Genome-wide expression analysis of paired diagnosis-relapse samples in ALL indicates involvement of pathways related to DNA replication, cell cycle and DNA repair, independent of immune phenotype. Leukemia. 2010;24:491-499. [PMID: 20072147 DOI: 10.1038/leu.2009.286]

Glucocorticoids paradoxically promote steroid resistance in B cell acute lymphoblastic leukemia through CXCR4/PLC signaling

Glucocorticoid (GC) resistance in childhood relapsed B-cell acute lymphoblastic leukemia (B-ALL) represents an important challenge. Despite decades of clinical use, the mechanisms underlying resistance remain poorly understood. Here, we report that in B-ALL, GC paradoxically induce their own resistance by activating a phospholipase C (PLC)-mediated cell survival pathway through the chemokine receptor, CXCR4. We identify PLC as aberrantly activated in GC-resistant B-ALL and its inhibition is able to induce cell death by compromising several transcriptional programs. Mechanistically, dexamethasone (Dex) provokes CXCR4 signaling, resulting in the activation of PLC-dependent Ca2+ and protein kinase C signaling pathways, which curtail anticancer activity. Treatment with a CXCR4 antagonist or a PLC inhibitor improves survival of Dex-treated NSG mice in vivo. CXCR4/PLC axis inhibition significantly reverses Dex resistance in B-ALL cell lines (in vitro and in vivo) and cells from Dex resistant ALL patients. Our study identifies how activation of the PLC signalosome in B-ALL by Dex limits the upfront efficacy of this chemotherapeutic agent.

The positive feedback loop of MAD2L1/TYK2/STAT3 induces progression in B-cell acute lymphoblastic leukaemia

PURPOSE

Mitotic arrest deficient 2 like 1 (MAD2L1) has been extensively studied in several malignancies; however, its role in B-cell acute lymphoblastic leukaemia (B-ALL) remains unclear.

METHODS

The expression of MAD2L1 was evaluated by real-time quantitative polymerase chain reaction. The biological functions of MAD2L1 in B-ALL were explored through Cell Counting Kit-8 (CCK-8), 5-Ethynyl-2'-deoxyuridine assay (EDU), transwell assay, flow cytometry and xenograft models. The Western blotting and co-immunoprecipitation were utilized to evaluate the interplay between MAD2L1 and the TYK2/STAT3 pathway. The luciferase reporter and chromatin immunoprecipitation (ChIP) assay were employed to identify interactions between STAT3 and MAD2L1.

RESULTS

We demonstrated that MAD2L1 was markedly upregulated in B-ALL, and its expression level not only correlated with the relapse and remission of the condition but also with a poor prognosis. MAD2L1 promoted the proliferation, migration and invasion of B-ALL cells in vitro and in vivo, whereas MAD2L1 knockdown had the opposite effects. Mechanistically, MAD2L1 induces the progression of B-ALL by activating the TYK2/STAT3 signaling pathway to phosphorylate. Interestingly, STAT3 induces the expression of MAD2L1 by binding directly to its promoter region, resulting in a positive-feedback loop of MAD2L1/TYK2/STAT3.

CONCLUSION

This study uncovered a reciprocal loop of MAD2L1/TYK2/STAT3, which contributed to the development of B-ALL. Therefore, MAD2L1 can be considered a potential diagnostic biomarker as well as a novel therapeutic target for B-ALL.

Absence of terminal deoxynucleotidyl transferase expression in T-ALL/LBL accumulates chromosomal abnormalities to induce drug resistance

T-acute lymphoblastic leukemia/lymphoma (T-ALL/LBL) is a malignant neoplasm of immature lymphoblasts. Terminal deoxynucleotidyl transferase (TDT) is a template-independent DNA polymerase that plays an essential role in generating diversity for immunoglobulin genes. T-ALL/LBL patients with TDT^- have a worse prognosis. However, how TDT^- promotes the disease progression of T-ALL/LBL remains unknown. Here we analyzed the prognosis of T-ALL/LBL patients in Shanghai Children's Medical Center (SCMC) and confirmed that TDT^- patients had a higher rate of recurrence and remission failure and worse outcomes. Cellular experiments demonstrated that TDT was involved in DNA damage repair. TDT knockout delayed DNA repair, arrested the cell cycle and decreased apoptosis to induce the accumulation of chromosomal abnormalities and tolerance to abnormal karyotypes. Our study demonstrated that the poor outcomes in TDT^- T-ALL/LBL might be due to the drug resistance (VP16 and MTX) induced by chromosomal abnormalities. Our findings revealed novel functions and mechanisms of TDT in T-ALL/LBL and supported that hematopoietic stem cell transplantation (HSCT) might be a better choice for these patients.

Targeting Glutaminolysis Shows Efficacy in Both Prednisolone-Sensitive and in Metabolically Rewired Prednisolone-Resistant B-Cell Childhood Acute Lymphoblastic Leukaemia Cells

The prognosis for patients with relapsed childhood acute lymphoblastic leukaemia (cALL) remains poor. The main reason for treatment failure is drug resistance, most commonly to glucocorticoids (GCs). The molecular differences between prednisolone-sensitive and -resistant lymphoblasts are not well-studied, thereby precluding the development of novel and targeted therapies. Therefore, the aim of this work was to elucidate at least some aspects of the molecular differences between matched pairs of GC-sensitive and -resistant cell lines. To address this, we carried out an integrated transcriptomic and metabolomic analysis, which revealed that lack of response to prednisolone may be underpinned by alterations in oxidative phosphorylation, glycolysis, amino acid, pyruvate and nucleotide biosynthesis, as well as activation of mTORC1 and MYC signalling, which are also known to control cell metabolism. In an attempt to explore the potential therapeutic effect of inhibiting one of the hits from our analysis, we targeted the glutamine-glutamate-α-ketoglutarate axis by three different strategies, all of which impaired mitochondrial respiration and ATP production and induced apoptosis. Thereby, we report that prednisolone resistance may be accompanied by considerable rewiring of transcriptional and biosynthesis programs. Among other druggable targets that were identified in this study, inhibition of glutamine metabolism presents a potential therapeutic approach in GC-sensitive, but more importantly, in GC-resistant cALL cells. Lastly, these findings may be clinically relevant in the context of relapse-in publicly available datasets, we found gene expression patterns suggesting that in vivo drug resistance is characterised by similar metabolic dysregulation to what we found in our in vitro model.

The role of high mobility group protein B3 (HMGB3) in tumor proliferation and drug resistance

The high mobility group protein B (HMGB) family (including HMGB1, HMGB2, HMGB3, and HMGB4) can regulate the mechanisms of DNA replication, transcription, recombination, and repair, and act as cytokines to mediate responses to infection, injury, and inflammation. HMGB1/2/3 has a high similarity in sequence and structure, while HMGB4 has no acidic C-terminal tail. Among them, HMGB3 can regulate the self-renewal and differentiation of normal hematopoietic stem cell population, but the decrease of its expression is easy to induce leukemia. Up-regulation of its expression promotes tumor development and chemotherapy resistance through a variety of mechanisms, and non-coding RNA can regulate to promote tumor cell proliferation, invasion, and migration and inhibit cancer cell apoptosis.

Latest perspectives on glucocorticoid-induced apoptosis and resistance in lymphoid malignancies

Glucocorticoids are essential drugs in the treatment protocols of lymphoid malignancies. These steroidal hormones trigger apoptosis of the malignant cells by binding to the glucocorticoid receptor (GR), which is a member of the nuclear receptor superfamily. Long term glucocorticoid treatment is limited by two major problems: the development of glucocorticoid-related side effects, which hampers patient quality of life, and the emergence of glucocorticoid resistance, which is a gradual process that is inevitable in many patients. This emphasizes the need to reevaluate and optimize the widespread use of glucocorticoids in lymphoid malignancies. To achieve this goal, a deep understanding of the mechanisms governing glucocorticoid responsiveness is required, yet, a recent comprehensive overview is currently lacking. In this review, we examine how glucocorticoids mediate apoptosis by detailing GR's genomic and non-genomic action mechanisms in lymphoid malignancies. We continue with a discussion of the glucocorticoid-related problems and how these are intertwined with one another. We further zoom in on glucocorticoid resistance by critically analyzing the plethora of proposed mechanisms and highlighting therapeutic opportunities that emerge from these studies. In conclusion, early detection of glucocorticoid resistance in patients remains an important challenge as this would result in a timelier treatment reorientation and reduced glucocorticoid-instigated side effects.

Six Candidate miRNAs Associated With Early Relapse in Pediatric B-Cell Acute Lymphoblastic Leukemia

BACKGROUND/AIM

Few studies have evaluated the role of miRNAs in pediatric acute lymphoblastic leukemia (ALL) relapse and a consensus of a clinically significant miRNA signature is yet to be identified. In this study, we evaluated miRNAs associated with pediatric B-ALL early relapse in two independent sample sets.

MATERIALS AND METHODS

We performed global miRNA profiling on diagnostic bone marrow specimens from six early relapse (≤3 years after diagnosis) and six age- and cytogenetics-matched prolonged remission (≥4 years) patients (first set) and an independent set of 14 early relapse and 14 matched prolonged remission specimens (second set).

RESULTS

Twelve and 39 top differentially expressed miRNAs were observed in the first and second sets, respectively; however, there was no overlap between the top candidates. In post-hoc analyses six miRNAs (miR-101-3p, miR-4774-5p, miR-1324, miR-631, miR-4699-5p and miR-922) among the top candidates in the second, but not the first set, were consistently upregulated in early relapse compared to remission specimens in both first (fold change=1.13-2.19, q<0.38) and second (fold change=1.48-4.78, all q<0.05) sets. Four (miR-631, mir-101-3p, miR-922 and miR-1324) of these miRNAs have been previously implicated in key functional oncogenic pathways in adult cancers.

CONCLUSION

This study suggests that six candidate miRNAs, not previously implicated in pediatric ALL, are associated with early relapse in pediatric B-ALL. Validation and investigation of mechanistic roles of these miRNAs in a larger cohort are warranted, so that they may be used as prognostic markers for early relapse of pediatric B-ALL.

HMGB3 silence inhibits breast cancer cell proliferation and tumor growth by interacting with hypoxia-inducible factor 1α

Background: Breast cancer is the most common malignant tumor that affects women with higher incidence. High-mobility group box 3 (HMGB3) plays critical functions in DNA repair, recombination, transcription and replication. This study aimed to investigate the effects of HMGB3 silence on mammosphere formation and tumor growth of breast cancer.

Methods: LV5-HMGB3 and LV3-siHMGB3 vectors were transfected into MCF10A, MDA-MB-231, HCC1937, ZR-75-1 and MCF7 cells. Cell counting kit-8 (CCK-8) assay was used to evaluate cell proliferation. Xenograft tumor mice model was established by injection of MDA-MB-231. qRT-PCR and western blot were used to examine the expression of Nanog, Sox2 and OCT-4. Mammosphere forming assay was employed to evaluate mammosphere formation both in vivo and in vitro. Dual luciferase assay was utilized to verify the interaction between HMGB3 and hypoxia-inducible factor 1α (HIF1α). CD44⁺/CD24⁻ was assessed with flow cytometry.

Results: HMGB3 expression was higher significantly (p<0.05) in cancer cells compared to normal cells. HMGB3 overexpression significantly (p<0.05) enhanced and HMGB3 silence reduced cell proliferative mice compared to MCF10A and MDA-MB-231, respectively. HMGB3 overexpression enhanced and HMGB3 silence inhibited mammosphere formation. HMGB3 overexpression upregulated and HMGB3 silence downregulated Nanog, SOX2 and OCT-4 genes/proteins in MCF10A and MDA-MB-231 cells, respectively. HMGB3 silence reduced CD44⁺/CD24⁻ levels in cancer cells. Silence of HMGB3 strengthened reductive effects of PTX on tumor sizes, iPSC biomarkers and mammosphere amounts in xenograft tumor mouse models. HMGB3 silence inhibited mammoshpere formation, cell proliferation and CD44⁺CD24⁻ by interacting with HIF1α.

Conclusion: HMGB3 silence could inhibit the cell proliferation in vitro and suppress tumor growth in vivo levels. The antitumor effects of HMGB3 silence were mediated by interacting with the HIF1α.

Pharmacogenomic and Pharmacotranscriptomic Profiling of Childhood Acute Lymphoblastic Leukemia: Paving the Way to Personalized Treatment

Personalized medicine is focused on research disciplines which contribute to the individualization of therapy, like pharmacogenomics and pharmacotranscriptomics. Acute lymphoblastic leukemia (ALL) is the most common malignancy of childhood. It is one of the pediatric malignancies with the highest cure rate, but still a lethal outcome due to therapy accounts for 1%⁻3% of deaths. Further improvement of treatment protocols is needed through the implementation of pharmacogenomics and pharmacotranscriptomics. Emerging high-throughput technologies, including microarrays and next-generation sequencing, have provided an enormous amount of molecular data with the potential to be implemented in childhood ALL treatment protocols. In the current review, we summarized the contribution of these novel technologies to the pharmacogenomics and pharmacotranscriptomics of childhood ALL. We have presented data on molecular markers responsible for the efficacy, side effects, and toxicity of the drugs commonly used for childhood ALL treatment, i.e., glucocorticoids, vincristine, asparaginase, anthracyclines, thiopurines, and methotrexate. Big data was generated using high-throughput technologies, but their implementation in clinical practice is poor. Research efforts should be focused on data analysis and designing prediction models using machine learning algorithms. Bioinformatics tools and the implementation of artificial i Lack of association of the CEP72 rs924607 TT genotype with intelligence are expected to open the door wide for personalized medicine in the clinical practice of childhood ALL.

Relapse-associated AURKB blunts the glucocorticoid sensitivity of B cell acute lymphoblastic leukemia

Glucocorticoids (GCs) are used in combination chemotherapies as front-line treatment for B cell acute lymphoblastic leukemia (B-ALL). Although effective, many patients relapse and become resistant to chemotherapy and GCs in particular. Why these patients relapse is not clear. We took a comprehensive, functional genomics approach to identify sources of GC resistance. A genome-wide shRNA screen identified the transcriptional coactivators EHMT2, EHMT1, and CBX3 as important contributors to GC-induced cell death. This complex selectively supports GC-induced expression of genes contributing to cell death. A metaanalysis of gene expression data from B-ALL patient specimens revealed that Aurora kinase B (AURKB), which restrains GC signaling by phosphorylating EHMT1-2, is overexpressed in relapsed B-ALL, suggesting it as a potential contributor to relapse. Inhibition of AURKB enhanced GC-induced expression of cell death genes, resulting in potentiation of GC cytotoxicity in cell lines and relapsed B-ALL patient samples. This function for AURKB is distinct from its canonical role in the cell cycle. These results show the utility of functional genomics in understanding mechanisms of resistance and rapidly identifying combination chemotherapeutics.

Overexpression of miR-758 inhibited proliferation, migration, invasion, and promoted apoptosis of non-small cell lung cancer cells by negatively regulating HMGB

Non-small cell lung cancer (NSCLC) is one of the most fatal types of cancer with significant mortality and morbidity worldwide. MicroRNAs (miRs) have been confirmed to have positive functions in NSCLC. In the present study, we try to explore the role of miR-758 in proliferation, migration, invasion, and apoptosis of NSCLC cells by regulating high-mobility group box (HMGB) 3 (HMGB3.) NSCLC and adjacent tissues were collected. Reverse transcription quantitative PCR (RT-qPCR) was employed to detect expression of miR-758 and HMGB3 in NSCLC and adjacent tissues, in BEAS-2B cells and NSCLC cell lines. The targetted relationship between miR-758 and HMGB3 was identified by dual luciferase reporter gene assay. The effects of miR-758 on proliferation, migration, invasion, cell cycle, and apoptosis of A549 cells. MiR-758 expression was lower in NSCLC tissues, which was opposite to HMGB3 expression. The results also demonstrated that miR-758 can target HMGB3. The cells transfected with miR-758 mimic had decreased HMGB3 expression, proliferation, migration, and invasion, with more arrested cells in G₁ phase and increased apoptosis. Our results supported that the overexpression of miR-758 inhibits proliferation, migration, and invasion, and promotes apoptosis of NSCLC cells by negative regulating HMGB2. The present study may provide a novel target for NSCLC treatment.

Nucleotide excision repair is a predictor of early relapse in pediatric acute lymphoblastic leukemia

BACKGROUND

Nucleotide Excision Repair (NER) is a major pathway of mammalian DNA repair that is associated with drug resistance and has not been well characterized in acute lymphoblastic leukemia (ALL). The objective of this study was to explore the role of NER in relapsed ALL patients. We hypothesized that increased expression of NER genes was associated with drug resistance and relapse in ALL.

METHODS

We performed secondary data analysis on two sets of pediatric ALL patients that all ultimately relapsed, and who had matched diagnosis-relapse gene expression microarray data (GSE28460 and GSE18497). GSE28460 included 49 precursor-B-ALL patients, and GSE18497 included 27 precursor-B-ALL and 14 T-ALL patients. Microarray data were processed using the Plier 16 algorithm and the 20 canonical NER genes were extracted. Comparisons were made between time of diagnosis and relapse, and between early and late relapsing subgroups. The Chi-square test was used to evaluate whether NER gene expression was altered at the level of the entire pathway and individual gene expression was compared using t-tests.

RESULTS

We found that gene expression of the NER pathway was significantly increased upon relapse in patients that took 3 years or greater to relapse (late relapsers, P = .007), whereas no such change was evident in patients that relapsed in less than 3 years (early relapsers, P = .180). Moreover, at diagnosis, the NER gene expression of the early relapsing subpopulation was already significantly elevated over that of the late relapsing group (P < .001). This pattern was validated by an 'NER score' established by averaging the relative expression of the 20 canonical NER genes. The NER score at diagnosis was found to be significantly associated with disease-free survival in precursor-B-ALL (P < .001).

CONCLUSION

Patients are over two times more likely to undergo early relapse if they have a high NER score at diagnosis, hazard ratio 2.008, 95% CI (1.256-3.211). The NER score may provide a underlying mechanism for "time to remission", a known prognostic factor in ALL, and a rationale for differential treatment.

Abnormally high expression of POLD1, MCM2, and PLK4 promotes relapse of acute lymphoblastic leukemia

This study aimed to explore the underlying mechanism of relapsed acute lymphoblastic leukemia (ALL).Datasets of GSE28460 and GSE18497 were downloaded from Gene Expression Omnibus (GEO). Differentially expressed genes (DEGs) between diagnostic and relapsed ALL samples were identified using Limma package in R, and a Venn diagram was drawn. Next, functional enrichment analyses of co-regulated DEGs were performed. Based on the String database, protein-protein interaction network and module analyses were also conducted. Moreover, transcription factors and miRNAs targeting co-regulated DEGs were predicted using the WebGestalt online tool.A total of 71 co-regulated DEGs were identified, including 56 co-upregulated genes and 15 co-downregulated genes. Functional enrichment analyses showed that upregulated DEGs were significantly enriched in the cell cycle, and DNA replication, and repair related pathways. POLD1, MCM2, and PLK4 were hub proteins in both protein-protein interaction network and module, and might be potential targets of E2F. Additionally, POLD1 and MCM2 were found to be regulated by miR-520H via E2F1.High expression of POLD1, MCM2, and PLK4 might play positive roles in the recurrence of ALL, and could serve as potential therapeutic targets for the treatment of relapsed ALL.

Constitutive Ras signaling and Ink4a/Arf inactivation cooperate during the development of B-ALL in mice

Despite recent advances in treatment, human precursor B-cell acute lymphoblastic leukemia (B-ALL) remains a challenging clinical entity. Recent genome-wide studies have uncovered frequent genetic alterations involving RAS pathway mutations and loss of the INK4A/ARF locus, suggesting their important role in the pathogenesis, relapse, and chemotherapy resistance of B-ALL. To better understand the oncogenic mechanisms by which these alterations might promote B-ALL and to develop an in vivo preclinical model of relapsed B-ALL, we engineered mouse strains with induced somatic Kras^G12D pathway activation and/or loss of Ink4a/Arf during early stages of B-cell development. Although constitutive activation of Kras^G12D in B cells induced prominent transcriptional changes that resulted in enhanced proliferation, it was not sufficient by itself to induce development of a high-grade leukemia/lymphoma. Instead, in 40% of mice, these engineered mutations promoted development of a clonal low-grade lymphoproliferative disorder resembling human extranodal marginal-zone lymphoma of mucosa-associated lymphoid tissue or lymphoplasmacytic lymphoma. Interestingly, loss of the Ink4a/Arf locus, apart from reducing the number of apoptotic B cells broadly attenuated Kras^G12D-induced transcriptional signatures. However, combined Kras activation and Ink4a/Arf inactivation cooperated functionally to induce a fully penetrant, highly aggressive B-ALL phenotype resembling high-risk subtypes of human B-ALL such as BCR-ABL and CRFL2-rearranged. Ninety percent of examined murine B-ALL tumors showed loss of the wild-type Ink4a/Arf locus without acquisition of highly recurrent cooperating events, underscoring the role of Ink4a/Arf in restraining Kras-driven oncogenesis in the lymphoid compartment. These data highlight the importance of functional cooperation between mutated Kras and Ink4a/Arf loss on B-ALL.

Copy number profiling of adult relapsed B-cell precursor acute lymphoblastic leukemia reveals potential leukemia progression mechanisms

The outcome of relapsed adult acute lymphoblastic leukemia (ALL) remains dismal despite new therapeutic approaches. Previous studies analyzing relapse samples have shown a high degree of heterogeneity regarding gene alterations without an evident relapse signature. Bone marrow or peripheral blood samples from 31 adult B-cell precursor ALL patients at first relapse, and 21 paired diagnostic samples were analyzed by multiplex ligation probe-dependent amplification (MLPA). Nineteen paired diagnostic and relapse samples of these 21 patients were also analyzed by SNP arrays. A trend to acquire homozygous CDKN2A/B deletions and a significant increase in the number of copy number alterations (CNA) was observed from diagnosis to first relapse. Evolution from an ancestral clone was the main pattern of clonal evolution. Relapse samples were extremely heterogeneous regarding CNA frequencies. However, CDKN2A/B, PAX5, ETV6, ATM, IKZF1, VPREB1, and TP53 deletions and duplications of 1q, 8q, 17q, 21, X/Y PAR1, and Xp were frequently detected at relapse. Duplications of genes involved in cell proliferation, drug resistance and stem cell homeostasis regulation, as well as deletions of KDM6A and STAG2 genes emerged as specific alterations at relapse. Genomics of relapsed adult B-cell precursor ALL is highly heterogeneous, although some recurrent lesions involved in essential pathways deregulation were frequently observed. Selective and simultaneous targeting of these deregulated pathways may improve the results of current salvage therapies.

Mutational Landscape of Pediatric Acute Lymphoblastic Leukemia

Current standard of care for patients with pediatric acute lymphoblastic leukemia (ALL) is mainly effective, with high remission rates after treatment. However, the genetic perturbations that give rise to this disease remain largely undefined, limiting the ability to address resistant tumors or develop less toxic targeted therapies. Here, we report the use of next-generation sequencing to interrogate the genetic and pathogenic mechanisms of 240 pediatric ALL cases with their matched remission samples. Commonly mutated genes fell into several categories, including RAS/receptor tyrosine kinases, epigenetic regulators, transcription factors involved in lineage commitment, and the p53/cell-cycle pathway. Unique recurrent mutational hotspots were observed in epigenetic regulators CREBBP (R1446C/H), WHSC1 (E1099K), and the tyrosine kinase FLT3 (K663R, N676K). The mutant WHSC1 was established as a gain-of-function oncogene, while the epigenetic regulator ARID1A and transcription factor CTCF were functionally identified as potential tumor suppressors. Analysis of 28 diagnosis/relapse trio patients plus 10 relapse cases revealed four evolutionary paths and uncovered the ordering of acquisition of mutations in these patients. This study provides a detailed mutational portrait of pediatric ALL and gives insights into the molecular pathogenesis of this disease. Cancer Res; 77(2); 390-400. ©2016 AACR.

Knockdown of High Mobility Group-Box 3 (HMGB3) Expression Inhibits Proliferation, Reduces Migration, and Affects Chemosensitivity in Gastric Cancer Cells

Background

High mobility group-box 3 (HMGB3) has been shown to affect tumor initiation and progression. This research aimed to investigate the role of HMGB3 in gastric cancer (GC) cell proliferation, migration, invasion, chemoresistance, and its potential molecular mechanisms.

Material/Methods

GC MGC803 and BGC823 cells were transfected with siRNA targeting the HMGB3 gene. The expressions of HMGB3 protein in MGC803 and BGC823 cells after transfection were detected by Western blot assays. We detected cell proliferation and cell cycle by MTT and flow cytometry assay. Cell migration and invasion were determined by wound scratch and transwell assay. MGC803 and BGC823 cells were treated with various concentrations of oxaliplatin, cisplatin, and paclitaxel. After 24 hours of drug exposure, we performed MTT assays to investigate chemoresistance in both groups. Western blot assays were used to detect related proteins expression.

Results

Silencing of HMGB3 inhibited cell proliferation and induced G0/G1 phase arrest of GC cells partly via modulating p53 and p21 pathways, and downregulating Bcl-2/Bax ratio. RNA interference of HMGB3 inhibited cell invasion and migration by downregulating MMP2 and MMP9. Silencing of HMGB3 enhanced sensitive to cisplatin and paclitaxel, and reduced sensitive to oxaliplatin.

Conclusions

These findings suggest the importance of HMGB3 in the regulation of growth, migration, and apoptosis of GC, improve our understanding of the mechanisms of GC pathogenesis, and may promote the development of novel targeted therapies.

Towards an understanding of the biology and targeted treatment of paediatric relapsed acute lymphoblastic leukaemia

Acute lymphoblastic leukaemia is the most common childhood cancer and for those children who relapse, prognosis is poor and new therapeutic strategies are needed. Recurrent pathways implicated in relapse include RAS, JAK STAT, cell cycle, epigenetic regulation, B cell development, glucocorticoid response, nucleotide metabolism and DNA repair. Targeting these pathways is a rational therapeutic strategy and may deliver novel, targeted therapies into the clinic. Relapse often stems from a minor clone present at diagnosis and thus analysis of persisting leukaemia during upfront therapy may allow targeted drug intervention to prevent relapse.

Relapsed childhood acute lymphoblastic leukemia in the Nordic countries: prognostic factors, treatment and outcome

Relapse is the main reason for treatment failure in childhood acute lymphoblastic leukemia. Despite improvements in the up-front therapy, survival after relapse is still relatively poor, especially for high-risk relapses. The aims of this study were to assess outcomes following acute lymphoblastic leukemia relapse after common initial Nordic Society of Paediatric Haematology and Oncology protocol treatment; to validate currently used risk stratifications, and identify additional prognostic factors for overall survival. Altogether, 516 of 2735 patients (18.9%) relapsed between 1992 and 2011 and were included in the study. There were no statistically significant differences in outcome between the up-front protocols or between the relapse protocols used, but an improvement over time was observed. The 5-year overall survival for patients relapsing in the period 2002-2011 was 57.5±3.4%, but 44.7±3.2% (P<0.001) if relapse occurred in the period 1992-2001. Factors independently predicting mortality after relapse included short duration of first remission, bone marrow involvement, age ten years or over, unfavorable cytogenetics, and Down syndrome. T-cell immunophenotype was not an independent prognostic factor unless in combination with hyperleukocytosis at diagnosis. The outcome for early combined pre-B relapses was unexpectedly poor (5-year overall survival 38.0±10.6%), which supports the notion that these patients need further risk adjustment. Although survival outcomes have improved over time, the development of novel approaches is urgently needed to increase survival in relapsed childhood acute lymphoblastic leukemia.

Olfactomedin 4 Serves as a Marker for Disease Severity in Pediatric Respiratory Syncytial Virus (RSV) Infection

Background

Respiratory viral infections follow an unpredictable clinical course in young children ranging from a common cold to respiratory failure. The transition from mild to severe disease occurs rapidly and is difficult to predict. The pathophysiology underlying disease severity has remained elusive. There is an urgent need to better understand the immune response in this disease to come up with biomarkers that may aid clinical decision making.

Methods

In a prospective study, flow cytometric and genome-wide gene expression analyses were performed on blood samples of 26 children with a diagnosis of severe, moderate or mild Respiratory Syncytial Virus (RSV) infection. Differentially expressed genes were validated using Q-PCR in a second cohort of 80 children during three consecutive winter seasons. FACS analyses were also performed in the second cohort and on recovery samples of severe cases in the first cohort.

Results

Severe RSV infection was associated with a transient but marked decrease in CD4+ T, CD8+ T, and NK cells in peripheral blood. Gene expression analyses in both cohorts identified Olfactomedin4 (OLFM4) as a fully discriminative marker between children with mild and severe RSV infection, giving a PAM cross-validation error of 0%. Patients with an OLFM4 gene expression level above -7.5 were 6 times more likely to develop severe disease, after correction for age at hospitalization and gestational age.

Conclusion

By combining genome-wide expression profiling of blood cell subsets with clinically well-annotated samples, OLFM4 was identified as a biomarker for severity of pediatric RSV infection.

Upregulation of miR-513b inhibits cell proliferation, migration, and promotes apoptosis by targeting high mobility group-box 3 protein in gastric cancer

The high mobility group-box 3 (HMGB3) protein belongs to the high mobility group box (HMG-box) subfamily, and recent studies have shown that HMGB3 is an oncogene for leukemia. HMGB3 is also expressed at a high level in the progression phase of breast and gastric cancer (GC). Using bioinformatic analyses, we found that HMGB3 is a potential target for miR-513b. However, the pathophysiological role of miR-513b and its relevance to the growth and development of GC have yet to be investigated. This study focuses on whether miR-513b acts as a tumor suppressor in GC. Compared with non-malignant adjacent tissues samples, qRT-PCR data showed significant downregulation of miR-513b in 74 GC tissue samples (P < 0.01). Furthermore, western blotting revealed that HMGB3 protein was overexpressed in tumor samples relative to matched, non-malignant adjacent tissues. Western blotting and qRT-PCR results showed that high expression of HMGB3 and low expression of miR-513b were both significantly associated with primary tumors, lymph node metastases, and the clinical stage (P < 0.01). MiR-513b was shown to not only inhibit the proliferation and migration of gastric cancer cells (MKN45 and SGC7901) in the CCK-8 and transwell assays, but also to promote cell apoptosis in a flow-cytometric apoptosis assay. In western blot and luciferase assays, HMGB3 was identified as a major target of miR-513b. Moreover, we also found that the expression of HMGB3 lacking in 3' UTR could abrogate the anti-migration and pro-apoptosis function of miR-513b. These findings suggest the importance of miR-513b targeting of HMGB3 in the regulation of growth, migration and apoptosis of GC, improve our understanding of the mechanisms of GC pathogenesis, and may promote the development of novel targeted therapies.

Current approach to relapsed acute lymphoblastic leukemia in children

Recurrent acute lymphoblastic leukaemia (ALL) is a common disease for pediatric oncologists and accounts for more deaths from cancer in children than any other malignancy. Although most patients achieve a second remission, about 50% of relapsed ALL patients do not respond to salvage therapy or suffer a second relapse and most children with relapse die. Treatment must be tailored after relapse of ALL, since outcome will be influenced by well-established prognostic features, including the timing and site of disease recurrence, the disease immunophenotype, and early response to retrieval therapy in terms of minimal residual disease (MRD). After reinduction chemotherapy, high risk (HR) patients are clear candidates for allogeneic stem cell transplantation (SCT) while standard risk patients do better with conventional chemotherapy and local therapy. Early MRD response assessment is currently applied to identify those patients within the more heterogeneous intermediate risk group who should undergo SCT as consolidation therapy. Recent evidence suggests distinct biological mechanisms for early vs late relapse and the recognition of the involvement of certain treatment resistance related genes as well cell cycle regulation and B-cell development genes at relapse, provides the opportunity to search for novel target therapies.

Preclinical evaluation of the PARP inhibitor, olaparib, in combination with cytotoxic chemotherapy in pediatric solid tumors

BACKGROUND

Poly(ADP-ribose) polymerase (PARP) signals DNA damage and facilitates DNA repair. PARP inhibitors are being evaluated in cancers with defective DNA repair mechanisms or in combination with cytotoxic therapy or radiation. We evaluated the PARP inhibitor, olaparib, in combination with chemotherapy using in vitro and in vivo pediatric solid tumor models.

PROCEDURE

The IC50 of olaparib alone and in combination with cytotoxic agents was determined in 10 pediatric solid tumor cell lines. Synergy was assessed using the combination index of Chou-Talalay. Olaparib alone and in combination with topotecan/cyclophosphamide was evaluated in xenograft models of Ewing sarcoma (RD-ES) and neuroblastoma (NGP). PAR activity was evaluated in cell lines and tumor lysates.

RESULTS

Olaparib induced growth inhibition, median (range) IC50 = 3.6 (1-33.8) µM, and inhibited PAR activity in pediatric solid tumor cell lines. The addition of olaparib to DNA damaging agents resulted in additive to synergistic interactions. In RD-ES and NGP xenografts, olaparib inhibited PAR activity by 88-100% as a single agent and 100% when administered with cyclophosphamide/topotecan. Although the addition of olaparib did not antagonize the activity of cyclophosphamide/topotecan, clear evidence of synergy could not be demonstrated.

CONCLUSIONS

In pediatric solid tumor cell lines, clinically achievable concentrations of single agent olaparib caused growth inhibition. Although the in vitro data demonstrated synergistic efficacy of olaparib when added to the camptothecins and alkylating agents, synergy was not discernible in vivo. Clinical trials of PARP inhibitors in combination DNA damaging agents are necessary to establish the role of PARP inhibitors in childhood cancer.

BubR1 is frequently repressed in acute myeloid leukemia and its re-expression sensitizes cells to antimitotic therapy

Spindle poison-based therapy is of only limited benefit in acute myeloid leukemia while lymphoblastic leukemia/lymphoma responds well. In this study, we demonstrated that the spindle assembly checkpoint protein BubR1 was down-regulated in the vast majority of cases of acute myeloid leukemia whereas its expression was high in lymphoblastic cells. Correct function of the spindle assembly checkpoint is pivotal in mediating mitotic delay in response to spindle poisons. Mitotic delay by the spindle assembly checkpoint is achieved by inhibition of anaphase-promoting complex-dependent proteolysis of cyclin B and securin. We demonstrated a link between the repression of the spindle assembly checkpoint protein BubR1 in acute myeloid leukemia and the limited response to spindle poison. In accordance with its established role as an anaphase-promoting complex-inhibitor, we found that repression of BubR1 was associated with enhanced anaphase-promoting complex activity and cyclin B and securin degradation, which leads to premature sister-chromatid separation and failure to sustain a mitotic arrest. This suggests that repression of BubR1 in acute myeloid leukemia renders the spindle assembly checkpoint-mediated inhibition of the anaphase-promoting complex insufficient, which facilitates completion of mitosis in the presence of spindle poison. As both direct and BubR1-mediated restoration of cyclin B expression enhanced response to spindle poison, we propose that the downstream axis of the spindle assembly checkpoint is a promising target for tailored therapies for acute myeloid leukemia.

Fat1 cadherin provides a novel minimal residual disease marker in acute lymphoblastic leukemia

Measurement of minimal residual disease (MRD) maintains an important role in the clinical management of acute lymphoblastic leukemia (ALL). Recently, we identified Fat1 cadherin as a unique and independent prognostic factor for relapse-free and overall survival in pediatric pre-B-ALL. Here, we analyzed Fat1 mRNA for its potential as a novel marker of MRD in cases of pre-B- and T-ALL. Analyses of microarray data from 125 matched diagnosis/relapse samples across three independent datasets indicate that Fat1 mRNA is detectable in an average of 31.3% of diagnosed pre-B-ALL, of which 67.5% of cases remained positive at relapse. Furthermore, some 20% of cases with undetectable levels of Fat1 mRNA at diagnosis became positive upon relapse. T-ALL cases were 83.3% positive for Fat1 expression at diagnosis with 77.7% remaining positive at relapse. Towards proof of concept, we developed a quantitative polymerase chain reaction assay and demonstrate detection of Fat1 mRNA in leukemic cells mixed with normal peripheral blood cells at a sensitivity of 1 in 10 000 to 100 000 cells. Fat1 may therefore provide a new marker of MRD for patients with ALL lacking known genomic aberrations or within a multiplex approach to MRD detection.

Rational design of an immunoconjugate for selective knock-down of leukemia-specific E2A-PBX1 fusion gene expression in human Pre-B leukemia

The t(1;19)(q23;p13) is one of the most common chromosomal translocations in acute lymphoblastic leukemia (ALL) and results in production of the transforming oncoprotein E2A-PBX1. Here we first report a novel, biomarker-guided biotherapy strategy for personalized treatment of t(1;19)(+) ALL. A supervised interrogation of the gene expression profiles of primary leukemic cells from a cohort of 207 children with high risk B-lineage ALL identified up-regulated CD19 gene expression as a biomarker for t(1;19)(+) ALL. A disulfide-linked immunoconjugate of a 5-amino-modified 24 mer phosphorothioate anti-sense E2A-PBX1 oligonucleotide (AON) with a mAb specific for a CD19 receptor (αCD19-AON) was prepared as a CD19-directed and leukemia-specific biotherapeutic agent against E2A-PBX1(+) B-lineage ALL. Treatment of E2A-PBX1(+) leukemia cells with low nanomolar concentrations of αCD19-AON resulted in selective depletion of E2A-PBX1 transcripts and caused apoptotic destruction and abrogation of clonogenic growth. Subcutaneously administered αCD19-AON at a total dose level of 93 nmol kg(-1) delivered over 14 days using a micro-osmotic pump more than doubled the leukemia-free survival time of SCID mice in a xenograft model of E2A-PBX1(+) human B-lineage ALL (82.0 ± 1.9 days vs. 37.0 ± 0.1 days, P < 0.0001). Both the AON moiety and the targeting CD19-specific mAb moiety were required for the in vitro as well as in vivo anti-leukemic activity of αCD19-AON. The observed in vitro and in vivo anti-leukemic potency of the αCD19-AON immunoconjugate provides the first preclinical proof-of-principle that t(1;19)(+) high risk B-lineage ALL can be treated with leukemia-specific biotherapeutic agents that knock-down E2A-PBX1 expression.

High mobility group-box 3 overexpression is associated with poor prognosis of resected gastric adenocarcinoma

AIM: To elucidate high mobility group-box 3 (HMGB3) protein expression in gastric adenocarcinoma, its potential prognostic relevance, and possible mechanism of action.

METHODS: Ninety-two patients with gastric adenocarcinomas surgically removed entered the study. HMGB3 expression was determined by immunohistochemistry through a tissue microarray procedure. The clinicopathologic characteristics of all patients were recorded, and regular follow-up was made for all patients. The inter-relationship of HMGB3 expression with histological and clinical factors was analyzed using nonparametric tests. Survival analysis was carried out by Kaplan-Meier (log-rank) and multivariate Cox (Forward LR) analyses between the group with overexpression of HMGB3 and the group with low or no HMGB3 expression to determine the prognosis value of HMGB3 expression on overall survival. Further, HMGB3 expression was knocked down by small hairpin RNAs (shRNAs) in the human gastric cancer cell line BGC823 to observe its influence on cell biological characteristics. The MTT method was utilized to detect gastric cancer cell proliferation changes, and cell cycle distribution was analyzed by flow cytometry.

RESULTS: Among 92 patients with gastric adenocarcinomas surgically removed in this study, high HMGB3 protein expression was detected in the gastric adenocarcinoma tissues vs peritumoral tissues (P < 0.001). Further correlation analysis with patients’ clinical and histology variables revealed that HMGB3 overexpression was obviously associated with extensive wall penetration (P = 0.005), a positive nodal status (P = 0.004), and advanced tumor-node-metastasis (TNM) stage (P = 0.001). But there was no correlation between HMGB3 overexpression and the age and gender of the patient, tumor localization or histologic grade. Statistical Kaplan-Meier survival analysis disclosed significant differences in overall survival between the HMGB3 overexpression group and the HMGB3 no or low expression group (P = 0.006). The expected overall survival time was 31.00 ± 3.773 mo (95%CI = 23.605-38.395) for patients with HMGB3 overexpression and 49.074 ± 3.648 mo (95%CI = 41.925-57.311) for patients with HMGB3 no and low-level expression. Additionally, older age (P = 0.040), extensive wall penetration (P = 0.008), positive lymph node metastasis (P = 0.005), and advanced TNM tumor stage (P = 0.007) showed negative correlation with overall survival. Multivariate Cox regression analysis indicated that HMGB3 overexpression was an independent variable with respect to age, gender, histologic grade, extent of wall penetration, lymph nodal metastasis, and TNM stage for patients with resectable gastric adenocarcinomas with poor prognosis (hazard ratio = 2.791, 95%CI = 1.233-6.319, P = 0.019). In the gene function study, after HMGB3 was knocked down in the gastric cell line BGC823 by shRNA, the cell proliferation rate was reduced at 24 h, 48 h and 72 h. Compared to BGC823 shRNA-negative control (NC) cells, the cell proliferation rate in cells that had HMGB3 shRNA transfected was significantly decreased (P < 0.01). Finally, cell cycle analysis by FACS showed that BGC823 cells that had HMGB3 knocked down were blocked in G1/G0 phase. The percentage of cells in G1/G0 phase in BGC823 cells with shRNA-NC and with shRNA-HMGB3 was 46.84% ± 1.7%, and 73.03% ± 3.51% respectively (P = 0.001), whereas G2/M cells percentage decreased from 26.51% ± 0.83% to 17.8% ± 2.26%.

CONCLUSION: HMGB3 is likely to be a useful prognostic marker involved in gastric cancer disease onset and progression by regulating the cell cycle.

Where do we stand in the treatment of relapsed acute lymphoblastic leukemia?

Acute lymphoblastic leukemia (ALL) is the most common and one of the most treatable cancers in children. Although the majority of children with ALL are now cured, 10%-20% of patients are predicted to relapse and outcomes with salvage therapy have been disappointing, with approximately only one-third of children surviving long-term after disease recurrence. Several prognostic factors have been identified, with timing of recurrence relative to diagnosis and site of relapse emerging as the most important variables. Despite heterogeneity in the elements of salvage therapy that are delivered in trials conducted internationally, outcomes have been remarkably similar and have remained static. Because most intensive salvage regimens have reached the limit of tolerability, current strategies are focusing on identifying new agents tailored to the unique biology of relapsed disease and identifying methods to develop these agents efficiently for clinical use. Recently, high-resolution genomic analyses of matched pairs of diagnostic and relapse bone marrow samples are emerging as a promising tool for identifying pathways that impart chemoresistance.

Excellent prognosis of late relapses of ETV6/RUNX1-positive childhood acute lymphoblastic leukemia: lessons from the FRALLE 93 protocol

BACKGROUND

The prognosis of patients with relapses of ETV6/RUNX1-positive acute lymphoblastic leukemia remains to be evaluated, particularly with regards to the frequency of late relapses. We performed a long-term, follow-up retrospective study to address the outcome of patients with ETV6/RUNX1-positive leukemia relapses.

DESIGN AND METHODS

Among the 713 children tested for ETV6/RUNX1 enrolled into the FRALLE 93 protocol, 43 ETV6/RUNX1-positive patients relapsed (19.4%). Most were initially stratified in the low or intermediate risk groups. The median follow-up after relapse was 54.2 months. All but three received second-line salvage therapy and 16 underwent allogeneic transplantation.

RESULTS

ETV6/RUNX1 had a strong effect on overall survival after relapse (3-year survival= 64.7% for positive cases versus 46.5% for negative cases) (P=0.007). The 5-year cumulative incidence of relapse was 19.4% and testes were more frequently involved in ETV6/RUNX1-positive relapses (P=0.04). In 81.4% of cases the relapses were late, early combined or isolated extramedullary relapses. The 5-year survival rate of patients with ETV6-RUNX1-positive acute lymphoblastic leukemia relapses reached 80.8% when the relapse occurred after 36 months (versus 31.2% when the relapse occurred earlier). In univariate analysis, female gender was associated with a poor survival, whereas site of relapse, age at diagnosis, leukocytosis and consolidation strategy had no effect. In multivariate analysis, only the duration of first remission remained associated with outcome.

CONCLUSIONS

We found an excellent outcome for patients with ETV6/RUNX1-positive leukemia relapses that occurred more than 36 months after diagnosis. The duration of first complete remission may, therefore, be a guide to define the treatment strategy for patients with relapsed ETV6/RUNX1- positive leukemia.

Gene expression signatures and ex vivo drug sensitivity profiles in children with acute lymphoblastic leukemia

INTRODUCTION

Causes of treatment failure in acute lymphoblastic leukemia (ALL) are still poorly understood. Microarray technology gives new possibilities for the analysis of the biology of leukemias. We hypothesize that drug sensitivity in pediatric ALL is driven by specific molecular mechanisms that correlate with gene expression profiles assessed by microarray analysis.

OBJECTIVE

The aim of the study was to determine the ex vivo resistance profiles of 20 antileukemic drugs and gene expression profiles, with relation to response to initial therapy.

PATIENTS AND METHODS

Lymphoblasts were analyzed after bone marrow biopsy was obtained from 56 patients. The profile of in vitro resistance to drugs was determined in the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazoliumbromide (MTT) cytotoxicity assay. High-quality total RNA was prepared and hybridized to oligonucleotide arrays HG-U133A 2.0 Chip (Affymetrix). The expression of selected genes was tested by qualitative reverse transcription polymerase chain reaction (qRT-PCR).

RESULTS AND CONCLUSIONS

The exposure of leukemic blasts to drugs initiates a complex cellular response, which reflects global changes in gene expression. Changes in the expression of several genes are highly correlated with drug resistance.

A set of miRNAs that involve in the pathways of drug resistance and leukemic stem-cell differentiation is associated with the risk of relapse and glucocorticoid response in childhood ALL

Relapse is a major challenge in the successful treatment of childhood acute lymphoblastic leukemia (ALL). Despite intensive research efforts, the mechanisms of ALL relapse are still not fully understood. An understanding of the molecular mechanisms underlying treatment outcome, therapy response and the biology of relapse is required. In this study, we carried out a genome-wide microRNA (miRNA) microarray analysis to determine the miRNA expression profiles and relapse-associated miRNA patterns in a panel of matched diagnosis–relapse or diagnosis–complete remission (CR) childhood ALL samples. A set of miRNAs differentially expressed either in relapsed patients or at diagnosis compared with CR was further validated by quantitative real-time polymerase chain reaction in an independent sample set. Analysis of the predicted functions of target genes based on gene ontology ‘biological process’ categories revealed that the abnormally expressed miRNAs are associated with oncogenesis, classical multidrug resistance pathways and leukemic stem cell self-renewal and differentiation pathways. Several targets of the miRNAs associated with ALL relapse were experimentally validated, including FOXO3, BMI1 and E2F1. We further investigated the association of these dysregulated miRNAs with clinical outcome and confirmed significant associations for miR-708, miR-223 and miR-27a with individual relapse-free survival. Notably, miR-708 was also found to be associated with the in vivo glucocorticoid therapy response and with disease risk stratification. These miRNAs and their targets might be used to optimize anti-leukemic therapy, and serve as novel targets for development of new countermeasures of leukemia. This fundamental study may also contribute to establish the mechanisms of relapse in other cancers.

Integrated genomic analysis of relapsed childhood acute lymphoblastic leukemia reveals therapeutic strategies

Despite an increase in survival for children with acute lymphoblastic leukemia (ALL), the outcome after relapse is poor. To understand the genetic events that contribute to relapse and chemoresistance and identify novel targets of therapy, 3 high-throughput assays were used to identify genetic and epigenetic changes at relapse. Using matched diagnosis/relapse bone marrow samples from children with relapsed B-precursor ALL, we evaluated gene expression, copy number abnormalities (CNAs), and DNA methylation. Gene expression analysis revealed a signature of differentially expressed genes from diagnosis to relapse that is different for early (< 36 months) and late (≥ 36 months) relapse. CNA analysis discovered CNAs that were shared at diagnosis and relapse and others that were new lesions acquired at relapse. DNA methylation analysis found increased promoter methylation at relapse. There were many genetic alterations that evolved from diagnosis to relapse, and in some cases these genes had previously been associated with chemoresistance. Integration of the results from all 3 platforms identified genes of potential interest, including CDKN2A, COL6A2, PTPRO, and CSMD1. Although our results indicate that a diversity of genetic changes are seen at relapse, integration of gene expression, CNA, and methylation data suggest a possible convergence on the WNT and mitogen-activated protein kinase pathways.

Clonal selection in xenografted human T cell acute lymphoblastic leukemia recapitulates gain of malignancy at relapse

Genomic studies in human acute lymphoblastic leukemia (ALL) have revealed clonal heterogeneity at diagnosis and clonal evolution at relapse. In this study, we used genome-wide profiling to compare human T cell ALL samples at the time of diagnosis and after engraftment (xenograft) into immunodeficient recipient mice. Compared with paired diagnosis samples, the xenograft leukemia often contained additional genomic lesions in established human oncogenes and/or tumor suppressor genes. Mimicking such genomic lesions by short hairpin RNA-mediated knockdown in diagnosis samples conferred a selective advantage in competitive engraftment experiments, demonstrating that additional lesions can be drivers of increased leukemia-initiating activity. In addition, the xenograft leukemias appeared to arise from minor subclones existing in the patient at diagnosis. Comparison of paired diagnosis and relapse samples showed that, with regard to genetic lesions, xenograft leukemias more frequently more closely resembled relapse samples than bulk diagnosis samples. Moreover, a cell cycle- and mitosis-associated gene expression signature was present in xenograft and relapse samples, and xenograft leukemia exhibited diminished sensitivity to drugs. Thus, the establishment of human leukemia in immunodeficient mice selects and expands a more aggressive malignancy, recapitulating the process of relapse in patients. These findings may contribute to the design of novel strategies to prevent or treat relapse.

Relapse of acute lymphoblastic leukemia in children in the context of microarray analyses

Over the last four decades the treatment of patients with newly diagnosed childhood acute lymphoblastic leukemia (ALL) has improved remarkably. However, still about 20% of children with ALL relapse despite risk-adapted polychemotherapy. The prognosis of relapsed ALL is relatively poor, even with modern aggressive chemotherapy. Identification of the biological and genetic mechanisms contributing to recurrence in patients with ALL is critical for the development of effective therapeutic strategies to treat refractory leukemic patients. Allogeneic hematopoietic stem-cell transplantation is the treatment of choice for many children with relapsed ALL. The gene expression profile obtained by microarray technology could provide important determinants of the drug response and clinical outcome in childhood ALL. Incorporation of the data on expression levels of newly identified genes into existing strategies of risk stratification might improve clinical management. Current microarray data show correlation of in vitro drug resistance with significant patterns of gene expression and explain clinical differences between early and late relapse. Genes involved in cell proliferation, self-renewal and differentiation, protein biosynthesis, carbohydrate metabolism, and DNA replication and repair are usually among those highly expressed in relapsed lymphoblasts. Current status and future perspectives of microarray data on gene expression and drug resistance profile in relapsed pediatric ALL are discussed in this review.

Genomic, immunophenotypic, and NPM1/FLT3 mutational studies on 17 patients with normal karyotype acute myeloid leukemia (AML) followed by aberrant karyotype AML at relapse

Normal karyotype (NK) is the most common cytogenetic group in acute myeloid leukemia (AML) diagnosis; however, up to 50% of these patients at relapse will have aberrant karyotype (AK) AML. To determine the etiology of relapsed AK AML cells, we evaluated cytogenetic, immunophenotypic, and molecular results of 17 patients with diagnostic NK AML and relapsed AK AML at our institute. AK AML karyotype was diverse, involving no favorable and largely (8 of 17) complex cytogenetics. Despite clear cytogenetic differences, immunophenotype and NPM1/FLT3 gene mutation status did not change between presentation and relapse in 83% (10 of 12) and 94% (15 of 16) cases, respectively. High-resolution array-based comparative genomic hybridization (aCGH) performed via paired aCGH on NK AML and AK AML samples from the same patient confirmed cytogenetic aberrations only in the relapse sample. Analysis of 16 additional diagnostic NK AML samples revealed no evidence of submicroscopic aberrations undetected by conventional cytogenetics in any case. These results favor evolution of NK AML leukemia cells with acquisition of novel genetic changes as the most common etiology of AK AML relapse as opposed to secondary leukemogenesis. Additional studies are needed to confirm whether AK AML cells represent selection of rare preexisting clones below aCGH detection and to further characterize the molecular lesions found at time of AK AML relapse.

TLX1 and NOTCH coregulate transcription in T cell acute lymphoblastic leukemia cells

BACKGROUND

The homeobox gene TLX1 (for T-cell leukemia homeobox 1, previously known as HOX11) is inappropriately expressed in a major subgroup of T cell acute lymphoblastic leukemia (T-ALL) where it is strongly associated with activating NOTCH1 mutations. Despite the recognition that these genetic lesions cooperate in leukemogenesis, there have been no mechanistic studies addressing how TLX1 and NOTCH1 functionally interact to promote the leukemic phenotype.

RESULTS

Global gene expression profiling after downregulation of TLX1 and inhibition of the NOTCH pathway in ALL-SIL cells revealed that TLX1 synergistically regulated more than 60% of the NOTCH-responsive genes. Structure-function analysis demonstrated that TLX1 binding to Groucho-related TLE corepressors was necessary for maximal transcriptional regulation of the NOTCH-responsive genes tested, implicating TLX1 modulation of the NOTCH-TLE regulatory network. Comparison of the dataset to publicly available biological databases indicated that the TLX1/NOTCH-coregulated genes are frequently targeted by MYC. Gain- and loss-of-function experiments confirmed that MYC was an essential mediator of TLX1/NOTCH transcriptional output and growth promotion in ALL-SIL cells, with TLX1 contributing to the NOTCH-MYC regulatory axis by posttranscriptional enhancement of MYC protein levels. Functional classification of the TLX1/NOTCH-coregulated targets also showed enrichment for genes associated with other human cancers as well as those involved in developmental processes. In particular, we found that TLX1, NOTCH and MYC coregulate CD1B and RAG1, characteristic markers of early cortical thymocytes, and that concerted downregulation of the TLX1 and NOTCH pathways resulted in their irreversible repression.

CONCLUSIONS

We found that TLX1 and NOTCH synergistically regulate transcription in T-ALL, at least in part via the sharing of a TLE corepressor and by augmenting expression of MYC. We conclude that the TLX1/NOTCH/MYC network is a central determinant promoting the growth and survival of TLX1+ T-ALL cells. In addition, the TLX1/NOTCH/MYC transcriptional network coregulates genes involved in T cell development, such as CD1 and RAG family members, and therefore may prescribe the early cortical stage of differentiation arrest characteristic of the TLX1 subgroup of T-ALL.