Acute lymphoblastic leukaemia

T-cell acute lymphoblastic leukaemia: recent molecular biology findings

For many years, T-cell acute lymphoblastic leukaemia (T-ALL) has been considered and treated as a single malignancy, but divergent outcomes in T-ALL patients receiving uniform treatment protocols encouraged intensive research on the molecular biology of this disease. Recent findings in the field demonstrate that T-ALL is much more heterogeneous than originally believed and extremely diverse outcomes of patients require refinement of T-ALL classification, leading to subtype-specific adjustment of treatment. Many different biological features of T-ALL blast cells have recently been found to contribute to disease development and patient outcome and their analysis could potentially be introduced into improved diagnostics and classification of the disease. This review focuses on five key issues of T-ALL biology: chromosome aberrations, gene expression profiles, gene mutations, DNA methylation patterns, and immunoglobulin/T cell receptor (Ig/TCR) gene rearrangements. Additionally, molecular monitoring of minimal residual disease, by far the most reliable independent prognostic factor in T-ALL, has been highlighted in the context of Ig/TCR gene rearrangements. Translation of this biological information into better prognostic classification and more effective treatment should lead to improvement of outcome in T-ALL patients.

Clinical significance of early T-cell precursor acute lymphoblastic leukaemia: results of the Tokyo Children's Cancer Study Group Study L99-15

Early T-cell precursor acute lymphoblastic leukaemia (ETP-ALL) is a recently identified subtype of T-ALL with distinctive gene expression and cell marker profiles, poor response to chemotherapy and a very high risk of relapse. We determined the reliability of restricted panel of cell markers to identify EPT-ALL using a previously classified cohort. Then, we applied the cell marker profile that best discriminated ETP-ALL to a cohort of 91 patients with T-ALL enrolled in the Tokyo Children's Cancer Study Group L99-15 study, which included allogeneic stem cell transplantation (allo-SCT) for patients with poor prednisone response. Five of the 91 patients (5·5%) met the ETP-ALL criteria. There were no significant differences in presenting clinical features between these and the remaining 86 patients. Response to early remission induction therapy was inferior in ETP-ALL as compared with T-ALL. The ETP-ALL subgroup showed a significantly poorer event-free survival (4-year rate; 40%) than the T-ALL subgroup (70%, P=0·014). Of note, three of four relapsed ETP-ALL patients survived after allo-SCT, indicating that allo-SCT can be effective for this drug-resistant subtype of T-ALL.

Variants of the MTHFR gene and susceptibility to acute lymphoblastic leukemia in children: a synthesis of genetic association studies

BACKGROUND

Acute lymphoblastic leukemia (ALL) is a complex disease with genetic background. The genetic association studies (GAS) that investigated the association between ALL and the MTHFR C677T and A1298C gene variants have produced contradictory or inconclusive results.

MATERIALS AND METHODS

In order to decrease the uncertainty of estimated genetic risk effects, a meticulous meta-analysis of published GAS related the variants in the MTFHR gene with susceptibility to ALL was conducted. The risk effects were estimated based on the odds ratio (OR) of the allele contrast and the generalized odds ratio (OR(G)). Cumulative and recursive cumulative meta-analyses were also performed.

RESULTS

The analysis showed marginal significant association for the C677T variant, overall [OR=0.91 (0.82-1.00) and OR(G)=0.89 (0.79-1.01)], and in Whites [OR=0.88 (0.77-0.99) and OR(G)=0.85 (0.73-0.99)]. The A1298C variant produced non-significant results. For both variants, the cumulative meta-analysis did not show a trend of association as evidence accumulates and the recursive cumulative meta-analysis indicated lack of sufficient evidence for denying or claiming an association.

CONCLUSION

The current evidence is not sufficient to draw definite conclusions regarding the association of MTHFR variants and development of ALL.

Acute leukemia incidence and patient survival among children and adults in the United States, 2001-2007

Since 2001, the World Health Organization classification for hematopoietic and lymphoid neoplasms has provided a framework for defining acute leukemia (AL) subtypes, although few population-based studies have assessed incidence patterns and patient survival accordingly. We assessed AL incidence rates (IRs), IR ratios (IRRs), and relative survival in the United States (2001-2007) in one of the first population-based, comprehensive assessments. Most subtypes of acute myeloid leukemia (AML) and acute lymphoblastic leukemia/lymphoma (ALL/L) predominated among males, from twice higher incidence of T-cell ALL/L among males than among females (IRR = 2.20) to nearly equal IRs of acute promyelocytic leukemia (APL; IRR = 1.08). Compared with non-Hispanic whites, Hispanics had significantly higher incidence of B-cell ALL/L (IRR = 1.64) and APL (IRR = 1.28); blacks had lower IRs of nearly all AL subtypes. All ALL/L but only some AML subtypes were associated with a bimodal age pattern. Among AML subtypes, survival was highest for APL and AML with inv(16). B-cell ALL/L had more favorable survival than T-cell ALL/L among the young; the converse occurred at older ages. Limitations of cancer registry data must be acknowledged, but the distinct AL incidence and survival patterns based on the World Health Organization classification support biologic diversity that should facilitate etiologic discovery, prognostication, and treatment advances.

Identification of hepatic niche harboring human acute lymphoblastic leukemic cells via the SDF-1/CXCR4 axis

In acute lymphoblastic leukemia (ALL) patients, the bone marrow niche is widely known to be an important element of treatment response and relapse. Furthermore, a characteristic liver pathology observed in ALL patients implies that the hepatic microenvironment provides an extramedullary niche for leukemic cells. However, it remains unclear whether the liver actually provides a specific niche. The mechanism underlying this pathology is also poorly understood. Here, to answer these questions, we reconstituted the histopathology of leukemic liver by using patients-derived primary ALL cells into NOD/SCID/Yc (null) mice. The liver pathology in this model was similar to that observed in the patients. By using this model, we clearly demonstrated that bile duct epithelial cells form a hepatic niche that supports infiltration and proliferation of ALL cells in the liver. Furthermore, we showed that functions of the niche are maintained by the SDF-1/CXCR4 axis, proposing a novel therapeutic approach targeting the extramedullary niche by inhibition of the SDF-1/CXCR4 axis. In conclusion, we demonstrated that the liver dissemination of leukemia is not due to nonselective infiltration, but rather systematic invasion and proliferation of leukemic cells in hepatic niche. Although the contribution of SDF-1/CXCR4 axis is reported in some cancer cells or leukemic niches such as bone marrow, we demonstrated that this axis works even in the extramedullary niche of leukemic cells. Our findings form the basis for therapeutic approaches that target the extramedullary niche by inhibiting the SDF-1/CXCR4 axis.

Connectivity mapping identifies HDAC inhibitors for the treatment of t(4;11)-positive infant acute lymphoblastic leukemia

MLL-rearranged infant acute lymphoblastic leukemia (ALL) is an aggressive type of leukemia characterized by a unique gene-expression profile. We uncovered that the activation of particular (proto-onco)genes is mediated by promoter hypomethylation. In search for therapeutic agents capable of targeting these potential cancer-promoting genes, we applied connectivity mapping on a gene expression signature based on the genes most significantly hypomethylated in t(4;11)-positive infant ALL as compared with healthy bone marrows. This analysis revealed histone deacetylase (HDAC) inhibitors as suitable candidates to reverse the unfavorable gene signature. We show that HDAC inhibitors effectively induce leukemic cell death in t(4;11)-positive primary infant ALL cells, accompanied by downregulation of MYC, SET, RUNX1, RAN as well as the MLL-AF4 fusion product. Furthermore, DNA methylation was restored after HDAC inhibitor exposure. Our data underlines the essential role for epigenetic de-regulation in MLL-rearranged ALL. Furthermore, we show, for the first time, that connectivity mapping can indirectly be applied on DNA methylation patterns, providing a rationale for HDAC inhibition in t(4;11)-positive leukemias. Given the presented potential of HDAC inhibitors to target important proto-oncogenes including the leukemia-specific MLL fusion in vitro, these agents should urgently be tested in in vivo models and subsequent clinical trials.

The leukemia-specific fusion gene ETV6/RUNX1 perturbs distinct key biological functions primarily by gene repression

BACKGROUND

ETV6/RUNX1 (E/R) (also known as TEL/AML1) is the most frequent gene fusion in childhood acute lymphoblastic leukemia (ALL) and also most likely the crucial factor for disease initiation; its role in leukemia propagation and maintenance, however, remains largely elusive. To address this issue we performed a shRNA-mediated knock-down (KD) of the E/R fusion gene and investigated the ensuing consequences on genome-wide gene expression patterns and deducible regulatory functions in two E/R-positive leukemic cell lines.

FINDINGS

Microarray analyses identified 777 genes whose expression was substantially altered. Although approximately equal proportions were either up- (KD-UP) or down-regulated (KD-DOWN), the effects on biological processes and pathways differed considerably. The E/R KD-UP set was significantly enriched for genes included in the "cell activation", "immune response", "apoptosis", "signal transduction" and "development and differentiation" categories, whereas in the E/R KD-DOWN set only the "PI3K/AKT/mTOR signaling" and "hematopoietic stem cells" categories became evident. Comparable expression signatures obtained from primary E/R-positive ALL samples underline the relevance of these pathways and molecular functions. We also validated six differentially expressed genes representing the categories "stem cell properties", "B-cell differentiation", "immune response", "cell adhesion" and "DNA damage" with RT-qPCR.

CONCLUSION

Our analyses provide the first preliminary evidence that the continuous expression of the E/R fusion gene interferes with key regulatory functions that shape the biology of this leukemia subtype. E/R may thus indeed constitute the essential driving force for the propagation and maintenance of the leukemic process irrespective of potential consequences of associated secondary changes. Finally, these findings may also provide a valuable source of potentially attractive therapeutic targets.

Acute lymphoblastic leukemia and developmental biology: a crucial interrelationship

The latest scientific findings in the field of cancer research are redefining our understanding of the molecular and cellular basis of the disease, moving the emphasis toward the study of the mechanisms underlying the alteration of the normal processes of cellular differentiation. The concepts best exemplifying this new vision are those of cancer stem cells and tumoral reprogramming. The study of the biology of acute lymphoblastic leukemias (ALLs) has provided seminal experimental evidence supporting these new points of view. Furthermore, in the case of B cells, it has been shown that all the stages of their normal development show a tremendous degree of plasticity, allowing them to be reprogrammed to other cellular types, either normal or leukemic. Here we revise the most recent discoveries in the fields of B-cell developmental plasticity and B-ALL research and discuss their interrelationships and their implications for our understanding of the biology of the disease.

AMP-dependent kinase/mammalian target of rapamycin complex 1 signaling in T-cell acute lymphoblastic leukemia: therapeutic implications

The mammalian target of rapamycin (mTOR) serine/threonine kinase is the catalytic subunit of two multi-protein complexes, referred to as mTORC1 and mTORC2. Signaling downstream of mTORC1 has a critical role in leukemic cell biology by controlling mRNA translation of genes involved in both cell survival and proliferation. mTORC1 activity can be downmodulated by upregulating the liver kinase B1/AMP-activated protein kinase (LKB1/AMPK) pathway. Here, we have explored the therapeutic potential of the anti-diabetic drug, metformin (an LKB1/AMPK activator), against both T-cell acute lymphoblastic leukemia (T-ALL) cell lines and primary samples from T-ALL patients displaying mTORC1 activation. Metformin affected T-ALL cell viability by inducing autophagy and apoptosis. However, it was much less toxic against proliferating CD4(+) T-lymphocytes from healthy donors. Western blot analysis demonstrated dephosphorylation of mTORC1 downstream targets. Unlike rapamycin, we found a marked inhibition of mRNA translation in T-ALL cells treated with metformin. Remarkably, metformin targeted the side population of T-ALL cell lines as well as a putative leukemia-initiating cell subpopulation (CD34(+)/CD7(-)/CD4(-)) in patient samples. In conclusion, metformin displayed a remarkable anti-leukemic activity, which emphasizes future development of LKB1/AMPK activators as clinical candidates for therapy in T-ALL.

Incidence of childhood leukemia in Yogyakarta, Indonesia, 1998-2009

BACKGROUND

In most developing countries, incidence data for childhood cancers are less reliable, because very few population-based registries exist. The aim of this study was to present the epidemiology of childhood leukemia in the Dr. Sardjito Hospital (DSH) region, which catchment area extends beyond the boundaries of the Yogyakarta Special Province (YSP).

PROCEDURE

Health records of children, 0-14 years of age, who were diagnosed with leukemia between January 1998 and December 2009, were reviewed. Diagnosis of leukemia was confirmed by morphological and histochemical examination of marrow samples.

RESULTS

The estimated average annual incidence rate (AAIR) of childhood acute leukemia in DSH was 46.2 per million per year. Interestingly, the annual incidence rate (AIR) of childhood acute leukemia from the catchment area of DSH significantly increased from 35 in 1999 to 70 in 2009 (ANOVA, P = 0.003). The YSP population data, analyzed separately, showed an increase in AIR from 15.7 to 32.9 (ANOVA, P = 0.325) and an AAIR of 28.8. Remarkably, a relatively high frequency (25.5% in DSH and 27.7% in YSP) of children with AML was found in the group of acute leukemias.

CONCLUSION

The DSH incidence calculations may be overestimated due to an underestimation of the population number. Since the population count for YSP is more precise, the data of YSP were used for comparison with developed countries. AAIR of ALL (20.8) is relatively low compared to Western countries (22.4-37.9). The AAIR of AML (8.0) is similar to Western countries (5.0-8.0) resulting a relatively high percentage of AML versus ALL (27.7%) in YSP.

Intellectual development after treatment in children with acute leukemia and brain tumor

BACKGROUND

The influence of central nervous system (CNS)-directed chemotherapy on intelligence remains controversial. In this study, we investigated the influence of treatment on intellectual development in acute lymphoblastic leukemia (ALL) and brain tumor patients undergoing CNS-directed treatments.

METHODS

Among patients treated in the Department of Pediatrics, St Luke's International Hospital between April 2000 and March 2009, the subjects were 38 patients with ALL or brain tumors who underwent regular Wechsler intelligence tests.

RESULTS

The subjects consisted of 26 patients with ALL and 12 with brain tumors. Prophylactic cranial irradiation was not performed in patients with ALL, whereas it was done for all those with brain tumor. In patients with ALL, the IQ 1 year later was not changed from the start of treatment. In those with brain tumors, the verbal IQ 1 year later was significantly lower than that at the start of treatment. In patients with ALL, intelligence tests were performed 3 years after the start of treatment and there were no marked changes between the two time-points (n = 11). In those with a brain tumor, intellectual functions further decreased after the completion of treatment to as late as 5 years after the initiation of treatment (n = 7).

CONCLUSIONS

There is no intellectual impairment in any patient with ALL at post-treatment follow-up 3 years after the start of treatment, while intelligence is serially reduced in brain tumor patients. An innovative intervention may be needed for this group of patients.

IKZF1 deletions predict a poor prognosis in children with B-cell progenitor acute lymphoblastic leukemia: a multicenter analysis in Taiwan

Despite current risk-directed therapy, approximately 15-20% of pediatric patients with acute lymphoblastic leukemia (ALL) have relapses. Recent genome-wide analyses have identified that an alteration of IKZF1 is associated with very poor outcomes in B-cell progenitor ALL. In this study, we determined the prognostic significance of IKZF1 deletions in patients with childhood ALL. This study analyzed 242 pediatric B-cell progenitor ALL patients in Taiwan. We developed a simple yet sensitive multiplex quantitative PCR coupled with capillary electrophoresis to accurately determine the allele dose of IKZF1, and high resolution melting was used for mutation screening for all coding exons of IKZF1. Twenty-six (10.7%) pediatric B-cell progenitor ALL patients were found to harbor these deletions. Most of the deletions were broader deletions that encompassed exon 3 to exon 6, consistent with previous reports. Genomic sequencing of IKZF1 was carried out in all cases and no point mutations were identified. Patients with IKZF1 deletions had inferior event-free survival (P < 0.001), and overall survival (P = 0.0016). The association between IKZF1 deletions and event-free survival was independent of age, leukocyte count at presentation, and cytogenetic subtype by multivariate Cox analysis (P = 0.003, hazard ratio = 2.45). This study indicates that detection of IKZF1 deletions upon diagnosis of B-cell progenitor ALL may help to identify patients at risk of treatment failure. IKZF1 deletions could be incorporated as a new high-risk prognostic factor in future treatment protocols. To the best of our knowledge, this is the first study to examine the poor prognosis of IKZF1 deletions in an Asian population.

Polymorphisms of the SLCO1B1 gene predict methotrexate-related toxicity in childhood acute lymphoblastic leukemia

BACKGROUND

Methotrexate (MTX) is an important component of the therapy for childhood acute lymphoblastic leukemia. Treatment with high-dose MTX often causes toxicity, recommending a dose reduction and/or cessation of treatment. Polymorphisms in genes involved in the MTX metabolism have been associated with toxicity with controversial results. The discrepancies could be due to differences in treatment protocols among studies, small, or non-homogeneous populations or the use of different toxicity criteria. The aim of the present study was to analyze the possible correlation of polymorphisms of genes involved in the MTX metabolism with the toxicity during therapy with the well-established LAL/SHOP protocol.

PROCEDURE

We analyzed 10 polymorphisms in seven genes (MTHFR, TS, SHMT1, RFC1, ABCB1, ABCG2, and SLCO1B1) from the MTX metabolism in 115 Spanish pediatric B-ALL patients, using MTX plasma concentration as an objective and quantifiable marker of toxicity.

RESULTS

We confirmed the suitability of MTX plasma levels as a toxicity marker. We found a statistically significant association between MTX plasma concentration and the SLCO1B1 rs11045879 CC genotype (P = 0.030). The rs4149081 AA genotype, in the same gene, could also be an indicator for high-MTX plasma concentrations. We did not find any significant association in the other genetic polymorphisms analyzed.

CONCLUSIONS

Identification of the rs4149081 and rs11045879 SLCO1B1 polymorphisms in children with ALL could be a useful tool for monitoring patients at risk of low-MTX clearance in order to avoid MTX-related toxicity.

Pathobiology of acute lymphoblastic leukemia

In the present review, the authors described the pathobiological features of B- and T-ALL, which appear to be quite heterogeneous with regard to molecular pathogenesis. The last edition of the World Health Organization Classification considered this aspect by defining many entities based on genetic findings. This approach is not only important for prognostic stratification, but also in the near future will surely represent the basis for the definition of patient-specific therapeutic approaches. A striking example is Ph+ acute lymphoblastic leukemia (ALL), which until the advent of tyrosine kinase inhibitors (TKI) has been regarded as the most aggressive ALL. The use of imatinib, dasatinib, and possibly more recent inhibitors has dramatically changed the clinical scenario, offering new opportunities to patients, especially the elderly. Similarly, the use of FLT3 inhibitors in mixed lineage leukemia-positive cases, gamma-secretase inhibitors in T-ALL, novel TKI, and monoclonal antibodies may represent a successful approach in the future.

Interactions between acute lymphoblastic leukemia and bone marrow stromal cells influence response to therapy

The cure rate for pediatric patients with B precursor acute lymphoblastic leukemia (pre-B ALL) is steadily improving, however relapses do occur despite initial response to therapy. To identify links between drug resistance and gene deregulation we used oligonucleotide microarray technology and determined in 184 pre-B ALL specimen genes differentially expressed compared to normal CD34(+) specimens. We identified 20 signature genes including CTGF, BMP-2, CXCR4 and IL7R, documented to regulate interactions in the bone marrow. We recorded remarkably similar levels of expression in three independent patient cohorts, and found distinct patterns in cytogenetically defined subgroups of pre-B ALL. The canonical pathways that were affected are involved in inter- and intra-cellular communication, regulating signaling within the microenvironment. We tested experimentally whether interaction with stromal cells conferred protection to four drugs used in current ALL therapy, and demonstrated that bone marrow stromal cells significantly influenced resistance to vincristine and cytosine arabinoside. Compounds designed to block the identified cellular interactions within the bone marrow microenvironment are expected to mobilise the leukemic cells and make them more accessible to contemporary antileukemic agents. The data provide novel insight into the pathobiology of ALL and indicate new therapeutic targets for patients with ALL.

The Study of Apoptosis Induced by Allicin in HT-9/HL-60 and its Transfection Cell

To detect the effect of reverse in transfected cells by allicin treated. Two different short hairpin RNAs were designed and constructed in a pSilencer 3.1-H1 neo plasmid. The shRNA recombinant plasmids were transfected into HT9 leukemia cells. Flow cytometry was used to select the stably transfected sells. The cell viability of the cells was assessed using MTT assay, flow cytometry was used to monitor cell cycle and apoptosis. Inverted fluorescence microscope and trasmission electron microscope were used to examine the cytomorphology and ultrastructural changes of cells. The results indicated that compared with HT9 cells, HT9-3.1-2 cells, HT9 cells transfected with shRNA recombinant plasmids, had lower cell viability and higher levels of apoptosis after treated with allicin. The characteristic features of apoptosis were more significantly. The results indicate that allicin can induce cell apoptosis of HT9 and HT9-3.1-2 cells, and after stable transfection with the shRNA vectors, the multidrug resistance in HT9 cells was partly reversed.

A perspectiva dos pais sobre a obtenção do diagnóstico de leucemia linfóide aguda em crianças e adolescentes: uma experiência no Brasil

OBJETIVOS: conhecer a percepção dos pais para o diagnóstico de leucemia em seus filhos. MÉTODOS: pesquisa qualitativa tendo como referencial a teoria das representações sociais ancorada na tradição da sociologia compreensiva. Utilizou-se entrevista semi estruturada para a coleta de dados. Foram entrevistados 20 pais de crianças e adolescentes com diagnóstico de leucemia linfóide aguda (LLA). Para análise dos dados empregou-se a técnica de "análise do conteúdo". As diretrizes de humanização da assistência e princípios bioéticos foram os eixos norteadores da análise dos dados. RESULTADOS: os pais recordaram-se claramente da progressão dos sintomas da doença até o diagnóstico. A palavra leucemia foi associada ao câncer e à morte. Dificuldades relacionadas à escuta dos sintomas, a particularidades clínicas da leucemia e ao encaminhamento no sistema de saúde foram os principais motivos para a demora do diagnóstico definitivo. Destacam-se as peregrinações por diferentes locais, perda da resolubilidade, gastos desnecessários, desgaste emocional e atraso nas ações de saúde. CONCLUSÕES: o câncer envolve valores culturais sobre a morte, cuja carga simbólica é maior no caso da criança. A busca do diagnóstico da leucemia pelos pais é exemplo emblemático do tortuoso caminho percorrido quando o mal que acomete a criança não se enquadra no rótulo das doenças "comuns".

Outcome of childhood acute lymphoblastic leukemia in Jordan

BACKGROUND

Accurate data about childhood acute lymphoblastic leukemia (ALL) in low- and middle-income countries are lacking. Our study is designed to assess survival of childhood ALL at King Hussein Cancer Center (KHCC) using modified St. Jude Children's Research Hospital protocols.

PATIENTS AND METHODS

We reviewed the medical records of children 1-18 years of age who were diagnosed with ALL and treated at KHCC from January 2003 through December 2009. Disease characteristics and outcome were analyzed.

RESULTS

Over a 7-year period, 300 children with ALL were treated. One hundred and seventy-three (57.7%) were males and 127 (42.3%) were females. The median age at diagnosis was 5 years. One hundred and fifty-seven (52.3%) children were classified as low-risk, 118 (39.3%) were standard-risk and 25 (8.3%) were high-risk. Two hundred and sixty-two (88.5%) children had pre-B cell phenotype and 34 (11.5%) had T-cell phenotype. Two hundred and seventy-three (91.3%) children were classified as having CNS I disease, 24 (8%) had CNS II, and 2 (0.67%) had CNS III. Cytogenetic abnormalities included: t(12;21) in 30 (12%) children and t(9;22) in 18 (7.4%). Four (1.3%) children died in induction, 6 (2%) died in first remission and 27 (9%) relapsed. After a median follow-up of 34.5 months (range 0.32-84.5), the estimated 5-year event free survival and overall survival were 80% and 89%, respectively.

CONCLUSION

Treatment protocols developed by major cooperative groups and institutions to treat childhood ALL was successfully adapted and suggest that such an approach may be useful in other low- and middle-income countries.

Childhood acute leukemias are frequent in Mexico City: descriptive epidemiology

Background

Worldwide, acute leukemia is the most common type of childhood cancer. It is particularly common in the Hispanic populations residing in the United States, Costa Rica, and Mexico City. The objective of this study was to determine the incidence of acute leukemia in children who were diagnosed and treated in public hospitals in Mexico City.

Methods

Included in this study were those children, under 15 years of age and residents of Mexico City, who were diagnosed in 2006 and 2007 with leukemia, as determined by using the International Classification of Childhood Cancer. The average annual incidence rates (AAIR), and the standardized average annual incidence rates (SAAIR) per million children were calculated. We calculated crude, age- and sex-specific incidence rates and adjusted for age by the direct method with the world population as standard. We determined if there were a correlation between the incidence of acute leukemias in the various boroughs of Mexico City and either the number of agricultural hectares, the average number of persons per household, or the municipal human development index for Mexico (used as a reference of socio-economic level).

Results

Although a total of 610 new cases of leukemia were registered during 2006-2007, only 228 fit the criteria for inclusion in this study. The overall SAAIR was 57.6 per million children (95% CI, 46.9-68.3); acute lymphoblastic leukemia (ALL) was the most frequent type of leukemia, constituting 85.1% of the cases (SAAIR: 49.5 per million), followed by acute myeloblastic leukemia at 12.3% (SAAIR: 6.9 per million), and chronic myeloid leukemia at 1.7% (SAAIR: 0.9 per million). The 1-4 years age group had the highest SAAIR for ALL (77.7 per million). For cases of ALL, 73.2% had precursor B-cell immunophenotype (SAAIR: 35.8 per million) and 12.4% had T-cell immunophenotype (SAAIR 6.3 per million). The peak ages for ALL were 2-6 years and 8-10 years. More than half the children (58.8%) were classified as high risk. There was a positive correlation between the average number of persons per household and the incidence of the pre-B immunophenotype (Pearson's r, 0.789; P = 0.02).

Conclusions

The frequency of ALL in Mexico City is among the highest in the world, similar to those found for Hispanics in the United States and in Costa Rica.

Obesity and craniopharyngioma

An epidemic of pediatric obesity has occurred across the world in recent years. There are subgroups within the population at high-risk of becoming obese and especially of having experience of precocious cardiovascular and metabolic co-morbidities of obesity. One of these subgroups comprises patients treated for childhood cancers and namely survivors of craniopharyngioma. The high incidence of obesity in this group makes these patients an important disease model to better understand the metabolic disturbances and the mechanisms of weight gain among cancer survivors. The hypothalamic-pituitary axis damage secondary to cancer therapies or to primary tumor location affect long-term outcomes. Nevertheless, the aetiology of obesity in craniopharyngioma is not yet fully understood. The present review has the aim of summarizing the published data and examining the most accepted mechanisms and main predisposing factors related to weight gain in this particular population.

Expression of Ikaros isoform 6 in chinese children with acute lymphoblastic leukemia

Ikaros is a zinc-finger transcription factor that plays an important role in the differentiation and proliferation of lymphocytes. Dominant-negative Ikaros isoform 6 (Ik6), one of its common subtypes, is overexpressed in leukemia patients and is associated with unfavorable prognosis in childhood B-cell progenitor acute lymphoblastic leukemia (ALL). This study was to identify specific isoforms, especially Ik6, in Chinese pediatric patients with ALL. The mRNA expression of Ikaros was detected in 88 children with previously untreated ALL by nested reverse transcription-polymerase chain reaction (RT-PCR). Sequencing of the PCR products was performed to identify specific isoforms. The expression of fusion genes was determined by using multiplex RT-PCR. The functional isoforms Ik1, Ik2/3, and dominant negative isoforms Ik4, 6, 8, 9, 10 identified by nested RT-PCR were further confirmed by sequence analysis. In the 88 cases, the Ik6 was found to be overexpressed in 8 of 70 cases of B-lineage ALL and in 1 of 18 cases of T-lineage ALL patients. Among Ik6 B-lineage ALL patients, 3 had expression of BCR/ABL fusion gene and 1 had HOX11 expression. Ik6 overexpression was independent of age, white blood cell count at diagnosis, risk group, and expression of the fusion genes currently measured in China except BCR/ABL (P<0.01). And it was strongly associated with elevated levels of minimal residual disease at day 28 (P<0.01). Ik6 can be included as a high-risk factor at diagnosis. In developing countries with limited resources, it can be economically detected by nested RT-PCR.

Deletion of genes encoding PU.1 and Spi-B in B cells impairs differentiation and induces pre-B cell acute lymphoblastic leukemia

The E26 transformation-specific (Ets) transcription factor PU.1 is required to generate lymphoid progenitor cells from hematopoietic stem cells, but it is not required to generate B cells from committed B-cell lineage progenitors. We hypothesized that PU.1 function in B-cell differentiation is complemented by the related Ets transcription factor Spi-B. To test this hypothesis, mice were generated lacking both PU.1 and Spi-B in the B-cell lineage. Unlike mice lacking PU.1 or Spi-B, mice deficient in both PU.1 and Spi-B in the B-cell lineage had reduced frequencies of B cells as well as impaired B-cell differentiation. Strikingly, all PU.1 and Spi-B-deficient mice developed pre-B cell acute lymphoblastic leukemia before 30 weeks of age. Pre-B cells accumulated in the thymus resulting in massive thymic enlargement and dyspnea. These findings demonstrate that PU.1 and Spi-B are essential transcriptional regulators of B-cell differentiation as well as novel tumor suppressors in the B-cell lineage.

Pharmacotherapeutic advances in the treatment of acute lymphoblastic leukaemia in adults

Acute lymphoblastic leukaemia (ALL) in adults is a challenging malignancy in that many patients will show evidence of initial chemotherapy responsiveness but will subsequently relapse. The disease is heterogeneous and outcomes vary dramatically depending on the prognostic factors present in an individual patient. An important determinant of outcome is the age of the patient. The stunning success of therapy in paediatric ALL has led to the use of intensive paediatric regimens in adolescents and young adults with what appear to be improved outcomes. For patients who relapse or have high-risk features, blood and marrow transplantation (BMT) continues to play an important role in the therapeutic armamentarium. The use of reduced-intensity conditioning regimens for allogeneic BMT suggests that outcomes may be improved by this approach. Monoclonal antibodies are showing benefit as single agents in the relapsed setting or in combination with chemotherapy in newly diagnosed patients. In recent years, several new chemotherapeutic agents have shown promise as single agents and are being incorporated into multi-agent chemotherapy. The development of tyrosine kinase inhibitors for Philadelphia chromosome-positive leukaemias has significantly improved outcomes. The molecular revolution has led to the identification of new aberrant molecular pathways in the pathogenesis of ALL, and drugs targeting these aberrancies are in various stages of development preclinically and clinically. These developments bring the hope that therapeutic outcomes in adult ALL can begin to approach those seen in the paediatric setting.

Apoptotic role of IKK in T-ALL therapeutic response

Despite considerable progress in the treatment of T cell acute lymphoblastic leukemia (T-ALL), it is still the highest risk malignancy among ALL. The outcome of relapsed patients remains dismal. The pro-survival role of NOTCH1 and NFκB in T-ALL is well documented; also, both factors were reported to be predictive of relapse. The NOTCH1 signaling pathway, commonly activated in T-ALL, was shown to enhance the transcriptional function of NFκB via several mechanisms. Thus, pharmacological inhibition of NOTCH1-NFκB signaling was suggested to be incorporated into existing T-ALL treatment protocols. However, conventional chemotherapy is based on activation of various types of stress, such as DNA damage, mitotic perturbations or endoplasmic reticulum overload. NFκB is frequently activated in response to stress and, depending on yet unknown mechanisms, it either protects cells from the drug action or mediates apoptosis. Here, we report that T-ALL cells respond to NFκB inhibition in opposite ways depending on whether they were treated with a stress-inducing chemotherapeutic agent or not. Moreover, we found that NOTCH1 enhances NFκB apoptotic function in the stressed cells. The data argue for further studies of NFκB status in T-ALL patients on different treatment protocols and the impact of activating NOTCH1 mutations on treatment response.

Challenging issues in pediatric oncology

Improvements in protocol-driven clinical trials and supportive care for children and adolescents with cancer have reduced mortality rates by more than 50% over the past three decades. Overall, the 5-year survival rate for patients with pediatric cancer has increased to approximately 80%. Recognition of the biological heterogeneity within specific subtypes of cancer, the discovery of genetic lesions that drive malignant transformation and cancer progression, and improved understanding of the basis of drug resistance will undoubtedly catalyze further advances in risk-directed treatments and the development of targeted therapies, boosting the cure rates further. Emerging new treatments include novel formulations of existing chemotherapeutic agents, monoclonal antibodies against cancer-associated antigens, and molecular therapies that target genetic lesions and their associated signaling pathways. Recent findings that link pharmacogenomic variations with drug exposure, adverse effects, and efficacy should accelerate efforts to develop personalized therapy for individual patients. Finally, palliative care should be included as an essential part of cancer management to prevent and relieve the suffering and to improve the quality of life of patients and their families.

Targeting survivin overcomes drug resistance in acute lymphoblastic leukemia

Relapse of drug-resistant acute lymphoblastic leukemia (ALL) has been associated with increased expression of survivin/BIRC5, an inhibitor of apoptosis protein, suggesting a survival advantage for ALL cells. In the present study, we report that inhibition of survivin in patient-derived ALL can eradicate leukemia. Targeting survivin with shRNA in combination with chemotherapy resulted in no detectable minimal residual disease in a xenograft model of primary ALL. Similarly, pharmacologic knock-down of survivin using EZN-3042, a novel locked nucleic acid antisense oligonucleotide, in combination with chemotherapy eliminated drug-resistant ALL cells. These findings show the importance of survivin expression in drug resistance and demonstrate that survivin inhibition may represent a powerful approach to overcoming drug resistance and preventing relapse in patients with ALL.

CASP8AP2 is a promising prognostic indicator in pediatric acute lymphoblastic leukemia

The prognostic significance of caspase 8 associated protein 2 (CASP8AP2) in pediatric ALL is controversial. We determined a cut-off of CASP8AP2 expression in bone marrow samples of 39 newly diagnosed patients, and found a significantly poor bone marrow relapse-free survival (p=0.019) in low-expression group and verified it in another cohort of 106 patients (p=0.002). Furthermore, as an independent prognostic factor, CASP8AP2 expression was correlated to minimal residual disease (MRD), and incorporating it with MRD would help to identify patients at greater risk of bone marrow relapse. We also developed an algorithm comprised of clinical risk and CASP8AP2 expression, which could predict bone marrow relapse more accurately.

Improving outcomes for high-risk ALL: translating new discoveries into clinical care

High-risk (HR) acute lymphoblastic leukemia (ALL) remains one of the greatest challenges in pediatric oncology. Relapsed ALL is a leading cause of death in young people, and further improvements in outcome will required the development of therapeutic approaches directed against rational therapeutic targets, as escalation of the intensity of existing therapies is limited by toxicity. This review summarizes advances in the biology and treatment of HR and relapsed ALL presented at a symposium at the 2010 American Society for Pediatric Hematology and Oncology Annual Meeting. Analysis of large patient cohorts has identified several factors associated with HR of relapse including older age, T-lineage disease, and persisting minimal residual disease (MRD) early in therapy. As the results of salvage therapy remain poor, new treatment approaches are needed. BCR-ABL1-positive (Ph+) ALL has historically had a very poor outcome, but recent studies have demonstrated the impressive improvements in treatment outcome with the use of tyrosine kinase inhibitors (TKIs). High-resolution genomic profiling of genetic alterations and gene expression has revolutionized our understanding of the genetic basis of ALL, and has identified several alterations associated with poor outcome, including mutations of the lymphoid transcription factor gene IKZF1 (IKAROS), activating mutations of Janus kinases, and rearrangement of the lymphoid cytokine receptor gene CRLF2. These data indicated that the genetic basis of HR-ALL is multifactorial, and have also provided a new potential therapeutic option directed at JAK inhibition.

Folate fortification and survival of children with acute lymphoblastic leukemia

BACKGROUND

The antifolate drug methotrexate is a mainstay of treatment for children diagnosed with acute lymphoblastic leukemia (ALL). There have been concerns regarding the impact of folate fortification on the efficacy of methotrexate therapy and hence treatment outcomes of ALL.

OBJECTIVE

The objective of this study was to evaluate whether folate fortification has been associated with a higher incidence of adverse outcomes in children with ALL.

METHODS

In a retrospective, population-based study, using data from the Pediatric Oncology Group of Ontario (POGO), Ontario, Canada, and the WHO, we examined yearly and population-adjusted mortality rates in Canada, the US, and several European countries.

RESULTS

Our analysis demonstrates that there has been a decreasing trend in ALL mortality numbers and rates between 1999 and 2005 in the US and Canada, in a similar degree to those in European countries where folate fortification is not implemented.

CONCLUSION

These data suggest that folate fortification does not appear to have caused an increase in therapeutic failures in children with ALL.

Advances in the Biology of Acute Lymphoblastic Leukemia-From Genomics to the Clinic

Despite impressive advances in cure rates for childhood acute lymphoblastic leukemia (ALL), ALL remains the leading cause of disease-related death in young people and new therapeutic approaches directed against rational therapeutic targets are urgently required to improve treatment outcomes. This is particularly true for ALL in older children, adolescents, and adults, in whom treatment outcomes are markedly inferior to those of young children. A major goal of current leukemia research is to use comprehensive genomic analysis of the leukemic cell genome, transcriptome, and epigenome to identify critical new genomic alterations that drive leukemogenesis and influence responsiveness to therapy. Genomic analyses in childhood ALL have been remarkably informative and have identified a number of new structural genetic alterations that play important roles in the establishment of the leukemic clone and determine risk of relapse. Notably, many high-risk ALL cases harbor loss-of-function and dominant mutations of genes that encode transcriptional regulators of lymphoid development coupled with mutations that result in activation of cytokine receptor and kinase signaling pathways. These advances have resulted in new diagnostic approaches and therapeutic trials in ALL. This review will discuss these advances and outline challenges for future studies, including the potential role of genome-wide sequencing approaches and the need for detailed studies of the genetics of ALL in the adolescent and young adult population.

Redundancy and specificity of the metalloprotease system mediating oncogenic NOTCH1 activation in T-ALL

Oncogenic mutations in NOTCH1 are present in over 50% of T-cell lymphoblastic leukemias (T-ALLs). Activation of NOTCH1 requires a double proteolytic processing in the extracellular region of the receptor (S2) and in the transmembrane domain (S3). Currently, anti-NOTCH1 therapies based on inhibition of S3 processing via small molecule γ-secretase inhibitors are in development. Here we report on the characterization of the protease system responsible for S2 processing of NOTCH1 in T-ALL. Analysis of NOTCH1 HD class I, NOTCH1 HD class II and NOTCH1 JME alleles characterized by increased and aberrant S2 processing shows that both ADAM10, a metalloprotease previously implicated in activation of wild type NOTCH1 in mammalian cells, and ADAM17, a closely related protease capable of processing NOTCH1 in vitro, contribute to the activation of oncogenic forms of NOTCH1. However, and despite this apparent functional redundancy, inhibition of either ADAM10 is sufficient to blunt NOTCH1 signaling in T-ALL lymphoblasts. These results provide further insight on the mechanisms that control the activation of oncogenic NOTCH1 mutants and identify ADAM10 as potential therapeutic target for the inhibition of oncogenic NOTCH1 in T-ALL.

High-risk pediatric acute lymphoblastic leukemia: to transplant or not to transplant?

Because survival with both chemotherapy and allogeneic hematopoietic stem cell transplantation (HSCT) approaches to high-risk pediatric acute lymphoblastic leukemia (ALL) generally improves through the years, regular comparisons of outcomes with either approach for a given indication are needed to decide when HSCT is indicated. Improvements in risk classification are allowing clinicians to identify patients at high risk for relapse early in their course of therapy. Whether patients defined as high risk by new methods will benefit from HSCT requires careful testing. Standardization and improvement of transplant approaches has led to equivalent survival outcomes with matched sibling and well-matched unrelated donors; however, survival using mismatched and haploidentical donors is generally worse. Trials comparing chemotherapy and HSCT must obtain sufficient data about therapy and stratify the analysis to assess the outcomes of best-chemotherapy with best-HSCT approaches.

WAVE1 regulates P-glycoprotein expression via Ezrin in leukemia cells

For children with acute myeloblastic leukemia (AML), multidrug resistance (MDR) reduces treatment effectiveness, and often leads to poor patient survival. While a number of factors have been described that affect MDR, the mechanisms underlying this effect remain unclear. In this study, the role of WAVE1 in MDR was investigated. Among 62 children with AML, high levels of WAVE1 were associated with poor patient outcomes. Proteomic techniques were used to identify novel WAVE1-interacting proteins from leukemia cells, one of which was the cytoskeleton regulator Ezrin. In leukemia cells, WAVE1 co-localized with both Ezrin and P-glycoprotein (P-gp), a critical regulator of the MDR phenotype. Overexpression of WAVE1 in K562 leukemia cells up-regulated P-gp and Ezrin, and reduced K562 cells' sensitivity to the chemotherapy drug adriamycin. The opposite effect was seen when WAVE1 expression was reduced via RNA interference. Critically, overexpression of WAVE1 in the absence of Ezrin did not affect P-gp levels or MDR. These data suggest that WAVE1 affects P-gp and MDR of leukemia cells through Ezrin.

Ebf1 or Pax5 haploinsufficiency synergizes with STAT5 activation to initiate acute lymphoblastic leukemia

As STAT5 is critical for the differentiation, proliferation, and survival of progenitor B cells, this transcription factor may play a role in acute lymphoblastic leukemia (ALL). Here, we show increased expression of activated signal transducer and activator of transcription 5 (STAT5), which is correlated with poor prognosis, in ALL patient cells. Mutations in EBF1 and PAX5, genes critical for B cell development have also been identified in human ALL. To determine whether mutations in Ebf1 or Pax5 synergize with STAT5 activation to induce ALL, we crossed mice expressing a constitutively active form of STAT5 (Stat5b-CA) with mice heterozygous for Ebf1 or Pax5. Haploinsufficiency of either Pax5 or Ebf1 synergized with Stat5b-CA to rapidly induce ALL in 100% of the mice. The leukemic cells displayed reduced expression of both Pax5 and Ebf1, but this had little effect on most EBF1 or PAX5 target genes. Only a subset of target genes was deregulated; this subset included a large percentage of potential tumor suppressor genes and oncogenes. Further, most of these genes appear to be jointly regulated by both EBF1 and PAX5. Our findings suggest a model whereby small perturbations in a self-reinforcing network of transcription factors critical for B cell development, specifically PAX5 and EBF1, cooperate with STAT5 activation to initiate ALL.

Clinical significance of aberrant DNA methylation in childhood acute lymphoblastic leukemia

Methylation profile was analyzed in ninety-five patients with childhood acute lymphoblastic leukemia (ALL). Methylation of both MGMT and p16 genes were associated with higher age (p=0.01 and p=0.03, respectively). Methylation of both p15 and SHP1 genes occurred more frequently in T-ALL than in precursor B-ALL (p=0.02 and p=0.01, respectively). In contrast, methylation of the DAPK gene was more frequent in precursor B-ALL (p=0.01). Patients with methylation of multiple genes more likely had T cell phenotype, and are classified as medium/high risk (p=0.004 and p=0.03, respectively). These results suggest that methylation status is associated with clinicopathological features in childhood ALL.

Focal adhesion kinase as a target in the treatment of hematological malignancies

Focal adhesion kinase (FAK) is a non-receptor protein tyrosine kinase that plays important regulatory roles in several basic cellular activities. During normal development, FAK is a critical mediator of the integrin signaling cascade, which modulates cell proliferation, apoptosis, adhesion, spreading and migration. Importantly, FAK overexpression is found in a large number of cancer types and FAK expression levels generally correlate with increased tumor malignancy. Though FAK has been a popular potential target for treatment of solid tumors, its roles in leukemias and lymphomas have not been well defined. Here, I briefly summarize the multifaceted functions of FAK in tumor progression, and discuss current efforts and exciting future directions of using RNAi-mediated knockdown of FAK as a potential therapy against leukemia and lymphomas.

Review of the Churchill County, NV ALL cluster, 1997-2004

Between 1997 and 2002, 16 cases of acute childhood leukemia were diagnosed in children who either lived in Churchill County, Nevada at the time of diagnosis or had lived in the county before their diagnosis. The cases were characterized as a cluster of like illnesses and the probability of having such a cluster occur by chance was estimated to be very small (approximately one in 2.33×10(8)). This suggested that the cluster could be linked to one or more physical, limnological, chemical, or biological agents. This review discusses the setting in which the cluster took place, the epidemiological investigations carried out by the Nevada Bureau of Health Protection Services, the National Center for Environmental Health Centers for Disease Control and Prevention and the Agency for Toxic Substances and Disease Registry, and subsequent investigations supported by a special allocation of federal funds through the US Environmental Protection Agency's Region IX office in San Francisco, CA. This review is meant as background for the papers in this special issue that report results from multi- and interdisciplinary research into environmental and biological factors potentially related to the Churchill County leukemia cluster.

Soluble Fas and Fas ligand and prognosis in children with acute lymphoblastic leukemia

The soluble forms of Fas and its ligand (sFas and sFasL) correlate with disease progression in various malignancies. We compared serum levels of sFas and sFasL in children with acute lymphoblastic leukemia and healthy children to determine the prognostic significance of these molecules. Serum levels of sFas and sFasL were measured with an enzyme-linked immunosorbent assay in 48 patients with newly diagnosed childhood acute lymphoblastic leukemia and 38 healthy children. Cut-off values of sFas and sFasL levels were based on their levels in controls. Clinical and laboratory characteristics were recorded on admission. The mean serum concentration of sFas was 243 ± 40 pg/mL in patients and 238 ± 29 pg/mL in controls. Serum levels of sFasL were 4.33 ± 0.25 ng/mL in patients and 4.27 ± 0.11 ng/mL in controls. Neither difference was significant. Based on the cut-off value, 12.5% of the patients were positive for sFas, and 16.6% were positive for sFasL. Survival was significantly longer in sFasL-positive patients (394 ± 69.6 vs. 254 ± 24.3 days) and the duration of complete remission was also longer (380 ± 65.0 vs. 246 ± 26.0 days) than in sFasL-negative patients (P < 0.02), indicating the important role of this molecule in the response to therapy. Higher sFas levels were associated with hepatosplenomegaly (P < 0.047). In conclusion, sFasL positivity was associated with a favorable outcome in ALL patients.