Acute lymphoblastic leukemia

Characterization of the gammadelta T cell response to acute leukemia

BACKGROUND

Previous work from our center has suggested a correlation between increased donor-derived Vdelta1+ gammadelta T cells and long-term relapse-free survival following bone marrow transplantation for leukemia. Questions remain, however, as to whether this observation can be explained by a gammadelta T cell-based immune response against primary leukemia.

METHODS

We examined gammadelta T cell receptor (TCR) phenotype, cell proliferation, and cytolytic activity following culture with irradiated primary leukemia blasts from a haploidentical first-degree relative. Subsequently, we also studied the gammadelta TCR phenotype and complimentarity determining region 3 (CDR3) cDNA sequences from 17 newly diagnosed leukemia patients.

RESULTS

In 17/28 (61%) of in vitro cultures, gammadelta T cells proliferated in culture with primary blasts. Vdelta1+ T cells were proportionally increased in all cultures and were the predominant cell population in 6/17. In the 7 cultures where cytotoxicity could be assessed, 6 (86%) showed some degree of cytotoxicity to the primary leukemia. Vdelta1+ T cells were also the predominant gammadelta T cell subtype in pre-treatment leukemia patients principally due to loss of Vdelta2+ T cells rather than expansion of Vdelta1+ cells. The Vdelta1 CDR3-region cDNA sequence from these patients revealed exclusive use of the Jdelta1 constant region and sequence conservation in 4/11 patients.

CONCLUSIONS

gammadelta T cells exhibit an in vitro response to primary leukemia blasts that is manifested by proliferation, an increased proportion of Vdelta1+ T cells, and cytotoxicity to the primary leukemia blasts. The Vdelta1+ T cell population is also predominant in newly diagnosed leukemia patients likely due to a loss of circulating Vdelta2+ T cells. A small proportion of newly diagnosed patients showed Vdelta1 CDR3 region similarity. These findings suggest a role for gammadelta T cells in the immune response to leukemia.

Cyclin D2 dysregulation by chromosomal translocations to TCR loci in T-cell acute lymphoblastic leukemias

Strong expression of at least one of the three D-type cyclins is common in human cancers. While the cyclin D1 and D3 genes (CCND1 and CCND3) are recurrently involved in genomic rearrangements, especially in B-cell lymphoid neoplasias, no clear involvement of the cyclin D2 gene (CCND2) has been reported to date. Here, we identified chromosomal translocations targeting the CCND2 locus at 12p13, and the T-cell receptor beta (TCRB) or the TCRA/D loci in T-cell acute lymphoblastic leukemias (T-ALLs). Expression analysis demonstrated dramatic cyclin D2 overexpression in the translocated cases (n=3) compared to other T-ALLs (total, n=89). In order to evaluate dysregulation in T-ALL with respect to normal T-cell differentiation, we analyzed CCND2 expression in normal purified human thymic subpopulations. CCND2 levels were downregulated through progression from the early stages of human T-cell differentiation, further suggesting that the massive and sustained expression in the CCND2-rearranged T-ALL cases was oncogenic. Association with other oncogene expression (TAL1, HOXAs, or TLX3/HOX11L2), NOTCH1 activating mutations, and/or CDKN2A/p16/ARF deletion, showed that cyclin D2 dysregulation could contribute to multi-event oncogenesis in various T-ALL groups. This report is the first clear evidence of a direct involvement of cyclin D2 in human cancer due to recurrent somatic genetic alterations.

[Necrotic myocarditis in acute eosinophilic lymphoblastic leukaemia]

INTRODUCTION

Hypereosinophilia can cause severe cardiac complications. The association between an acute lymphoblastic leukemia and hypereosinophilia was rare. We report a case of a 29-year-old man who presented a heart failure secondary to necrotic myocarditis related to an acute eosinophilic lymphoblastic leukaemia.

EXEGESIS

The patient developed a heart failure and secondary a cardio-embolic stroke, due to a large mobile left ventricle thrombosis. His peripheral blood showed a total white count of 28,500 leucocytes/mm3 with 18,800 eosinophils/mm3. The myelogram cytology showed precursor B-cell acute lymphoblastic leukaemia with hypereosinophilia.

CONCLUSION

The possibility of the rapid emergence of cardiac lesions in hypereosinophilic syndromes warrants very close physician vigilance. An Echocardiography and MRI performed at the early stage and in the follow-up allow to detect and to manage these cardiac disorders.

Role of radiation therapy in pediatric cancer

Whether in its preventive role of CNS prophylaxis for high-risk ALL, its central role in brain tumors, its adjunct role combined with chemotherapy for disease such as Hodgkin's lymphoma, Ewing's sarcoma, and rhabdomyosarcoma, or its palliative role for metastatic disease, radiation remains an important therapy for pediatric cancers.

Loss of antibodies and response to (re-)vaccination in children after treatment for acute lymphocytic leukemia: a systematic review

Intensified chemotherapy regimens resulting in improved survival of children with acute lymphocytic leukemia (ALL) lead to concerns about therapy-induced immune damage reflected by the loss of protection of previous immunizations and the efficacy of (re-)vaccination. The severity of secondary immunodeficiency, however, is not clear and knowledge is based on a limited number of studies. We performed a systematic review on literature concerning vaccination data of children with ALL published since 1980. Eight studies fulfilled the inclusion criteria. Regarding antibody titers after treatment, the number of children who had preserved the defined protection level for antibodies differed widely, ranging from 17 to 98% for diphtheria, 27 to 82% for Bordetella pertussis, 20 to 98% for tetanus, 62 to 100% for poliomyelitis, 35 to 100% for Haemophilus influenzae type B (HiB), 29 to 92% for mumps, 29 to 60% for measles and 72 to 92% for rubella. Most patients however responded to revaccination, demonstrating immunological recovery. Although the designs and results of the included studies varied widely, it can be concluded that cytostatic therapy for ALL in children results in a temporarily reduction of specific antibody levels. Memory is preserved but revaccination may be warranted. This is the first systematic review and the best possible current approximation of chemotherapy-induced immune damage in children after ALL treatment.

Molecular biology in acute leukemia

Acute leukemia is a clonal expansion of tumoral cells in bone marrow, blood or other tissues. The acute leukemias are classified as myeloid or lymphoid based on the lineage of the blast cells. Over the past three decades, remarkable advances have been made in the classification and treatment of acute leukemias. In the last years, the research into the molecular pathogenesis of acute leukemia has progressed. The knowledge of chromosomal translocations breakpoints and possible candidate oncogenes and tumor suppressor genes has allowed the integration of all these events into multistep cascades that impact specific signal transduction pathways and lead to leukemic transformation.

Epigenetic regulation of human gamma-glutamyl hydrolase activity in acute lymphoblastic leukemia cells

Gamma-glutamyl hydrolase (GGH) catalyzes degradation of the active polyglutamates of natural folates and the antifolate methotrexate (MTX). We found that GGH activity is directly related to GGH messenger RNA expression in acute lymphoblastic leukemia (ALL) cells of patients with a wild-type germline GGH genotype. We identified two CpG islands (CpG1 and CpG2) in the region extending from the GGH promoter through the first exon and into intron 1 and showed that methylation of both CpG islands in the GGH promoter (seen in leukemia cells from approximately 15% of patients with nonhyperdiploid B-lineage ALL) is associated with significantly reduced GGH mRNA expression and catalytic activity and with significantly higher accumulation of MTX polyglutamates (MTXPG(4-7)) in ALL cells. Furthermore, methylation of CpG1 was leukemia-cell specific and had a pronounced effect on GGH expression, whereas methylation of CpG2 was common in leukemia cells and normal leukocytes but did not significantly alter GGH expression. These findings indicate that GGH activity in human leukemia cells is regulated by epigenetic changes, in addition to previously recognized genetic polymorphisms and karyotypic abnormalities, which collectively determine interindividual differences in GGH activity and influence MTXPG accumulation in leukemia cells.

Genes contributing to minimal residual disease in childhood acute lymphoblastic leukemia: prognostic significance of CASP8AP2

In childhood acute lymphoblastic leukemia (ALL), early response to treatment is a powerful prognostic indicator. To identify genes associated with this response, we analyzed gene expression of diagnostic lymphoblasts from 189 children with ALL and compared the findings with minimal residual disease (MRD) levels on days 19 and 46 of remission induction treatment. After excluding genes associated with genetic subgroups, we identified 17 genes that were significantly associated with MRD. The caspase 8-associated protein 2 (CASP8AP2) gene was studied further because of its reported role in apoptosis and glucocorticoid signaling. In a separate cohort of 99 patients not included in the comparison of gene expression profiles and MRD, low levels of CASP8AP2 expression predicted a lower event-free survival (P = .02) and a higher rate of leukemia relapse (P = .01) and were an independent predictor of outcome. High levels of CASP8AP2 expression were associated with a greater propensity of leukemic lymphoblasts to undergo apoptosis. We conclude that measurement of CASP8AP2 expression at diagnosis offers a means to identify patients whose leukemic cells are highly susceptible to chemotherapy. Therefore, this gene is a strong candidate for inclusion in gene expression arrays specifically designed for leukemia diagnosis.

Cytogenetics and molecular genetics of T-cell acute lymphoblastic leukemia: from thymocyte to lymphoblast

For long, T-cell acute lymphoblastic leukemia (T-ALL) remained in the shadow of precursor B-ALL because it was more seldom, and showed a normal karyotype in more than 50% of cases. The last decennia, intense research has been carried out on different fronts. On one side, development of normal thymocyte and its regulation mechanisms have been studied in multiple mouse models and subsequently validated. On the other side, molecular cytogenetics (fluorescence in situ hybridization) and mutation analysis revealed cytogenetically cryptic aberrations in almost all cases of T-ALL. Also, expression microarray analysis disclosed gene expression signatures that recapitulate specific stages of thymocyte development. Investigations are still very much actual, fed by the discovery of new genetic aberrations. In this review, we present a summary of the current cytogenetic changes associated with T-ALL. The genes deregulated by translocations or mutations appear to encode proteins that are also implicated in T-cell development, which prompted us to review the 'normal' and 'leukemogenic' functions of these transcription regulators. To conclude, we show that the paradigm of multistep leukemogenesis is very much applicable to T-ALL and that the different genetic insults collaborate to maintain self-renewal capacity, and induce proliferation and differentiation arrest of T-lymphoblasts. They also open perspectives for targeted therapies.

Proteomic analysis reveals a novel role for the actin cytoskeleton in vincristine resistant childhood leukemia--an in vivo study

Intrinsic or acquired resistance to vincristine (VCR), an antimicrotubule agent used in the treatment of childhood acute lymphoblastic leukemia (ALL), is a major clinical problem. Using a clinically relevant NOD/SCID mouse xenograft model of ALL, we established that alterations in the actin and tubulin cytoskeleton are involved in in vivo VCR resistance. Altered protein expression between VCR-sensitive ALL xenografts, and xenografts with intrinsic or acquired VCR resistance, was identified using 2-D DIGE coupled with MS. Of the 19 proteins displaying altered expression, 11 are associated with the actin cytoskeleton. Altered expression of the actin- and/or tubulin-binding proteins gelsolin, moesin, ezrin, tropomyosin, CAP-G, HSP27, HSP70, TCP-1, and stathmin were associated with in vivo VCR resistance. The actin-regulating protein gelsolin was increased in both acquired and resistant leukemia as confirmed by immunoblotting and gene expression. The major cytoskeletal protein, gamma-actin, was down-regulated in the VCR-resistant leukemia xenografts; in contrast, there was no significant change in beta-actin expression. This study provides the first evidence for a role of the actin cytoskeleton in intrinsic and acquired in vivo antimicrotubule drug resistance in childhood leukemia and highlights the power of 2-D DIGE for the discovery of resistance markers, pharmacoproteomics, and signaling pathways in cancer.

Loss of heterozygosity on chromosome 6q14-q24 is associated with poor outcome in children and adolescents with T-cell lymphoblastic lymphoma

Deletions of chromosome 6q have been reported in several hematological malignancies, but data are not conclusive regarding their biological and prognostic impact. Therefore, we focused on pediatric patients diagnosed with T-cell lymphoblastic lymphoma (T-LBL) treated uniformly according to the NHL-BFM95 protocol. We used loss-of-heterozygosity (LOH) analysis of 25 microsatellite markers located on chromosome 6q14-q24. Fragment-length analysis was performed on ABI-PRISM3100 Genetic-Analyzer. Eligibility criterion was > or =3 informative markers. Between April 1995 and March 2003, 185 T-LBL patients were treated according to the NHL-BFM95 protocol. Five-year event-free (EFS) and disease-free survival (DFS) were 79+/-3 and 87+/-3% (median follow-up 4.7 [1.2-10.1] years). Sixty-one patients were evaluable for LOH analysis, including 18 out of 23 patients with relapse. EFS and DFS were 67+/-6 and 69+/-6% for these 61 patients. Testing of 853 markers in the 61 patients identified the presence of LOH in 19 patients (31%): 13 of the 18 relapse patients and five of the 41 in complete remission (odds ratio 18.7, 95% confidence interval 4.7-75.3). One LOH-positive patient died from treatment-related toxicity. We conclude that LOH on chromosome 6q14-q24 may have conferred a high risk of relapse on our group of children with T-LBL treated according to the NHL-BFM95 protocol.

CUTLL1, a novel human T-cell lymphoma cell line with t(7;9) rearrangement, aberrant NOTCH1 activation and high sensitivity to gamma-secretase inhibitors

Activating mutations in NOTCH1 are present in over 50% of human T-cell lymphoblastic leukemia (T-ALL) samples and inhibition of NOTCH1 signaling with gamma-secretase inhibitors (GSI) has emerged as a potential therapeutic strategy for the treatment of this disease. Here, we report a new human T-cell lymphoma line CUTLL1, which expresses high levels of activated NOTCH1 and is extremely sensitive to gamma-secretase inhibitors treatment. CUTLL1 cells harbor a t(7;9)(q34;q34) translocation which induces the expression of a TCRB-NOTCH1 fusion transcript encoding a membrane-bound truncated form of the NOTCH1 receptor. GSI treatment of CUTLL1 cells blocked NOTCH1 processing and caused rapid clearance of activated intracellular NOTCH1. Loss of NOTCH1 activity induced a gene expression signature characterized by the downregulation of NOTCH1 target genes such as HES1 and NOTCH3. In contrast with most human T-ALL cell lines with activating mutations in NOTCH1, CUTLL1 cells showed a robust cellular phenotype upon GSI treatment characterized by G1 cell cycle arrest and increased apoptosis. These results show that the CUTLL1 cell line has a strong dependence on NOTCH1 signaling for proliferation and survival and supports that T-ALL patients whose tumors harbor t(7;9) should be included in clinical trials testing the therapeutic efficacy NOTCH1 inhibition with GSIs.

A new recurrent 9q34 duplication in pediatric T-cell acute lymphoblastic leukemia

Over the last decade, genetic characterization of T-cell acute lymphoblastic leukemia (T-ALL) has led to the identification of a variety of chromosomal abnormalities. In this study, we used array-comparative genome hybridization (array-CGH) and identified a novel recurrent 9q34 amplification in 33% (12/36) of pediatric T-ALL samples, which is therefore one of the most frequent cytogenetic abnormalities observed in T-ALL thus far. The exact size of the amplified region differed among patients, but the critical region encloses approximately 4 Mb and includes NOTCH1. The 9q34 amplification may lead to elevated expression of various genes, and MRLP41, SSNA1 and PHPT1 were found significantly expressed at higher levels. Fluorescence in situ hybridization (FISH) analysis revealed that this 9q34 amplification was in fact a 9q34 duplication on one chromosome and could be identified in 17-39 percent of leukemic cells at diagnosis. Although this leukemic subclone did not predict for poor outcome, leukemic cells carrying this duplication were still present at relapse, indicating that these cells survived chemotherapeutic treatment. Episomal NUP214-ABL1 amplification and activating mutations in NOTCH1, two other recently identified 9q34 abnormalities in T-ALL, were also detected in our patient cohort. We showed that both of these genetic abnormalities occur independently from this newly identified 9q34 duplication.

Molecular cytogenetic study of 126 unselected T-ALL cases reveals high incidence of TCRbeta locus rearrangements and putative new T-cell oncogenes

Chromosomal aberrations of T-cell receptor (TCR) gene loci often involve the TCRalphadelta (14q11) locus and affect various known T-cell oncogenes. A systematic fluorescent in situ hybridization (FISH) screening for the detection of chromosomal aberrations involving the TCR loci, TCRalphadelta (14q11), TCRbeta (7q34) and TCRgamma (7p14), has not been conducted so far. Therefore, we initiated a screening of 126 T-cell acute lymphoblastic leukemia (T-ALL) and T-cell lymphoblastic lymphoma cases and 19 T-ALL cell lines using FISH break-apart assays for the different TCR loci. Genomic rearrangements of the TCRbeta locus were detected in 24/126 cases (19%), most of which (58.3%) were not detected upon banding analysis. Breakpoints in the TCRalphadelta locus were detected in 22/126 cases (17.4%), whereas standard cytogenetics only detected 14 of these 22 cases. Cryptic TCRalphadelta/TCRbeta chromosome aberrations were thus observed in 22 of 126 cases (17.4%). Some of these chromosome aberrations target new putative T-cell oncogenes at chromosome 11q24, 20p12 and 6q22. Five patients and one cell line carried chromosomal rearrangements affecting both TCRbeta and TCRalphadelta loci. In conclusion, this study presents the first inventory of chromosomal rearrangements of TCR loci in T-ALL, revealing an unexpected high number of cryptic chromosomal rearrangements of the TCRbeta locus and further broadening the spectrum of genes putatively implicated in T-cell oncogenesis.

Lymphoblastic leukemia/lymphoma in mice overexpressing the Mer (MerTK) receptor tyrosine kinase

Mer (MerTK) is a receptor tyrosine kinase important in platelet aggregation, as well as macrophage cytokine secretion and clearance of apoptotic cells. Mer is not normally expressed in thymocytes or lymphocytes; however, ectopic Mer RNA transcript and protein expression is found in a subset of acute lymphoblastic leukemia cell lines and patient samples, suggesting a role in leukemogenesis. To investigate the oncogenic potential of Mer in vivo, we created a transgenic mouse line (Mer(Tg)) that expresses Mer in the hematopoietic lineage under control of the Vav promoter. Ectopic expression and activation of the transgenic Mer protein was demonstrated in lymphocytes and thymocytes of the Mer(Tg) mice. At 12-24 months of age, greater than 55% of the Mer(Tg) mice, compared to 12% of the wild type, developed adenopathy, hepatosplenomegaly, and circulating lymphoblasts. Histopathological analysis and flow cytometry were consistent with T-cell lymphoblastic leukemia/lymphoma. Mer may contribute to leukemogenesis by activation of Akt and ERK1/2 anti-apoptotic signals, which were upregulated in Mer(Tg) mice. Additionally, a significant survival advantage was noted in Mer(Tg) lymphocytes compared to wild-type lymphocytes after dexamethasone treatment. These data suggest that Mer plays a cooperative role in leukemogenesis and may be an effective target for biologically based leukemia/lymphoma therapy.

Childhood acute lymphoblastic leukemia in the age of genomics

The recent sequencing of the human genome and technical breakthroughs now make it possible to simultaneously determine mRNA expression levels of almost all of the identified genes in the human genome. DNA "chip" or microarray technology holds great promise for the development of more refined, biologically-based classification systems for childhood ALL, as well as the identification of new targets for novel therapy. To date gene expression profiles have been described that correlate with subtypes of ALL defined by morphology, immunophenotype, cytogenetic alterations, and response to therapy. Mechanistic insights into treatment failure have come from the definition of mRNA signatures that predict in vitro chemoresistance, as well as differences between blasts at relapse and new diagnosis. New bioinformatics tools optimize data mining, but validation of findings is essential since "over-fitting" the data is a common danger. In the future, genomic analysis will be complemented by evaluation of the cancer proteome.

Notch 1 activation in the molecular pathogenesis of T-cell acute lymphoblastic leukaemia

The chromosomal translocation t(7;9) in human T-cell acute lymphoblastic leukaemia (T-ALL) results in deregulated expression of a truncated, activated form of Notch 1 (TAN1) under the control of the T-cell receptor-beta (TCRB) locus. Although TAN1 efficiently induces T-ALL in mouse models, t(7;9) is present in less than 1% of human T-ALL cases. The recent discovery of novel activating mutations in NOTCH1 in more than 50% of human T-ALL samples has made it clear that Notch 1 is far more important in human T-ALL pathogenesis than previously suspected.

Proteomic-based prediction of clinical behavior in adult acute lymphoblastic leukemia

BACKGROUND

Response in adult acute lymphoblastic leukemia (ALL) can be achieved in a majority of patients. However, unlike pediatric ALL, recurrence is common in adult ALL, and the ability to predict at an early stage which patients are most likely to experience recurrence may help in devising new therapeutic approaches to prevent recurrence.

METHODS

Peripheral blood plasma from 57 patients with confirmed ALL was obtained before induction therapy for proteomic analysis. Follow-up continued for a median period of 71 weeks. For each plasma sample, 4 fractions eluted from a strong anion column were applied to 3 different ProteinChip array surfaces, and 12 surface-enhanced laser desorption/ionization (SELDI) spectra were generated. Peaks that correlated with recurrence were identified and decision trees were constructed and evaluated, using only 2 peaks per predictive tree.

RESULTS

The best decision trees provided strong positive prediction of recurrence, with correct predictions 84% to 92% of the time, whereas negative prediction of patients who did not experience recurrence was less robust, with 62% to 74% accuracy. Prediction of recurrence was independent of cytogenetics, bone marrow blast count, lactate dehydrogenase, beta-2-microglobulin, or surface markers. Positive prediction of L3 morphological classification was achieved in 80% of test cases.

CONCLUSIONS

Peripheral blood plasma is adequate to predict clinical behavior in ALL patients irrespective of the percentage of bone marrow blasts. Proteomic analysis of plasma offers a useful approach for profiling patients with ALL.

Monitoring minimal residual disease by quantification of genomic chromosomal breakpoint sequences in acute leukemias with MLL aberrations

An estimated 10% of acute leukemias carry mixed-lineage leukemia (MLL) fusion genes. Approximately 50 different fusion partners of the MLL gene have already been molecularly identified. These leukemias are commonly regarded as high-risk cases and are treated accordingly with intensified therapy regimens, including hematopoietic stem cell transplantation. However, a subset of patients may achieve long-term remissions with conventional therapy. Monitoring minimal residual disease (MRD) is undoubtedly of great value in clinical decision making, also in the pre- and post-transplant setting. Here, we describe a novel method for detecting MRD in leukemias with MLL aberrations. The method is based on monitoring patient-specific chromosomal breakpoint DNA sequences. This has several advantages over other methods that are based either on detecting specific RNA molecules of MLL fusion genes or on surrogate markers. An accurate and absolute quantification of the MRD level is possible. No reference to housekeeping genes is necessary and the target structure is much more stable than any mRNA fusion transcript.

Activating NOTCH1 mutations predict favorable early treatment response and long-term outcome in childhood precursor T-cell lymphoblastic leukemia

Activating mutations of the transmembrane receptor NOTCH1 are common in precursor T-cell lymphoblastic leukemia (T-ALL). We systematically analyzed the impact of activating NOTCH1 mutations on early treatment response and long-term outcome in 157 patients with T-ALL of the pediatric ALL-Berlin-Frankfurt-Munster (BFM) 2000 study. We confirm previous results that NOTCH1 mutations occur in more than 50% of T-ALL in children. In 82 patients (82/157; 52.2%), activating NOTCH1 mutations were identified either in the heterodimerization (55/82; 67.1%), in the PEST (13/82; 15.9%), or in both domains (14/82; 17.0%). The presence of NOTCH1 mutations was significantly correlated with a good prednisone response and favorable minimal residual disease (MRD) kinetics, which was independent from sex, age, white blood cell count, and T-cell immunophenotype at the time of diagnosis. Furthermore, activating NOTCH1 mutations specified a large subgroup of patients with an excellent prognosis. These findings indicate that in the context of the ALL-BFM 2000 treatment strategy, NOTCH1 mutations predict a more rapid early treatment response and a favorable long-term outcome in children with T-ALL.

Allogeneic stem cell transplantation in children with acute lymphoblastic leukemia after isolated central nervous system relapse: our experiences and review of the literature

The prognosis of patients with acute lymphoblastic leukemia (ALL) and central nervous system (CNS) relapse has historically been very poor. Although chemo-radiotherapy has improved outcomes, some patients still have a poor prognosis after CNS relapse. Therefore, allogeneic hematopoietic stem cell transplantation (allo-SCT) has recently become an option for treatment of CNS leukemia; however, information, particularly on the long-term outcome of transplant recipients, is limited. We performed allo-SCT in eight pediatric patients with ALL (n=7) or T-cell type non-Hodgkin's lymphoma (n=1), who had isolated CNS relapse. All patients survived for a median of 70.5 (range, 13-153) months after SCT. Sequelae developed late in some patients: mental retardation (IQ=47) in one patient, severe alopecia in two patients, limited chronic graft-versus-host-disease in three patients, and amenorrhea and/or hypothyroidism in three patients. Except for a pre-school child with post transplant CNS relapse, six out of seven patients show normal school/social performance. Our results clearly indicate a high cure rate of isolated CNS relapse by allo-SCT in pediatric lymphoid malignancies; however, there needs to be further studies to determine which are the appropriate candidates for transplantation and what is the best transplant regimen to achieve high cure rate and maintain good quality of life.

Immunogenotype changes prevail in relapses of young children with TEL-AML1-positive acute lymphoblastic leukemia and derive mainly from clonal selection

PURPOSE

Variations of the immunogenotype and TEL deletions in children with TEL-AML1+ acute lymphoblastic leukemia support the hypothesis that relapses derive from a persistent TEL-AML1+ preleukemic/leukemic clone rather than a resistant leukemia. We aimed at elucidating the relationship between the immunogenotype patterns at diagnosis and relapse as well as their clinical and biological relevance.

PATIENTS AND METHODS

Immunoglobulin and T-cell receptor gene rearrangements were analyzed in 41 children with a TEL-AML1+ acute lymphoblastic leukemia and an early (up to 30 months after diagnosis; n = 12) or late (at 30 months or later; n = 29) disease recurrence by a standardized PCR approach.

RESULTS

In 68% of the patients (group I), we identified differences in the immunogenotype patterns, whereas no changes were observed in the remaining 32% (group II). The divergence resulted more often from clonal selection than clonal evolution and consisted predominantly of losses (0-6, median 5) and/or gains (0-4, median 1) of rearrangements. The frequency and number of clonal immunoglobulin/T-cell receptor rearrangements in group I was higher at diagnosis (2-13, median 5) than at relapse (2-7, median 4), whereas it was the lowest in group II (1-5, median 3). Although group I children were younger at diagnosis, there was no correlation between particular immunogenotype patterns and remission duration.

CONCLUSION

These findings imply that the clonal heterogeneity in younger children most likely reflects an ongoing high recombinatorial activity in the preleukemic/leukemic cells, whereas the more uniform repertoire observed in older children mirrors end-stage rearrangement patterns of selected cell clones that evolved during the prolonged latency period.

A simplified flow cytometric assay identifies children with acute lymphoblastic leukemia who have a superior clinical outcome

Bone marrow normal lymphoid progenitors (CD19+, CD10+, and/or CD34+) are exquisitely sensitive to corticosteroids and other antileukemic drugs. We hypothesized that, in patients with B-lineage acute lymphoblastic leukemia (ALL), cells with this phenotype detected early in treatment should be leukemic rather than normal. We therefore developed a simple and inexpensive flow cytometric assay for such cells and prospectively applied it to bone marrow samples collected on day 19 from 380 children with B-lineage ALL. In 211 patients (55.5%), these cells represented 0.01% or more of the mononuclear cells; results correlated remarkably well with those of more complex flow cytometric and molecular minimal residual disease (MRD) evaluations. Among 84 uniformly treated children, the 10-year incidence of relapse or remission failure was 28.8% +/- 7.1% (SE) for the 42 patients with 0.01% or more leukemic cells on day 19 detected by the simplified assay versus 4.8% +/- 3.3% for the 42 patients with lower levels (P = .003). These assay results were the strongest predictor of outcome, even after adjustment for competing clinicobiologic variables. Thus, this new assay would enable most treatment centers to identify a high proportion of children with ALL who have an excellent early treatment response and a high likelihood of cure.

Infection, immune responses and the aetiology of childhood leukaemia

Childhood leukaemia is the principal subtype of paediatric cancer and, despite success in treatment, its causes remain enigmatic. A plethora of candidate environmental exposures have been proposed, but most lack a biological rationale or consistent epidemiological evidence. Although there might not be a single or exclusive cause, an abnormal immune response to common infection(s) has emerged as a plausible aetiological mechanism.

Towards targeted therapy for infant acute lymphoblastic leukaemia

Despite the greatly improved treatment regimes for childhood acute lymphoblastic leukaemia (ALL) in general, resulting in long-term survival in approximately 80% of cases, current therapies still fail in >50% of ALL cases diagnosed within the first year of life (i.e. in infants). Therefore, more adequate treatment strategies are urgently needed to also improve the prognosis for these very young patients with ALL. Here we review the current acquaintance with the biology of infant ALL and describe how this knowledge may lead to innovative therapeutic approaches.

Targeting leukemic fusion proteins with small interfering RNAs: recent advances and therapeutic potentials

RNA interference has become an indispensable research tool to study gene functions in a wide variety of organisms. Because of their high efficacy and specificity, RNA interference-based approaches may also translate into new therapeutic strategies to treat human diseases. In particular, oncogenes such as leukemic fusion proteins, which arise from chromosomal translocations, are promising targets for such gene silencing approaches, because they are exclusively expressed in precancerous and cancerous tissues, and because they are frequently indispensable for maintaining the malignant phenotype. This review summarizes recent developments in targeting leukemia-specific genes and discusses problems and approaches for possible clinical applications.

Translocation (5;10)(q22;q24) in a case of acute lymphoblastic leukemia

The activation of genes important to acute lymphoblastic leukemia (ALL) may be evidenced by somatically acquired chromosomal translocations found recurrently in different patient subgroups. It is for this reason that research efforts have focused on the molecular dissection of recurring chromosomal rearrangements. However, even though a large number of leukemia-causing genes have been identified, the genetic basis of many ALL cases remains unknown. We and others have reasoned that novel translocations found in the leukemic cells of ALL patients may mark the location of more frequent gene rearrangements that are otherwise hidden submicroscopically within normal or complex karyotypes. Towards this end, we here describe the first reported association of a t(5;10)(q22;q24) with adult ALL. Fluorescence in situ hybridization (FISH) and Southern blot hybridization studies have eliminated likely involvement of the candidate genes APC and MCC on chromosome 5, and PAX2, TLX1, and NFKB2 on chromosome 10. Results further suggest that the breakpoint on chromosome 5 lies centromeric of APC and the chromosome 10 breakpoint is centromeric of PAX2. The genomic regions disrupted by this t(5;10)(q22;q24) have not previously been associated with leukemia.

Prospective analysis of TEL/AML1-positive patients treated on Dana-Farber Cancer Institute Consortium Protocol 95-01

In a retrospective analysis, we previously reported that children whose leukemia cells harbored the TEL/AML1 gene rearrangement have excellent outcomes. From 1996 to 2000, we conducted a prospective study to determine the incidence and outcomes of children with TEL/AML1-positive acute lymphoblastic leukemia (ALL). Children with newly diagnosed ALL were treated on DFCI ALL Consortium Protocol 95-01. Patients were risk stratified primarily by current National Cancer Institute (NCI)-Rome risk criteria. With a median follow-up of 5.2 years, the 5-year event-free survival for TEL/AML1-positive patients was 89% compared with 80% for TEL/AML1-negative B-precursor patients (P = .05). The 5-year overall survival rate was 97% among TEL/AML-positive patients compared with 89% among TEL/AML1-negative patients (P = .03). However, in a multivariable analysis, risk group (age and leukocyte count at diagnosis) and asparaginase treatment group, but not TEL/AML1 status, were found to be independent predictors of outcome. We conclude that TEL/AML1-positive patients have excellent outcomes, confirming our previous findings. However, factors such as age at diagnosis and presenting leukocyte count should be taken into consideration when treating this group of patients.

Smaller white-matter volumes are associated with larger deficits in attention and learning among long-term survivors of acute lymphoblastic leukemia

BACKGROUND

The primary objective of this study was to test the hypothesis that survivors of childhood acute lymphoblastic leukemia (ALL) have deficits in neurocognitive performance, and smaller white-matter volumes are associated with these deficits.

METHODS

The patients studied included 112 ALL survivors (84 patients who had received chemotherapy only, 28 patients who had received chemotherapy and irradiation; 63 males, 49 females; mean age +/- standard deviation, 4.1 yrs +/- 2.6 yrs at diagnosis; mean +/- standard deviation yrs since diagnosis, 6.0 +/- 3.5 yrs), and 33 healthy siblings who participated as a control group. Neurocognitive tests of attention, intelligence, and academic achievement were performed; and magnetic resonance images were obtained and subsequently were segmented to yield tissue volume measurements. Comparisons of neurocognitive measures and tissue volumes between groups were performed, and the correlations between volumes and neurocognitive performance measures were assessed.

RESULTS

Most performance measures demonstrated statistically significant differences from the normative test scores, but only attention measures exceeded 1.0 standard deviation from normal. Patients who had received chemotherapy alone had significantly larger volumes of white matter than patients who had received treatment that also included cranial irradiation, but their volumes remained significantly smaller than the volumes in the control group. Smaller white-matter volumes were associated significantly with larger deficits in attention, intelligence, and academic achievement.

CONCLUSIONS

Survivors of childhood ALL had significant deficits in attention and smaller white-matter volumes that were associated directly with impaired neurocognitive performance. Cranial irradiation exacerbated these deficits.

TLX1/HOX11-mediated disruption of primary thymocyte differentiation prior to the CD4+CD8+ double-positive stage

The TLX1/HOX11 homeobox gene is frequently activated in T-cell acute lymphoblastic leukaemia (T-ALL) by the t(10;14)(q24;q11) and t(7;10)(q35;q24) chromosomal translocations or by as yet unknown transcriptional mechanisms in the absence of 10q24 cytogenetic abnormalities. Almost all TLX1(+) T-ALLs exhibit a CD4(+)CD8(+) double-positive (DP) phenotype. To investigate the role of TLX1 as an initiating oncogene in T-ALL pathogenesis, we assessed the consequences of retroviral vector-directed TLX1 expression during the differentiation of murine and human thymocytes in fetal thymic organ cultures. Interestingly, enforced expression of TLX1 disrupted the differentiation of murine fetal liver precursors and human cord blood CD34(+) stem/progenitor cells prior to the DP thymocyte stage. Although differentiation arrest was associated with an increased percentage of apoptotic thymocytes, it could only be partially bypassed by coexpression of transgenic BCL2. Mutation of the invariant asparagine residue at position 51 of the homeodomain - which is required for efficient DNA binding - released the block, consistent with the notion that TLX1 inhibits thymocyte differentiation and promotes T-cell oncogenesis by functioning as a transcription factor. The relevance of these findings is discussed in the context of activating NOTCH1 mutations and the other genetic lesions implicated in the multistep transformation process of TLX1(+) T-ALL.

Acute lymphoblastic leukaemia: a model for the pharmacogenomics of cancer therapy

The use of combination chemotherapy to cure acute lymphoblastic leukaemia (ALL) in children emerged in the 1980s as a paradigm for curing any disseminated cancer, and many of the therapeutic principles were subsequently applied to the treatment of other disseminated human cancers. Similarly, elucidation of the pharmacogenomics of ALL and its translation into new chemotherapeutic approaches might serve as a model for optimizing the treatment of other human cancers. Germline polymorphisms and gene-expression patterns in ALL cells have been linked to the toxicity and efficacy of chemotherapy for ALL and are beginning to emerge as useful clinical diagnostics.

PHARMACOGENOMICS OF ACUTE LEUKEMIA

Over the past four decades, treatment of acute leukemia in children has made remarkable progress, from this disease being lethal to now achieving cure rates of 80% for acute lymphoblastic leukemia and 45% for acute myeloid leukemia. This progress is largely owed to the optimization of existing treatment modalities rather than the discovery of new agents. However, the annual number of patients with leukemia who experience relapse after initial therapy remains greater than that of new cases of most childhood cancers. The aim of pharmacogenetics is to develop strategies to personalize medications and tailor treatment regimens to individual patients, with the goal of enhancing efficacy and safety through better understanding of the person's genetic makeup. In this review, we summarize recent pharmacogenomic studies related to the treatment of pediatric acute leukemia. These include work using candidate-gene approaches, as well as genome-wide studies using haplotype mapping and gene expression profiling. These strategies illustrate the promise of pharmacogenomics to further advance the treatment of human cancers, with childhood leukemia serving as a paradigm.

The tumor suppressor menin regulates hematopoiesis and myeloid transformation by influencing Hox gene expression

Menin is the product of the tumor suppressor gene Men1 that is mutated in the inherited tumor syndrome multiple endocrine neoplasia type 1 (MEN1). Menin has been shown to interact with SET-1 domain-containing histone 3 lysine 4 (H3K4) methyltransferases including mixed lineage leukemia proteins to regulate homeobox (Hox) gene expression in vitro. Using conditional Men1 knockout mice, we have investigated the requirement for menin in hematopoiesis and myeloid transformation. Men1 excision causes reduction of Hoxa9 expression, colony formation by hematopoietic progenitors, and the peripheral white blood cell count. Menin directly activates Hoxa9 expression, at least in part, by binding to the Hoxa9 locus, facilitating methylation of H3K4, and recruiting the methylated H3K4 binding protein chd1 to the locus. Consistent with signaling downstream of menin, ectopic expression of both Hoxa9 and Meis1 rescues colony formation defects in Men1-excised bone marrow. Moreover, Men1 excision also suppresses proliferation of leukemogenic mixed lineage leukemia-AF9 fusion-protein-transformed myeloid cells and Hoxa9 expression. These studies uncover an important role for menin in both normal hematopoiesis and myeloid transformation and provide a mechanistic understanding of menin's function in these processes that may be used for therapy.

Changes in bone mineral density in survivors of childhood acute lymphoblastic leukemia

BACKGROUND

There is little information about factors modulating bone mineral density (BMD) in survivors of childhood acute lymphoblastic leukemia (ALL).

PROCEDURE

We analyzed data from 57 survivors (26 male, 52 Caucasian) who underwent two serial quantitative computed tomography (QCT) studies of BMD. Using multiple linear regression, we evaluated the association of BMD change with demographic variables, treatment history, hormone therapy, exercise, and tobacco and alcohol use.

RESULTS

The median age was 3.4 years (range, 0.9-17.4 years) at diagnosis of ALL; the median age at the first QCT (Study I) was 15.0 years (range, 10.6-31.0 years) and at the second QCT (Study II) was 18.2 years (range, 14.2-35.3 years). Mean height increased 4.7 cm and mean weight increased 8.8 kg between Studies I and II. While the mean BMD increased 9.33 mg/cc (P = 0.003), the BMD Z-score increased only slightly (0.21 SD, P = 0.035). Cortical bone density increased significantly (approximately 25.3 mg/cc; P = 0.001), but the ratio of trabecular to cortical BMD decreased significantly (P = 0.045). Factors independently associated with unfavorable BMD changes included older age at diagnosis (P = 0.001), female sex (P = 0.018), and nutritional supplementation (0.032). Alcohol (P = 0.009) was an unfavorable factor in a univariable analysis.

CONCLUSIONS

Bone mineral accretion during adolescence is attenuated in childhood ALL survivors by a comparative deficit in trabecular versus cortical bone deposition. BMD is influenced favorably by exercise in early adolescence and unfavorably by the use of nutritional supplements and alcohol. These results provide new information about behavioral factors that affect bone accrual in survivors of childhood ALL and warrant definitive evaluation in a larger cohort.

Jumping translocation of 17q11∼qter and 3q25∼q28 duplication in a variant Philadelphia t(9;14;22)(q34;q32;q11) in a childhood chronic myelogenous leukemia

The virtually obligatory presence of the Philadelphia chromosome may suggest a causal homogeneity, but chronic myelogenous leukemia (CML) is a clinically heterogeneous disease. This may be a consequence of the variable BCR breakpoints on chromosome 22 and of nonrandom secondary chromosomal abnormalities. We present the case of a boy, age 12, investigated in blastic phase of CML. Karyotyping with conventional and multiplex fluorescence in situ hybridization (FISH and M-FISH) karyotyping, complemented with reverse transcriptase-polymerase chain reaction, identified a variant Philadelphia translocation t(9;14;22)(q34;q32;q11) involving a cryptic BCR/ABL fusion with formation of the p190(Bcr-Abl) oncoprotein. M-FISH revealed also an unbalanced jumping translocation of 17q11 approximately qter alternatively present on chromosomes 14 or 20, apparently hithertofore unreported in hematological malignancies. Another secondary aberration, dup(3)(q25q28), was revealed by multipoint interphase FISH (mpI-FISH). Gain of this region is known in adult hematological malignancies and solid tumors, suggesting its general involvement in tumor initiation or progression (or both), regardless of tissue origin.

Tumor-Specific Genetic Lesions and Their Influence on Therapy in Pediatric Acute Lymphoblastic Leukemia

Pharmacogenomics has traditionally focused on the identification of inherited genetic differences that influence a patient’s response to a specific therapeutic agent. These differences can range from inherited variability in the genes that affect drug absorption, distribution, intracellular transport, metabolism, and elimination, to variability in the genes that encode either the target of the drug or components of the pathway affected by the drug. The main goal of pharmacogenomics is to improve our understanding of how these variations, either individually or collectively, influence the therapeutic response. The genetic differences inherent within cancer cells constitute the other major variable in a patient’s ultimate response to therapy. In this review, we provide an overview of high-throughput genomic methods that can be used to identify genetic lesions within cancer cells. These efforts will ultimately allow the identification of the full complement of genetic lesions that underlie the establishment and maintenance of the leukemic clone. The identification of these lesions should provide the bases for defining the molecular “Achilles heels” against which new targeted therapies can be developed.

Aberrant methylation in promoter-associated CpG islands of multiple genes in acute lymphoblastic leukemia

Methylation profile was analyzed in 10 childhood acute lymphoblastic leukemia (ALL) and nine adult ALL cases. Four genes (p15, p16, RARbeta, FHIT) had methylation in both diseases, four genes (p14, Rb, MLH1, DAPK) showed no methylation in both diseases, and the two genes (APC, RIZ) demonstrated methylation only in adult ALL. Methylation of the RARbeta was more frequent in adult ALL than that in childhood ALL (p=0.01). The number of patients with methylation of multiple genes was higher in adult ALL than that in childhood ALL (p=0.006). Moreover, overall frequency of methylation was higher in adult ALL than that in childhood ALL (p=0.01).

Asparagine synthetase chemotherapy

Modern clinical treatments of childhood acute lymphoblastic leukemia (ALL) employ enzyme-based methods for depletion of blood asparagine in combination with standard chemotherapeutic agents. Significant side effects can arise in these protocols and, in many cases, patients develop drug-resistant forms of the disease that may be correlated with up-regulation of the enzyme glutamine-dependent asparagine synthetase (ASNS). Though the precise molecular mechanisms that result in the appearance of drug resistance are the subject of active study, potent ASNS inhibitors may have clinical utility in treating asparaginase-resistant forms of childhood ALL. This review provides an overview of recent developments in our understanding of (a) the structure and catalytic mechanism of ASNS, and (b) the role that ASNS may play in the onset of drug-resistant childhood ALL. In addition, the first successful, mechanism-based efforts to prepare and characterize nanomolar ASNS inhibitors are discussed, together with the implications of these studies for future efforts to develop useful drugs.

Comparison of mRNA abundance quantified by gene expression profiling and percentage of positive cells using immunophenotyping for diagnostic antigens in acute and chronic leukemias

BACKGROUND

Microarray analysis is considered a future diagnostic tool in leukemias. Whereas data accumulate on specific gene expression patterns in biologically defined leukemia entities, data on the correlation between flow cytometrically determined protein expression, which are essential in the diagnostic setting today, and microarray results are limited.

METHODS

The results obtained by microarray analysis were compared using the Affymetrix GeneChip HG-U133 system in parallel with flow cytometric findings of 36 relevant targets in 814 patients with newly diagnosed acute and chronic leukemias as well as in normal bone marrow samples.

RESULTS

In a total of 21,581 individual comparisons between signal intensities obtained by microarray analysis and percentages of positive cell as determined by flow cytometry, coefficients of correlation in the range of 0.171 to 0.807 were obtained. In particular, the degree of correlation was high in the following genes critical in the diagnostic setting: CD4, CD8, CD13 (ANPEP), CD33, CD23 (FCER2), CD64 (FCGR1A), CD117 (KIT), CD34, MPO, CD20 (MS4A1), CD7 (range of r, 0.589-0.807).

CONCLUSIONS

The present data prove the high degree of correlation between findings obtained by microarray analysis and flow cytometry. They are in favor of a future application of the microarray technology as a robust diagnostic tool in leukemias.

New agents in the treatment of childhood leukemias and myelodysplastic syndromes

Relapsed or refractory leukemia remains the most common therapeutic problem in pediatric oncology. Particularly challenging is the patient who has recurrence following a stem cell transplant. Insights into the molecular pathogenesis of the leukemias have produced an array of new agents. These new agents will be more selective in hitting their targets, and so their use will be more narrowly defined than with classical cytotoxic drugs. These new agents include all-trans retinoic acid, gemtuzumab ozogamicin, imatinib mesylate, rituximab, and a bevy of signal transduction inhibitors and therapeutic monoclonal antibodies. Other new agents, such as liposomal daunorubicin, PEG-asparaginase, or clofarabine, represent chemical modifications of established antileukemic drugs. Increasingly, molecular profiling will be used to guide the development and application of new drugs.

Genomic assessment of pediatric acute leukemia

Advances in molecular genetics have revolutionized our understanding of acute myeloid and lymphoblastic leukemia. Structural and numerical chromosomal aberrations are common, and their detection is vital for leukemia diagnosis, risk stratification, and monitoring of response to therapy. Fusion proteins resulting from chromosomal translocations are necessary but not sufficient for leukemogenesis, and there is intense research activity to elucidate the cooperating molecular abnormalities that may be suitable targets for novel therapeutic approaches. Candidate gene approaches have identified mutations in kinases and transcription factors in a proportion of patients, but more comprehensive genomic approaches are required. Gene expression profiling accurately classifies known subtypes of acute leukemia and has highlighted potentially leukemogenic abnormalities in gene expression. Newer techniques, such as single-nucleotide polymorphism arrays to analyze changes in gene copy number and zygosity, cancer genome sequencing, and RNA interference, are promising tools to identify mutations, although at present, data from these approaches are limited. This review provides an overview of these techniques in clinical practice and as research tools to develop new therapeutic approaches in pediatric leukemia.

C-kit receptor tyrosine kinase (CD117) expression and its positive predictive value for the diagnosis of Thai adult acute myeloid leukemia

We examined the expression of c-kit receptor tyrosine kinase in 195 Thai adult patients with acute leukemia and determined its specificity and predictive values for the diagnosis of adult acute myeloid leukemia (AML). CD117 was used to detect c-kit expression on CD45 and side-scatter-gated blast cells by flow cytometry. Of 163 AML cases, 67% expressed CD117. None of acute lymphoid leukemia (ALL) had CD117 expression, except one case of T-ALL. The majority of AML patients carrying t(8;21), inv(16), and t(15;17) had high CD117 expression. High proportion of AML cases without c-kit expressed monocytic markers. Significant associations between CD117 and CD34 (P<0.001), CD13 (P=0.006), CD7 (P=0.034), and CD19 (P<0.001) were found in AML cases. The calculated specificity of CD117 for the diagnosis of AML was 0.97, which was higher than CD13 (0.78) and CD33 (0.75) but comparable to MPO (0.97). The positive predictive value (PPV) of CD117 for AML was 0.99, with the negative predictive value of 0.35. In conclusion, the majority of Thai adult AML cases expressed c-kit. C-kit is infrequently expressed in ALL and appeared to be specific for AML with high PPV. Future targeting therapy using c-kit as a therapeutic target should benefit the majority of Thai AML patients who had high c-kit expression.

Allele quantification using molecular inversion probes (MIP)

Detection of genomic copy number changes has been an important research area, especially in cancer. Several high-throughput technologies have been developed to detect these changes. Features that are important for the utility of technologies assessing copy number changes include the ability to interrogate regions of interest at the desired density as well as the ability to differentiate the two homologs. In addition, assessing formaldehyde fixed and paraffin embedded (FFPE) samples allows the utilization of the vast majority of cancer samples. To address these points we demonstrate the use of molecular inversion probe (MIP) technology to the study of copy number. MIP is a high-throughput genotyping technology capable of interrogating >20 000 single nucleotide polymorphisms in the same tube. We have shown the ability of MIP at this multiplex level to provide copy number measurements while obtaining the allele information. In addition we have demonstrated a proof of principle for copy number analysis in FFPE samples.

Identification of glucocorticoid-response genes in children with acute lymphoblastic leukemia

The ability of glucocorticoids (GCs) to kill lymphoid cells led to their inclusion in essentially all chemotherapy protocols for lymphoid malignancies, particularly childhood acute lymphoblastic leukemia (ALL). GCs mediate apoptosis via their cognate receptor and subsequent alterations in gene expression. Previous investigations, including expression profiling studies with subgenome microarrays in model systems, have led to a number of attractive, but conflicting, hypotheses that have never been tested in a clinical setting. Here, we present a comparative whole-genome expression profiling approach using lymphoblasts (purified at 3 time points) from 13 GC-sensitive children undergoing therapy for ALL. For comparisons, expression profiles were generated from an adult patient with ALL, peripheral blood lymphocytes from GC-exposed healthy donors, GC-sensitive and -resistant ALL cell lines, and mouse thymocytes treated with GCs in vivo and in vitro. This generated an essentially complete list of GC-regulated candidate genes in clinical settings and experimental systems, allowing immediate analysis of any gene for its potential significance to GC-induced apoptosis. Our analysis argued against most of the model-based hypotheses and instead identified a small number of novel candidate genes, including PFKFB2, a key regulator of glucose metabolism; ZBTB16, a putative transcription factor; and SNF1LK, a protein kinase implicated in cell-cycle regulation.

Gene expression analysis reveals a strong signature of an interferon-induced pathway in childhood lymphoblastic leukemia as well as in breast and ovarian cancer

On the basis of epidemiological studies, infection was suggested to play a role in the etiology of human cancer. While for some cancers such a role was indeed demonstrated, there is no direct biological support for the role of viral pathogens in the pathogenesis of childhood leukemia. Using a novel bioinformatic tool that alternates between clustering and standard statistical methods of analysis, we performed a 'double-blind' search of published gene expression data of subjects with different childhood acute lymphoblastic leukemia (ALL) subtypes, looking for unanticipated partitions of patients, induced by unexpected groups of genes with correlated expression. We discovered a group of about 30 genes, related to the interferon response pathway, whose expression levels divide the ALL samples into two subgroups; high in 50, low in 285 patients. Leukemic subclasses prevalent in early childhood (the age most susceptible to infection) are over-represented in the high-expression subgroup. Similar partitions, induced by the same genes, were found also in breast and ovarian cancer but not in lung cancer, prostate cancer and lymphoma. About 40% of breast cancer samples expressed the 'interferon-related' signature. It is of interest that several studies demonstrated mouse mammary tumor virus-like sequences in about 40% of breast cancer samples. Our discovery of an unanticipated strong signature of an interferon-induced pathway provides molecular support for a role for either inflammation or viral infection in the pathogenesis of childhood leukemia as well as breast and ovarian cancer.

Utility of cranial boost in addition to total body irradiation in the treatment of high risk acute lymphoblastic leukemia

PURPOSE

Total body irradiation (TBI) as part of a conditioning regimen before hematopoietic stem cell transplant (HSCT) is an important component in the management of acute lymphoblastic leukemia (ALL) that has relapsed or has other certain high-risk features. Controversy exists, however, as to whether a cranial boost in addition to TBI is necessary to prevent central nervous system (CNS) recurrences in these high-risk cases. Previous national trials have included a cranial boost in the absence of data to justify its use. Therefore, the aim of this study was to assess risk of CNS recurrence in ALL patients treated with TBI, to identify subsets of these high-risk patients at an increased or decreased risk of CNS recurrence after TBI, and to investigate whether regimens with higher doses of cranial irradiation further reduce the risk of CNS recurrence.

METHODS AND MATERIALS

Charts of 67 consecutively treated patients with ALL who received TBI before HSCT were reviewed. Data including patient demographics, clinical features at presentation, conditioning regimen, donor source, use of a cranial boost, remission stage at transplant, histologic subtype, cytogenetics, and extramedullary site of presentation were retrospectively collected and correlated with the risk of subsequent CNS recurrence.

RESULTS

At the time of analysis, 30 (45%) patients were alive with no evidence of disease, 8 (12%) were alive with recurrence of leukemia, 7 (10.5%) had recurrent ALL but with successful salvage, 7 (11%) died subsequent to recurrence, 14 (21%) died from complications related to HCST, and 1 patient was lost to follow-up (1.5%). Of the patients who recurred after HSCT, the relapses were hematologic in 13 (57%), CNS with or without simultaneous marrow involvement in 3 (13%), and other sites in 7 (30%). Forty-one (61%) patients did not receive an extracranial boost of irradiation with TBI. Two of these patients (4.9%) suffered CNS failures compared with 1 of 26 (3.8%) who received a cranial boost (p = 0.84). None of the 40 patients who presented only with hematologic disease developed a CNS recurrence despite the fact that only 13 of 40 of these patients received a cranial boost after TBI. Cranial boost was therefore not associated with a reduction in CNS recurrence, especially in patients with only hematologic disease at presentation for which there were no failures regardless of the use of additional cranial radiotherapy.

CONCLUSIONS

Patients who present with hematologic disease only at the time of HSCT have a low risk of CNS recurrence after TBI regardless of the use of a cranial boost, suggesting that a cranial boost may not be necessary in these patients.