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

Mutations of PHF6 are associated with mutations of NOTCH1, JAK1 and rearrangement of SET-NUP214 in T-cell acute lymphoblastic leukemia

BACKGROUND

Mutations in the PHF6 gene were recently described in patients with T-cell acute lymphoblastic leukemia and in those with acute myeloid leukemia. The present study was designed to determine the prevalence of PHF6 gene alterations in T-cell acute lymphoblastic leukemia.

DESIGN AND METHODS

We analyzed the incidence and prognostic value of PHF6 mutations in 96 Chinese patients with T-cell acute lymphoblastic leukemia. PHF6 deletions were screened by real-time quantitative polymerase chain reaction and array-based comparative genomic hybridization. Patients were also investigated for NOTCH1, FBXW7, WT1, and JAK1 mutations together with CALM-AF10, SET-NUP214, and SIL-TAL1 gene rearrangements.

RESULTS

PHF6 mutations were identified in 11/59 (18.6%) adult and 2/37 (5.4%) pediatric cases of T-cell acute lymphoblastic leukemia, these incidences being significantly lower than those recently reported. Although PHF6 is X-linked and mutations have been reported to occur almost exclusively in male patients, we found no sex difference in the incidences of PHF6 mutations in Chinese patients with T-cell acute lymphoblastic leukemia. PHF6 deletions were detected in 2/79 (2.5%) patients analyzed. NOTCH1 mutations, FBXW7 mutations, WT1 mutations, JAK1 mutations, SIL-TAL1 fusions, SET-NUP214 fusions and CALM-AF10 fusions were present in 44/96 (45.8%), 9/96 (9.4%), 4/96 (4.1%), 3/49 (6.1%), 9/48 (18.8%), 3/48 (6.3%) and 0/48 (0%) of patients, respectively. The molecular genetic markers most frequently associated with PHF6 mutations were NOTCH1 mutations (P=0.003), SET-NUP214 rearrangements (P=0.002), and JAK1 mutations (P=0.005). No differences in disease-free survival and overall survival between T-cell acute lymphoblastic leukemia patients with and without PHF6 mutations were observed in a short-term follow-up.

CONCLUSIONS

Overall, these results indicate that, in T-cell acute lymphoblastic leukemia, PHF6 mutations are a recurrent genetic abnormality associated with mutations of NOTCH1, JAK1 and rearrangement of SET-NUP214.

Promoter methylation-mediated inactivation of PCDH10 in acute lymphoblastic leukemia contributes to chemotherapy resistance

PCDH10 has been implicated as a tumor suppressor, since epigenetic alterations of this gene have been noted in multiple tumor types. However, to date, studies regarding its role in acute and chronic leukemias are lacking. Here, we have investigated the presence of promoter hypermethylation of two CpG islands of the PCDH10 gene by methylation-specific PCR in 215 cases of various subsets of myeloid- and lymphoid-lineage leukemias. We found that PCDH10 promoter hypermethylation was frequent in both B-cell (81.9%) and T-cell (80%) acute lymphoblastic leukemia (ALL), while it was present in low frequency in most subtypes of myeloid leukemias (25.9%) and rare in chronic myeloid leukemia (2.2%). PCDH10 expression was downregulated via promoter hypermethylation in primary ALL samples (N = 4) and leukemia cell lines (N = 11). The transcriptional repression caused by PCDH10 methylation could be restored by pharmacologic inhibition of DNA methyltransferases. ALL cell lines harboring methylation-mediated inactivation of PCDH10 were less sensitive to commonly used leukemia-specific drugs suggesting that PCDH10 methylation might serve as a biomarker of chemotherapy response. Our results demonstrate that PCDH10 is a target of epigenetic silencing in ALL, a phenomenon that may impact lymphoid-lineage leukemogenesis, serve as an indicator of drug resistance and may also have potential implications for targeted epigenetic therapy.

Immunophenotypic, cytogenetic, and clinical features of 207 cases of childhood acute lymphoblastic leukemia in china

OBJECTIVE

In this study, we investigated the immunophenotypic subtype profiles of 207 Chinese children with acute lymphoblastic leukemia (ALL) and its association with cytogenetics and clinical features.

METHODS

A total of 207 children with ALL were immunophenotyped by 4-color flow cytometry using a panel of monoclonal antibodies. Among the 207 patients enrolled in this study, 146 cases were also subjected to karyotype analysis by R-banding technology.

RESULTS

Of the 207 children with ALL, 11.6% were identified as T-ALL and 88.4% as B-ALL. Among B-ALL, 6.6% were identified as Pro-B ALL, 67.2% as Com-B ALL, 24.0% as Pre-B ALL, and 2.2% as mature-B ALL. Myeloid antigen (MyAg) expression was documented in 42.5% of the 207 cases analyzed and CD13 was the most commonly expressed MyAg (31.4%). No difference was observed in the expression of MyAg between the groups of patients with T-ALL (41.7%) and B-ALL (42.6%). Abnormal karyotypes were detected in 84 of 146 (57.5%) children. The clinical and biological characteristics of ALL patients between the MyAg⁺ and MyAg⁻ groups showed that a higher percentage of patients with high WBC count (>50×10⁹/L) and higher CD34 positivity were found to be correlated with MyAg⁺ ALL.

CONCLUSIONS

Our results indicate that the distribution of ALL in Chinese children was similar to the general distribution pattern in other countries. Unlike previous studies, we found that the expression of MyAg in children with T-ALL and B-ALL was comparable, and the percentage of patients with a high WBC count (>50×10⁹/L) and CD34 positivity in MyAg⁺ was higher than that in MyAg⁻ ALL types, but no differences were found with regard to other clinical features.

The role of cytotoxic therapy with hematopoietic stem cell transplantation in the treatment of adult acute lymphoblastic leukemia: update of the 2006 evidence-based review

Clinical research published since the first evidence-based review on the role of hematopoietic stem cell transplantation (SCT) in the treatment of acute lymphoblastic leukemia (ALL) in adults is presented and critically evaluated in this update. Treatment recommendations changed or modified based on new evidence include: (1) myeloablative allogeneic SCT is an appropriate treatment for adult (<35 years) ALL in first complete remission for all disease risk groups; and (2) reduced-intensity conditioning may produce similar outcomes to myeloablative regimens. Treatment recommendations unchanged or strengthened by new evidence include: (1) allogeneic SCT is recommended over chemotherapy for ALL in second complete remission or greater; (2) allogeneic is superior to autologous SCT; and (3) there are similar survival outcomes after related and unrelated allogeneic SCT. New treatment recommendations based on new evidence include: (1) in the absence of a suitable allogeneic donor, autologous SCT may be an appropriate therapy, but results in a high relapse rate; (2) it is appropriate to consider cord blood transplantation for patients with no HLA well-matched donor; and (3) imatinib therapy before and/or after SCT (for Ph+ ALL) yields significantly superior survival outcomes. Areas of needed research in the treatment of adult ALL with SCT were identified and presented in the review.

Regulation of Src family kinases involved in T cell receptor signaling by protein-tyrosine phosphatase CD148

CD148 is a receptor-like protein-tyrosine phosphatase known to inhibit transduction of mitogenic signals in non-hematopoietic cells. Similarly, in the hematopoietic lineage, CD148 inhibited signal transduction downstream of T cell receptor. However, it also augmented immunoreceptor signaling in B cells and macrophages via dephosphorylating C-terminal tyrosine of Src family kinases (SFK). Accordingly, endogenous CD148 compensated for the loss of the main SFK activator CD45 in murine B cells and macrophages but not in T cells. Hypothetical explanations for the difference between T cells and other leukocyte lineages include the inability of CD148 to dephosphorylate a specific set of SFKs involved in T cell activation or the lack of CD148 expression during critical stages of T cell development. Here we describe striking differences in CD148 expression between human and murine thymocyte subsets, the only unifying feature being the absence of CD148 during the positive selection when the major developmental block occurs under CD45 deficiency. Moreover, we demonstrate that similar to CD45, CD148 has both activating and inhibitory effects on the SFKs involved in TCR signaling. However, in the absence of CD45, activating effects prevail, resulting in functional complementation of CD45 deficiency in human T cell lines. Importantly, this is independent of the tyrosines in the CD148 C-terminal tail, contradicting the recently proposed phosphotyrosine displacement model as a mechanism of SFK activation by CD148. Collectively, our data suggest that differential effects of CD148 in T cells and other leukocyte subsets cannot be explained by the CD148 inability to activate T cell SFKs but rather by its dual inhibitory/activatory function and specific expression pattern.

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.

Multiparameter flow cytometry in the diagnosis and management of acute leukemia

CONTEXT

Timely and accurate diagnosis of hematologic malignancies is crucial to appropriate clinical management. Acute leukemias are a diverse group of malignancies with a range of clinical presentations, prognoses, and preferred treatment protocols. Historical classification systems relied predominantly on morphologic and cytochemical features, but currently, immunophenotypic, cytogenetic, and molecular data are incorporated to define clinically relevant diagnostic categories. Multiparameter flow cytometry provides rapid and detailed determination of antigen expression profiles in acute leukemias which, in conjunction with morphologic assessment, often suggests a definitive diagnosis or a narrow differential. Many recurrent molecular or cytogenetic aberrations are associated with distinct immunophenotypic features, and therefore flow cytometry is an important tool to direct further testing. In addition, detection of specific antigens may have prognostic or therapeutic implications even within a single acute leukemia subtype. After initial diagnosis, a leukemia's immunophenotypic fingerprint provides a useful reference to monitor response to therapy, minimal residual disease, and recurrence.

OBJECTIVE

To provide an overview of the application of flow cytometric immunophenotyping to the diagnosis and management of acute leukemias, including salient features of those entities described in the 2008 World Health Organization classification.

DATA SOURCES

Published articles pertaining to flow cytometry, acute leukemia classification, and experiences of a reference flow cytometry laboratory.

CONCLUSION

Immunophenotypic evaluation is essential to accurate diagnosis and classification of acute leukemia. Multiparameter flow cytometry provides a rapid and effective means to collect this information, as well as providing prognostic information and a modality for minimal residual disease evaluation.

Surrogate marker profiles for genetic lesions in acute leukemias

The basic hypothesis of surrogate marker profiles is that individual genetic lesions result in characteristic distortions of the cellular phenotype with some predictable consistency that can be exploited by sophisticated immunophenotyping. While cytogenetic and molecular aberrancies currently are accepted prognostic predictors in acute leukemias, single antigen expression and even antigenic profiles rarely impact on prognosis. However, increasingly, phenotypes are delineated which can serve as surrogates for underlying genetic aberrations of clinical importance. This development is of particular significance as antileukemic therapy becomes available that targets any component of the disturbed molecular pathways associated with these genetic lesions. This chapter will focus on established surrogate marker profiles, such as those for PML/RARα, AML1/ETO, FLT3-gene mutated acute lymphocytic leukemia (ALL), and BCR/ABL(POS) ALL. As the list of therapeutic targets grows, the role of surrogate antigen profiles will grow, as they can predict for the efficacy of targeted approaches in lieu of expensive, time-consuming and not always accessible genetic analyses.

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.

Leukemia-initiating cells in human T-lymphoblastic leukemia exhibit glucocorticoid resistance

T-cell acute lymphoblastic leukemia (T-ALL) is associated with a significant risk of disease relapse, but the biological basis for relapse is poorly understood. Here, we identify leukemiainitiating cells (L-ICs) on the basis of functional assays and prospective isolation and report a role for L-ICs in T-ALL disease and relapse. Long-term proliferation in response to NOTCH1 activating signals in OP9-DL1 coculture system or capacity to initiate leukemia in xenografts by the CD7(+)CD1a(-) subset of primary T-ALL samples was superior to other subsets, refining the identity of T-ALL L-ICs. T-ALL engraftment was improved in nonobese diabetic/severe combined immunodeficiency (NOD/scid)IL2Rγ(null) (NSG) mice compared with NOD/scid with anti-CD122 treatment (NS122), but both showed changes in leukemia immunophenotype. Clonal analysis of xenografts using the TCRG locus revealed the presence of subclones of T-ALL L-ICs, some of which possess a selective growth advantage and correlated with the capacity of CD7(+)CD1a(+) xenograft cells to engraft secondary NSG mice. Treatment of high-risk T-ALL xenografts eliminated CD1a(+) T-ALL cells, but CD1a(-) cells were resistant and their number was increased. Our results establish that primary CD1a(-) T-ALL cells are functionally distinct from CD1a(+) cells and that the CD7(+)CD1a(-) subset is enriched for L-IC activity that may be involved in mediating disease relapse after therapy.

Notch1 expression predicts an unfavorable prognosis and serves as a therapeutic target of patients with neuroblastoma

PURPOSE

Notch signaling has been implicated to play a critical role in the tumorigenesis of neuroblastoma (NB) and can modulate calreticulin (CRT) expression that strongly correlates with tumor differentiation and favorable prognosis of NB. We thus sought to determine how Notch regulates CRT expression and affects NB tumor behavior.

EXPERIMENTAL DESIGN

The Notch-dependent regulation of CRT expression in cultured NB cells was analyzed by confocal microscopy and Western blotting. Notch1 protein expression in 85 NB tumors was examined by immunohistochemistry and correlated with the clinicopathologic/biological characters of NB patients. The progression of NB tumors in response to attenuated Notch signaling was examined by using a xenograft mouse model.

RESULTS

We showed that CRT is essential for the neuronal differentiation of NB cells elicited by inhibition of Notch signaling. This effect was mediated by a c-Jun-NH(2)-kinase-dependent pathway. Furthermore, NB tumors with elevated Notch1 protein expression were strongly correlated with advanced tumor stages, MYCN amplification, an undifferentiated histology, as well as a low CRT expression level. Most importantly, the opposing effect between Notch1 and CRT could reciprocally affect the survival of NB patients. The administration of a gamma-secretase inhibitor into a xenograft mouse model of NB significantly suppressed the tumor progression.

CONCLUSIONS

Our findings provide the first evidence that a c-Jun-NH(2)-kinase-CRT-dependent pathway is essential for the neuronal differentiation elicited by Notch signaling blockade and that Notch1 and CRT can synergistically predict the clinical outcomes of NB patients. The present data suggest that Notch signaling could be a therapeutic target for NB.

Absence of biallelic TCRgamma deletion predicts early treatment failure in pediatric T-cell acute lymphoblastic leukemia

PURPOSE

To identify children with T-cell acute lymphoblastic leukemia (T-ALL) at high risk of induction chemotherapy failure by using DNA copy number analysis of leukemic cells collected at diagnosis.

PATIENTS AND METHODS

Array comparative genomic hybridization (CGH) was performed on genomic DNA extracted from diagnostic lymphoblasts from 47 children with T-ALL treated on Children's Oncology Group Study P9404 or Dana-Farber Cancer Institute Protocol 00-01. These samples represented nine patients who did not achieve an initial complete remission, 13 who relapsed, and 25 who became long-term, event-free survivors. The findings were confirmed in an independent cohort of patients by quantitative DNA polymerase chain reaction (DNA-PCR), an assay that is well suited for clinical application.

RESULTS

Analysis of the CGH findings in patients in whom induction chemotherapy failed compared with those in whom induction chemotherapy was successful identified the absence of biallelic TCRgamma locus deletion (ABD), a characteristic of early thymocyte precursors before V(D)J recombination, as the most robust predictor of induction failure (P < .001). This feature was also associated with markedly inferior event-free (P = .002) and overall survival (P < .001) rates: 25% versus 58% and 25% versus 72%, respectively. Using a rapid and inexpensive quantitative DNA-PCR assay, we validated ABD as a predictor of a poor response to induction chemotherapy in an independent series of patients.

CONCLUSION

Lymphoblasts from children with T-ALL should be evaluated at diagnosis for deletion within the TCRgamma locus. Patients lacking biallelic deletion, which confers a high probability of induction failure with contemporary therapy, should be assigned to alternative therapy in the context of a prospective clinical trial.

Prognostic effect of chromosomal abnormalities in childhood B-cell precursor acute lymphoblastic leukaemia: results from the UK Medical Research Council ALL97/99 randomised trial

BACKGROUND

Chromosomal abnormalities in childhood acute lymphoblastic leukaemia are well established disease markers and indicators of outcomes. However, the long-term prognosis and independent prognostic effect of some abnormalities has been questioned. Also, little is known about the association between cytogenetics and the characteristics of relapse (eg, time and site of relapse) that are known to predict outcome after relapse.

METHODS

We analysed cytogenetic data from 1725 children with B-cell precursor acute lymphoblastic leukaemia who were included in the UK Medical Research Council ALL97/99 study and followed up for a median time of 8.2 years. Univariate and multivariate analysis were done to examine risk of relapse, event-free survival, and overall survival associated with 21 chromosomal abnormalities and three cytogenetic risk groups constructed from these data.

FINDINGS

Two chromosomal abnormalities were associated with a significantly better outcome (ETV6-RUNX1, hazard ratio [HR] 0.51, 95% CI 0.38-0.70 and high hyperdiploidy, 0.60, 0.47-0.78), whereas five abnormalities were associated with an increased risk of relapse (intrachromosomal amplification of chromosome 21 [iAMP21], 6.04, 3.90-9.35; t(9;22), 3.55, 2.21-5.72; MLL translocations, 2.98, 1.71-5.20; abnormal 17p, 2.09, 1.30-3.37; and loss of 13q, 1.87, 1.09-3.20). Multivariate analysis incorporating age, white-cell count, and treatment parameters showed that six cytogenetic abnormalities (ETV6-RUNX1, high hyperdiploidy, iAMP21, t(9;22), loss of 13q, and abnormal 17p) retained their significance for effect on relapse risk. Based on these data, patients were classified into good, intermediate, and poor cytogenetic risk groups. Slow early treatment response correlated with cytogenetic risk group: 34 of 460 (7%) in the good-risk group, 22 of 211 (10%) in the intermediate-risk group, and 27 of 95 (28%) in the poor-risk group had a slow response (p<0.0001). Additionally, the proportion of patients with a very early (<18 months) relapse varied by cytogenetic risk group: eight of 129 (6%) patients in the good-risk group had a very early relapse, compared with 24 of 98 (24%) in the intermediate-risk group, and 37 of 82 (45%) in the poor-risk group (p<0.0001). However, there was no difference in the site of relapse by cytogenetic risk group.

INTERPRETATION

Individual chromosomal abnormalities are strong independent indicators of outcome, especially risk of relapse. Diagnostic cytogenetics identifies patients with a higher rate of relapse and those who are likely to have a high-risk relapse.

FUNDING

Leukaemia and Lymphoma Research (LLR).

PHF6 mutations in T-cell acute lymphoblastic leukemia

Tumor suppressor genes on the X chromosome may skew the gender distribution of specific types of cancer. T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy with an increased incidence in males. In this study, we report the identification of inactivating mutations and deletions in the X-linked plant homeodomain finger 6 (PHF6) gene in 16% of pediatric and 38% of adult primary T-ALL samples. Notably, PHF6 mutations are almost exclusively found in T-ALL samples from male subjects. Mutational loss of PHF6 is importantly associated with leukemias driven by aberrant expression of the homeobox transcription factor oncogenes TLX1 and TLX3. Overall, these results identify PHF6 as a new X-linked tumor suppressor in T-ALL and point to a strong genetic interaction between PHF6 loss and aberrant expression of TLX transcription factors in the pathogenesis of this disease.

Treating the "older" adult with acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) in adults is a rare disease. The results of therapy remain unsatisfactory, and progress has been relatively slow. This article will focus on curative therapy in patients aged 30 to 60 years, but will also discuss the management of elderly patients with ALL. Recent large trials have increased our knowledge of the factors that determine outcome, and have clarified the role of blood and marrow transplantation in the management of this disease. These trials have also highlighted the major issues we need to focus on if we are to improve outcomes. This article describes the results of chemotherapy and blood and marrow transplantation for Philadelphia chromosome negative and positive adult ALL in the "older" adult patient, but also critically examines the major controversies and suggests how they might be resolved. The role of allografting in adult ALL is comprehensively discussed. Results of recent studies on T-cell ALL and reduced-intensity allografting are reviewed. A better understanding of the biology of the disease (including gene profiling) may allow individualization of therapy and, in time, targeted therapy.