Childhood myeloid leukaemias

Pediatric acute myeloid leukemia and hyperleukocytosis with WBC count greater than 50 × 109/L

BACKGROUND

Acute myeloid leukemia (AML) and hyperleukocytosis have an unfavorable prognosis, but the impact of hyperleukocytosis on the prognosis of pediatric AML remains uncertain. We investigated the clinical characteristics and prognosis of pediatric AML with hyperleukocytosis, defined as WBC ≥ 50 × 109/L.

METHODS

A total of 132 patients with newly diagnosed childhood AML with hyperleukocytosis were consecutively enrolled at our center from September 2009 to August 2021 to investigate prognostic factors and clinical outcomes.

RESULTS

Hyperleukocytosis occurred in 27.4% of AML patients. Pediatric patients with hyperleukocytosis had similar CR and OS rates to those without hyperleukocytosis, but had a lower EFS rate. In our study, rates of CR1, mortality, relapsed/refractory disease, and HSCT were comparable between AML patients with WBC counts of 50-100 × 109/L and ≥ 100 × 109/L. AML patients with a WBC count of 50-100 × 109/L had a similar 5-year OS rate to patients with a WBC count ≥ 100 × 109/L (74.6% vs. 75.4%, P = 0.921). Among all patients with hyperleukocytosis, the FAB M5 subtype was associated with significantly inferior survival, and the prognosis of CBF-AML was good.

CONCLUSIONS

Pediatric AML patients with hyperleukocytosis have the similar prognosis regardless of whether their WBC count is 50-100 × 109/L or ≥ 100 × 109/L.

Sequential administration of methotrexate and asparaginase in relapsed or refractory pediatric acute myeloid leukemia

BACKGROUND

The efficacy of combination chemotherapy with methotrexate (MTX) and asparaginase is not well known in relapsed and refractory acute leukemia after contemporary therapy.

PROCEDURE

A retrospective study of pediatric patients with relapsed or refractory acute myeloid leukemia (AML) who received MTX and asparaginase as a salvage therapy at St. Jude Children Research Hospital was performed. MTX was given intravenously followed by a dose of asparaginase intramuscularly or intravenously 24 hours later. The chemotherapy cycle was repeated every 7-10 days. Response, survival, and toxicities were evaluated.

RESULTS

Fifteen patients, median age 10.5 years (range, 1.1-18.5 years), were treated. Median number of previous therapeutic regimens was three (range, 1-4). Six patients responded to treatment (three had morphologic complete remission with incomplete blood count recovery, two had partial remission, and one had stable disease for 16 months), and four are still alive. Three of six responders had monoblastic leukemia, and also developed tumor lysis syndrome. The 1- and 2-year overall survival rates are 35.6% and 17.8%, respectively. The most common adverse event was transient elevation of transaminases (nine patients). Two patients developed pancreatitis. Episodes of febrile neutropenia were rare (two patients), and most courses (75 out of 93 total courses) were given in an outpatient setting.

CONCLUSIONS

Combination chemotherapy with MTX and asparaginase appears to be an effective salvage therapy and well tolerated in patients with relapsed or refractory childhood AML, even in those heavily pretreated with contemporary frontline or salvage therapy.

Diagnostic and prognostic value of cytogenetics in acute myeloid leukemia

The last 4 decades have seen major advances in understanding the genetic basis of acute myeloid leukemia (AML), and substantial improvements in survival of children and young adults with the disease. A key step forward was the discovery that AML cells harbor recurring cytogenetic abnormalities. The identification of the genes involved in chromosomal rearrangements has provided insights into the regulation of normal hematopoiesis and how disruption of key transcription factors and epigenetic modulators promote leukemic transformation. Cytogenetics has been widely adopted to provide the framework for development of risk-stratified treatment approaches to patient management.

Molecular pathogenesis of secondary acute promyelocytic leukemia

Balanced chromosomal translocations that generate chimeric oncoproteins are considered to be initiating lesions in the pathogenesis of acute myeloid leukemia. The most frequent is the t(15;17)(q22;q21), which fuses the PML and RARA genes, giving rise to acute promyelocytic leukemia (APL). An increasing proportion of APL cases are therapy-related (t-APL), which develop following exposure to radiotherapy and/or chemotherapeutic agents that target DNA topoisomerase II (topoII), particularly mitoxantrone and epirubicin. To gain insights into molecular mechanisms underlying the formation of the t(15;17) we mapped the translocation breakpoints in a series of t-APLs, which revealed significant clustering according to the nature of the drug exposure. Remarkably, in approximately half of t-APL cases arising following mitoxantrone treatment for breast cancer or multiple sclerosis, the chromosome 15 breakpoint fell within an 8-bp “hotspot” region in PML intron 6, which was confirmed to be a preferential site of topoII-mediated DNA cleavage induced by mitoxantrone. Chromosome 15 breakpoints falling outside the “hotspot”, and the corresponding RARA breakpoints were also shown to be functional topoII cleavage sites. The observation that particular regions of the PML and RARA loci are susceptible to topoII-mediated DNA damage induced by epirubicin and mitoxantrone may underlie the propensity of these agents to cause APL.

Banding and molecular cytogenetic studies detected a CBFB-MYH11 fusion gene that appeared as abnormal chromosomes 1 and 16 in a baby with acute myeloid leukemia FAB M4-Eo

The acute myeloid leukemia (AML) subtype M4Eo occurs in 5% of all AML cases and is usually associated with either an inv(16)(p13.1q22) or a t(16;16)(p13.1;q22) chromosomal abnormality. At the molecular level, these abnormalities generate a CBFB-MYH11 fusion gene. Patients with this genetic alteration are usually assigned to a low-risk group and thus receive standard chemotherapy. AML-M4Eo is rarely found in infants. We describe clinical, conventional banding, and molecular cytogenetic data for a 12-month-old baby with AML-M4Eo and a chimeric CBFB-MYH11 fusion gene masked by a novel rearrangement between chromosomes 1 and 16. This rearrangement characterizes a new type of inv(16)(p13.1q22) masked by a chromosome translocation.

Establishment of a novel childhood acute myeloid leukaemia cell line, KOPM-88, containing partial tandem duplication of the MLL gene and an in vivo model for childhood acute myeloid leukaemia using NOD/SCID mice

MLL gene rearrangement is common in both adult and childhood acute myeloid leukaemia (AML), and its role in oncogenesis has been investigated. While over 50 translocated-partner genes have been identified so far, few studies have detailed the molecular mechanism of partial tandem duplication (PTD) of the MLL gene. The prognostic impact and contribution to leukaemogenesis of MLL-PTD, especially in childhood cases, remain unknown. We have established a novel cell line containing MLL-PTD derived from an 11-year-old patient with AML and designated as KOPM-88. KOPM-88 cells exhibited certain characteristics associated with the myeloid lineage including abundant primary granules in the cytoplasm and the expression of myeloperoxidase. The cell growth of KOPM-88 was cytokine independent but was accelerated by granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor. MLL-PTD of exon 2 to exon 6 and exon 2 to exon 8 was revealed using Southern blotting, fluorescence in situ hybridisation, and reverse transcription polymerase chain reaction/DNA sequencing. Furthermore, non-obese diabetic/severe combined immunodeficient mice inoculated with KOPM-88 cells exhibited leukaemic infiltrations in the bone marrow and hemiparalysis because of compression myelopathy. This is the first report of an in vivo animal model exhibiting the systemic involvement of childhood AML containing MLL-PTD. KOPM-88 cells and our murine model may be useful for investigating the pathogenesis of childhood AML associated with MLL gene rearrangement.

Microarray-based classification of a consecutive series of 121 childhood acute leukemias: prediction of leukemic and genetic subtype as well as of minimal residual disease status

Gene expression analyses were performed on 121 consecutive childhood leukemias (87 B-lineage acute lymphoblastic leukemias (ALLs), 11 T-cell ALLs and 23 acute myeloid leukemias (AMLs)), investigated during an 8-year period at a single center. The supervised learning algorithm k-nearest neighbor was utilized to build gene expression predictors that could classify the ALLs/AMLs according to clinically important subtypes with high accuracy. Validation experiments in an independent data set verified the high prediction accuracies of our classifiers. B-lineage ALLs with uncharacteristic cytogenetic aberrations or with a normal karyotype displayed heterogeneous gene expression profiles, resulting in low prediction accuracies. Minimal residual disease status (MRD) in T-cell ALLs with a high (>0.1%) MRD at day 29 could be classified with 100% accuracy already at the time of diagnosis. In pediatric leukemias with uncharacteristic cytogenetic aberrations or with a normal karyotype, unsupervised analysis identified two novel subgroups: one consisting mainly of cases remaining in complete remission (CR) and one containing a few patients in CR and all but one of the patients who relapsed. This study of a consecutive series of childhood leukemias confirms and extends further previous reports demonstrating that global gene expression profiling provides a valuable tool for genetic and clinical classification of childhood leukemias.

Karyotypic Identification of Abnormal Clones Preceding Morphological Changes or Occurring with No Definite Morphological Features of Myelodysplastic Syndrome: A Preliminary Study

The diagnosis of myelodysplastic syndrome (MDS) is difficult to establish based on morphologic features alone because dysplasia may not always be detectable and the presence of dysplasia is not itself evidence of clonal disorder. As a result, the detection of a clonal cytogenetic abnormality has a major role in difficult cases in regard to diagnosis and the recognition of morphological cytogenetic correlates. In an attempt to assess the frequency and characteristic type of abnormal clones when it is not clear whether or not a hematological condition is neoplastic, cytogenetics have been analyzed necessarily in 159 patients with unexplained cytopenia or suspected MDS. We found 14 patients (8.8%) with cytogenetic abnormalities in the absence of concomitant dysplastic features of the marrow at diagnosis. The cytogenetic changes were characteristic of those reported for myeloid malignancies: 3 del(20q), 2 Y chromosome losses, 2 del(5q), 2 11q23 abnormalities, and one each of t(3;5), i(7q), trisomy 8, and del(13q). One case of ring chromosome 4 was also found. A few months later, 3 of these patients showed marrow changes consistent with MDS. Our data demonstrated that a significant proportion of otherwise uncertain diagnoses presented abnormal clones. Long-term follow-up will be required to help determine the malignant potential of these clones.

Mutation analysis of SBDS in pediatric acute myeloblastic leukemia

BACKGROUND

Shwachman-Diamond syndrome (SDS) is associated with a high risk of myelodysplasia, acute myeloid leukemia (AML), and chromosome 7 abnormalities. Ninety percent of SDS patients have mutations in SBDS on 7q11. Herein, we studied the role of genetic alterations in SBDS in AML.

PROCEDURE

DNA was extracted from marrows of SDS patients with AML, as well as from children with de novo AML. Direct sequencing of PCR amplified genomic DNA was performed using specific primers flanking each exon. To study whether SBDS heterozygosity confers a risk for MDS/AML, data on family members of SDS patients on the Canadian Inherited Marrow Failure Registry (CIMFR) was analyzed.

RESULTS

Of two SDS patients with SDS/AML one was homozygous 258 + 2T > C, and one was compound heterozygous 183-184TA > CT/258 + 2T > C. To determine whether a subset of patients with SDS can present with AML, we analyzed 48 AML samples at remission, but no mutations were identified. To address whether acquired mutated SBDS gene is associated with leukemic transformation in de novo AML, we analyzed 77 AML samples at diagnosis or relapse (4 with -7 and 7q-) for SBDS mutations; no alterations were detected. Also, among the relatives of an SDS patient cohort on the registry no cases of MDS/AML were reported.

CONCLUSIONS

Common mutations occurred in our SDS patients who develop AML, and thus, AML is not confined to a rare genetic subgroup of SDS. Newly diagnosed patients with AML are unlikely to have an underlying undiagnosed SDS. Acquired SBDS gene mutations also would appear unlikely to play a mechanistic role in de novo AML, and might not be involved in the pathogenesis of chromosome 7 abnormalities as well.

Molecular biomarkers for the study of childhood leukemia

Various specific chromosome rearrangements, including t(8;21), t(15;17), and inv(16), are found in acute myeloid leukemia (AML) and in childhood acute lymphocytic leukemia (ALL), t(12;21) and t(1;19) are common. We sequenced the translocation breakpoints of 56 patients with childhood ALL or AML harboring t(12;21), t(8;21), t(15;17), inv(16), and t(1;19), and demonstrated, with the notable exception of t(1;19), that these rearrangements are commonly detected in the neonatal blood spots (Guthrie cards) of the cases. These findings show that most childhood leukemias begin before birth and that maternal and perinatal exposures such as chemical and infectious agents are likely to be critical. Indeed, we have reported that exposure to indoor pesticides during pregnancy and the first year of life raises leukemia risk, but that later exposures do not. We have also examined aberrant gene methylation in different cytogenetic subgroups and have found striking differences between them, suggesting that epigenetic events are also important in the development of some forms of childhood leukemia. Further, at least two studies now show that the inactivating NAD(P)H:quinone acceptor oxidoreductase (NQO1) C609T polymorphism is positively associated with leukemias arising in the first 1-2 years of life and polymorphisms in the 5,10-methylenetetrahydrofolate reductase (MTHFR) gene have been associated with adult and childhood ALL. Thus, low folate intake and compounds that are detoxified by NQO1 may be important in elevating leukemia risk in children. Finally, we are exploring the use of proteomics to subclassify leukemia, because cytogenetic analysis is costly and time-consuming. Several proteins have been identified that may serve as useful biomarkers for rapidly identifying different forms of childhood leukemia.

Childhood acute myeloid leukemia with CBFbeta-MYH11 rearrangement: study of incidence, morphology, cytogenetics, and clinical outcomes of Chinese in Hong Kong

We analyzed 43 consecutive cases of pediatric acute myeloid leukemia (AML) for the presence of the CBFbeta-MYH11 rearrangement using molecular techniques in a regional hospital in Hong Kong. Five cases (11.6%), 3 girls and 2 boys, ranging in age from 8 months to 14 years old, were found positive for the CBFbeta-MYH11 rearrangement. Morphologically, they were FAB M2 or M4 with or without eosinophilia (Eo). Typical M4Eo was observed in only one case. The molecular findings were in complete concordance with cytogenetic data, which revealed inv(16)(p13q22) in all and also gains of chromosome 4, 8, 22, and Y in one patient. Clinically, all 5 patients achieved complete remission after chemotherapy with favorable outcomes except for the patient with infantile AML, who relapsed 11 months after diagnosis, underwent cord blood transplantation, and was in second remission. This is the first clinicopathological study and documentation of the incidence of CBFbeta-MYH11 in childhood AML of Chinese in Hong Kong.

Translocation (11;13)(q23;q14) as the sole abnormality in a childhood de novo acute myelocytic leukemia

We report a case of childhood de novo acute myelocytic leukemia (AML) with hyperleukocytosis with monoblastic features and deranged hemostasic function. G-band karyotyping demonstrated a previously unreported t(11;13)(q23;q14) in metaphase preparations from a fluorodeoxyuridine synchronized 1-day culture of leukophoresed cells. Multicolor fluorescence in situ hybridization revealed no cryptic rearrangements except for the translocation. Reverse transcriptase polymerase chain reaction showed no concomitant positivity of AML1/ETO, BCR/ABL, PML/RARA, and CBFbeta/MYH11 resulting from t(8;21)(q22;q22), t(9;22)(q34;q11), t(15;17)(q22;q11), and inv(16) (p13q22), respectively. This report of childhood de novo AML harboring t(11;13)(q23;q14) as the sole cytogenetic abnormality provides more data on the leukemogenesis of de novo AML with a 11q23 rearrangement.

Telomerase activity is prognostic in pediatric patients with acute myeloid leukemia: comparison with adult acute myeloid leukemia

BACKGROUND

Significantly elevated telomerase activity (TA) has been found in samples from patients with almost all malignant hematologic diseases. The impact of elevated TA on the course of pediatric patients with acute myeloid leukemia (P-AML) is unknown.

METHODS

Using a modified polymerase chain reaction-based, telomeric repeat-amplification protocol assay, the authors measured TA in bone marrow samples from 40 patients with P-AML and, for comparison, in 65 adult patients with AML (A-AML), excluding patients with French-American-British M3 disease. The results were correlated with patient characteristics and survival.

RESULTS

TA in patients with P-AML was significantly lower compared with TA in patients with A-AML (P = 0.005). Patients who had P-AML with low TA had a projected 5-year survival rate of 88%, whereas patients who had P-AML with high TA had a projected 5-year survival rate of 43% (P = 0.009). Conversely, patients who had A-AML with very high TA (upper quartile) had significantly longer survival compared with patients who had A-AML with lower TA (P = 0.03). There was no correlation between complete remission rate or disease free survival and TA in P-AML or A-AML. In the A-AML group, when patients were separated by cytogenetic findings (poor prognosis vs. others), it was found that TA was significantly lower in patients with a poor prognosis, but the prognostic value of TA was not independent of cytogenetic status.

CONCLUSIONS

The current results suggest, that for patients with P-AML, bone marrow TA is a highly significant prognostic factor.