Clinical outcome of de novo acute myeloid leukaemia patients with normal cytogenetics is affected by molecular genetic alterations: a concise review

Background. Cytogenetically normal acute myeloid leukaemia (CN-AML) occurs in 50% adult AML and is a group of diseases with diverse mutations and distinct clinical outcome. CEBPα, NPM1 and FLT3 mutations that are commonly seen in CN-AML have been incorporated into risk stratification. However, prognostic impacts of other gene mutations and their combinations in this AML subtype have remained unclear. In this study, we examined a cohort of young adults with de novo CN-AML who have received uniform treatment protocol in Hong Kong and identified a mutation pentad that might define their clinical outcome. Methodology. Young adults (18-60 years old) with de novo CN-AML, diagnosed from 1st August 2003 to 7th August 2018 in 8 regional hospitals in Hong Kong, were included. They received standard "7+3" induction (Daunorubicin 60-90 mg/m2 and Cytarabine 100 mg/m2) followed by up to 4 courses of high dose cytarabine consolidation (Cytarabine 3 gram/m2 for 4-6 doses). Decision on allogeneic haematopoietic stem cell transplantation (HSCT) was based on clinical grounds and gene mutations according to ELN recommendations. Next generation sequencing (NGS) was performed in diagnostic bone marrow (BM) in 362 patients for 36 recurrent mutated genes and analyzed by in-house bioinformatics pipelines. Relapse-free survival (RFS) was defined by the time from first complete remission (CR) to relapse or death and overall survival (OS) by the time from diagnosis to death. Patients were censored at last follow up. Survivals were evaluated by Kaplan-Meier analysis and compared by log-rank test. Multivariate analyses of clinical and genetic parameters were analyzed by Cox-regression. P-values of <0.05 were considered statistically significant. Results. A total of 436 patients (Male=189; Female=247) were recruited. Their median age of onset was 49 years old (Range 18-60); median presenting white cell counts (WCC) was 21.85x109/L (range 0.25-411x109/L), median circulating blast % was 46% (range 1-99). 416 patients received induction of whom 90.1% achieved CR or CRi (N=375) after 1 (N=268), 2 (N=78) or ≥ 3 courses of induction (N=29). One hundred and sixty three patients received allogeneic HSCT at CR1 (N=102), CR2 (N=51), ≥ CR3 (N=2) and relapsed state (N=8). Eight mutations with ≥ 10% prevalence occurred in 79.8% patients (Figure 1). Univariate analyses showed that mutations of CEBPα, TET2, IDH2-R172K and RAS were not associated with treatment outcome and survival. Five genetic subgroups based on NPM1, FLT3 and DNMT3A mutations could be identified: NPM1 mutation only; NPM1 mutation and FLT3-ITD; All wildtype; FLT3-ITD only; DNMT3A irrespective of NPM1 and FLT3-ITD status. These subgroups showed distinct RFS and OS (Figure 2). Impacts of IDH1-R132 and IDH2-R140Q mutations were evaluated in these 5 subgroups. Interestingly, adverse impacts of IDH1-R132 on RFS and OS were only significant in the all wildtype subgroup and the adverse impact of IDH2-R140Q was only significant for RFS in the NPM1 mutation only subgroup. Conclusion. A mutation pentad comprising NPM1, FLT3, DNMT3A, IDH1-R132 and IDH2-R140Q seemed to define distinct prognostic subgroups in young adults with de novo CN-AML. A limited gene panel based on this pentad using conventional PCR may provide a practical and cost-effective means to guide post-remission therapy in these patients, especially in places where NGS may not be readily available. Acknowledgements: SK Yee Medical Foundation; Li Shu Fan Medical Foundation, LKS Faculty of Medicine, University of Hong Kong, Hong Kong Blood Cancer Foundation Disclosures Leung: Curegenix: Research Funding; Servier: Research Funding; Merck: Research Funding; Pfizer: Research Funding.

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Cdx2 Cooperates with Flt3-ITD to Induce Acute Myeloid Leukaemia in Mice

Blood ◽

10.1182/blood.v126.23.557.557 ◽

2015 ◽

Vol 126 (23) ◽

pp. 557-557

Author(s):

Therese Vu ◽

Claudia Bruedigam ◽

Axia Song ◽

Solene Guignes ◽

Rebecca Austin ◽

...

Keyword(s):

Acute Myeloid Leukaemia ◽

Myeloid Leukaemia ◽

Median Survival ◽

De Novo ◽

Genetic Alterations ◽

Survival Curves ◽

Cdx2 Expression ◽

Long Latency ◽

Acute Myeloid

Abstract The caudal-related homeobox gene CDX2 is ectopically expressed in 90% of human acute myeloid leukaemia (AML), but not normal haematopoietic stem and progenitor cells (HSPC). Retroviral expression of Cdx2 causes a highly penetrant, lethal AML in mouse models, while short hairpin RNA-mediated targeted knockdown of CDX2 in vitro impairs growth and clonogenic potential of AML cell lines (Scholl et al. 2007). These findings implicate Cdx2 overexpression as a clinically relevant model of myeloid leukaemogenesis, however existing studies have been limited by the requirement for ex vivo manipulation, retroviral overexpression and transplantation. To understand the role of Cdx2 expression in de novo leukaemic transformation of HSC, we generated an inducible transgenic mouse model of Cdx2 expression linked to the mCherry fluorescent reporter. Cdx2 was specifically activated in adult HSC using the tamoxifen-inducible SclCreERT:Cdx2 model and compared with LysMCre:Cdx2 mice that selectively activated Cdx2 in the myeloid lineage, commencing at committed myeloid progenitors. SclCreERT:Cdx2 mice developed a lethal myelodysplastic phenotype with a long latency (median survival, 184 days) characterised by leukopenia, anaemia, thrombocytopenia and reduced marrow cellularity. Bone marrow histology revealed prominent megakaryocytic dysplasia. Competitive transplantation assays showed dramatic loss of long-term HSC self-renewal after tamoxifen induction of Cdx2 in the secondary recipients. Conversely, LysMCre:Cdx2 mice developed a myeloproliferative phenotype with leukocytosis, splenomegaly and extramedullary haematopoiesis. Interestingly, both cohorts exhibited marked neutrophil hypersegmentation compared to non-Cdx2 controls, a characteristic that is compatible with myelodysplasia, and suggests that Cdx2 not only controls HSC development and differentiation, but is required for granulocyte maturation. In contrast to retroviral models, AML was never observed with Cdx2 expression alone. FLT3-internal tandem duplication (ITD) represents a tyrosine kinase mutation that is present in 35% of AML patients, making it one of the most common genetic alterations found in AML. Transgenic Flt3ITD mice develop myelodysplastic syndrome (MDS)/myeloproliferative neoplasm (MPN) with long latency (approx. 10-15 months) but do not develop AML (Lee et al. 2007), suggesting that additional mutations are required for complete leukaemogenesis. Preliminary data has shown a correlation between CDX2 and FLT3 expression in AML. We therefore crossed SclCreERT:Cdx2 with Flt3ITD/+ and Flt3ITD/ITD mice. SclCreERT:Cdx2xFlt3ITD/+ mice developed a rapidly progressive lethal MDS with marked anaemia and thrombocytopenia, splenomegaly, morphological dysplasia and a shorter latency (median survival, 45 days) with a low incidence of transformation to AML. Strikingly, SclCreERT:Cdx2xFlt3ITD/ITD mice developed a fully penetrant AML characterised by marked leukocytosis, splenomegaly and hepatomegaly, and >20% circulating blast cells, demonstrating that Cdx2 cooperates with Flt3ITD to induce AML in a Flt3ITD gene dosage-dependent manner (Fig 1). Transplantation experiments of these samples into lethally irradiated, syngeneic wildtype (WT) recipients revealed that cells from SclCreERT:Cdx2xFlt3ITD/+ or SclCreERT:Cdx2xFlt3ITD/ITD but not WT, Flt3ITD/+ or Flt3ITD/ITD resulted in direct phenocopy of the primary disease with a short latency lethality, demonstrating the disease is intrinsic to transformed HSPC populations. Mechanistically, SclCreERT:Cdx2xFlt3ITD/+ and SclCreERT:Cdx2xFlt3ITD/ITD samples showed marked depletion of long-term HSC, abnormal cell cycle regulation and widespread gene expression changes leading to the activation of a leukaemia stem cell (LSC) program, including the aberrant expression of several Hox genes. Altogether, this work demonstrates that conditional Cdx2 expression has a critical role in the transformation of HSPC populations to AML LSC. This is a novel, inducible model of de novo leukaemic transformation and reflects common genetic aberrations seen in human AML. Thus, this model may help to identify tractable susceptibilities to target LSC populations and improve clinical outcomes. Figure 1. Survival curves for SclCreERT:WT, Flt3ITD/+, Flt3ITD/ITD, SclCreERT:Cdx2, SclCreERT:Cdx2xFlt3ITD/+ and SclCreERT:Cdx2xFlt3ITD/ITD mice. Figure 1. Survival curves for SclCreERT:WT, Flt3ITD/+, Flt3ITD/ITD, SclCreERT:Cdx2, SclCreERT:Cdx2xFlt3ITD/+ and SclCreERT:Cdx2xFlt3ITD/ITD mice. Disclosures No relevant conflicts of interest to declare.

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