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Mast cells (MCs) are critical components of the innate immune system and important for host defense, allergy, autoimmunity, tissue regeneration and tumor progression. Dysregulated MC development leads to systemic mastocytosis (SM), a clinically variable but often devastating family of hematologic disorders. Here we report that induced expression of Lin28, a heterochronic gene and pluripotency factor implicated in driving a fetal hematopoietic program, caused MC accumulation in adult mice in target organs such as the skin and peritoneal cavity. In vitro assays revealed a skewing of myeloid commitment in LIN28B-expressing hematopoietic progenitors, with increased levels of LIN28B in common myeloid and basophil-MC progenitors altering gene expression patterns to favor cell fate choices that enhanced MC specification. In addition, LIN28B-induced MCs appeared phenotypically and functionally immature, and in vitro assays suggested a slowing of MC terminal differentiation in the context of LIN28B upregulation. Finally, interrogation of human MC leukemia samples revealed upregulation of LIN28B in abnormal MCs from patients with SM. This work identifies Lin28 as a novel regulator of innate immune function and a new protein of interest in MC disease. [ABSTRACT FROM AUTHOR]

On the basis of the data suggesting that adolescents and young adult patients with acute lymphoblastic leukemia (ALL) have improved outcomes when treated on pediatric protocols, we assessed the feasibility of treating adult patients aged 18-50 years with ALL with the DFCI Pediatric ALL Consortium regimen utilizing a 30-week course of pharmacokinetically dose-adjusted E. coli L-asparaginase during consolidation. Between 2002 and 2008, 92 eligible patients aged 18-50 years were enrolled at 13 participating centers. Seventy-eight patients (85%) achieved a complete remission (CR) after 1 month of intensive induction therapy. With a median follow-up of 4.5 years, the 4-year disease-free survival (DFS) for the patients achieving a CR was 69% (95% confidence interval (CI) 56-78%) and the 4-year overall survival (OS) for all eligible patients was 67% (95% CI 56-76%). The 4-year DFS for the 64 patients who achieved a CR and were Philadelphia chromosome negative (Ph−) was 71% (95% CI 58-81%), and for all 74 Ph− patients the 4-year OS was 70% (95% CI 58-79%). We conclude that a pediatric-like treatment strategy for young adults with de novo ALL is feasible, associated with tolerable toxicity, and results in improved outcomes compared with historical regimens in young adult patients with ALL. [ABSTRACT FROM AUTHOR]

Spleen tyrosine kinase (SYK) was recently identified as a new target in acute myeloid leukemia (AML); however, its mechanistic role in this disease is poorly understood. Based on the known interaction between SYK and mammalian target of rapamycin (mTOR) signaling in lymphoma, we hypothesized that SYK may regulate mTOR signaling in AML. Both small-molecule inhibition of SYK and SYK-directed shRNA suppressed mTOR and its downstream signaling effectors, as well as its upstream activator, AKT. Moreover, the inhibition of multiple nodes of the phosphatidylinositol 3′-kinase (PI3K) signaling pathway enhanced the effects of SYK suppression on AML cell viability and differentiation. Evaluation of the collateral mitogen-activated protein kinase (MAPK) pathway revealed a heterogeneous response to SYK inhibition in AML with downregulation of MEK and extracellular signal-regulated kinase (ERK) phosphorylation in some AML cell lines but a paradoxical increase in MEK/ERK phosphorylation in RAS-mutated AML. These studies reveal SYK as a regulator of mTOR and MAPK signaling in AML and demonstrate that inhibition of PI3K pathway activity enhances the effects of SYK inhibition on AML cell viability and differentiation. [ABSTRACT FROM AUTHOR]

Panobinostat is a potent oral pandeacetylase inhibitor that leads to acetylation of intracellular proteins, inhibits cellular proliferation and induces apoptosis in leukemic cell lines. A phase Ia/II study was designed to determine the maximum-tolerated dose (MTD) of daily panobinostat, administered on two schedules: three times a week every week or every other week on a 28-day treatment cycle in patients with advanced hematologic malignancies. The criteria for hematologic dose-limiting toxicities differed between patients with indications associated with severe cytopenias at baseline (leukemia and myeloid disorders) and those less commonly associated with baseline cytopenias (lymphoma and myeloma). In patients with leukemia and myeloid disorders, 60 mg was the MTD for weekly as well as biweekly panobinostat. In patients with lymphoma and myeloma, 40 mg was the recommended dose for phase II evaluation (formal MTD not determined) of weekly panobinostat, and 60 mg was the MTD for biweekly panobinostat. Overall, panobinostat-related grade 3-4 adverse events included thrombocytopenia (41.5%), fatigue (21%) and neutropenia (21%). Single-agent activity was observed in several indications, including Hodgkin lymphoma and myelofibrosis. This phase Ia/II study provided a broad analysis of the safety profile and efficacy of single-agent panobinostat in patients with hematologic malignancies. [ABSTRACT FROM AUTHOR]

This phase 1b trial investigated several doses and schedules of midostaurin in combination with daunorubicin and cytarabine induction and high-dose cytarabine post-remission therapy in newly diagnosed patients with acute myeloid leukemia (AML). The discontinuation rate on the 50-mg twice-daily dose schedule was lower than 100 mg twice daily, and no grade 3/4 nausea or vomiting was seen. The complete remission rate for the midostaurin 50-mg twice-daily dose schedule was 80% (FMS-like tyrosine kinase 3 receptor (FLT3)-wild-type: 20 of 27 (74%), FLT3-mutant: 12 of 13 (92%)). Overall survival (OS) probabilities of patients with FLT3-mutant AML at 1 and 2 years (0.85 and 0.62, respectively) were similar to the FLT3-wild-type population (0.78 and 0.52, respectively). Midostaurin in combination with standard chemotherapy demonstrated high complete response and OS rates in newly diagnosed younger adults with AML, and was generally well tolerated at 50 mg twice daily for 14 days. A phase III prospective trial is ongoing (CALGB 10603, NCT00651261). [ABSTRACT FROM AUTHOR]

Lonafarnib is an orally bio-available farnesyltransferase inhibitor that prevents farnesylation of specific target proteins including Ras. In a multicenter study, 67 patients with advanced myelodysplastic syndrome (MDS) and chronic myelomonocytic leukemia (CMML) were treated with a continuous oral dose of 200-300 mg of lonafarnib and were evaluated for hematologic, pathologic and pharmacodynamic response. The median age of patients was 70 years (range 44-86). There were 32 patients with MDS (RAEB-20 and RAEB-t-12) and 35 with CMML. Overall 16 (24%) of the patients responded with two patients achieving a complete remission and one a partial response. Responses were seen in 6/32 and 10/35 patients with MDS and CMML, respectively. Of the 19 patients who were platelet transfusion-dependent prior to treatment, 5 (26%) became transfusion-free for a median duration of 185 days. A decrease in the farnesylation of the HDJ-2 protein measured in patient-derived cells was observed in the majority of patients during treatment with lonafarnib, but no clear correlation between changes in farnesylation and clinical effect could be made. Gastrointestinal toxicity was significant with 19% of patients discontinuing therapy due to diarrhea, nausea and/or anorexia. Lonafarnib has demonstrable activity in patients with advanced MDS and CMML. [ABSTRACT FROM AUTHOR]

We report the cloning of a novel PDGFRB fusion gene partner in a patient with a chronic myeloproliferative disorder characterized by t(5;14)(q33;q32), who responded to treatment with imatinib mesylate. Fluorescence in situ hybridization demonstrated that PDGFRB was involved in the translocation. Long distance inversion PCR identified KIAA1509 as the PDGFRB fusion partner. KIAA1509 is an uncharacterized gene with a predicted coiled-coil oligomerization domain with homology to the HOOK family of proteins. The predicted KIAA1509-PDGFRßfusion protein contains the KIAA1509 coiled-coil domain fused to the cytoplasmic domain of PDGFRßthat includes the tyrosine kinase domain. Imatinib therapy resulted in rapid normalization of the patient's blood counts, and subsequent bone marrow biopsies and karyotypic analysis were consistent with sustained complete remission.Leukemia (2005) 19, 27-30. doi:10.1038/sj.leu.2403548 Published online 21 October 2004 [ABSTRACT FROM AUTHOR]