Daiichiro Hasegawa

IKZF1 deletion is associated with a poor outcome in pediatric B-cell precursor acute lymphoblastic leukemia in Japan

Genetic alterations of Ikaros family zinc finger protein 1 (IKZF1), point mutations in Janus kinase 2 (JAK2), and overexpression of cytokine receptor‐like factor 2 (CRLF2) were recently reported to be associated with poor outcomes in pediatric B‐cell precursor (BCP)‐ALL. Herein, we conducted genetic analyses of IKZF1 deletion, point mutation of JAK2 exon 16, 17, and 21, CRLF2 expression, the presence of P2RY8‐CRLF2 fusion and F232C mutation in CRLF2 in 202 pediatric BCP‐ALL patients newly diagnosed and registered in Japan Childhood Leukemia Study ALL02 protocol to find out if alterations in these genes are determinants of poor outcome. All patients showed good response to initial prednisolone (PSL) treatment. Ph+, infantile, and Down syndrome–associated ALL were excluded. Deletion of IKZF1 occurred in 19/202 patients (9.4%) and CRLF2 overexpression occurred in 16/107 (15.0%), which are similar to previous reports. Patients with IKZF1 deletion had reduced event‐free survival (EFS) and overall survival (OS) compared to those in patients without IKZF1 deletion (5‐year EFS, 62.7% vs. 88.8%, 5‐year OS, 71.8% vs. 90.2%). Our data also showed significantly inferior 5‐year EFS (48.6% vs. 84.7%, log rank P = 0.0003) and 5‐year OS (62.3% vs. 85.4%, log rank P = 0.009) in NCI‐HR patients (n = 97). JAK2 mutations and P2RY8‐CRLF2 fusion were rarely detected. IKZF1 deletion was identified as adverse prognostic factor even in pediatric BCP‐ALL in NCI‐HR showing good response to PSL.

Improved outcome of refractory Langerhans cell histiocytosis in children with hematopoietic stem cell transplantation in Japan.

Langerhans cell histiocytosis (LCH) that is refractory to conventional chemotherapy has a poor outcome. Hematopoietic stem cell transplanta tion (SCT) is a promising approach for refractory LCH because of its immunomodulatory effect. In this study, the outcomes of children with refractory LCH undergoing SCT in Japan were analyzed. Between November 1995 and March 2007, 15 children younger than 15 years (9 males, 6 females) with refractory LCH underwent SCT. The patients’ median age at diagnosis was 8 months (range, 28 days to 28 months), and all had failed conventional chemotherapy. The median age at SCT was 23 months (range, 13–178 months). Nine had risk organ involvement at diagnosis, including liver (n=6), spleen (n=5), lung (n=5), and/or hematopoietic system (n=4). For SCT, a myeloablative regimen was used for 10 patients, and a reduced-intensity conditioning regimen (RIC) was used for five. The donor source varied among the patients, but allogeneic cord blood was primarily used (n=10). Subsequently, 11 of 15 patients have survived with no evidence of disease, with a 10-year overall survival (OS) rate (median±standard error) of 73.3±11.4%. The 10-year OS rate of nine patients with risk organ involvement at diagnosis was 55.6±16.6%, whereas six without risk organ involvement have all survived with no evidence of disease (P=0.07). These results indicate that SCT is promising as a salvage approach for children with refractory LCH.

Mutations in the ribosomal protein genes in Japanese patients with Diamond-Blackfan anemia

Background Diamond-Blackfan anemia is a rare, clinically heterogeneous, congenital red cell aplasia: 40% of patients have congenital abnormalities. Recent studies have shown that in western countries, the disease is associated with heterozygous mutations in the ribosomal protein (RP) genes in about 50% of patients. There have been no studies to determine the incidence of these mutations in Asian patients with Diamond-Blackfan anemia. Design and Methods We screened 49 Japanese patients with Diamond-Blackfan anemia (45 probands) for mutations in the six known genes associated with Diamond-Blackfan anemia: RPS19, RPS24, RPS17, RPL5, RPL11, and RPL35A. RPS14 was also examined due to its implied involvement in 5q- syndrome. Results Mutations in RPS19, RPL5, RPL11 and RPS17 were identified in five, four, two and one of the probands, respectively. In total, 12 (27%) of the Japanese Diamond-Blackfan anemia patients had mutations in ribosomal protein genes. No mutations were detected in RPS14, RPS24 or RPL35A. All patients with RPS19 and RPL5 mutations had physical abnormalities. Remarkably, cleft palate was seen in two patients with RPL5 mutations, and thumb anomalies were seen in six patients with an RPS19 or RPL5 mutation. In contrast, a small-for-date phenotype was seen in five patients without an RPL5 mutation. Conclusions We observed a slightly lower frequency of mutations in the ribosomal protein genes in patients with Diamond-Blackfan anemia compared to the frequency reported in western countries. Genotype-phenotype data suggest an association between anomalies and RPS19 mutations, and a negative association between small-for-date phenotype and RPL5 mutations.

Second allogeneic hematopoietic SCT for relapsed ALL in children

A second SCT is generally accepted as the only potentially curative approach for ALL patients that relapse after SCT, but the role of second SCT for pediatric ALL is not fully understood. We performed a retrospective analysis of 171 pediatric patients who received a second allo-SCT for relapsed ALL after allo-SCT. OS at 2 years was 29.4±3.7%, the cumulative incidence of relapse was 44.1±4.0% and non-relapse mortality was 18.8±3.5%. Relapse occurred faster after the second SCT than after the first SCT (117 days vs 164 days, P=0.04). Younger age (9 years or less), late relapse (180 days or more after first SCT), CR at the second SCT, and myeloablative conditioning were found to be related to longer survival. Neither acute GVHD nor the type of donor influenced the outcome of second SCT. Multivariate analysis showed that younger age and late relapse were associated with better outcomes. Our analysis suggests that second SCT for relapsed pediatric ALL is an appropriate treatment option for patients that have achieved CR, which is associated with late relapse after the first SCT.

Quantitative assessment of PTPN11 or RAS mutations at the neonatal period and during the clinical course in patients with juvenile myelomonocytic leukaemia.

To evaluate minimal residual disease (MRD) after chemotherapy and haematopoietic stem cell transplantation in juvenile myelomonocytic leukaemia (JMML), a locked nucleic acid‐allele specific quantitative polymerase chain reaction (LNA‐AS‐qPCR) was developed for 13 patients (four types of PTPN11 mutation and four types of RAS mutation). The post‐transplant MRD detected by LNA‐AS‐qPCR analysis was well correlated with chimerism assessed by short tandem repeat PCR analysis. Non‐intensive chemotherapy exerted no substantial reduction of the tumour burden in three patients. There was no significant difference in the quantity of RAS mutant DNA after spontaneous haematological improvement in 4 patients with NRAS or KRAS 34G > A during a 2‐ to 5‐year follow‐up. PTPN11, NRAS, or KRAS mutant DNA was detected from Guthrie card dried blood in five of seven patients (who were aged <2 years at diagnosis) at a level of 1·0–6·5 × 10−1 of the values at diagnosis. Accordingly, these five patients might have already reached a subclinical status at birth. Considering the negative correlation between mutant DNA level in neonatal blood spots and age at diagnosis, JMML patients with a larger tumour burden at birth appeared to show earlier onset.

Collaboration of cancer-associated fibroblasts and tumour-associated macrophages for neuroblastoma development.

Neuroblastoma is the most common extracranial solid tumour in children and is histologically classified by its Schwannian stromal cells. Although having fewer Schwannian stromal cells is generally associated with more aggressive phenotypes, the exact roles of other stromal cells (mainly macrophages and fibroblasts) are unclear. Here, we examined 41 cases of neuroblastoma using immunohistochemistry for the tumour‐associated macrophage (TAM) markers CD68, CD163, and CD204, and a cancer‐associated fibroblast (CAF) marker, alpha smooth muscle actin (αSMA). Each case was assigned to low/high groups on the basis of the number of TAMs or three groups on the basis of the αSMA‐staining area for CAFs. Both the number of TAMs and the area of CAFs were significantly correlated with clinical stage, MYCN amplification, bone marrow metastasis, histological classification, histological type, and risk classification. Furthermore, TAM settled in the vicinity of the CAF area, suggesting their close interaction within the tumour microenvironment. We next determined the effects of conditioned medium of a neuroblastoma cell line (NBCM) on bone marrow‐derived mesenchymal stem cells (BM‐MSCs) and peripheral blood mononuclear cell (PBMC)‐derived macrophages in vitro. The TAM markers CD163 and CD204 were significantly up‐regulated in PBMC‐derived macrophages treated with NBCM. The expression of αSMA by BM‐MSCs was increased in NBCM‐treated cells. Co‐culturing with CAF‐like BM‐MSCs did not enhance the invasive ability but supported the proliferation of tumour cells, whereas tumour cells co‐cultured with TAM‐like macrophages had the opposite effect. Intriguingly, TAM‐like macrophages enhanced not only the invasive abilities of tumour cells and BM‐MSCs but also the proliferation of BM‐MSCs. CXCL2 secreted from TAM‐like macrophages plays an important role in tumour invasiveness. Taken together, these results indicate that PBMC‐derived macrophages and BM‐MSCs are recruited to a tumour site and activated into TAMs and CAFs, respectively, followed by the formation of favourable environments for neuroblastoma progression.

Involvement of aldehyde dehydrogenase 1A2 in the regulation of cancer stem cell properties in neuroblastoma

Despite the introduction of 13-cis-retinoic acid (13-cis-RA) into the current chemotherapy, more than half of high-risk neuroblastoma patients have experienced tumor relapses driven by chemoresistant cancer stem cells (CSCs) that can be isolated by their ability to grow as spheres. Although aldehyde dehydrogenase (ALDH) has been used to characterize CSCs in certain cancers, ALDH remains elusive in neuroblastoma. In the present study, we determined ALDH activity and expression of its 19 isoforms in spheres and parental cells of neuroblastoma. ALDH activity and several ALDH isoforms were consistently induced in spheres of different neuroblastoma cells. While ALDH1A2, ALDH1L1 and ALDH3B2 expression was consistently induced in spheres and associated with the sphere and colony formation, only ALDH1A2 expression was significantly correlated with the poor prognosis of neuroblastoma patients. ALDH1A2 expression was further associated with the growth and undifferentiation of neuroblastoma xenografts and the resistance of neuroblastoma cells to 13-cis-RA. These results suggest that ALDH1A2 is involved in the regulation of CSC properties in neuroblastoma.

An overall characterization of pediatric acute lymphoblastic leukemia with CRLF2 overexpression

For an overall characterization of pediatric B‐cell precursor acute lymphoblastic leukemia (BCPALL) with CRLF2 overexpression (OE), we conducted genetic analysis of CRLF2 in 167 pediatric BCPALL patients. CRLF2 OE was detected in 30 (18%) of 167 patients, the P2RY8‐CRLF2 fusion was identified in only 3 (1.8%) of 167 patients, all of which demonstrated CRLF2 OE. Moreover, CRLF2 gain was identified in 18 (11%) of 167 patients. Messenger RNA sequencing revealed a novel fusion transcript, CSF2RA‐CRLF2, in a case with CRLF2 OE, suggesting that this fusion is associated with CRLF2 OE. In survival analysis, no significant differences in 5‐year event‐free survival (EFS) and overall survival were observed between patients with and without CRLF2 OE (70.7 vs. 75.4%, log rank P = 0.68 and 96.4 vs. 82.1%, log rank P = 0.11, respectively). However, a significant difference in 5‐year EFS between CRLF2 OE patients with and without IKZF1 deletion was observed (44.4 vs. 83.1%, log rank P = 0.02). In multivariate analysis, only IKZF1 deletion was a significant predictor of inferior OS (hazard ratio: 2.427, P = 0.04).These findings suggest that CRLF2 OE is not an independent prognostic factor in pediatric BCPALL.

Identification of novel kinase fusion transcripts in paediatric B cell precursor acute lymphoblastic leukaemia with IKZF1 deletion

Activating tyrosine kinase mutations or cytokine receptor signalling alterations have attracted attention as therapeutic targets for high‐risk paediatric acute lymphoblastic leukaemia (ALL). We identified two novel kinase fusions, OFD1‐JAK2 and NCOR1‐LYN, in paediatric ALL patients with IKZF1 deletion, by mRNA sequencing. The patient with CSF2RA‐CRLF2 also harboured IGH‐EPOR. All these patients had high‐risk features, such as high initial white blood cell counts and initial poor response to prednisolone. The functional analysis of these novel fusions is on‐going to determine whether these genetic alterations can be targeted by drugs.

Outcome of non-T-cell-depleted HLA-haploidentical hematopoietic stem cell transplantation from family donors in children and adolescents.

Non-T-cell-depleted HLA-haploidentical hematopoietic stem cell transplantation (SCT) from family members has been reported, but its effectiveness and safety are not fully known. In this study, we examined the outcomes of 83 children and adolescents with nonmalignant (n = 11) or malignant (n = 72) disorders who underwent SCT mismatched at 2 or 3 HLA loci, either from the mother (n = 56), a noninherited maternal antigen (NIMA)-mismatched sibling (n = 14), or the father/a noninherited paternal antigen (NIPA)-mismatched sibling (n = 13). Engraftment was satisfactory. Severe (grade III-IV) acute graft-versus-host disease (GVHD) was noted only in malignant disease, with an incidence of 21 of 64 evaluable patients. GVHD prophylaxis with a combination of tacrolimus and methotrexate was significantly associated with a lower risk of severe acute GVHD, compared with other types of prophylaxis(P = .04). Nine of 11 patients with nonmalignant disease and 29 of 72 patients with malignant disease were alive at a median follow-up of 26 months (range, 4-57 months). Outcomes were not significantly different among the 3 donor groups (mother versus NIMA-mismatched sibling versus father/NIPA-mismatched sibling) for the malignancy disorders. Our results indicate that non-T-cell-depleted HLA-haploidentical SCT may be feasible, with appropriate GVHD prophylaxis, for young recipients who lack immediate access to a conventional stem cell source.