an appealing target for inhibition. Multiple small molecule TKIs are currently in development for FLT3-mutated AML, and agents are beginning to show promising efficacy. In other malignancies, the development of resistance to TKIs during the course of therapy has proven to be a challenge, and thus far, in clinical trials of FLT3 TKIs, resistance to inhibition represents a significant barrier to successful FLT3 inhibition. Understanding the mechanisms of resistance and overcoming these obstacles to target inhibition will be central to the success of these agents.