Long non-coding RNAs as novel therapeutic targets in juvenile myelomonocytic leukemia.

Juvenile myelomonocytic leukemia (JMML) treatment primarily relies on hematopoietic stem cell transplantation and results in long-term overall survival of 50-60%, demonstrating a need to develop novel treatments. Dysregulation of the non-coding RNA transcriptome has been demonstrated before in this rare and unique disorder of early childhood. In this study, we investigated the therapeutic potential of targeting overexpressed long non-coding RNAs (lncRNAs) in JMML. Total RNA sequencing of bone marrow and peripheral blood mononuclear cell preparations from 19 untreated JMML patients and three healthy children revealed 185 differentially expressed lncRNA genes (131 up- and 54 downregulated). LNA GapmeRs were designed for 10 overexpressed and validated lncRNAs. Molecular knockdown (≥ 70% compared to mock control) after 24 h of incubation was observed with two or more independent GapmeRs in 6 of them. For three lncRNAs (lnc-THADA-4, lnc-ACOT9-1 and NRIR) knockdown resulted in a significant decrease of cell viability after 72 h of incubation in primary cultures of JMML mononuclear cells, respectively. Importantly, the extent of cellular damage correlated with the expression level of the lncRNA of interest. In conclusion, we demonstrated in primary JMML cell cultures that knockdown of overexpressed lncRNAs such as lnc-THADA-4, lnc-ACOT9-1 and NRIR may be a feasible therapeutic strategy.

SARS-CoV-2 convalescent plasma therapy in pediatric patient after hematopoietic stem cell transplantation.

Immunocompromised patients, including HSCT recipients, may have a poor prognosis after contracting COVID-19 due to the absence of a pathogen-specific adaptive immune response. One of the possible options for severe COVID-19 treatment may be the transfusion of hyperimmune SARS-CoV-2 convalescent plasma. A 9-month-old girl with juvenile myelomonocytic leukemia received an HSCT from a haploidentical donor. On day +99, during routine virologic monitoring, SARS-CoV-2 was detected without any clinical symptoms. On day +144, the child developed a polysegmental bilateral viral pneumonia with 60 % damage to the lung tissue and confirm a positive SARS-Cov-2 results in throat swab. The patient was treated with tocilizumab and three doses of fresh frozen plasma obtained from a SARS-CoV-2 convalescent patient. Therapy with tocilizumab and three doses of fresh frozen plasma was well tolerated. In spite of full resolution of the lung lesions, complete elimination of SARS-CoV-2 has not been achieved 4 months after the first detection, which is due to persistence of secondary immunodeficiency after HSCT and the lack of reconstitution of the adaptive immune response. This case represents a demonstration of an atypical course of COVID-19 and the delayed development of lung lesions, which was most likely associated with the features of the patient's immune status after HSCT. SARS-CoV-2 convalescent plasma in combination with other therapeutic approaches is one of the possible curative options for this clinical situation.

Vitamin D status in children with leukemia, its predictors, and association with outcome.

BACKGROUND: Children and adolescents with leukemia are potentially at high risk of vitamin D inadequacy, which may have clinical relevance for skeletal morbidity, infections, and cancer outcome. This study aimed to evaluate vitamin D status at the time of diagnosis to investigate its predictors and association with overall survival in children with leukemia. PROCEDURE: We included all 295 children and adolescents diagnosed with leukemia at our institution between 1990 and 2016 who had available serum sample from the time of diagnosis. We analyzed serum 25-hydroxyvitamin D and parathyroid hormone levels and correlated them with clinical data. RESULTS: The 25-hydroxyvitamin D level was deficient (< 25 nmol/L), insufficient (25-50 nmol/L), sufficient (50-75 nmol/L), and optimal (> 75 nmol/L) in 6.4%, 26.8%, 39.7%, and 27.1% of the children, respectively. Older age and a more recent time of sampling (calendar year) predicted lower 25-hydroxyvitamin D level. In preschool children (age ≤6 years), lower 25-hydroxyvitamin D level was also associated with acute myeloid leukemia, and a 25-hydroxyvitamin D level < 50 nmol/L was associated with inferior overall survival. In school-aged children (age > 6 years), the 25-hydroxyvitamin D level showed significant seasonal variation. CONCLUSION: It remains unclear whether vitamin D supplementation in pediatric leukemia patients will improve outcome.

Molecular assessment of pretransplant chemotherapy in the treatment of juvenile myelomonocytic leukemia.

BACKGROUND: Despite the intensity of hematopoietic stem cell transplantation (HCT), relapse remains the most common cause of death in juvenile myelomonocytic leukemia (JMML). In contrast to other leukemias where therapy is used to reduce leukemic burden prior to transplant, many patients with JMML proceed directly to HCT with active disease. The objective of this study was to elucidate whether pre-HCT therapy has an effect on the molecular burden of disease and how this affects outcome post-HCT. PROCEDURE: Twenty-one patients with JMML who received pre-HCT therapy and were transplanted at UCSF were analyzed in this study. The mutant allele frequency of the driver mutation was assessed before and after pre-HCT therapy, using custom amplicon next-generation sequencing. RESULTS: Of the 21 patients, seven patients (33%) responded to therapy with a significant reduction in their mutant allele frequency and were classified as molecular responders. Six of these patients received moderate-intensity chemotherapy, one patient received only azacitidine. The 5-year progression-free survival after HCT of molecular responders was 100% versus 61% for nonresponders (P = .12). Survival of molecular nonresponders was not improved by use of high-intensity conditioning, but patients were salvaged if they experienced severe graft versus host disease. There were no baseline clinical characteristics that were associated with response to pre-HCT therapy. CONCLUSIONS: Despite the myelodysplastic nature of JMML, patients treated with pre-HCT therapy can achieve molecular remissions. These patients experienced a trend toward improved outcomes post-HCT. Importantly, molecular testing can be helpful to distinguish between responders and nonresponders and should become an integral part of clinical care.

Genome-wide DNA methylation is predictive of outcome in juvenile myelomonocytic leukemia.

Juvenile myelomonocytic leukemia (JMML) is a myeloproliferative disorder of childhood caused by mutations in the Ras pathway. Outcomes in JMML vary markedly from spontaneous resolution to rapid relapse after hematopoietic stem cell transplantation. Here, we hypothesized that DNA methylation patterns would help predict disease outcome and therefore performed genome-wide DNA methylation profiling in a cohort of 39 patients. Unsupervised hierarchical clustering identifies three clusters of patients. Importantly, these clusters differ significantly in terms of 4-year event-free survival, with the lowest methylation cluster having the highest rates of survival. These findings were validated in an independent cohort of 40 patients. Notably, all but one of 14 patients experiencing spontaneous resolution cluster together and closer to 22 healthy controls than to other JMML cases. Thus, we show that DNA methylation patterns in JMML are predictive of outcome and can identify the patients most likely to experience spontaneous resolution.

[Gene mutations and clinical characteristics in children with juvenile myelomonocytic leukemia].

OBJECTIVE: To study gene mutations and clinical features in children with juvenile myelomonocytic leukemia (JMML). METHODS: The clinical data of 14 children who were diagnosed with JMML and were examined for the detection of common gene mutations were retrospectively analyzed. RESULTS: Eleven (79%) out of 14 cases were male, and 3 (21%) were female. The median age at diagnosis was 2.0 years (age range: 0.6-6.0 years). Among 14 cases, there were 4 cases (29%) with PTPN11 mutation, 3 cases (21%) with N-RAS mutation, 1 case (7%) with PTPN11 mutation and K-RAS mutation, and 6 cases (43%) without any mutation. All four cases in the PTPN11 mutation group were male, and their median age was 2.5 years; interval from onset to diagnosis was 1.0 month; the white blood cell (WBC) count and absolute monocytes in peripheral blood were significantly higher, while the platelet (PLT) count was lower, as compared with the other three groups; they were followed up, and 3 cases died and 1 case had a progressive disease. In the N-RAS mutation group, there were two male cases and one female case, and their median age was 2.0 years; interval from onset to diagnosis was 13.7 months; after follow-up, 2 cases died and 1 case did not have an obviously progressive disease. CONCLUSIONS: PTPN11 mutation is the most common mutation in JMML. The cases with PTPN11 mutation often have higher WBC count and absolute monocytes in peripheral blood, a lower PLT count, and a rapid disease progression, and their clinical outcomes are poor. The cases with N-RAS mutation have a slow disease progression. The clinical characteristics of the patients with compound mutations are not sure because of the small number of cases, and further clinical observation is indispensable.

Aberrant phosphorylation of STAT5 by granulocyte-macrophage colony-stimulating factor in infant cytomegalovirus infection mimicking juvenile myelomonocytic leukemia.

Juvenile myelomonocytic leukemia (JMML) progenitor cells exhibit in vitro hypersensitivity to granulocyte-macrophage colony-stimulating factor (GM-CSF). Phospho-specific flow cytometry using anti-phosphorylated STAT5 antibody is a new method recently reported to detect GM-CSF hypersensitivity of cells. However, colony assays using methylcellulose medium to measure GM-CSF-hypersensitivity remain as the current gold standard. Interestingly, cytomegalovirus (CMV) infection in infancy often presents with a variety of clinical symptoms that mimic JMML, with CMV giving a positive result by colony assay. We wanted to determine whether aberrant STAT5 activation occurs in CMV infection by using phospho-specific flow cytometry, and to ascertain whether this method is effective at discriminating CMV infection from JMML. Peripheral blood mononuclear cells from patients with JMML and CMV infection displayed an elevated proportion of p-STAT5 cells after low-dose GM-CSF stimulation when compared with cells from normal individuals. However, we found no significant differences in the percentage of p-STAT5 positive cells from patients with CMV infection and JMML at any doses of the GM-CSF doses used. We conclude that patients with CMV infection cannot be discriminated from patients with JMML by this new diagnostic method.