Treatment Of Adult Acute Myeloid Leukemia Research Articles

Recent advances in AML with mutated NPM1.

Nucleophosmin 1 (NPM1) mutation is one of the most prevalent genetic mutations in adult acute myeloid leukemia (AML) and is particularly predominant in AML with a normal karyotype. NPM1 is a chaperone protein that plays various roles in several cellular processes. Wild-type NPM1 is normally localized to the nucleus, whereas mutant NPM1 proteins exhibit altered cytoplasmic localization. Clinically, AML with mutated NPM1 without FLT3-ITD is associated with a higher complete remission rate and improved overall survival. AML with mutated NPM1 is categorized as a distinct genetic entity in the World Health Organization classification of hematopoietic malignancies due to its unique clinical and biological features. However, the precise roles of NPM1 in normal hematopoiesis and in AML development remain unclear. Recent studies have revealed various clinical applications of NPM1 mutations in AML treatment, particularly in measurable residual disease analyses that target mutant NPM1 transcripts and in potential therapeutic applications of menin inhibitors and XPO-1 inhibitors for AML with mutated NPM1. Thus, NPM1 mutation is highly significant in AML classification, prognosis, response assessment, and molecular targeted therapies. Here, we review recent progress in clinical and biological aspects of AML with mutated NPM1 including molecular targeted therapy.

Inhibition of NRF2 enhances the acute myeloid leukemia cell death induced by venetoclax via the ferroptosis pathway

Venetoclax, an inhibitor that selectively targets B cell lymphoma-2 (BCL-2) that has been approved for treating adult acute myeloid leukemia (AML) in combination with hypomethylating agents. However, its short duration of response and emergence of resistance are significant issues. In this study, we found that the sensitivity of AML cells to venetoclax was considerably enhanced by ML385, an inhibitor of the ferroptosis factor nuclear transcription factor erythroid 2-related factor 2 (NRF2). Using AML samples, we verified that NRF2 and its target gene ferritin heavy chain 1 (FTH1) were highly expressed in patients with AML and correlated with poor prognosis. Downregulation of NRF2 could inhibit FTH1 expression and significantly enhance the venetoclax-induced labile iron pool and lipid peroxidation. By contrast, NRF2 overexpression or administration of the reactive oxygen species inhibitor N-acetylcysteine and vitamin E could effectively suppress the anti-AML effects of ML385+venetoclax. Furthermore, the ferroptosis inducer erastin increased the anti-AML effects of venetoclax. Our study demonstrated that NRF2 inhibition could enhance the AML cell death induced by venetoclax via the ferroptosis pathway. Thus, the combination of ML385 with venetoclax may offer a favorable strategy for AML treatment.

Frontline Aspacytarabine with Venetoclax for Older/Unfit Patients with Acute Myeloid Leukemia: Preliminary Results of a Phase 1 Study

Introduction: Venetoclax (VEN), a selective BCL2 inhibitor, in combination with hypomethylating agents (HMA) or low-dose cytarabine is currently the standard of care for first line treatment of older/unfit patients with acute myeloid leukemia (AML). This, however, requires indefinite cycles of treatment and results in prolonged cytopenias. Aspacytarabine (ASPA, formerly BST-236), a novel pyrimidine antagonist, is a cytarabine prodrug designed to enable high cytarabine dose treatment with reduced systemic toxicity, that was previously proven safe and effective for the treatment of AML in adults unfit for intensive chemotherapy. Given excellent outcomes with intensive chemotherapy with VEN, we hypothesized that higher cytarabine dose using ASPA and VEN followed by a limited consolidation with ASPA may provide superior outcomes than the current standard. Aims: To assess the safety and efficacy of VEN plus ASPA induction treatment regimen in older/unfit AML patients followed by limited consolidation course(s) with ASPA alone. Methods: A phase I/II dose escalation and expansion study using 1 or 2 induction courses with intravenous (IV) ASPA 2.3 or 4.5 g/m 2 daily for 6 consecutive days plus VEN at a dose of 200 mg or 400 mg for 7 days without azole antifungals. Followed by up to 3 consolidation courses with single agent ASPA 2.3/4.5 g/m 2/day for 6 days, in patients with newly diagnosed AML unfit for intensive chemotherapy. Patients with secondary AML are allowed. MRD was evaluated centrally by flow cytometry at Dr. Wood's laboratory, with a sensitivity of 0.1%. Results: Two cohorts are completed with 7 patients enrolled. Table 1 details the cohort treatment. Baseline characteristics and outcome are provided in Table 2. To date, the combination is well-tolerated. As expected, all patients had cytopenia (16% grade 4, and 84% grade 3 and lower), following the induction treatment and non-hematological grade ≥3 reported in more than 1 patient were pneumonia and sepsis both reported in 2 patients). One death occurred in cohort 1: an 80 year-old patient with a cardiac medical history died at home on day 27 of induction, prior to bone marrow analysis, but with full count recovery; death was deemed unrelated to study treatment. One 79-year-old patient from cohort 2 discontinued the study following the 1 st consolidation, while in CR MRD-, due to prolonged laryngitis. In the first, cohort, 1 patient attained a CR MRD- after 1 induction course, and this response is still maintained 6 months from study entry (after 3 consolidation courses of ASPA monotherapy). In the second cohort, all 3 patients' disease entered a CR after 1 course of ASPA and VEN Two achieved CR MRD-, and the 3 rd patient is currently receiving a second induction course, as per protocol. All responding patients had a full count recovery within 35 days and disease continues to be in CR. Conclusions: The combination induction regimen of ASPA and VEN followed by consolidation with ASPA alone, is a promising therapy. The regimen is tolerable, and all patients in cohort 2 have attained a CR with 2/3 MRDneg and the third with treatment ongoing. This treatment may overcome the limitations of prolonged cytopenia and indefinite therapy with HMA/VEN along with a high CR rate. This study is ongoing, and updates will be provided at the conference.

Venetoclax Combined with Homoharringtonine and Cytarabine ( HAV) As Induction Treatment in Elder or Intensive Chemotherapy (IC) Ineligible Patients with Newly Diagnosed Acute Myeloid Leukemia

INTRODUCTION In recent years, venetolax (Ven)-based combination therapy has significantly improved the efficacy of patients with newly diagnosed acute myeloid leukemia (AML). In CAVEAT trial (VEN+IA), both 200mg and 400mg Ven combining with IA 2+5 achieved promising results. Homoharringtonine (HHT, omacetaxine mepesuccinate) is an alkaloid derived from trees of the genus Cephalotaxus. HHT combined with Ara-C (HA) based regimens as induction regimen have been used broadly in new diagnosed AML patients in China. Previous reports shown that HHT could inhibit the anti-apoptotic protein MCL-1, BCL-XL and may exert a synergistic effect when combining with Ven. Therefore, we designed the VEN combining HA (HAV) as induction regimen in newly diagnosed AML patients. We retrospectively collected and analyzed the clinical data of HAV as induction treatment in thirty-threeelder or intensive chemotherapy ineligible patients with newly diagnosed AML. The purpose of this study was to evaluate the efficacy and safety of the regimen. METHODS Retrospectively collected and analyzed the clinical data of thirty-three patients treated with Ven+HA as induction therapy between July 2020 and April 2023. The induction regimen consisted of oral Ven (100mg Day 0; 200mg Day 1-14), intravenous HHT (2 mg/m², days 3-9), and cytarabine (50 mg/m 2, days 3-9). After achieving CR or CRi, allogeneic hematopoietic stem-cell transplantation (Allo-HSCT) were recommended according to ELN guideline and Chinese guidelines for the diagnosis and treatment of adult AML. Patients who are ineligible to allo-HSCT received consolidation and maintenance therapy. The consolidation therapy included two cycles of Ven combining with intermediate-dose Ara-C (Ven 400 mg on Days 1-7, Ara-C 1 g/m 2/q12 h Days 2-4, or Ara-C 0.5g/m 2/q12h Days in the patient older than 65 years ), one cycles DA (DNR 45 mg/m², Days 1-2 and Ara-C 100 mg/m², Days 1-5) chemotherapy and two cycle HA (HHT 2 mg/m², Days 1-5 and Ara-C 100 mg/m², Days 1-5). Patient (intermediate and adverse risk) who remained in CR after consolidation therapy received maintenance therapy. The maintenance treatment adopted AZA (100 mg/d, Days 1-5) every month for at least four cycles. The primary purpose was evaluated the efficacy and safety of HAV regimen in elder or intensive chemotherapy ineligible patients with de novo AML. Secondary purpose was overall survival (OS), event-free survival (EFS), disease-free survival (DFS). RESULTS Until April 2023, thirty-three patients with de novo AML were treated with HAV as induction therapy. Baseline characteristics of the 33 patients are shown in table 1. The ORR (CR+PR) after one cycle of induction was 90.9% (95% CI, 80.6-100%)with CR rate of 87.9% (95% CI, 76.1-99.6%). Moreover, 79.3% (23/29) of the CR patients were MRD undetectable (95% CI 63.6-95.0%). Grade 3 or worse adverse effects included neutropenia (100%), thrombocytopenia (100%), febrile neutropenia (100%). None of patients died during the induction therapy. The median neutrophil and platelet recovery times were 10 (range: 5-15) and 10 (range: 3-17) days, respectively. Until June 30, 2023, with a median follow-up of 10 (2-23) months, 5 patients proceed allo-HSCT, the estimated 12-month OS, EFS, and DFS rates were 83.0% (95% CI: 73.4-92.6%), 71.3% (95% CI: 60.0-82.6%), and 75.9% (95% CI: 64.4-87.4%), respectively. (Figure 1) Conclusion: HAV is a highly effective and safe induction therapy for elderly or IC ineligible newly diagnosed AML. 【Keywords】Venetoclax; HAV; AML; induction treatment; elder ; ineligible

Clinical characteristics and prognosis analysis of patients with de novo ASXL1-mutated AML treated with the C-HUNAN-AML-15 protocol: A multicenter study by the South China Pediatric AML Collaborative Group.

ASXL1 mutation is an independent prognostic factor in adult acute myeloid leukemia (AML), but its effect on the prognosis of pediatric AML is poorly understood. This study aimed to investigate the clinical characteristics and prognostic factors of ASXL1-mutant pediatric AML from a large Chinese multicenter cohort. A total of 584 pediatric patients with newly diagnosed AML from 10 centers in South China were enrolled. The exon 13 of ASXL1 was amplified by polymerase chain reaction (PCR), and then analyzed the mutation status of the locus. (n = 59 for ASXL1-mut group, n = 487 for ASXL1-wt group). ASXL1 mutations were found in 10.81% of all patients with AML. A complex karyotype was significantly less common in the ASXL1-mut AML group than in the ASXL1-wt group (1.7% vs. 11.9%, p = 0.013). Furthermore, TET2 or TP53 mutations were predominantly found in the ASXL1+ group (p = 0.003 and 0.023, respectively). The 5-year overall survival (OS) and event-free survival (EFS) of the total cohort were 76.9% and 69.9%. In ASXL1-mut AML patients, a white blood cell (WBC) count ≥50 × 109 /L had significantly poorer 5-year OS and EFS than a WBC count <50 × 109 /L (78.0% vs. 44.6%, p = 0.001; 74.8% vs. 44.6%, p = 0.003, respectively), while receiving hematopoietic stem cell transplantation (HSCT) had a higher 5-year OS and EFS (84.5% vs. 48.5%, p = 0.024; 79.5% vs. 49.3%, p = 0.047, respectively). In the multivariate Cox regression analysis, patients with high-risk AML undergoing HSCT tended to have a better 5-year OS and EFS than those receiving chemotherapy as a consolidation (HR = 0.168 and 0.260, both p < 0.001), and WBC count ≥50 × 109 /L or failure to achieve complete response after the first course were independent adverse predictors of OS and EFS (HR = 1.784 and 1.870, p = 0.042 and 0.018; HR = 3.242 and 3.235, both p < 0.001). The C-HUANA-AML-15 protocol is a well-tolerated and effective in the treatment of pediatric AML. ASXL1 mutation is not an independent adverse prognosis predictor for survival in AML, whereas ASXL1-mut patients tend to have a poor prognosis if WBC count ≥50 × 109 /L, but they can benefit from HSCT.

Adherence to guidelines on nutrition support during intensive treatment of acute myeloid leukemia patients: A nationwide comparison

Rationale: The level of adherence to the updated guidelines of The European Societies for Clinical Nutrition and Metabolism (ESPEN) and for Blood and Marrow Transplantation (EBMT) on nutrition in intensively treated adult acute myeloid leukemia (AML) patients in clinical practice is unknown. The aim of this nationwide survey was to investigate ESPEN/EBMT nutritional guideline adherence during intensive AML treatment, variation in nutrition support practices among hospitals and whether these practices changed after guideline publication.

IDH1/2 mutations in acute myeloid leukemia patients and risk of coronary artery disease and cardiac dysfunction\u2014a retrospective propensity score analysis

Clonal hematopoiesis of indeterminate potential (CHIP) is linked to leukemia gene mutations and associates with an increased risk for coronary artery disease and poor prognosis in ischemic cardiomyopathy. Two recurrently mutated genes in CHIP and adult acute myeloid leukemia (AML) encode for isocitrate dehydrogenases 1 and 2 (IDH1 and IDH2). Global expression of mutant IDH2 in transgenic mice-induced dilated cardiomyopathy and muscular dystrophy. In this retrospective observational study, we investigated whether mutant IDH1/2 predisposes to cardiovascular disease in AML patients. Among 363 AML patients, IDH1 and IDH2 mutations were detected in 26 (7.2%) and 39 patients (10.7%), respectively. Mutant IDH1 patients exhibited a significantly higher prevalence of coronary artery disease (26.1% vs. 6.4%, p = 0.002). Applying inverse probability-weighting analysis, patients with IDH1/2 mutations had a higher risk for a declining cardiac function during AML treatment compared to IDH1/2 wild type patients [left ventricular ejection fraction pretreatment compared to 10 months after diagnosis: 59.2% to 41.9% (p < 0.001) vs 58.5% to 55.4% (p = 0.27), respectively]. Mechanistically, RNA sequencing and immunostaining in hiPS-derived cardiomyocytes indicated that the oncometabolite R-2HG exacerbated doxorubicin mediated cardiotoxicity. Evaluation of IDH1/2 mutation status may therefore help identifying AML patients at risk for cardiovascular complications during cytotoxic treatment.

Adherence to guidelines on nutrition support during intensive treatment of acute myeloid leukemia patients: A nationwide comparison

The level of adherence to the updated guidelines of The European Societies for Clinical Nutrition and Metabolism (ESPEN) and for Blood and Marrow Transplantation (EBMT) on nutrition in intensively treated adult acute myeloid leukemia (AML) patients in clinical practice is unknown. The aim of this nationwide survey was to investigate ESPEN/EBMT nutritional guideline adherence during intensive AML treatment, variation in nutrition support practices among hospitals and whether these practices changed after guideline publication. All 22 Dutch hospitals providing (aftercare following) high-dose chemotherapy and/or hematopoietic stem cell transplantation for adult AML patients were surveyed on nutrition support practices during these intensive AML treatments. We used an online questionnaire in 2015 and semi-structured telephone interviews in 2018-2019. Both surveys were completed by registered dieticians and addressed the use of enteral (EN) and parenteral (PN) nutrition. The ESPEN/EBMT nutritional guideline adherence was investigated through the telephone interviews. High-level ESPEN/EBMT guideline adherence and/or uniformity among hospitals regarding nutrition support practices during intensive AML treatment were observed for nutritional screening, -aims, safe food handling and exercise training. Adherence to ESPEN/EBMT recommendations that were not implemented into national guidelines, including nutritional assessment and use of medical nutrition, was poor. All hospitals assessed nutritional intake, -impact symptoms and body weight, but muscle mass, physical performance and degree of systemic inflammation were rarely and variably monitored. Although the number of hospitals using EN as first-choice nutritional intervention increased from 3 hospitals in 2015 to 8 in 2019, PN remained the preferred method of nutrition support. Furthermore, the timing of medical nutrition varied. Although the use of EN increased after publication of the updated ESPEN/EBMT nutritional guidelines, adherence to these standards was limited and there was heterogeneity in nutrition support practices during intensive AML treatment among hospitals. Incorporating international nutritional standards into national guidelines by nutrition expert groups immediately upon publication may improve adherence.

SPRED1 Is Downregulated and a Prognostic Biomarker in Adult Acute Myeloid Leukemia.

We report herein that Sprouty-Related EVH1 Domain-Containing Protein1 (SPRED1) is downregulated and a prognostic biomarker in adult acute myeloid leukemia (AML). We determined mRNA levels of SPRED1 in the bone marrow mononuclear cells from adult patients, including 113 AMLs and 22 acute lymphoblastic leukemias (ALLs), as well as in 37 healthy control subjects. Significantly decreased SPRED1 mRNA expression was found in AML patients comparing to those in ALL patients and healthy controls, which was confirmed by immunocytochemistry analysis of SPRED1 protein and ELISA measurement of serum SPRED1 level. Further analysis demonstrated that SPRED1 expression was significantly higher for most patients at complete remission after induction treatment than at diagnosis. Moreover, SPRED1 expression was significantly downregulated in M2 and M3 types. Non-acute promyelocytic leukemia (non-APL) patients with decreased SPRED1 had significantly lower 2-year progression-free survival and event-free survival rates. In vitro, ectopic overexpression of SPRED1 leads to a decrease of extracellular signal-regulated kinase (ERK) phosphorylation, induction of apoptosis and reduction of proliferation of THP-1 cells. Our findings suggest SPRED1 is not only a predictor of treatment response, but also an independent prognostic factor for non-APL, and targeting Ras- Mitogen-activated protein kinase (MAPK) signaling may be a promising strategy for the treatment of AML with downregulation of SPRED1.

Adult acute myeloid leukemia with TLS-ERG fusion gene positive: report of two cases and review of literature

Objective To investigate the clinical characteristics and prognosis of adult acute myeloid leukemia (AML) with TLS-ERG fusion gene positive. Methods Adult two AML patients with TLS-ERG fusion gene positive in the First Affiliated Hospital of Zhengzhou University in January 2017 and March 2018, respectively were enrolled, and their clinical characteristics and prognosis were analyzed. Results Both patients with TLS-ERG fusion gene positive were males. According to morphology classification, the first case was classified to AML-M5, and the other one was AML-M4. Both patients' immunophenotypic features showed CD56 expression, and CD25 was expressed in the first patient simultaneously. Both patients were treated with induction and consolidated intensive therapy based on Chinese guidelines for diagnosis and treatment of adult AML (not acute promyelocytic leukemia) and the guidelines for diagnosis and treatment of AML (relapse/refractory) in China. The first patient died 11 months after diagnosis, and the second patient remained in remission until the end of follow-up in February 2019 (12 months after diagnosis). Conclusion TLS-ERG fusion gene has low incidence rate, high recurrence rate, poor reinduction effect, poor prognosis and short survival time in adult AML. Key words: Leukemia, myeloid, acute; Translocation, genetic; TLS-ERG fusion gene

1,123 Consecutive Adults with Non-APL Acute Myeloid Leukemia: The Mayo Clinic Experience

Background:Pre-treatment determinants of survival in adult acute myeloid leukemia (AML) include performance status, age, karyotype, the distinction between primary and non-primary AML and FLT3-ITD/NPM1 mutational status. Current literature on AML natural history and risk factors is often based on information derived from stringent protocol studies. In the current series of 1,123 adult patients seen at the Mayo Clinic between 2004 and 2017, we examined long-term survival specified by a number of primarily established risk factors.Methods:Diagnosis of AML and its sub-classification was according to World Health Organization criteria. Study subjects were recruited from the Mayo Clinic AML database. Conventional response criteria were used for CR and CRi assignment; the latter met all criteria for CR with the exception of platelet count <100 x 109/l or absolute neutrophil cunt <1 x 109/l. Standard statistical methods were used for analysis of overall survival, calculated from the initial diagnosis of AML to date of death or last follow-up; analyses were performed both in the absence and in the presence of censoring of survival at time of allogenic stem cell transplant (ASCT). The JMP® Pro 13.0.0 software from SAS Institute, Cary, NC, USA, was used for all calculations.Results:1,123 adult patients (median age 65 years, range 18-94; 61% males) with non-APL AML were considered; 61% were age >60 years. 351 (31%) patients were seen between 2004 and 2009 and 772 (69%) between 2010 and 2017. AML subcategories were primary (56%), post-myelodysplastic syndromes (post-MDS; 24%), therapy-related (10%), post-myeloproliferative neoplasm (post-MPN; 8%) and post-MDS/MPN (3%). Cytogenetic risk distribution, according to the European LeukemiaNet classification, was favorable in 47 (4%), intermediate in 650 (58%) and adverse risk in 426 (38%) patients. FLT3, NPM1 and CEBPA mutation information was available in 462 (24% mutated), 393 (27% mutated) and 228 (11% mutated) patients, respectively.Treatment included intensive chemotherapy (IC) in 766 (68%) patients, less aggressive chemotherapy, including the use of hypomethylating agents in 144 (13%) and supportive care alone in 213 (19%) patients. ASCT was utilized in 258 (23%) cases, almost all performed after achieving CR/CRi. Complete remission (CR) and CR with incomplete count recovery (CRi) were listed in 333 (30%) and 248 (22%) patients, respectively; the corresponding rates in IC-treated patients were 43% and 32%. Almost all cases of CR/CRi occurred in IC-treated patients; 2 (1.4%) CRs were listed for less aggressive chemotherapy.After a median follow-up of 11 months, 798 (71%) deaths were recorded. Median survival for all 1,123 patients was 14 months with 1-, 3- and 5-year survival rates of 54%, 29% and 23%, respectively; a slight but significant (p=0.01) improvement in survival was apparent in more recent years (Figure 1a). Figures 1b, 1c and 1d depict analysis stratified by AML subcategories, treatment received and response obtained, respectively. Similarly, figures 2a, 2b and 2c depict analysis stratified by karyotype, use of ASCT and age.Multivariable analysis of pre-treatment parameters evaluable in all 1,123 patients identified age >60 years (HR 2.2, 1.9-2.6), adverse karyotype (HR 2.9, 1.9-4.9), intermediate-risk karyotype (HR 1.6, 1.02-2.6), post-MPN AML (HR 1.9, 1.5-2.4) and other secondary AML (HR 1.3 (1.1-1.6), as risk factors for shortened survival; the inclusion in the model of FLT3/NPM1 mutational status in 392 informative cases confirmed the adverse prognostic effect of age >60 years (HR 1.8, 1.4-2.5), adverse karyotype (HR 3.7, 1.4-15.3), post-MPN AML (HR 2.8, 1.6-4.6), other secondary AML (HR 1.4, 1.0-1.9) and FLT3+NPM1- (HR 2.8, 1.6-4.9) and FLT3-NPM1- (HR 1.7, 1.2-2.7) profile. Results were unchanged when survival was censored at time of ASCT. Additional prognostic interaction with treatment strategy and ASCT is further elaborated in an accompanying abstract to be presented.Conclusions:The current study, the largest coming from a single institution, provides practically useful information that should assist with patient consultation on AML prognosis and treatment. The study confirms the primary prognostic importance of age, karyotype and FLT3/NPM1 mutational status, in real-life practice. Novel observations included comparable value of CRi vs CR and the particularly worse prognosis associated with post-MPN AML. [Display omitted] DisclosuresAl-Kali:Novartis: Research Funding.

Advances of Targeting Therapy in Acute Myeloid Leukemia--Review

Although the application of combined chemotherapy has made a great progress in treatment of adult acute myeloid leukemia (AML), the overall survival rate is still not high, mainly because of high recurrence rate and drug resistance. The treatment regimen for relapsed/refractory AML is always strong. Due to the chemotherapy drugs lacking of specific identification of tumor cells, significant adverse reactions often come out and sometimes even endanger the life of patients. In order to improve the life quality and survival rate, the new treatment strategy is urgently needed. With the deepening of research, the new molecular targets of tumor cells including the abnormal expression of cell surface morecules, gene mutation and abnormal gene methylation has been found. Targeted drugs for these abnormal changes could improve the prognosis of AML patients, providing a new way for AML treatment. This review summarizas the progress of molecular targeted therapy of AML.

Advances of MicroRNA in Adult Acute Myeloid Leukemia

MicroRNA (miRNA) is a noncoding single strand RNA that regulates mRNA and protein expression of target genes at post-transcriptional level.Characteristic expression of miRNA has been demonstrated to play an essential role in the occurrence and development of adult acute myeloid leukemia (AML),associated with its morphologic subtypes,cytogenetics and molecular biological features,and clinical prognosis.Taking deep insights into the miRNA expression profiles in AML,will provide new theoretical basis and application solutions for the diagnosis,treatment and prognosis of adult AML. Key words: MicroRNAs; Leukemia,myeloid,acute; Adult; Cytogenetics; Molecular biology; Prognosis

Nucleophosmin Gene Mutations Identify a Favorable Risk Group in Childhood Acute Myeloid Leukemia with a Normal Karyotype.

Exon 12 gene mutations in nucleophosmin (NPM1) were recently discovered in approximately 30% of adult acute myeloid leukemia (AML) samples, and cluster in the normal karyotype subgroup (NK-AML). NPM1-mutated adult NK-AML has a favorable outcome (pOS in the 40-50% range), but in case a FLT3 internal tandem duplication (FLT3/ITD) is also present outcome is worse with 25–30% pOS. In pediatric AML, NPM1 mutations are less frequent (6–8%; Cazzaniga, Blood 2005 & Brown, Blood 2007). No studies have specifically addressed pediatric NK-AML, a subgroup lacking favorable prognostic cytogenetic aberrations and therefore mostly stratified in the intermediate risk arm of pediatric AML treatment protocols. We screened 292 newly diagnosed AML samples, and detected NPM1 mutations in 25 cases (8.6%). We also screened 46 initial diagnosis-relapse pairs, and no clonal instability was observed, which suggests that NPM1 mutations may be used for minimal residual disease detection. In contrast to adults, where type A mutations (TCTG-insertion) are most frequent (80%), in our cohort type B (CATG-insertion) mutations were found in 39% and type A in 23%. In the NK-AML cohort (n=98), 20% was NPM1-mutated, which was age dependent: <3 years, 0%; 3–10 years, 19%; >10 years, 29% (p=0.04). None of the 10 FAB M5 cases was NPM1 mutated (p=0.09). NPM1 mutations had an independent favorable prognostic impact on outcome in patients with NK-AML (5-year pEFS 77% vs. 41% for wild type patients; p=0.003), irrespective of FLT3 mutational status. In fact, NPM1-mutated patients with a FLT3/ITD did better than patients without an ITD, although this was not statistically significant (5-year pEFS 90% vs. 63%, respectively; p=0.48). In NK-AML without NPM1 mutations, patients with FLT3/ITD positive AML did significantly worse than wild type FLT3 AML patients (5-year pEFS 18% vs. 52%, p=0.002). The differential prognostic impact of FLT3/ITD between the NPM1-mutated vs. the wild type patients was not caused by differences in the FLT3/ITD allelic ratio or ITD length, nor was there a relationship with the type of NPM1 mutations. Multivariate analysis, including age, white blood cell count, NPM1 and FLT3 status and stem cell transplantation as time-dependent co-variable, showed that only NPM1 mutations had independent prognostic significance for pEFS (RR 0.34, p=0.02). We conclude that the incidence of NPM1 mutations increases with age, and that NPM1 mutations define a subgroup with favorable prognosis in pediatric NK-AML. Our data suggest that these molecular abnormalities allow stratification of children with NK-AML. However, different from adult NK-AML, we observed that all children with NPM1 mutations did well, irrespective of FLT3 status. Therefore, treatment in the ‘good risk' arm should be considered for children with NPM1-mutated NK-AML.

Lyn is an important component of the signal transduction pathway specific to FLT3/ITD and can be a therapeutic target in the treatment of AML with FLT3/ITD

Fms-like tyrosine kinase 3 (FLT3) is expressed in hematopoietic progenitor cells. An internal tandem duplication (ITD) of FLT3 (FLT3/ITD) is the most frequent mutation in human adult acute myeloid leukemia (AML). FLT3/ITD contributes to the constitutive activation of FLT3 itself and its downstream signal components, mitogen-activated protein kinase and signal transducers and activators of transcription 5 (STAT5), and enables interleukin (IL)-3-dependent cell lines to grow autonomously. In the present study, we showed the specific association of FLT3/ITD with Lyn, which led to the phosphorylation of Lyn in vivo. We also demonstrated that FLT3/ITD receptors displayed a higher affinity to bind to Lyn than wild-type FLT3 receptors in vitro and that this affinity was relative to the intensity of tyrosil phosphorylation of the receptor. Both treatment with small interfering RNA (siRNA) targeting Lyn and the Src family kinase inhibitor PP2 suppressed the IL-3-independent growth of FLT3/ITD-expressing 32D cells (FLT3/ITD-32D), reducing the constitutive phosphorylation of Lyn and STAT5. PP2 treatment of mice transplanted with FLT3/ITD-32D cells blocked the onset of tumors and decreased the size of established tumors. These results demonstrate that Lyn is an important component of the signal transduction pathway specific to FLT3/ITD and can be a therapeutic target in the treatment of AML with FLT3/ITD.

Lyn Is an Important Component of the Signal Transduction Pathway Specific to FLT3/ITD and Can Be a Therapeutic Target in the Treatment of AML with FLT3/ITD.

Fms-like tyrosine kinase 3 (FLT3) is expressed in hematopoietic progenitor cells. An internal tandem duplication (ITD) of the FLT3 juxtamembrane domain (FLT3/ITD) is the most frequent mutation in human adult acute myeloid leukemia (AML). Being transfected into IL-3 dependent cell line, 32D, FLT3/ITD causes constitutive activation of FLT3 itself and its downstream signal components, which leads to IL-3 independent cell growth. In particular, STAT5 activation is thought to be a key signaling event since it is induced only by FLT3/ITD not by wild type FLT3. However the signal component which mediates FLT3/ITD to STAT5 is yet to be clarified. In the present study, we showed the mutant- specific association of FLT3/ITD with Lyn, which led to the phosphorylation of Lyn in vivo. We also demonstrated that Lyn directly bound to FLT3 through its SH2 domain in vitro and that the association depended on tyrosyl-phosphorylation at juxtamembrane domain of FLT3. We revealed the critical role of Lyn for STAT5 activation and the autonomous cell growth in FLT3/ITD transfectant of 32D by using anti-Lyn siRNA and the Src family kinase inhibitor PP2. More importantly, we demonstrated successful treatment of FLT3/ITD induced tumors with PP2 in the mice model. These results demonstrate that Lyn is a critical component of the signal transduction pathway specific to FLT3/ITD and can be a therapeutic target in the treatment of AML with FLT3/ITD.