Successful hematopoietic stem cell transplantation from an HLA-mismatched parent for engraftment failure after unrelated cord blood transplantation in patients with juvenile myelomonocytic leukemia: Report of two cases.

JMML is an aggressive hematopoietic malignancy of early childhood, and allogeneic HSCT is the only curative treatment for this disease. Umbilical cord blood is one of donor sources for HSCT in JMML patients who do not have an HLA-compatible relative, but engraftment failure remains a major problem. Here, we report two cases of JMML who were successfully rescued by HSCT from an HLA-mismatched parent after development of primary engraftment failure following unrelated CBT. Both patients had severe splenomegaly and underwent unrelated CBT from an HLA-mismatched donor. Immediately after diagnosis of engraftment failure, both patients underwent HSCT from their parent. For the second HSCT, we used RIC regimens consisting of FLU, CY, and a low dose of rabbit ATG with or without TBI and additionally administered ETP considering their persistent severe splenomegaly. Both patients achieved engraftment without severe treatment-related adverse effects. After engraftment of second HSCT, their splenomegaly was rapidly regressed, and both patients showed no sign of relapse for over 4 years. These observations demonstrate that HSCT from an HLA-mismatched parent could be a feasible salvage treatment for primary engraftment failure in JMML patients.

Epidemiology of the koch phenomenon of infants after bacillus calmette-Guerin vaccination by interferon-γ release assay status, Japan, 2013-2019.

Background: The epidemiology of infants who exhibited the Koch-like phenomenon after Bacillus Calmette-Guérin vaccination and who subsequently tested positive in interferon-γ release assay (IGRA) was compared to that of those who tested negative. The reports of pediatricians on the phenomenon to the health authorities of Japan were retrieved and analyzed. Methods: In 2013-2019, 790 infants with such events were reported with IGRA test results available, of whom 81 (10.3%) tested positive and 709 (89.7%) negative. Results: The infants who were IGRA positive did not show an increasing trend (P = 0.06, P = 0.60), whereas those who were IGRA negative showed a significantly increasing trend (P = 0.42, P = 0.0002). The infants who were IGRA positive did not exhibit seasonality, whereas those who were IGRA negative had a higher number of cases in winter than in summer. The rates of infants who were IGRA positive per 10 million live births showed a significant correlation with the tuberculosis (TB) notification rates by prefecture (P = 0.41, P = 0.004), whereas those who were IGRA negative did not (P = 0.04, P = 0.78). Conclusion: The IGRA-positive infants were distributed quite differently from those who were IGRA negative and appeared more likely to be infected with TB. Reports of pediatricians on the Koch-like phenomenon should continuously be collected as the reports reflect a risk of TB infection including TB outbreaks among infants in Japan. The reports should include IGRA test results as IGRA is more specific than tuberculin skin testing. Infants with IGRA-positive results should be followed up for 2-3 years to determine their final outcomes.

Fms-like tyrosine kinase 3 ligand stimulation induces MLL-rearranged leukemia cells into quiescence resistant to antileukemic agents.

Fms-like tyrosine kinase 3 (FLT3) is highly expressed in acute lymphoblastic leukemia with the mixed-lineage leukemia (MLL) gene rearrangement refractory to chemotherapy. We examined the biological effect of FLT3-ligand (FL) on 18 B-precursor leukemic cell lines with variable karyotypic abnormalities, and found that nine of nine MLL-rearranged cell lines with wild-type FLT3, in contrast to other leukemic cell lines, are significantly inhibited in their proliferation in a dose-dependent manner by FL. This inhibition was due to induction of the G0-G1 arrest. A marked up-regulation of p27 by suppression of its protein degradation and an abrogation of constitutive signal transducers and activators of transcription 5 phosphorylation were revealed in arrested leukemia cells after FL stimulation. Importantly, FL treatment rendered not only cell lines but also primary leukemia cells with MLL rearrangement resistant to chemotherapeutic agents. MLL-rearranged leukemia cells adhering to the bone marrow stromal cell line, which expresses FL as the membrane-bound form, were induced to quiescent state resistant to chemotherapeutic agents, but their chemosensitivity was significantly restored in the presence of neutralizing anti-FL antibody. The FL/FLT3 interaction between leukemia cells and bone marrow stromal cells expressing FL at high levels should contribute, at least in part, to persistent minimal-residual disease of MLL-rearranged leukemia in bone marrow.

Chemosensitivity is differentially regulated by the SDF-1/CXCR4 and SDF-1/CXCR7 axes in acute lymphoblastic leukemia with MLL gene rearrangements.

Although recent advances in chemotherapy have markedly improved outcome of acute lymphoblastic leukemia (ALL), infantile ALL with MLL gene rearrangements (MLL+ALL) is refractory to chemotherapy. We have shown that specific cytokines FLT3 ligand and TGFß1 both of which are produced from bone marrow stromal cells synergistically induced MLL+ALL cells into chemo-resistant quiescence, and that treatment of MLL+ALL cells with inhibitors against FLT3 and/or TGFß1 receptor partially but significantly converts them toward chemo-sensitive. In the present study, we showed that MLL+ALL cells expressed CXCR4 and CXCR7, both receptors for the same chemokine stromal cell derived factor-1 (SDF-1), but their biological events were differentially regulated by the SDF-1/CXCR4 and SDF-1/CXCR7 axes and particularly exerted an opposite effect for determining chemo-sensitivity of MLL+ALL cells; enhancement via the SDF-1/CXCR4 axis vs. suppression via the SDF-1/CXCR7 axis. Because cytosine-arabinoside-induced apoptosis of MLL+ALL cells was inhibited by pretreatment with the CXCR4 inhibitor but rather accelerated by pretreatment with the CXCR7 inhibitor, an application of the CXCR7 inhibitor may become a good treatment option in future for MLL+ALL patients. MLL+ALL has a unique gene profile distinguishable from other types of ALL and AML, and should be investigated separately in responses to biological active agents including chemokine inhibitors.

Inflammatory mediator ultra-low-molecular-weight hyaluronan triggers necrosis of B-precursor leukemia cells with high surface CD44 expression.

Acute lymphoblastic leukemia (ALL) with mixed lineage leukemia (MLL) gene rearrangements (MLL+ALL) has a dismal prognosis and is characterized by high surface CD44 expression. Known that CD44 has the specific binding sites for a natural ligand hyaluronan (HA), we investigated biological effects of HA with different molecular sizes on MLL+ALL cell lines, and found that the addition of ultra-low-molecular-weight (ULMW)-HA strongly suppressed their thymidine uptakes. The MLL+ALL cell line lacking surface CD44 expression established by genome editing showed no suppression of thymidine uptake. Surface CD44-high B-precursor ALL cell lines other than MLL+, but not T-ALL cell lines, were also suppressed in their thymidine uptakes. The inhibition of thymidine uptakes was because of induction of cell death, but dead cells lacked features of apoptosis on cytospin smears and flow cytometric analysis. The cell death was neither blocked by pan-caspase inhibitor nor autophagy inhibitor, but was completely blocked by necrosis inhibitor necrostatin-1. Necrotic cell death was further supported by a marked release of a high-mobility protein group B1 and morphological changes on transmission electron microscopy. Elevation of intracellular reactive oxygen species production suggested a role for inducing this necrotic cell death. ULMW-HA-triggered cell death was similarly demonstrated in surface CD44-high primary B-precursor leukemia cells. Assuming that ULMW-HA is abundantly secreted at the site of infection and inflammation, this study sheds light on understanding the mechanism of a transient inflammation-associated remission of leukemia. Further, the CD44-targeting may become an effective approach in future for the treatment of refractory B-precursor ALL by its capability of predominantly eradicating CD44-high leukemia-initiating cells.

[Prevention of hepatic veno-occlusive disease by a combination of heparin and prostaglandin E1 in children undergoing hematopoietic stem cell transplantation].

The effect and safety of combination prophylaxis for hepatic veno-occlusive disease (VOD) following stem cell transplantation (SCT) was retrospectively evaluated in a total of 53 children who survived until day 30. Prophylaxis was started on the day before conditioning, and heparin (10 unit/kg/hr) alone was used in 6 patients, PGE1 (5 ng/kg/min) plus heparin plus PTX (200 mg/day) in 17 patients, lipo-PGE1 (0.5 ng/kg/min) plus heparin plus PTX in 7 patients, and lipo-PGE1 plus heparin in 23 patients. Diagnosis of VOD was made based on McDonald's criteria in 5 cases (9.4%), but not on Jones' criteria. No statistically significant difference was observed in the incidence of VOD among each prophylaxis group. The degree of VOD was mild in all of 5 cases, and all recovered with continuation of the prophylactic procedure. Each prophylactic procedure was performed without any significant adverse effect except for seizure induced by lipo-PGE1 in one patient with Lennox syndrome. Since both the incidence and fatality rate of VOD in children undergoing SCT are approximately 20% according to most of the previous reports, the present study suggests the effectiveness of combination prophylaxis.

FLT3 mutations in the activation loop of tyrosine kinase domain are frequently found in infant ALL with MLL rearrangements and pediatric ALL with hyperdiploidy.

Point mutations of D835/I836 of the FLT3 gene have been reported in adult acute myeloid leukemia (AML), but not in pediatric AML or acute lymphoblastic leukemia (ALL). FLT3-D835/I836 mutations were found in 6 (5.4%) of 112 children with ALL older than 1 year and in 8 (16.0%) of 50 infants with ALL. Missense mutations were found in 11 patients, 3-base pair deletions in 2 patients, and a deletion/insertion in 1 patient. Remarkably, FLT3-D835/I836 mutations were found in 8 (18.2%) of 44 infants with ALL with MLL rearrangements and in 4 (21.5%) of 19 patients with hyperdiploid ALL, but they were not found in any patients older than 1 year who had TEL-AML1 (n = 11), E2APBX1 (n = 4), or BCR-ABL (n = 6) fusion genes. Although infant ALL patients with mutations had poorer prognoses than did those without mutations, pediatric ALL patients with mutations who were older than 1 year had good prognoses. We also found FLT3-D835 mutations in 2 of 11 leukemic cell lines with MLL rearrangements. FLT3 was highly phosphorylated in these cell lines with FLT3-D835 mutations, leading to constitutive activation of downstream targets such as signal transducer and activator of transcription 5 (STAT5) without FLT3 ligand stimulation. These results suggested that FLT3-D835/I836 mutations are one of the second genetic events in infant ALL with MLL rearrangements or pediatric ALL with hyperdiploidy.