NOTCH1/FBXW7 mutation identifies a large subgroup with favorable outcome in adult T-cell acute lymphoblastic leukemia (T-ALL): a Group for Research on Adult Acute Lymphoblastic Leukemia (GRAALL) study

The molecular basis of T cell acute lymphoblastic leukemia

T cell acute lymphoblastic leukemias (T-ALLs) arise from the malignant transformation of hematopoietic progenitors primed toward T cell development, as result of a multistep oncogenic process involving constitutive activation of NOTCH signaling and genetic alterations in transcription factors, signaling oncogenes, and tumor suppressors. Notably, these genetic alterations define distinct molecular groups of T-ALL with specific gene expression signatures and clinicobiological features. This review summarizes recent advances in our understanding of the molecular genetics of T-ALL.

Cytogenetic and molecular predictors of outcome in acute lymphocytic leukemia: recent developments

During the last decade a tremendous technologic progress based on genome-wide profiling of genetic aberrations, structural DNA alterations, and sequence variations has allowed a better understanding of the molecular basis of pediatric and adult B/T-acute lymphoblastic leukemia (ALL), contributing to a better recognition of the biological heterogeneity of ALL and to a more precise definition of risk factors. Importantly, these advances identified novel potential targets for therapeutic intervention. This review will be focused on the cytogenetic/molecular advances in pediatric and adult ALL based on recently published articles.

Clinical impact of NOTCH1 and/or FBXW7 mutations, FLASH deletion, and TCR status in pediatric T-cell lymphoblastic lymphoma

PURPOSE

Pediatric T-cell lymphoblastic lymphomas (T-LBL) are commonly treated on T-cell acute lymphoblastic leukemia (T-ALL) -derived protocols. Therapeutic stratification based on response to the prephase treatment and on minimal residual disease assessment is well established in T-ALL but is not easy to extrapolate to T-LBL. The identification of molecular prognostic markers at diagnosis in T-LBL could provide an alternative for early therapeutic stratification. Our study determines the frequency and prognostic value of NOTCH1/FBXW7 mutations (N/F(mut)), FLASH deletion at chromosome 6q, and TCR rearrangements in a prospective cohort of pediatric T-LBL.

PATIENTS AND METHODS

Pathologic samples were obtained at diagnosis for 54 patients treated according to the EuroLB02 protocol in France. N/F(mut) were identified by direct sequencing and allelic dosage was used to detect FLASH and TCRγ deletions, which were interpreted in conjunction with TCRγ, TCRβ, and TCRδ rearrangements.

RESULTS

N/F(mut) were found in 55% of T-LBL patients, in whom they were associated with improved event-free survival (P < .01) and overall survival (P < .01). FLASH monoallelic deletions were observed in 18% of patients; they were predominantly N/F wild-type (six of nine) and tended to be of inferior prognosis (P = .09). Absence of biallelic TCRγ deletion (ABD) was seen in 7%, all of which were N/F(mut) and identified a poor prognosis group (P = .02). On multivariate analysis of N/F(mut), TCRγ ABD, and FLASH deletion, only N/F(mut) was an independent factor for good prognosis.

CONCLUSION

Mutational status of NOTCH1/FBXW7 represents a promising marker for early therapeutic stratification in pediatric T-LBL.

Prognostic factors in adult acute leukemia

The prognostic factors in acute leukemia have undergone a major change over the past decade and are likely to be further refined in the coming years. While age is the single most important prognostic factor in both AML and in ALL, recurring cytogenetic abnormalities and molecular markers have become crucial for the prognosis of patients and for new directions in the development of targeted therapies. No less important is the development of a personalized approach for therapy as determined by the response to therapy using increasingly sensitive technologies. The assessment of MRD is rapidly superseding other prognostic factors in ALL and, somewhat lacking behind, coming into its own in AML. The next decade should see further refinement of response-driven prognostication, to include epigenetics as well as pharmacogenetics and pharmacodynamics of individual drugs used and the responses to them. It is hoped that these refinements and better predictors of response will also lead to a significantly improved overall outcome of patients with both AML and ALL.

Mutations increased overexpression of Notch1 in T-cell acute lymphoblastic leukemia

Background

The Notch signaling pathway is crucial in T-cell development, Notch1 mutations are frequently present in T-cell acute lymphoblastic leukemia (T-ALL). To investigate the feature of Notch1 mutation and its corresponding expression level in Chinese patients with T-ALL, detection of mutation and the expression level of Notch1 gene was preformed using RT-PCR, sequencing and real-time PCR respectively.

Results

Two Notch1 point mutations (V1578E and L1593P) located on HD-N domain were identified in three cases out of 13 T-ALL patients. The mutation on 4733 position (V1578E) found in two cases was a novel mutation. The overexpression of Notch1 was detected in all samples with T-ALL, moreover, significantly higher expression of Notch1 was detected in the T-ALL with Notch1 mutation group compared with T-ALL with WT Notch1 group (p = 0.0192).

Conclusions

Higher expression of Notch1 was associated with Notch1 mutation, more novel mutation of this gene might be identified in different populations and its contribution to the molecular pathogenesis of T-ALL is needed further research.

The significance of PTEN and AKT aberrations in pediatric T-cell acute lymphoblastic leukemia

BACKGROUND

PI3K/AKT pathway mutations are found in T-cell acute lymphoblastic leukemia, but their overall impact and associations with other genetic aberrations is unknown. PTEN mutations have been proposed as secondary mutations that follow NOTCH1-activating mutations and cause cellular resistance to γ-secretase inhibitors.

DESIGN AND METHODS

The impact of PTEN, PI3K and AKT aberrations was studied in a genetically well-characterized pediatric T-cell leukemia patient cohort (n=146) treated on DCOG or COALL protocols.

RESULTS

PTEN and AKT E17K aberrations were detected in 13% and 2% of patients, respectively. Defective PTEN-splicing was identified in incidental cases. Patients without PTEN protein but lacking exon-, splice-, promoter mutations or promoter hypermethylation were present. PTEN/AKT mutations were especially abundant in TAL- or LMO-rearranged leukemia but nearly absent in TLX3-rearranged patients (P=0.03), the opposite to that observed for NOTCH1-activating mutations. Most PTEN/AKT mutant patients either lacked NOTCH1-activating mutations (P=0.006) or had weak NOTCH1-activating mutations (P=0.011), and consequently expressed low intracellular NOTCH1, cMYC and MUSASHI levels. T-cell leukemia patients without PTEN/AKT and NOTCH1-activating mutations fared well, with a cumulative incidence of relapse of only 8% versus 35% for PTEN/AKT and/or NOTCH1-activated patients (P=0.005).

CONCLUSIONS

PI3K/AKT pathway aberrations are present in 18% of pediatric T-cell acute lymphoblastic leukemia patients. Absence of strong NOTCH1-activating mutations in these cases may explain cellular insensitivity to γ-secretase inhibitors.

Beyond the 2008 World Health Organization classification: the role of the hematopathology laboratory in the diagnosis and management of acute lymphoblastic leukemia

The diagnosis of acute lymphoblastic leukemia (ALL) is made by evaluating morphology and immunophenotype. However, appropriate risk stratification and decisions regarding the intensity of therapy are influenced by additional clinical and laboratory testing that reflect the biology of the disease. Recent years have seen tremendous progress in uncovering genetic lesions that influence the biology of ALL. In recognition of these advances, the 2008 WHO classification incorporated the category of B-lymphoblastic leukemia/lymphoma with recurrent genetic abnormalities into the classification of precursor lymphoid neoplasms. Based on the knowledge available at the time, genetic lesions associated with distinct clinical features, immunophenotype, prognosis, or other unique biological characteristics were included in this category. Not surprisingly, significant novel genetic lesions that profoundly affect the biology of ALL have since been identified and will have a major impact on risk stratification and may ultimately be incorporated into future classification schemes. After establishing an initial diagnosis and treatment regimen, hematopathologists must also evaluate for minimal residual disease (MRD) to determine the need for additional intervention because MRD remains the most useful clinical indicator of disease progression and response to treatment. Doing so requires familiarity with not only morphology, but also flow cytometry and molecular genetics. Although not all of these applications are handled directly by the hematopathologist, it is our strong belief that meaningful involvement in patient care dictates that hematopathologists appreciate all aspects of ALL diagnosis and disease monitoring. This review covers the salient aspects of recent advances in the biology of ALL and evaluation of MRD, placing emphasis on how this information may ultimately be used to improve risk stratification and, as a result, patient outcomes.

Therapeutic potential of Notch inhibition in T-cell acute lymphoblastic leukemia: rationale, caveats and promises

T-cell acute lymphoblastic leukemia (T-ALL) is a malignancy that presents with poor prognosis. Treatment relies on the application of aggressive therapies that produce deleterious side-effects, justifying the quest for novel, more efficient and selective molecular targeting agents. Mutations leading to abnormal Notch-1 activity are present in more than half of the T-ALL patients, underscoring the potential therapeutic relevance of targeting Notch-1 inhibition and further reinforcing the need to better comprehend the mechanisms by which Notch-1 drives T cell leukemogenesis. Clinical application of γ-secretase inhibitors to block Notch signaling in T-ALL revealed new challenges that involve improvement of the therapeutic benefit and reduction of intestinal toxicity. Here, we review the latest advances in the development and use of Notch antagonists and summarize the current knowledge on Notch function in T-ALL to understand how it may translate into novel therapeutic strategies that increment the efficiency of Notch inhibition.

The indicative effect of Notch1 expression for the prognosis of T-cell acute lymphocytic leukemia: a systematic review

To explore the relationship of Notch1 mutation in T-ALL with the survival rate of T-ALL patients. The PubMed database, the Cochrane Library, conference proceedings, EMBASE databases, and references of published trials and review articles were searched. Two reviewers independently assessed the quality of the trials and extracted data. Hazard ratios (HRs) for event-free survival (EFS) were pooled by STATA package. Seven trials involving 964 patients with T-ALL were ultimately analyzed. Seven hundred and eleven patients were children (age <18 years), 253 patients were adults (age ≥18 years). The pooled HR showed that Notch1 mutated group could not prolong EFS than Notch1 WT group both in children and adult patients. Although constitutively activated forms of the NOTCH1 receptor are potent inducers of T-ALL, our results suggest that Notch1 mutation could not become an indicator for EFS in T-ALL.

The double-edged sword of Notch signaling in cancer

Recent deep sequencing of cancer genomes has produced an explosion of new data implicating Notch signaling in several human cancers. Unlike most other pathways, these data indicate that Notch signaling can be either oncogenic or tumor suppressive, depending on the cellular context. In some instances, these relationships were predicted from mouse models or presaged by developmental roles for Notch, but in other cases were unanticipated. This review discusses the pathogenic and translational significance of these new findings.

Recent advances on NOTCH signaling in T-ALL

NOTCH1 receptor signaling plays a central role in T-cell lineage specification and in supporting the growth and proliferation of immature T-cell progenitors in the thymus during lymphoid development. In T-cell acute lymphoblastic leukemia (T-ALL), a tumor resulting from the malignant transformation of T-cell progenitors, aberrant and constitutively active NOTCH1 signaling triggered by activating mutations in the NOTCH1 gene contributes to oncogenic transformation and is a hallmark of this disease. Most notably, small molecule γ-secretase inhibitors (GSIs) can effectively block NOTCH1 signaling in T-ALL, and could be exploited as a targeted therapy in this disease. In addition, a number of emerging anti-NOTCH therapeutic strategies including anti-NOTCH1 inhibitory antibodies, small peptide inhibitors of NOTCH signaling and combination therapies with GSIs and glucocorticoids, have recently been proposed. Finally, the identification of NOTCH1 mutations in solid tumors and chronic lymphocytic leukemias has increased even further the clinical relevance of NOTCH signaling as a therapeutic target in human cancer. Here we review our current understanding of NOTCH1-induced transformation, the mechanisms of action of oncogenic NOTCH1 in T-ALL and the therapeutic and prognostic implications of NOTCH1 mutations in T-ALL.

Notch signaling in acute lymphoblastic leukemia: any role for stromal microenvironment?

Notch signaling pathway regulates many different events of embryonic and adult development; among them, Notch plays an essential role in the onset of hematopoietic stem cells and influences multiple maturation steps of developing lymphoid and myeloid cells. Deregulation of Notch signaling determines several human disorders, including cancer. In the last decade it became evident that Notch signaling plays pivotal roles in the onset and development of T- and B-cell acute lymphoblastic leukemia by regulating the intracellular molecular pathways involved in leukemia cell survival and proliferation. On the other hand, bone marrow stromal cells are equally necessary for leukemia cell survival by preventing blast cell apoptosis and favoring their reciprocal interactions and cross-talk with bone marrow microenvironment. Quite surprisingly, the link between Notch signaling pathway and bone marrow stromal cells in acute lymphoblastic leukemia has been pointed out only recently. In fact, bone marrow stromal cells express Notch receptors and ligands, through which they can interact with and influence normal and leukemia T- and B-cell survival. Here, the data concerning the development of T- and B-cell acute lymphoblastic leukemia has been critically reviewed in light of the most recent findings on Notch signaling in stromal microenvironment.

Notch1 regulates chemotaxis and proliferation by controlling the CC-chemokine receptors 5 and 9 in T cell acute lymphoblastic leukaemia

Tumour cells often express deregulated profiles of chemokine receptors that regulate cancer cell migration and proliferation. Notch1 pathway activation is seen in T cell acute lymphoblastic leukaemia (T-ALL) due to the high frequency of Notch1 mutations affecting approximately 60% of patients, causing ligand-independent signalling and/or prolonging Notch1 half-life. We have investigated the possible regulative role of Notch1 on the expression and function of chemokine receptors CCR5, CCR9 and CXCR4 that play a role in determining blast malignant properties and localization of extramedullary infiltrations in leukaemia. We inhibited the pathway through γ-Secretase inhibitor and Notch1 RNA interference and analysed the effect on the expression and function of chemokine receptors. Our results indicate that γ-Secretase inhibitor negatively regulates the transcription level of the CC chemokine receptors 5 and 9 in T-ALL cell lines and patients' primary leukaemia cells, leaving CXCR4 expression unaltered. The Notch pathway also controls CCR5- and CCR9-mediated biological effects, ie chemotaxis and proliferation. Furthermore, engaging CCR9 through CCL25 administration rescues proliferation inhibition associated with abrogation of Notch activity. Finally, through RNA interference we demonstrated that the oncogenic isoform in T-ALL, Notch1, plays a role in controlling CCR5 and CCR9 expression and functions. These findings suggest that Notch1, acting in concert with chemokine receptors pathways, may provide leukaemia cells with proliferative advantage and specific chemotactic abilities, therefore influencing tumour cell progression and localization.

T-cell acute lymphoblastic leukaemia: recent molecular biology findings

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

Sequential mutations in Notch1, Fbxw7, and Tp53 in radiation-induced mouse thymic lymphomas

T-cell acute lymphoblastic lymphomas commonly demonstrate activating Notch1 mutations as well as mutations or deletions in Fbxw7. However, because Fbxw7 targets Notch1 for degradation, genetic alterations in these genes are expected to be mutually exclusive events in lymphomagenesis. Previously, by using a radiation-induced Tp53-deficient mouse model for T-cell acute lymphoblastic lymphoma, we reported that loss of heterozygosity at the Fbxw7 locus occurs frequently in a Tp53-dependent manner. In the current study, we show that these thymic lymphomas also commonly exhibit activating Notch1 mutations in the proline-glutamic acid-serine-threonine (PEST) domain. Moreover, concurrent activating Notch1 PEST domain mutations and single-copy deletions at the Fbxw7 locus occur with high frequency in the same individual tumors, indicating that these changes are not mutually exclusive events. We further demonstrate that although Notch1 PEST domain mutations are independent of Tp53 status, they are completely abolished in mice with germline Fbxw7 haploinsufficiency. Therefore, Notch1 PEST domain mutations only occur when Fbxw7 expression levels are intact. These data suggest a temporal sequence of mutational events involving these important cancer-related genes, with Notch1 PEST domain mutations occurring first, followed by Fbxw7 deletion, and eventually by complete loss of Tp53.

Pediatric-inspired intensified therapy of adult T-ALL reveals the favorable outcome of NOTCH1/FBXW7 mutations, but not of low ERG/BAALC expression: a GRAALL study

Despite recent progress in the understanding of acute lymphoblastic leukemia (T-ALL) oncogenesis, few markers are sufficiently frequent in large subgroups to allow their use in therapeutic stratification. Low ERG and BAALC expression (E/Blow) and NOTCH1/FBXW7 (N/F) mutations have been proposed as powerful prognostic markers in large cohorts of adult T-ALL. We therefore compared the predictive prognostic value of N/F mutations versus E/Blow in 232 adult T-ALLs enrolled in the LALA-94 and Group for Research on Adult Acute Lymphoblastic Leukemia (GRAALL) protocols. The outcome of T-ALLs treated in the pediatric-inspired GRAALL trials was significantly superior to the LALA-94 trial. Overall, 43% and 69% of adult T-ALL patients were classified as E/Blow and N/F mutated, respectively. Strikingly, the good prognosis of N/F mutated patients was stronger in more intensively treated, pediatric-inspired GRAALL patients. The E/B expression level did not influence the prognosis in any subgroup. N/F mutation status and the GRAALL trial were the only 2 independent factors that correlated with longer overall survival by multivariate analysis. This study demonstrates that the N/F mutational status and treatment protocol are major outcome determinants for adults with T-ALL, the benefit of pediatric inspired protocols being essentially restricted to the N/F mutated subgroup.

T-cell lymphoblastic lymphoma shows differences and similarities with T-cell acute lymphoblastic leukemia by genomic and gene expression analyses

T-cell acute lymphoblastic leukemia (T-ALL) and lymphoma (T-LBL) share common morphological and immunophenotypic features and are treated with similar therapeutic approaches. Nonetheless, they show distinct clinical presentations, suggesting that they may represent two different biological entities. To investigate the genetic characteristics of T-LBL and T-ALL, we used genomic and transcriptional profiling approaches. Genome-wide gene expression profiling, performed on 20 T-LBL and 10 T-ALL diagnostic specimens, revealed that the two malignancies shared a large fraction of their transcriptional profile while a subset of genes appeared to be differentially expressed in T-LBL versus T-ALL. This signature included genes involved in chemotactic responses and angiogenesis, which may play a role in tumor cell localization. Genome-wide copy number alteration analysis was performed on a subset of the samples analyzed by gene expression profiling and detected 41 recurrently altered genetic loci. Although most aberrations were found in both entities, several were selectively identified in T-LBL or T-ALL. In addition, NOTCH1 mutational status was found to correlate with a subset of genetic aberrations. Taken together, these results suggest that T-LBL and T-ALL are indeed two distinct diseases with unique transcriptional and genetic characteristics.

Prognostic implications of NOTCH1 and FBXW7 mutations in adult acute T-lymphoblastic leukemia

BACKGROUND

NOTCH1 mutations have been associated with a favorable outcome in pediatric acute T-lymphoblastic leukemia. However, the results of studies on the prognostic significance of NOTCH1 mutations in adult T-lymphoblastic leukemia remain controversial.

DESIGN AND METHODS

Here we have investigated the prognostic impact of mutations in the NOTCH1 pathway, in particular, the NOTCH1 and FBXW7 genes, in a large cohort of adult patients with T-lymphoblastic leukemia (n=126). We determined the occurrence of mutations in NOTCH1 and FBXW7 by DNA amplification and direct sequencing of polymerase chain reaction products.

RESULTS

Mutations were identified in 57% and 12% of the NOTCH1 and FBXW7 genes, respectively. The characteristics of patients carrying NOTCH1 and/or FBXW7 (NOTCH1-FBXW7) mutations were similar to those with wild-type genes. Patients with NOTCH1-FBXW7 mutations more often showed a thymic immunophenotype (p=0.001). In the overall cohort, no significant differences were seen in the complete remission or event-free survival rates between patients with mutated or wild-type NOTCH1-FBXW7 (p=0.39).

CONCLUSIONS

NOTCH1 and FBXW7 mutations were not predictive of outcome in the overall cohort of adult patients with T-lymphoblastic leukemia, but there was a trend towards a favorable prognostic impact of NOTCH1-FBXW7 mutations in the small subgroup of patients with low-risk ERG/BAALC expression status. Our findings further confirm the high frequency of NOTCH1 mutations in adult T-lymphoblastic leukemia.

A cooperative microRNA-tumor suppressor gene network in acute T-cell lymphoblastic leukemia (T-ALL)

The importance of individual microRNAs (miRNAs) has been established in specific cancers. However, a comprehensive analysis of the contribution of miRNAs to the pathogenesis of any specific cancer is lacking. Here we show that in T-cell acute lymphoblastic leukemia (T-ALL), a small set of miRNAs is responsible for the cooperative suppression of several tumor suppressor genes. Cross-comparison of miRNA expression profiles in human T-ALL with the results of an unbiased miRNA library screen allowed us to identify five miRNAs (miR-19b, miR-20a, miR-26a, miR-92 and miR-223) that are capable of promoting T-ALL development in a mouse model and which account for the majority of miRNA expression in human T-ALL. Moreover, these miRNAs produce overlapping and cooperative effects on tumor suppressor genes implicated in the pathogenesis of T-ALL, including IKAROS (also known as IKZF1), PTEN, BIM, PHF6, NF1 and FBXW7. Thus, a comprehensive and unbiased analysis of miRNA action in T-ALL reveals a striking pattern of miRNA-tumor suppressor gene interactions in this cancer.

PTPN2 negatively regulates oncogenic JAK1 in T-cell acute lymphoblastic leukemia

We have recently reported inactivation of the tyrosine phosphatase PTPN2 (also known as TC-PTP) through deletion of the entire gene locus in ∼ 6% of T-cell acute lymphoblastic leukemia (T-ALL) cases. T-ALL is an aggressive disease of the thymocytes characterized by the stepwise accumulation of chromosomal abnormalities and gene mutations. In the present study, we confirmed the strong association of the PTPN2 deletion with TLX1 and NUP214-ABL1 expression. In addition, we found cooperation between PTPN2 deletion and activating JAK1 gene mutations. Activating mutations in JAK1 kinase occur in ∼ 10% of human T-ALL cases, and aberrant kinase activity has been shown to confer proliferation and survival advantages. Our results reveal that some JAK1 mutation-positive T-ALLs harbor deletions of the tyrosine phosphatase PTPN2, a known negative regulator of the JAK/STAT pathway. We provide evidence that down-regulation of Ptpn2 sensitizes lymphoid cells to JAK1-mediated transformation and reduces their sensitivity to JAK inhibition.

Posttranscriptional deregulation of MYC via PTEN constitutes a major alternative pathway of MYC activation in T-cell acute lymphoblastic leukemia

Cumulative evidence indicates that MYC, one of the major downstream effectors of NOTCH1, is a critical component of T-cell acute lymphoblastic leukemia (T-ALL) oncogenesis and a potential candidate for targeted therapy. However, MYC is a complex oncogene, involving both fine protein dosage and cell-context dependency, and detailed understanding of MYC-mediated oncogenesis in T-ALL is still lacking. To better understand how MYC is interspersed in the complex T-ALL oncogenic networks, we performed a thorough molecular and biochemical analysis of MYC activation in a comprehensive collection of primary adult and pediatric patient samples. We find that MYC expression is highly variable, and that high MYC expression levels can be generated in a large number of cases in absence of NOTCH1/FBXW7 mutations, suggesting the occurrence of multiple activation pathways in addition to NOTCH1. Furthermore, we show that posttranscriptional deregulation of MYC constitutes a major alternative pathway of MYC activation in T-ALL, operating partly via the PI3K/AKT axis through down-regulation of PTEN, and that NOTCH1(m) might play a dual transcriptional and posttranscriptional role in this process. Altogether, our data lend further support to the significance of therapeutic targeting of MYC and/or the PTEN/AKT pathways, both in GSI-resistant and identified NOTCH1-independent/MYC-mediated T-ALL patients.

Modern Therapy of Acute Lymphoblastic Leukemia

Although acute lymphoblastic leukemia is curable in one third of adult patients, results vary greatly on account of different clinical, immunologic, and cytogenetic/genetic characteristics. These data, along with the kinetics of response to early treatment, help establish the individual risk class with considerable accuracy, and support risk-specific treatments that should warrant optimal results with as little as possible nonrelapse mortality. Modern first-line therapy consists of standard- and high-dose chemotherapy (increasingly inspired to pediatric principles), hematopoietic stem-cell transplantation, and new targeted therapy, all integrated with the analysis of prognostic factors and the study of subclinical residual disease for key therapeutic decisions. These changes are improving long-term outcome, which in ongoing studies is expected close to 50% or greater.

Fbxw7β resides in the endoplasmic reticulum membrane and protects cells from oxidative stress

Oxidative stress has been implicated in cancer initiation and progression. Fbxw7 (also known as Fbw7, SEL-10, hCdc4, or hAgo) is the F-box protein subunit of an Skp1-Cul1-F-box (SCF)-type ubiquitin ligase complex that plays a central role in the degradation of oncoproteins such as c-Myc, c-Jun, Notch, and cyclin E. Fbxw7 is therefore thought to function as a tumor suppressor, and indeed the Fbxw7 gene is frequently mutated in many human malignancies. The Fbxw7 gene locus encodes three protein isoforms: Fbxw7α, Fbxw7β, and Fbxw7γ. Whereas Fbxw7α and Fbxw7γ are resident in the nucleus, Fbxw7β shows a cytoplasmic distribution suggestive of localization to the endoplasmic reticulum (ER). The specific function of Fbxw7β has remained unknown, however. We now show that Fbxw7β contains a putative transmembrane domain near its NH(2) -terminus, and topological analysis revealed that Fbxw7β is inserted in the ER membrane. Fbxw7β assembled with Skp1, Cul1, and Rbx1 to form an SCF complex, although the efficiency of this process appeared lower than that for Fbxw7α or Fbxw7γ. To explore the physiological role of Fbxw7β, we generated mice specifically lacking this isoform of Fbxw7. Although these animals did not exhibit any apparent abnormalities in development, primary cultures of neurons prepared from the mutant mice were more vulnerable to oxidative stress than were those prepared from wild-type mice. Conversely, overexpression of Fbxw7β rendered cells resistant to oxidative stress, without affecting sensitivity to ER stress or other apoptosis-inducing agents. Our results thus suggest that Fbxw7β contributes to the protection of cells from oxidative stress.

Transient responses to NOTCH and TLX1/HOX11 inhibition in T-cell acute lymphoblastic leukemia/lymphoma

To improve the treatment strategies of T-cell acute lymphoblastic leukemia/lymphoma (T-ALL), further efforts are needed to identify therapeutic targets. Dysregulated expression of HOX-type transcription factors occurs in 30–40% of cases of T-ALL. TLX1/HOX11 is the prototypical HOX-type transcription factor. TLX1 may be an attractive therapeutic target because mice that are deficient in TLX1 are healthy. To test this possibility, we developed a conditional doxycycline-regulated mouse model of TLX1-initiated T-ALL. TLX1 induced T-ALL after ∼5–7 months with penetrance of 15–60%. Similar to human TLX1-type T-ALLs, the TLX1-induced tumors were arrested at the cortical stage of T-cell development and acquired activating NOTCH1 mutations. Inhibition of NOTCH signaling abrogated growth of cell lines derived from the TLX1-induced tumors. NOTCH inhibition also transiently delayed leukemia progression in vivo. Suppression of TLX1 expression slowed the growth of TLX1 tumor cell lines. Suppression of TLX1 in vivo also transiently delayed leukemia progression. We have shown that TLX1 functions as a T-cell oncogene that is active during both the induction and the maintenance phases of leukemia. However, the effect of suppressing NOTCH or TLX1 was transient. The tumors eventually “escaped” from inhibition. These data imply that the biological pathways and gene sets impacted by TLX1 and NOTCH have largely lost their importance in the fully established tumor. They have been supplanted by stronger oncogenic pathways. Although TLX1 or NOTCH inhibitors may not be effective as single agents, they may still contribute to combination therapy for TLX1-driven acute leukemia.

Adolescents and Young Adults with Acute Lymphoblastic Leukemia

During the last decade, increasing attention has been paid to a unique group of patients with acute lymphoblastic leukemia (ALL) who lie at the crossroad of therapeutic care by pediatric and adult hematologists/oncologists. ALL is a disease that affects infants, children, adolescents, and adult patients. With current therapies, the vast majority of children with ALL are now long-term survivors; unfortunately, the same good results have not yet been obtained for adults with ALL. This review will describe current controversies surrounding the treatment of adolescents and young adults with ALL—a group who finds themselves in the transition from “pediatric” to “adult” treatment approaches. The review focuses on recent insights into disease biology, prognostic factors, and treatment outcomes that have led to a series of prospective clinical trials specifically designed for adolescents and younger adults (AYAs) with ALL. These trials have been designed to provide important new clinical, psychosocial, and biological insights, and to further improve the survival of this challenging and unique group of patients.

Inactivation of FBXW7/hCDC4-β expression by promoter hypermethylation is associated with favorable prognosis in primary breast cancer

INTRODUCTION

Mutational inactivation of the FBXW7/hCDC4 tumor suppressor gene (TSG) is common in many cancer types, but infrequent in breast cancers. This study investigates the presence and impact of FBXW7/hCDC4 promoter methylation in breast cancer.

METHODS

FBXW7/hCDC4-β expression and promoter methylation was assessed in 161 tumors from two independent breast cancer cohorts. Associations between methylation status and clinicopathologic characteristics were assessed by Fisher's exact test. Survival was analyzed using the Kaplan-Meier method in addition to modeling the risk by use of a multivariate proportional hazard (Cox) model adjusting for possible confounders of survival.

RESULTS

Methylation of the promoter and loss of mRNA expression was found both in cell lines and primary tumors (43% and 51%, respectively). Using Cox modeling, a trend was found towards decreased hazard ratio (HR) for death in women with methylation of FBXW7/hCDC4-β in both cohorts (HR 0.53 (95% CI 0.23 to 1.23) and HR 0.50 (95% CI 0.23 to 1.08), respectively), despite an association between methylation and high-grade tumors (P = 0.017). Interestingly, in subgroups of patients whose tumors are p53 mutated or lymph-node positive, promoter methylation identified patients with significantly improved survival (P = 0.048 and P = 0.017, respectively).

CONCLUSIONS

We demonstrate an alternative mechanism for inactivation of the TSG FBXW7/hCDC4, namely promoter specific methylation. Importantly, in breast cancer, methylation of FBXW7/hCDC4-β is related to favorable prognosis despite its association with poorly differentiated tumors. Future work may define whether FBXW7/hCDC4 methylation is a biomarker of the response to chemotherapy and a target for epigenetic modulation therapy.

Notch signalling in T-cell lymphoblastic leukaemia/lymphoma and other haematological malignancies

Notch receptors participate in a highly conserved signalling pathway that regulates normal development and tissue homeostasis in a context- and dose-dependent manner. Deregulated Notch signalling has been implicated in many diseases, but the clearest example of a pathogenic role is found in T-cell lymphoblastic leukaemia/lymphoma (T-LL), in which the majority of human and murine tumours have acquired mutations that lead to aberrant increases in Notch1 signalling. Remarkably, it appears that the selective pressure for Notch mutations is virtually unique among cancers to T-LL, presumably reflecting a special context-dependent role for Notch in normal T-cell progenitors. Nevertheless, there are some recent reports suggesting that Notch signalling has subtle, yet important roles in other forms of haematological malignancy as well. Here, we review the role of Notch signalling in various blood cancers, focusing on T-LL with an eye towards targeted therapeutics.

Molecular pathogenesis and targeted therapies for NOTCH1-induced T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic tumor resulting from the malignant transformation of immature T-cell progenitors. Originally associated with a dismal prognosis, the outcome of T-ALL patients has improved remarkably over the last two decades as a result of the introduction of intensified chemotherapy protocols. However, these treatments are associated with significant acute and long-term toxicities, and the treatment of patients presenting with primary resistant disease or those relapsing after a transient response remains challenging. T-ALL is a genetically heterogeneous disease in which numerous chromosomal and genetic alterations cooperate to promote the aberrant proliferation and survival of leukemic lymphoblasts. However, the identification of activating mutations in the NOTCH1 gene in over 50% of T-ALL cases has come to define aberrant NOTCH signaling as a central player in this disease. Therefore, the NOTCH pathway represents an important potential therapeutic target. In this review, we will update our current understanding of the molecular basis of T-ALL, with a particular focus on the role of the NOTCH1 oncogene and the development of anti-NOTCH1 targeted therapies for the treatment of this disease.

The favorable effect of activating NOTCH1 receptor mutations on long-term outcome in T-ALL patients treated on the ALL-BFM 2000 protocol can be separated from FBXW7 loss of function

Precursor T-cell acute lymphoblastic leukemia (T-ALL) remains an important challenge in pediatric oncology. Because of the particularly poor prognosis of relapses, it is vital to identify molecular risk factors allowing early and effective treatment stratification. Activating NOTCH1 mutations signify a favorable prognosis in patients treated on ALL–BFM protocols. We have now tested if NOTCH pathway activation at different steps has similar clinical effects and if multiple mutations in this pathway function synergistically. Analysis of a validation set of 151 T-ALL patients and of the total cohort of 301 patients confirms the low relapse rate generally and the overall favorable effect of activating NOTCH1 mutations. Subgroup analysis shows that the NOTCH1 effect in ALL–BFM is restricted to patients with rapid early treatment response. Inactivation of the ubiquitin ligase FBXW7 is associated with rapid early treatment response and synergizes with NOTCH1 receptor activation. However, the effect of FBXW7 inactivation is separable from NOTCH1 activation by not synergizing with NOTCH1 mutations in predicting favorable long-term outcome, which can probably be explained by the interaction of FBXW7 with other clients. Finally, the comparison with other European protocols suggests that the NOTCH effect is treatment dependent generally and may depend on the intensity of central nervous system-directed therapy specifically.

Future perspectives: therapeutic targeting of notch signalling may become a strategy in patients receiving stem cell transplantation for hematologic malignancies

The human Notch system consists of 5 ligands and 4 membrane receptors with promiscuous ligand binding, and Notch-initiated signalling interacts with a wide range of other intracellular pathways. The receptor signalling seems important for regulation of normal and malignant hematopoiesis, development of the cellular immune system, and regulation of immune responses. Several Notch-targeting agents are now being developed, including natural receptor ligands, agonistic and antagonistic antibodies, and inhibitors of intracellular Notch-initiated signalling. Some of these agents are in clinical trials, and several therapeutic strategies seem possible in stem cell recipients: (i) agonists may be used for stem cell expansion and possibly to enhance posttransplant lymphoid reconstitution; (ii) receptor-specific agonists or antagonists can be used for immunomodulation; (iii) Notch targeting may have direct anticancer effects. Although the effects of therapeutic targeting are difficult to predict due to promiscuous ligand binding, targeting of this system may represent an opportunity to achieve combined effects with earlier posttransplant reconstitution, immunomodulation, or direct anticancer effects.

NOTCH1 and FBXW7 mutations have a favorable impact on early response to treatment, but not on outcome, in children with T-cell acute lymphoblastic leukemia (T-ALL) treated on EORTC trials 58881 and 58951

Risk-adjusted treatment stratification in T-cell acute lymphoblastic leukemias (T-ALLs) is currently based only on early response to chemotherapy. We investigated the prognostic implication of hyperactivation of NOTCH pathway resulting from mutations of NOTCH1 or FBXW7 in children with T-ALL enrolled in EORTC-CLG trials. Overall, 80 out of 134 (60%) patients were NOTCH+ (NOTCH1 and/or FBXW7 mutated). Although clinical presentations were not significantly associated with NOTCH status, NOTCH+ patients showed a better early response to chemotherapy as compared with NOTCH- patients, according to the rate of poor pre-phase 'responders' (25% versus 44%; P=0.02) and the incidence of high minimal residual disease (MRD) levels (11% (7/62) versus 32% (10/31); P=0.01) at completion of induction. However, the outcome of NOTCH+ patients was similar to that of NOTCH- patients, with a 5-year event-free survival (EFS) of 73% and 70% (P=0.82), and 5-year overall survival of 82% and 79% (P=0.62), respectively. In patients with high MRD levels, the 5-year EFS rate was 0% (NOTCH+) versus 42% (NOTCH-), whereas in those with low MRD levels, the outcome was similar: 76% (NOTCH+) versus 78% (NOTCH-). The incidence of isolated central nervous system (CNS) relapses was relatively high in NOTCH1+ patients (8.3%), which could be related to a higher propensity of NOTCH+ leukemic blasts to target the CNS.

NOTCH1 and/or FBXW7 mutations predict for initial good prednisone response but not for improved outcome in pediatric T-cell acute lymphoblastic leukemia patients treated on DCOG or COALL protocols

Aberrant activation of the NOTCH1 pathway by inactivating and activating mutations in NOTCH1 or FBXW7 is a frequent phenomenon in T-cell acute lymphoblastic leukemia (T-ALL). We retrospectively investigated the relevance of NOTCH1/FBXW7 mutations for pediatric T-ALL patients enrolled on Dutch Childhood Oncology Group (DCOG) ALL7/8 or ALL9 or the German Co-Operative Study Group for Childhood Acute Lymphoblastic Leukemia study (COALL-97) protocols. NOTCH1-activating mutations were identified in 63% of patients. NOTCH1 mutations affected the heterodimerization, the juxtamembrane and/or the PEST domains, but not the RBP-J-κ-associated module, the ankyrin repeats or the transactivation domain. Reverse-phase protein microarray data confirmed that NOTCH1 and FBXW7 mutations resulted in increased intracellular NOTCH1 levels in primary T-ALL biopsies. Based on microarray expression analysis, NOTCH1/FBXW7 mutations were associated with activation of NOTCH1 direct target genes including HES1, DTX1, NOTCH3, PTCRA but not cMYC. NOTCH1/FBXW7 mutations were associated with TLX3 rearrangements, but were less frequently identified in TAL1- or LMO2-rearranged cases. NOTCH1-activating mutations were less frequently associated with mature T-cell developmental stage. Mutations were associated with a good initial in vivo prednisone response, but were not associated with a superior outcome in the DCOG and COALL cohorts. Comparing our data with other studies, we conclude that the prognostic significance for NOTCH1/FBXW7 mutations is not consistent and may depend on the treatment protocol given.

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.

Prognostic factors in adult acute lymphoblastic leukaemia

Treatment of acute lymphoblastic leukaemia (ALL) in adults presents a formidable challenge. While overall results have improved over the past 3 decades, the long-term survival for patients aged less than 60 years is only in the range of 30-40% and is 10-15% if between 60 and 70 years and <5% for those over 70 years. The historic lack of clear-cut biological prognostic factors has led to over- or under-treatment of some patients. Response to initial therapy is an important prognosticator of outcome based on disease biology, as well as pharmacogenetics, which include the patient's response to drugs given. The more widespread availability of allogeneic transplantation and reduced-intensity regimens for older patients have opened up this curative modality to a greater number of patients. Hopefully, those options, as well as novel cytogenetic and molecular markers, will enable a better selection of patients who undergo intensive therapies and finally break the 30-40% cure barrier for adults with ALL.

Gene expression profiling identifies a subset of adult T-cell acute lymphoblastic leukemia with myeloid-like gene features and over-expression of miR-223

BACKGROUND

Until recently, few molecular aberrations were recognized in acute lymphoblastic leukemia of T-cell origin; novel lesions have recently been identified and a certain degree of overlap between acute myeloid leukemia and T-cell acute lymphoblastic leukemia has been suggested. To identify novel T-cell acute lymphoblastic leukemia entities, gene expression profiling was performed and clinico-biological features were studied.

DESIGN AND METHODS

Sixty-nine untreated adults with T-cell acute lymphoblastic leukemia were evaluated by oligonucleotide arrays: unsupervised and supervised analyses were performed. The up-regulation of myeloid genes and miR-223 expression were validated by quantitative polymerase chain reaction analysis.

RESULTS

Using unsupervised clustering, we identified five subgroups. Of these, one branch included seven patients whose gene expression profile resembled that of acute myeloid leukemia. These cases were characterized by over-expression of a large set of myeloid-related genes for surface antigens, transcription factors and granule proteins. Real-time quantitative polymerase chain reaction analysis confirmed over-expression of MPO, CEBPA, CEBPB, GRN and IL8. We, therefore, evaluated the expression levels of miR-223, involved in myeloid differentiation: these cases had significantly higher levels of miR-223 than had the other cases of T-cell acute lymphoblastic leukemia, with values comparable to those observed in acute myeloid leukemia. Finally, these patients appear to have an unfavorable clinical course.

CONCLUSIONS

Using gene profiling we identified a subset of adult T-cell acute lymphoblastic leukemia, accounting for 10% of the cases analyzed, which displays myeloid features. These cases were not recognized by standard approaches, underlining the importance of gene profiling in identifying novel acute leukemia subsets. The recognition of this subgroup may have clinical, prognostic and therapeutic implications.

Identification of two critically deleted regions within chromosome segment 7q35-q36 in EVI1 deregulated myeloid leukemia cell lines

Chromosomal rearrangements involving the EVI1 proto-oncogene are a recurrent finding in myeloid leukemias and are indicative of a poor prognosis. Rearrangements of the EVI1 locus are often associated with monosomy 7 or cytogenetic detectable deletions of part of 7q. As EVI1 overexpression alone is not sufficient to induce leukemia, loss of a 7q tumour suppressor gene might be a required cooperating event. To test this hypothesis, we performed high-resolution array comparative genomic hybridization analysis of twelve EVI1 overexpressing patients and three EVI1 deregulated cell lines to search for 7q submicroscopic deletions. This analysis lead to the delineation of two critical regions, one of 0.39 Mb on 7q35 containing the CNTNAP2 gene and one of 1.33 Mb on chromosome bands 7q35-q36 comprising nine genes in EVI1 deregulated cell lines. These findings open the way to further studies aimed at identifying the culprit EVI1 implicated tumour suppressor genes on 7q.

T-cell acute lymphoblastic leukemia in adults: clinical features, immunophenotype, cytogenetics, and outcome from the large randomized prospective trial (UKALL XII/ECOG 2993)

The biology and outcome of adult T-cell acute lymphoblastic leukemia are poorly understood. We present here the clinical and biologic features of 356 patients treated uniformly on the prospective trial (UKALL XII/ECOG 2993) with the aim of describing the outcome and identifying prognostic factors. Complete remission was obtained in 94% of patients, and 48% survived 5 years. Positivity of blasts for CD1a and lack of expression of CD13 were associated with better survival (P = .01 and < .001, respectively). NOTCH1 and CDKN2A mutations were seen in 61% and 42% of those tested. Complex cytogenetic abnormalities were associated with poorer survival (19% vs 51% at 5 years, P = .006). Central nervous system involvement at diagnosis did not affect survival (47% vs 48%, P = not significant). For 99 patients randomized between autograft and chemotherapy, 5-year survival was 51% in each arm. Patients with a matched sibling donor had superior 5-year survival to those without donors (61% vs 46%, chi(2), P = .02); this was the result of less relapse (25% vs 51% at 5 years, P < .001). Only 8 of 123 relapsed patients survive. This study provides a baseline for trials of new drugs, such as nelarabine, and may allow risk-adapted therapy in patients with poor-prognosis T-cell ALL.

Hematopoietic stem cell transplantation for adults with acute lymphoblastic leukemia

PURPOSE OF REVIEW

The long-term survival for patients with adult acute lymphoblastic leukemia (ALL) has not significantly changed over the past two decades and, as opposed to pediatric ALL, it is less than 40% despite high initial complete remission rate. These observations raise several important issues regarding the pathobiology of adult leukemic stem cells, the ability of adults to tolerate intensive treatment and the best postremission approach.

RECENT FINDINGS

Progress has been made in understanding the biology of adult ALL and its prognostic significance. The follow-up of minimal residual disease status, adopting protocols from childhood ALL to young adults and use of targeted therapy may improve long-term survival. Transplantation for standard-risk ALL in first remission proved to be beneficial in a large cooperative group study. Limited data on the use of alternative donor transplantation as well as reduced intensity protocols are now available for consideration in specific groups of patients.

SUMMARY

Data suggest that the best antileukemic treatment should be applied in first remission and type of treatment should be based on individualized risk stratification, while incorporating recent information on alternative donors and reduced intensity approaches to transplantation.

Paediatric lymphoblastic T-cell leukaemia and lymphoma: one or two diseases?

There is ongoing discussion on whether paediatric acute T-cell lymphoblastic leukaemia (T-ALL) and paediatric lymphoblastic T-cell lymphoma (T-LBL) are two distinct entities or whether they represent two variant manifestations of one and the same disease and the distinction is arbitrary. Both show overlapping clinical, morphological and immunophenotypic features. Many clinical trials use the amount of blast infiltration of the bone marrow as the sole criterion to distinguish between T-ALL and T-LBL. The current World Health Organization classification designates both malignancies as T lymphoblastic leukaemia/lymphoma. However, subtle immunophenotypic, molecular and cytogenetic differences suggest that T-ALL and T-LBL might be biologically different in certain aspects. The current review summarizes and discusses the recent advances and understanding of the molecular profile of paediatric T-ALL and T-LBL.

Prognostic implications of NOTCH1 and FBXW7 mutations in adults with T-cell acute lymphoblastic leukemia treated on the MRC UKALLXII/ECOG E2993 protocol

PURPOSE

Notch pathway activation by mutations in either NOTCH1 and/or FBXW7 is one of the most common molecular events in T-cell acute lymphoblastic leukemia (T-ALL) and, in pediatric disease, predicts for favorable outcome. Their prognostic significance in adult T-ALL is unclear. We sought to evaluate the outcome according to mutation status of patients with adult T-ALL treated on the United Kingdom Acute Lymphoblastic Leukaemia XII (UKALLXII)/Eastern Cooperative Oncology Group (ECOG) E2993 protocol.

METHODS

NOTCH1 and FBXW7 were screened by a combination of denaturing high-performance liquid chromatography and sequencing in 88 adult patients with T-ALL treated on the UKALLXII/ECOG E2993 protocol and compared with clinical characteristics and outcome.

RESULTS

NOTCH1 and FBXW7 mutations were common (60% and 18%, respectively) and were not associated with age or WBC count. NOTCH1 heterodimerization domain mutations were associated with FBXW7 mutations (P = .02), and NOTCH1 proline, glutamic acid, serine, threonine (PEST) rich domain and FBXW7 mutations were mutually exclusive. There were an equal number of high- and standard-risk patients in the NOTCH1 and FBXW7 mutated (MUT) groups. Patients wild type (WT) for both markers trended toward poorer event-free survival (EFS; MUT v WT, 51% v 27%, P = .10; hazard ratio, 0.6). Analysis by each marker individually was not significantly predictive of outcome (NOTCH1 MUT v WT, EFS 49% v 34%, P = .20; FBXW7 MUT v WT, EFS 53% v 41%, P.72).

CONCLUSION

NOTCH1 and FBXW7 mutant-positive patients do not fare sufficiently well to warrant an individualized treatment approach in future studies.

NOTCH inhibition and glucocorticoid therapy in T-cell acute lymphoblastic leukemia

Inhibition of NOTCH1 signaling with gamma-secretase inhibitors (GSIs) has been proposed as a molecularly targeted therapy in T-cell acute lymphoblastic leukemia (T-ALL). However, GSIs seem to have limited antileukemic activity in human T-ALL and are associated with severe gastrointestinal toxicity resulting from inhibition of NOTCH signaling in the gut. Inhibition of NOTCH1 signaling in glucocorticoid-resistant T-ALL restored glucocorticoid sensitivity and co-treatment with glucocorticoids inhibited GSI-induced gut toxicity. Thus, combination therapies with GSIs plus glucocorticoids may offer a new opportunity for the use of anti-NOTCH1 therapies in human T-ALL.

NOTCH inhibition and glucocorticoid therapy in T-cell acute lymphoblastic leukemia

Inhibition of NOTCH1 signaling with gamma-secretase inhibitors (GSIs) has been proposed as a molecularly targeted therapy in T-cell acute lymphoblastic leukemia (T-ALL). However, GSIs seem to have limited antileukemic activity in human T-ALL and are associated with severe gastrointestinal toxicity resulting from inhibition of NOTCH signaling in the gut. Inhibition of NOTCH1 signaling in glucocorticoid-resistant T-ALL restored glucocorticoid sensitivity and co-treatment with glucocorticoids inhibited GSI-induced gut toxicity. Thus, combination therapies with GSIs plus glucocorticoids may offer a new opportunity for the use of anti-NOTCH1 therapies in human T-ALL.