Gain-of-function mutations in NOTCH1 are common in T-cell lymphoblastic leukemias (T-ALL), making this receptor a promising target for drugs such as γ-secretase inhibitors, which block a proteolytic cleavage required for NOTCH1 activation. However, the enthusiasm for these therapies has been tempered by tumor resistance and the paucity of information on the oncogenic programs regulated by oncogenic NOTCH1. Here we show that NOTCH1 regulates PTEN expression and the activity of the PI3K-AKT signaling pathway in normal and leukemic T cells. Notch signaling and the PI3K-AKT pathway synergize in vivo in a Drosophila model of Notch-induced tumorigenesis, and mutational loss of PTEN is associated with resistance to NOTCH1 inhibition in human T-ALL. Overall, these findings identify the transcriptional control of PTEN and the regulation of the PI3K/ AKT pathway as key elements of the leukemogenic program activated by NOTCH1 and provide the basis for the design of new therapeutic strategies for T-ALL.NOTCH receptors directly transduce extracellular signals at the cell surface into changes in gene expression that regulate differentiation, self renewal, proliferation and apoptosis 1 . Constitutively active forms of the NOTCH1 receptor contribute to over 50% of human T-cell lymphoblastic leukemias and lymphomas (T-ALL) 2 , and have also been implicated in the pathogenesis of solid tumors, such as breast carcinomas, gliomas and neuroblastoma 3-5 . #Adolfo A. Ferrando (af2196@columbia.edu) and Maria Dominguez (m.dominguez@umh.es) are co-senior corresponding authors.

Fluorescence in situ hybridization showed ALK rearrangements in nine cases (47%), aneuploidy in three cases (16%), and no rearrangement in seven cases (37%). IMTs with ALK abnormalities by immunohistochemistry and/or fluorescence in situ hybridization originated in the abdomen/pelvis/retroperitoneum, chest, and extremities. The mean age was 6.6 years, with a male/female ratio of 1.3. 64% of patients had no evidence of disease at last followup, 45% had one or more recurrences, and 18% displayed histologic evidence of malignant transformation. The IMTs without ALK abnormalities occurred in older children, were more frequent in females, and had fewer recurrences. However, in

A previous study (LMB89) of the French Society of Pediatric Oncology for childhood mature B-cell lymphoma (B-NHL) demonstrated a 92% 3-year event-free survival (EFS) for intermediate-risk group B defined as "non-resected" stage II/I and CNS-negative advanced-stage IIV/IV (70% of cases). We performed the FAB/LMB96 trial to assess the possibility of reducing treatment in children/adolescents with intermediate-risk B-NHL without jeopardizing survival. "Early responding" patients (tumor response > 20% at day 7) were randomized in a factorial design between 4 arms, 2 receiving half-dose of cyclophosphamide in the second induction course with cyclophosphamide, Oncovin (vincristine), prednisone, Adriamycin (doxorubicin), methotrexate (COPADM) and 2 not receiving the maintenance course M1. A total of 657 patients were randomized (May 1996 to June 2001) and 637 were analyzed. The analysis showed no significant effect of any of the treatment reductions on EFS and survival. The 4-year EFS was 93.4% and 90.9% in the groups with full-dose and half-dose of cyclophosphamide (RR = 1.3, P = .40) and 91.9% and 92.5% in the groups with and without M1 (RR = 1.01, P = .98). There was no interaction between the 2 treatment reductions or between each treatment reduction and LDH level or histologic subtypes (Burkitt/Burkitt-like or large B-cell). Children/adolescents with intermediate-risk B-NHL who have an early response and achieve a complete remission after the first consolidation course can be cured with a 4-course treatment with a total dose of only 3.3 g/m2 cyclophosphamide and 120 mg/m2 doxorubicin.

The prognosis for higher risk childhood B-cell non-Hodgkin lymphoma has improved over the past 20 years but the optimal intensity of treatment has yet to be determined. Children 21 years old or younger with newly diagnosed B-cell nonHodgkin lymphoma/B-cell acute lymphoblastic leukemia (B-NHL/B-ALL) with higher risk factors (bone marrow [BM] with or without CNS involvement) were randomized to standard intensity FrenchAmerican-British/Lymphoma Malignancy B (FAB/LMB) therapy or reduced intensity (reduced cytarabine plus etoposide and deletion of 3 maintenance courses M2, M3, M4). All patients with CNS disease had additional high-dose methotrexate (8 g/m 2 ) plus extra intrathecal therapy. Fifty-one percent had BM involvement, 20% had CNS involvement, and 29% had BM and CNS involvement. One hundred ninety patients were randomized. The probabilities of 4-year event-free survival (EFS) and survival (S) were 79% ؎ 2.7% and 82% ؎ 2.6%, respectively. In patients in remission after 3 cycles who were randomized to standard versus reducedintensity therapy, the 4-year EFS after randomization was 90% ؎ 3.1% versus 80% ؎ 4.2% (one-sided P ‫؍‬ .064) and S was 93% ؎ 2.7% versus 83% ؎ 4.0% (onesided P ‫؍‬ .032). Patients with either combined BM/CNS disease at diagnosis or poor response to cyclophosphamide, Oncovin [vincristine], prednisone (COP) reduction therapy had a significantly inferior EFS and S (P < .001). Standardintensity FAB/LMB therapy is recommended for children with high-risk B-NHL (B-ALL with or without CNS involvement).

Recent studies with cDNA microarrays showed that diffuse large B-cell lymphoma (DLBCL) cases with gene expression profiles similar to germinal center (GC) B cells had much better prognosis than DLBCL cases with gene expression profiles resembling activated B cells. The goal of the current study is to evaluate if using a panel of GC B-cell (CD10 and Bcl-6) and activation (MUM1/IRF4 and CD138) markers by immunohistochemistry defines prognosis in patients with de novo DLBCL. Immunohistochemical stains for the above markers were performed on paraffin-embedded tissues from 42 de novo DLBCL patients. Median follow-up in all patients was 41 months (range, 1-103 months) and in surviving patients was 65 months (range, 14-103 months). These cases could be classified into three expression patterns: GC B-cell pattern (pattern A) expressing CD10 and/or Bcl-6 but not activation markers; activated GC B-cell pattern (pattern B) expressing at least one of GC B-cell markers and one of activation markers; and activated non-GC B-cell pattern (pattern C) expressing MUM1/IRF4 and/or CD138 but not GC B-cell markers. Patients with pattern A had much better overall survival than those with the other two patterns (Kaplan-Meier survival analysis, P < 0.008, log rank test). Using multivariate Cox proportional hazards regression analysis, the international prognostic index scores and the expression pattern of these markers were independent prognostic indicators. Our results suggest that expression patterns of this panel of GC B-cell and activation markers by immunohistochemistry correlate with the prognosis of patients with DLBCL. Immunohistochemical analysis on paraffin-embedded tissues is more readily available than gene expression profiling by cDNA microarray and may provide similar prognostic information.

Inflammatory myofibroblastic tumor (IMT), a tumor of myofibroblastic spindle cells accompanied by a lymphoplasmacytic and eosinophilic inflammatory infiltrate, and anaplastic large cell lymphoma share clonal aberrations involving the short arm of chromosome 2 in region p21-p23 (1-5). Chromosome 2p23 is the site of the human ALK gene, which codes for anaplastic lymphoma kinase, a tyrosine kinase receptor and member of the insulin growth factor receptor superfamily. Antibodies to the protein product of the ALK gene detect both ALK expression associated with 2p23 rearrangements and other abnormalities in ALK deregulation. ALK rearrangements and/or ALK1 and p80 immunoreactivity have been reported in 36 -60% of IMTs and 8 -33% of "inflammatory pseudotumors" (3, 5, 6 -9). Fusion oncogenes have been identified in a small proportion of IMTs with ALK rearrangements and include TPM3-ALK and TPM4-ALK (4). In anaplastic large cell lymphoma, the clonal abnormalities of ALK include a characteristic translocation t(2, 5)(p23;q35), variant translocations, and a TPM3-ALK fusion oncogene in some cases (2, 10 -15). Various investigators have shown that ALK gene rearrangements and ALK expression are found

Non-Hodgkin lymphoma is the fourth most common malignancy in children, has an even higher incidence in adolescents, and is primarily represented by only a few histologic subtypes. Dramatic progress has been achieved, with survival rates exceeding 80%, in large part because of a better understanding of the biology of the different subtypes and national and international collaborations. Most patients with Burkitt lymphoma and diffuse large B-cell lymphoma are cured with short intensive pulse chemotherapy containing cyclophosphamide, cytarabine, and high-dose methotrexate. The benefit of the addition of rituximab has not been established except in the case of primary mediastinal B-cell lymphoma. Lymphoblastic lymphoma is treated with intensive, semi-continuous, longer leukemia-derived protocols. Relapses in B-cell and lymphoblastic lymphomas are rare and infrequently curable, even with intensive approaches. Event-free survival rates of approximately 75% have been achieved in anaplastic large-cell lymphomas with various regimens that generally include a short intensive B-like regimen. Immunity seems to play an important role in prognosis and needs further exploration to determine its therapeutic application. ALK inhibitor therapeutic approaches are currently under investigation. For all pediatric lymphomas, the intensity of induction/consolidation therapy correlates with acute toxicities, but because of low cumulative doses of anthracyclines and alkylating agents, minimal or no long-term toxicity is expected. Challenges that remain include defining the value of prognostic factors, such as early response on positron emission tomography/computed tomography and minimal disseminated and residual disease, using new biologic technologies to improve risk stratification, and developing innovative therapies, both in the first-line setting and for relapse

LDH level at diagnosis, mediastinal disease, and combined BM-positive/CNS-positive involvement are independent risk factors in children with mature B-cell NHL. Future studies should be developed to identify specific therapeutic strategies (immunotherapy) to overcome these risk factors and to identify the biologic basis associated with these prognostic factors in children with mature B-cell NHL.