Acute lymphoblastic leukemia in children: an update of clinical, biological, and therapeutic aspects

Regulation of the miRNA expression by TEL/AML1, BCR/ABL, MLL/AF4 and TCF3/PBX1 oncoproteins in acute lymphoblastic leukemia (Review)

MicroRNAs (miRNAs) are a class of small endogenous non-coding RNAs that play important regulatory roles by targeting mRNAs for cleavage or translational repression. miRNAs act in diverse biological processes including development, cell growth, apoptosis, and hematopoiesis. The miRNA expression is associated with specific cytogenetic changes and can also be used to discriminate between the different subtypes of leukemia in acute lymphoblastic leukemia with common translocations, it is shown that the miRNAs have the potential to be used for clinical diagnosis and prognosis. We reviewed the roles of miRNA here with emphasis on their function in human leukemia and the mechanisms of the TEL/AML1, BCR/ABL, MLL/AF4 and TCF3/PBX1 oncoproteins on miRNAs expression in acute lymphoblastic leukemia.

HLA-B*40 allele plays a role in the development of acute leukemia in Mexican population: a case-control study

Among oncohematological diseases, acute lymphoid leukemia (ALL) and acute myeloid leukemia (AML) are characterized by the uncontrolled production and accumulation of blasts that can lead to death. Although the physiopathology of these diseases is multifactorial, a genetic factor seems to be at play. Several studies worldwide have shown association of ALL and AML with several alleles of the major histocompatibility complex (MHC). Objective. To determine gene frequencies of HLA-B alleles in Mexicans (individuals with Native American genetic background admixed with European descent) with ALL and AML. Methods. We compared the HLA-B alleles in 213 patients with ALL and 85 patients with AML to those present in 731 umbilical cord blood (UCB) samples as a control group; this was done by means of the PCR-SSP technique. Results. We found an increased frequency of the HLA-B*40 allele in ALL patients as compared to the control group (14.5% versus 9.84%, P = 0.003, OR = 1.67); this was particularly evident in a subgroup of young (less than 18 years old) ALL patients (P = 0.002, OR = 1.76); likewise, a decreased frequency of HLA-B*40 allele in AML patients was observed as compared to the control group (4.70% versus 9.84%, P = 0.02, OR = 0.42). Conclusions. These results might suggest opposing effects of the HLA-B*40 in the genetic susceptibility to develop ALL or AML and offer the possibility to study further the molecular mechanisms of cell differentiation within the bone marrow lineage.

Diagnosis and management of acute myeloid leukemia in children and adolescents: recommendations from an international expert panel

Despite major improvements in outcome over the past decades, acute myeloid leukemia (AML) remains a life-threatening malignancy in children, with current survival rates of ∼70%. State-of-the-art recommendations in adult AML have recently been published in this journal by Döhner et al. The primary goal of an international expert panel of the International BFM Study Group AML Committee was to set standards for the management, diagnosis, response assessment, and treatment in childhood AML. This paper aims to discuss differences between childhood and adult AML, and to highlight recommendations that are specific to children. The particular relevance of new diagnostic and prognostic molecular markers in pediatric AML is presented. The general management of pediatric AML, the management of specific pediatric AML cohorts (such as infants) or subtypes of the disease occurring in children (such as Down syndrome related AML), as well as new therapeutic approaches, and the role of supportive care are discussed.

Direct association of socio-economic status with T-cell acute lymphoblastic leukaemia in children

Lymphoblasts from 186 consecutive untreated children <18 years were analysed by flow cytometry in Brazil. Socio-economic status was defined by family income; undernourishment by height and weight for age standardised z scores below -1.28. The observed frequencies were precursor-B (pre-B) CD10 positive acute lymphoblastic leukaemia (ALL) (CD10+) 65%, pre-B CD10 negative (CD10-) 13%, and T-ALL 18%. The typical incidence peak at age 2-5 years was observed among the CD10 positive cases. Nutritional variables were not associated with immunophenotypes. Low monthly per capita income was associated with T-immunophenotype (P=0.024). In conclusion, a direct association between unfavourable socio-economic status and the T-phenotype indicates a potential role of socio-economic factors on the genesis of ALL in children, thus confirming indirect data of the international literature.

Childhood leukemia: Understanding the significance of chromosomal abnormalities

The survival for children with acute lymphoblastic leukemia (ALL) has increased from 3% to greater than 70% in the last 30 years, with some patients achieving 95% survival. These advances have been made not only because therapy has improved, but also because there is a much greater understanding of the diversity of ALL. The identification of clinical and biological prognostic factors associated with ALL has resulted in the formation of subsets of patients classified into risk groups. Although age, initial white blood cell count, and central nervous system or testicular disease are all important prognostic factors, cytogenetic abnormalities have now emerged as the single most important prognostic factor for children with ALL. There are specific cytogenetic findings in the leukemic blast cells of these children that influence their prognosis. Some of these findings are positive factors and some adverse. Treatment protocols for ALL today are now determined by these specific chromosomal abnormalities.

The present role of bone marrow and stem cell transplantation in the therapy of children with acute leukemia

Hematopoetic stem cell transplantation (SCT) often represents a unique opportunity for curing children with leukemia. Nevertheless, selecting the patient who could really benefit from this procedure remains a controversial issue. The current consensus is as follows: About 20% of children with ALL can be defined as high-risk patients by criteria such as t(9;22), t(4;11), no complete remission at day 42, poor prednisone response, and T-immunophenotype or pre-pre B-ALL, myeloid markers or more than 100,000 white blood cells/microliter. This high-risk group is eligible for alloBMT in first remission, provided a family-matched donor is available. At relapse the majority of patients will benefit from alloBMT, and alternative donor sources can be considered in high-risk patients. Only early alloBMT relapses (up to 6 months after end of initial therapy) are sure candidates, whereas late relapses, especially extramedullary sites, may equally benefit from an intensive conventional relapse treatment. However, any alloBMT relapse beyond second remission should be transplanted with allogeneic stem cells (bone marrow or peripheral stem cells). In particular, family mismatched donors or matched unrelated donors may be acceptable in high-risk cases beyond first remission. In contrast, ASCR in ALL seems not to be superior to conventional therapy. In AML the standard-risk patient, defined by criteria such as FAB M1/M2-Auer rods positive, all FAB M3, and FAB M4, is not a candidate for SCT in first remission. Patients presenting other criteria or more than 5% of blasts in the bone marrow at day 15 are at high risk in first remission and should be considered for allo BMT if a family matched donor is available. ASCR in first remission AML remains a controversial issue. In contrast, in second remission alloBMT as well as ASCR are superior to conventional chemotherapy.

Molecular analysis in the diagnosis of pediatric lymphomas

Thirty-five pediatric lymphomas were categorized as either Burkitt's lymphoma (BL), lymphoblastic lymphoma (LL), or large cell anaplastic lymphoma (LCAL) by histological and immunophenotypic methods. They were further characterized by molecular analysis of their antigen receptor genes. Southern blot (SB) and polymerase chain reaction (PCR) techniques were compared in the detection of immunogloblin heavy chain gene (IgH) rearrangement. T cell receptor beta (TCR beta) rearrangements were analyzed by SB and TCR gamma gene rearrangements by PCR. The PCR method of IgH and TCR gamma gene analysis was preferred to the SB methods, because there were fewer equivocal results in IgH gene analysis, TCR gamma rearrangement was more frequently detected than TCR beta in both lymphoblastic and large cell anaplastic lymphomas, and the PCR technique was more rapid, required less DNA, and could be used with archival material. In addition, analysis of IgH gene rearrangement by PCR was more specific for assessing B cell lineage. Although most of the molecular data were easily interpreted, occasional ambiguous results were seen due to genetic events other than antigen receptor gene rearrangement affecting the genetic analysis. Thus, it is imperative to interpret these genetic data in the context of adequate morphological and immunophenotypic analysis.

Malnutrition as a prognostic factor in lymphoblastic leukaemia: a multivariate analysis

One hundred and twenty eight Brazilian children with lymphoblastic leukaemia were intensively treated with a Berlin-Frankfurt-Munich based protocol. More children had a white cell count above 50 x 10(9)/l (31%) then observed in developed countries. After a median follow up of 31 months (11-58 months), the estimated probability of relapse free survival was 41% (7%) for the whole group. After adjustment in the Cox's multivariate model, malnutrition was the most significant adverse factor affecting duration of complete remission. Age above 8 years and high peripheral white cell count were also significant adverse factors. Among the nutritional indices, the height for age and weight for age z scores were both significant, whether the cut off points of z-2 or z = -1.28 were chosen to define malnutrition. A strong statistical association between the two indices was found; the contribution of height for age z score to the prediction of relapse free survival was more significant. Children with height for age z score < -2 had a relapse risk of 8.2 (95% confidence interval 3.1 to 21.9) relative to children with z score > -2. The results of this study suggest that socioeconomic and nutritional factors should be considered in the prognostic evaluation of children with leukaemia in developing countries.

Multiple genetic events involving RB1 gene deletion and amplification of chromosome 21 in a case of acute lymphocytic leukemia

A patient with acute lymphocytic leukemia was found to have a hyperdiploid karyotype, characterized by hexasomy 21 and del(7)(p15). It was shown that the four extra copies of chromosome 21 were all derived from only one of the homologous chromosomes. Molecular analysis showed that the patient had a deletion of both alleles of the retinoblastoma (RBI) gene. These results suggest that multiple events, including loss of RBI gene function and amplification of a key gene(s) on chromosome 21, have contributed to the leukemic transformation.

Four-agent induction/consolidation therapy for childhood acute lymphoblastic leukemia: an Indian experience

During 1984-1986, a total of 128 children with acute lymphoblastic leukemia (ALL) were treated with an induction-consolidation regimen consisting of doxorubicin, vincristine, cytosine-arabinoside, and prednisolone. One hundred two (80%) patients belonged to high-risk group. The complete remission rate for all the patients was 91%. The event-free survival at 5 years was 32.0% +/- 23%. On multivariate analysis the event-free survival and disease-free survival was not altered by age, sex, WBC count, platelet count, LDH level, and surface phenotype. Infection due to prolonged marrow aplasia was a common complication, leading to mortality of 8 patients during induction and 33 patients during first remission. The relapse rate has been 36% (42 patients). The predominance of high-risk ALL in the Indian population underscores the need for intensive therapy. Improved supportive care during induction and remission seems essential to decrease therapy-related mortality, leading to improved survival.