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Allogeneic hematopoietic stem cell transplantation (HSCT) is the only curative therapy for most children with juvenile myelomonocytic leukemia (JMML). Novel therapies controlling the disorder prior to HSCT are needed. We conducted a phase 2, multicenter, open-label study to evaluate the safety and antileukemic activity of azacitidine monotherapy prior to HSCT in newly diagnosed JMML patients. Eighteen patients enrolled from September 2015 to November 2017 were treated with azacitidine (75 mg/m2) administered IV once daily on days 1 to 7 of a 28-day cycle. The primary end point was the number of patients with clinical complete remission (cCR) or clinical partial remission (cPR) after 3 cycles of therapy. Pharmacokinetics, genome-wide DNA-methylation levels, and variant allele frequencies of leukemia-specific index mutations were also analyzed. Sixteen patients completed 3 cycles and 5 patients completed 6 cycles. After 3 cycles, 11 patients (61%) were in cPR and 7 (39%) had progressive disease. Six of 16 patients (38%) who needed platelet transfusions were transfusion-free after 3 cycles. All 7 patients with intermediate- or low-methylation signatures in genome-wide DNA-methylation studies achieved cPR. Seventeen patients received HSCT; 14 (82%) were leukemia-free at a median follow-up of 23.8 months (range, 7.0-39.3 months) after HSCT. Azacitidine was well tolerated and plasma concentration-–time profiles were similar to observed profiles in adults. In conclusion, azacitidine monotherapy is a suitable option for children with newly diagnosed JMML. Although long-term safety and efficacy remain to be fully elucidated in this population, these data demonstrate that azacitidine provides valuable clinical benefit to JMML patients prior to HSCT. This trial was registered at www.clinicaltrials.gov as #NCT02447666.

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ABSTRACTA-kinase anchor protein 12 (AKAP12) is a regulator of protein kinase A and protein kinase C signaling, acting downstream of RAS. Epigenetic silencing of AKAP12has been demonstrated in different cancer entities and this has been linked to the process of tumorigenesis. Here, we used quantitative high-resolution DNA methylation measurement by MassARRAY to investigate epigenetic regulation of all three AKAP12promoters (i.e., α, β, and γ) within a large cohort of juvenile myelomonocytic leukemia (JMML) patient samples. The AKAP12α promoter shows DNA hypermethylation in JMML samples, which is associated with decreased AKAP12α expression. Promoter methylation of AKAP12α correlates with older age at diagnosis, elevated levels of fetal hemoglobin and poor prognosis. In silicoscreening for transcription factor binding motifs around the sites of most pronounced methylation changes in the AKAP12α promoter revealed highly significant scores for GATA-2/-1 sequence motifs. Both transcription factors are known to be involved in the haematopoietic differentiation process. Methylation of a reporter construct containing this region resulted in strong suppression of AKAP12promoter activity, suggesting that DNA methylation might be involved in the aberrant silencing of the AKAP12promoter in JMML. Exposure to DNMT- and HDAC-inhibitors reactivates AKAP12α expression in vitro, which could potentially be a mechanism underlying clinical treatment responses upon demethylating therapy. Together, these data provide evidence for epigenetic silencing of AKAP12α in JMML and further emphasize the importance of dysregulated RAS signaling in JMML pathogenesis.

Aberrant DNA methylation at specific genetic loci is a key molecular feature of juvenile myelomonocytic leukemia (JMML) with poor prognosis. Using quantitative high-resolution mass spectrometry, we identified RASA4isoform 2, which maps to chromosome 7 and encodes a member of the GAP1 family of GTPase-activating proteins for small G proteins, as a recurrent target of isoform-specific DNA hypermethylation in JMML (51% of 125 patients analyzed). RASA4isoform 2 promoter methylation correlated with clinical parameters predicting poor prognosis (older age, elevated fetal hemoglobin), with higher risk of relapse after hematopoietic stem cell transplantation, and with PTPN11mutation. The level of isoform 2 methylation increased in relapsed cases after transplantation. Interestingly, most JMML cases with monosomy 7 exhibited hypermethylation on the remaining RASA4allele. The results corroborate the significance of epigenetic modifications in the phenotype of aggressive JMML.

Aberrant DNA methylation contributes to the malignant phenotype in virtually all types of cancer, including myeloid leukemia. We hypothesized that CpG island hypermethylation also occurs in juvenile myelomonocytic leukemia (JMML) and investigated whether it is associated with clinical, hematologic, or prognostic features. Based on quantitative measurements of DNA methylation in 127 JMML cases using mass spectrometry (MassARRAY), we identified 4 gene CpG islands with frequent hypermethylation: BMP4 (36% of patients), CALCA (54%), CDKN2B (22%), and RARB (13%). Hypermethylation was significantly associated with poor prognosis: when the methylation data were transformed into prognostic scores using a LASSO Cox regression model, the 5-year overall survival was 0.41 for patients in the top tertile of scores versus 0.72 in the lowest score tertile (P = .002). Among patients given allogeneic hematopoietic stem cell transplantation, the 5-year cumulative incidence of relapse was 0.52 in the highest versus 0.10 in the lowest score tertile (P = .007). In multivariate models, DNA methylation retained prognostic value independently of other clinical risk factors. Longitudinal analyses indicated that some cases acquired a more extensively methylated phenotype at relapse. In conclusion, our data suggest that a high-methylation phenotype characterizes an aggressive biologic variant of JMML and is an important molecular predictor of outcome.

Allogeneic hematopoietic stem cell transplantation (HSCT) is the only proven curative therapy for juvenile myelomonocytic leukemia (JMML). We, the European Working Group on Childhood MDS (EWOG-MDS) and the European Blood and Marrow Transplantation (EBMT) Group, report the outcome of 100 children (67 boys and 33 girls) with JMML given unmanipulated HSCT after a preparative regimen including busulfan, cyclophosphamide, and melphalan. Forty-eight and 52 children received transplants from an HLA-identical relative or an unrelated donor (UD), respectively. The source of hematopoietic stem cells was bone marrow, peripheral blood, and cord blood in 79, 14, and 7 children, respectively. Splenectomy had been performed before HSCT in 24 children. The 5-year cumulative incidence of transplantation-related mortality and leukemia recurrence was 13% and 35%, respectively. Age older than 4 years predicted an increased risk of disease recurrence. The 5-year probability of event-free survival for children given HSCT from either a relative or a UD was 55% and 49%, respectively (P= NS), with median observation time of patients alive being 40 months (range, 6 to 144). In multivariate analysis, age older than 4 years and female sex predicted poorer outcome. Results of this study compare favorably with previously published reports. Disease recurrence remains the major cause of treatment failure. Outcome of UD-HSCT recipients is comparable to that of children receiving transplants from an HLA-identical sibling. (Blood. 2005;105:410-419)

Primary myelodysplasia (MDS) without an increased number of blasts is a rare finding in childhood. We performed a retrospective analysis of 67 children with a diagnosis of primary MDS to determine the clinical and hematologic course of the disease. The median age at diagnosis was 8.3 years (range, 0.3-18.1 years). In contrast to refractory anemia in adults, 44% of patients had hemoglobin levels greater than 10 g/100 mL. The median white blood cell count and the absolute neutrophil count were 3.6 × 109/L and 0.9 × 109/L, respectively. Seventy-five percent of patients had thrombocytopenia. Bone marrow was hypocellular in 43% of the patients. Results of cytogenetic analysis showed monosomy 7 in 49%, trisomy 8 in 9%, and other abnormalities in 9% of the patients. The probability of survival 10 years after diagnosis was 0.48 (standard error [SE] = 0.10). Patients with monosomy 7 had significantly higher estimated probabilities of progression to advanced MDS than did patients with other chromosomal anomalies or normal karyotype. Of the 67 children, 41 underwent allogeneic stem cell transplantation (SCT). Patients whose disease did not progress to advanced MDS before SCT had significantly greater probability of survival than patients who experienced progression (0.76 [SE = 0.09] vs 0.36 [SE = 0.16]). SCT improved the outcomes for patients with monosomy 7 and should be offered early in the course of the disease. Recommendations for best treatment options for children with other chromosomal abnormalities or normal karyotype may have to await results of prospective clinical trials.

No relevant conflicts of interest to declare.

Monosomy 7 (−7) and deletion 7q [del(7q)] are rare in childhood AML and are considered to be associated with a poor outcome. We retrospectively analyzed data on 267 children with de novo AML or RAEB-T (PB or BM blasts > 20%) with −7 or del(7q) with or without additional cytogenetic aberrations (other). Patients were diagnosed between 1985 and 2003. Karyotypes showed −7 (n=90), −7 other (n=82), del(7q) (n=22), and del(7q) other (n=73). All 24 patients with RAEB-T had −7 +/− other. The median age at diagnosis was 7.6 years (range; 0–18.1) with no difference in age distribution between cytogenetic subgroups. The most common additional cytogenetic aberrations were inv(3)/t(3;3) in 19 patients (−7, n=17; del(7q), n=2) and favorable aberrations [t(8;21), inv(16), and t(15;17)] observed in 25 patients (−7, n=3; del(7q), n=22). The 5-year overall probability of survival for the whole group was 39%, SE=3%, and survival was higher in patients with del(7q) +/− other compared with −7 +/− other (52% vs. 30%). The survival of patients with del(7q) and favorable cytogenetic aberrations (n=22) was higher than that of other patients with del(7q) (75% vs. 46%, p=0.026). There was no significant difference in survival for patients with −7 and −7 other. Complete remission (CR) was obtained in 188 patients (−7 +/− other 62%; del(7q) +/− other 88%), of these, 67 received hematopoietic stem cell transplantation (HSCT) in CR1. There was no significant difference (Mantel-Byar test) in survival for patients who received HSCT in CR1 (49%, SE= 7%) and those who received chemotherapy only (51%, SE=5%, 54% for patients surviving at least the median time to HSCT). In conclusion childhood AML subgroups −7 and del(7q) differ in their associated cytogenetic aberrations and response to therapy.