The clinical significance of FLT3 ITD mutation on the prognosis of adult acute promyelocytic leukemia

Favorable outcome of PML-RARα short isoform and FLT3-ITD mutation in a patient with several adverse prognostic markers: A case report

Key Clinical Message

Complete molecular remission in a "variant APL" patient with short isoform of PML-RARα and FLT3-ITD mutation was achieved in response to ATRA and ATO plus IDA instead of standard treatment protocol. The use of FLT3 inhibitor in APL induction management is implicated to prevent differentiation syndrome and coagulopathy experienced in in patients with FLT3-ITD.

Abstract

FLT3-ITD mutations are the most common activating mutations in FLT3 gene, occurring in about 12 to 38% of acute promyelocytic leukemia cases, and are mainly associated with high white blood cell counts and poor clinical outcomes. Here, we present a case of APL variant with adverse prognostic features who showed short isoform [bcr3] of PML-RARα and FLT3-ITD mutation at diagnosis. The patient received all-trans retinoic acid (ATRA) and arsenic trioxide (ATO) plus idarubicin (IDA) instead of standard treatment protocol, and achieved a complete morphological, cytogenetic and molecular response. However, the patient experienced differentiation syndrome, and coagulopathy that was subsequently resolved by continuous oxygen therapy, dexamethasone, and enoxaparin. The use of FLT3 inhibitor in APL induction management is implicated to prevent differentiation syndrome and coagulopathy in patients with FLT3-ITD mutation.

Association between FLT3-ITD and additional chromosomal abnormalities in the prognosis of acute promyelocytic leukemia

OBJECTIVES

Internal tandem duplications of the Fms-like tyrosine kinase 3 gene (FLT3-ITD) and additional chromosomal abnormalities (ACA) are prognostic factors in patients with acute promyelocytic leukemia (APL). This study aimed to determine the effect of the association between FLT3-ITD and ACA in the prognosis of APL.

METHODS

This was a retrospective cohort study including 60 patients with APL treated with all-trans retinoic acid (ATRA) and chemotherapy. Five-year overall survival (OS) and progression-free survival (PFS) were analyzed in patient groups according to the presence of FLT3-ITD and ACA.

RESULTS

FLT3-ITD was an independent adverse factor for 5-year PFS, and ACA was an independent adverse factor for 5-year OS. There were significant differences in OS and PFS among the groups: FLT3-ITD-negative without ACA, FLT3-ITD-positive without ACA, FLT3-ITD-negative with ACA, and FLT3-ITD-positive with ACA. The OS times were 52.917, 45.813, 25.375, and 23.417 months, and the PFS times were 48.833, 38.563, 23.250, and 17.333 months, respectively.

CONCLUSION

FLT3-ITD and ACA are associated with the poorest OS and PFS outcomes in patients with APL treated with chemotherapy plus ATRA.

'FLT3-ITD Mutation Does Not Influence Survival Outcome in Adult Acute Promyelocytic Leukemia Patients Treated With ATO and ATRA-Based Therapeutic Regimen: Experience From a North Indian Tertiary Care Centre'

INTRODUCTION

NPM1 and FLT3-ITD are frequently mutated genes in acute myeloid leukemia. We studied clinico-hematological profile and survival outcome of adult acute promyelocytic leukemia (APL) patients harboring these mutations.

MATERIALS AND METHODS

De novo APL cases (> 12 years), enrolled between January 2019 and June 2020, were evaluated for FLT3-ITD and NPM1 mutations (A, B, D mutations) by conventional and real-time qualitative PCR respectively.

RESULTS

FLT3-ITD mutation was detected in 12 of 36 (33.3%) de novo APLs cases while NPM1 mutation was not detected. FLT3-ITD was more frequently associated with Sanz high-risk category as compared to the intermediate-risk category (75% vs. 29%, P = .02), with BCR3 transcript type (P = .08) and higher median WBC count [22.7 × 10⁹/L)(range 1.3-184), P = .018]. One and half-years overall survival (OS) and event-free survival (EFS) were not significantly altered by the presence/absence of FLT3-ITD mutation (OS 86% vs. 70%, P = .32; EFS 86% vs. 70%, P = .33), between genders (OS, EFS both 89% in males vs. 69% in females, P = .15) and between adolescent and younger adults (AYA) (≤ 30 years) and older adult APL cases (> 30 years) (OS 86% vs. 78%, P = .55; EFS 85% vs. 77%, P = .55), however were significantly lower with BCR3 transcript as compared to BCR1 transcript (OS 56% vs. 91%, P = .019; EFS 56% vs. 91%, P = .016) in univariate analysis, although not in multivariate analysis. One and half-year OS and EFS was 57% (6/14, P = .009 for each) in high-risk APL.

CONCLUSION

FLT3-ITD mutation did not influence survival outcome in adult APL treated with ATO and ATRA-based therapeutic regimen.

Acute Promyelocytic Leukemia Presenting With a Myeloid Sarcoma of the Spine: A Case Report and Literature Review

Myeloid sarcoma is a rare extramedullary tumor of immature myeloid cells. Certain known acute myeloid leukemia cytogenetic abnormalities, in particular t(8,21), has been associated with a higher incidence. Myeloid sarcoma, which rarely happens in acute promyelocytic leukemias, is more common in recurrent patients after the advent of all-trans retinoic acid (ATRA) and are rare in untreated acute promyelocytic leukemia. We described a case of, to our knowledge, de novo myeloid sarcoma of the spine confirmed as acute promyelocytic leukemia. Myeloid sarcoma is diagnosed by spinal tumor biopsy, and microscopic examination of a bone marrow smear and cytogenetic analysis led to a confirmed diagnosis of acute promyelocytic leukemia.

All-trans Retinoic Acid, Arsenic Trioxide, and Anthracycline-based Chemotherapy Improves Outcome in Newly Diagnosed Acute Promyelocytic Leukemia Regardless of FLT3-ITD Mutation Status

All-trans retinoic acid (ATRA) and pre-upfront arsenic trioxide (ATO) have revolutionized the therapy of acute promyelocytic leukemia (APL). However, internal tandem duplication of FMS-like tyrosine kinase 3 (FLT3-ITD) mutations is associated with increased risk of relapse. The aim of this study was to analyze the prognostic impact of FLT3-ITD on APL patients who received remission induction with ATRA, idarubicin (IDA) and/or ATO, followed by ATRA plus ATO along with anthracycline, as consolidation therapy. A total of 72 patients newly diagnosed with APL were included in this study. 83.3% of the patients achieved complete remission (CR) after induction therapy. FLT3-ITD mutations were detected in 16 (22.2%) patients and closely related to bcr-3 PML-RARa transcript (P<0.001). The 5-year overall survival (OS) rate was 100% in both FLT3-ITD^positive and FLT3-ITD^negative groups, and there was no significant difference in 5-year event-free survival (EFS) between the two groups (78.3% vs. 83.3%, P=0.85). ATRA plus ATO and anthracycline-based chemotherapy achieved great outcome in newly diagnosed APL regardless of the FLT3-ITD mutation status.

Wu-5, a novel USP10 inhibitor, enhances crenolanib-induced FLT3-ITD-positive AML cell death via inhibiting FLT3 and AMPK pathways

The kinase FLT3 internal tandem duplication (FLT3-ITD) is related to poor clinical outcomes of acute myeloid leukemia (AML). FLT3 inhibitors have provided novel strategies for the treatment of FLT3-ITD-positive AML. But they are limited by rapid development of acquired resistance and refractory in monotherapy. Recent evidence shows that inducing the degradation of FLT3-mutated protein is an attractive strategy for the treatment of FLT3-ITD-positive AML, especially those with FLT3 inhibitor resistance. In this study we identified Wu-5 as a novel USP10 inhibitor inducing the degradation of FLT3-mutated protein. We showed that Wu-5 selectively inhibited the viability of FLT3 inhibitor-sensitive (MV4-11, Molm13) and -resistant (MV4-11R) FLT3-ITD-positive AML cells with IC₅₀ of 3.794, 5.056, and 8.386 μM, respectively. Wu-5 (1-10 μM) dose-dependently induced apoptosis of MV4-11, Molm13, and MV4-11R cells through the proteasome-mediated degradation of FLT3-ITD. We further demonstrated that Wu-5 directly interacted with and inactivated USP10, the deubiquitinase for FLT3-ITD in vitro (IC₅₀ value = 8.3 µM) and in FLT3-ITD-positive AML cells. Overexpression of USP10 abrogated Wu-5-induced FLT3-ITD degradation and cell death. Also, the combined treatment of Wu-5 and crenolanib produced synergistic cell death in FLT3-ITD-positive cells via the reduction of both FLT3 and AMPKα proteins. In support of this, AMPKα inhibitor compound C synergistically enhanced the anti-leukemia effect of crenolanib, while AMPKα activator metformin inhibited the anti-leukemia effect of crenolanib. In summary, we demonstrate that Wu-5, a novel USP10 inhibitor, can overcome FLT3 inhibitor resistance and synergistically enhance the anti-AML effect of crenolanib through targeting FLT3 and AMPKα pathway.

Potential Effects of the FLT3-ITD Mutation on Chemotherapy Response and Prognosis of Acute Promyelocytic Leukemia

PURPOSE

To evaluate the influence of FLT3-ITD mutations on the treatment response and long-term survival of newly-diagnosed patients with acute promyelocytic leukemia (APL) treated with all-trans retinoic acid and arsenic trioxide.

METHODS

The long-term survival of 90 newly-diagnosed APL patients (age range 12-75 years) was retrospectively analyzed.The FLT3-ITD mutation rate was assayed by polymerase chain reaction (PCR) amplification and sequencing analysis. Its impact on the treatment response, event-free survival(EFS), or overall survival(OS) was investigated in patients with and without the mutations.

RESULTS

The FLT3-ITD mutation rate in newly-diagnosed APL patients was 20% (18/90). The white blood cell (WBC) count at diagnosis in patients with mutations was significantly higher than that in patients without mutations while the FLT3-ITD mutation rate was higher in the high-risk group than in the low/intermediate-risk group. Patients with mutations had a significantly higher early death (ED) rate (16.67% vs 1.39%) for those lacking the mutation (P =0.024). However, the complete remission (CR) and differentiation syndrome (DS) rates in the two groups were similar. Kaplan Meier analysis for EFS and OS at five years showed a significant difference between the patients stratified by FLT3-ITD mutation status (log-rank P =0.010 and P =0.009, respectively).

CONCLUSION

FLT3-ITD mutations can be related to high peripheral WBC counts in APL patients. APL patients with mutations displayed a higher ED rate compared to those without mutations. Patients carrying mutations had reduced five-year EFS and OS rates. Thus, reducing the overall death rate during induction treatment might be an effective way to improve the prognosis of patients with FLT3-ITD mutations.

Classic and Variants APLs, as Viewed from a Therapy Response

Most acute promyelocytic leukemia (APL) are caused by PML-RARA, a translocation-driven fusion oncoprotein discovered three decades ago. Over the years, several other types of rare X-RARA fusions have been described, while recently, oncogenic fusion proteins involving other retinoic acid receptors (RARB or RARG) have been associated to very rare cases of acute promyelocytic leukemia. PML-RARA driven pathogenesis and the molecular basis for therapy response have been the focus of many studies, which have now converged into an integrated physio-pathological model. The latter is well supported by clinical and molecular studies on patients, making APL one of the rare hematological disorder cured by targeted therapies. Here we review recent data on APL-like diseases not driven by the PML-RARA fusion and discuss these in view of current understanding of "classic" APL pathogenesis and therapy response.

Outcomes of high-risk acute promyelocytic leukemia patients treated with arsenic trioxide (ATO)/all trans retinoic acid (ATRA) based induction and consolidation without maintenance phase: A case Series

Patients with high-risk acute promyelocytic leukemia (APL) have inferior outcomes compared with patients with low-risk APL, predominantly due to higher risk of early mortality related to hemorrhage. The majority of regimens contain prolonged maintenance, but the impact of this phase is not clear in the era of all trans retinoic acid (ATRA) and arsenic trioxide (ATO). We present a retrospective analysis of 10 patients that were treated for high risk APL based on the consolidation treatment phase of APL 0406 study without subsequent maintenance. With a median follow up of 38 months, all patients remain in remission.