Karoline Schubert

Prognostic relevance of DNMT3A R882 mutations in AML patients undergoing non-myeloablative conditioning hematopoietic stem cell transplantation

Mutations in the epigenetic modifying gene DNA methyltransferase 3A (DNMT3A) are found in 14–35% of acute myeloid leukemia (AML) patients [1–6]. The majority of DNMT3A mutations cluster at codon R882 in exon 23 [1–6]. Most of the studies that have investigated the prognostic impact of these alterations reported inferior outcomes associated with the presence of DNMT3A mutations—particularly in codon R882 [1–4, 6–9]. However, the negative impact on outcomes may be dependent on the clinical and biological context, such as the presence of concurrent gene mutations (i.e. NPM1 mutations and/or presence of FLT3ITD) and the DNMT3A mutation type (i.e. R882 vs. nonR882) [1–6, 9]. In older AML patients, DNMT3A mutations are more prevalent [7] and have been associated with poor outcomes [1, 6, 8]. DNMT3A mutations are often found to persist during remission (possibly due to a preexisting clonal hematopoiesis) and at AML relapse, and might contribute to chemotherapy resistance [10]. This raises the issue of allogeneic hematopoietic stem cell transplantation (HSCT) as a therapeutic approach specifically for DNMT3A mutated AML. Studies that included HSCT treated patients—most of which focused on younger AML patients—observed no influence of an HSCT on the negative prognostic impact of DNMT3A mutations [3–5, 9, 11]. For example, Gaidzik et al. [5]. described a shorter relapse-free survival in younger DNMT3A R882 mutated AML patients independent of the use of HSCT. Similarly, Ahn et al. [9]. and Xu et al. [11]. reported a negative impact of DNMT3A R882 mutations after HSCT in mainly younger patients with normal karyotype (NK) AML. Since DNMT3A R882 mutations occur more frequently with age [7] and data on the influence of DNMT3A R882 mutations on outcome in older AML patients receiving HSCT are limited, we analyzed the prognostic impact of DNMT3A R882 mutations at diagnosis among mainly older (>60 years) AML patients who underwent nonmyeloablative (NMA)-HSCT. NMA-HSCT relies on an immunological donor leukocyte-mediated GvL effect and, because of the lower treatment-related toxicity, represents a feasible consolidating therapy for older AML patients and/or those with comorbidities [12, 13]. The patients studied here were treated with cytarabinebased chemotherapies followed by conditioning with fludarabine and 2 Gy TBI or 2 Gy TBI only before NMAHSCT (for further details, see Supplementary Information) at the University Hospital Leipzig between February 2003 and December 2012. We retrospectively analyzed the presence of DNMT3A R882 mutations in pre-treatment bone marrow (n= 98) or peripheral blood (n= 10) samples of 108 AML patients (for further details, see Supplementary Information). All patients gave written informed consent in accordance with the declaration of Helsinki. Pre-treatment cytogenetics and the mutation status of NPM1, CEBPA, and the presence of FLT3-ITD were determined as previously Laura K. Schmalbrock and Lynn Bonifacio contributed equally to this work.

Prognostic Impact of the CD34+/CD38‐ Cell Burden in Patients with Acute Myeloid Leukemia receiving Allogeneic Stem Cell Transplantation

In acute myeloid leukemia (AML), leukemia‐initiating cells exist within the CD34+/CD38− cell compartment. They are assumed to be more resistant to chemotherapy, enriched in minimal residual disease cell populations, and responsible for relapse. Here we evaluated clinical and biological associations and the prognostic impact of a high diagnostic CD34+/CD38− cell burden in 169 AML patients receiving an allogeneic stem cell transplantation in complete remission. Here, the therapeutic approach is mainly based on immunological graft‐versus‐leukemia effects. Percentage of bone marrow CD34+/CD38− cell burden at diagnosis was measured using flow cytometry and was highly variable (median 0.5%, range 0%–89% of all mononuclear cells). A high CD34+/CD38− cell burden at diagnosis associated with worse genetic risk and secondary AML. Patients with a high CD34+/CD38− cell burden had shorter relapse‐free and overall survival which may be mediated by residual leukemia‐initiating cells in the CD34+/CD38− cell population, escaping the graft‐versus‐leukemia effect after allogeneic transplantation. Evaluating the CD34+/CD38− cell burden at diagnosis may help to identify patients at high risk of relapse after allogeneic transplantation. Further studies to understand leukemia‐initiating cell biology and develop targeting therapies to improve outcomes of AML patients are needed.