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To maintain lifelong production of blood cells, haematopoietic stem cells (HSCs) are tightly regulated by inherent programs and extrinsic regulatory signals received from their microenvironmental niche. Long-term repopulating HSCs reside in several, perhaps overlapping, niches that produce regulatory molecules and signals necessary for homeostasis and for increased output after stress or injury. Despite considerable advances in the specific cellular or molecular mechanisms governing HSC-niche interactions, little is known about the regulatory function in the intact mammalian haematopoietic niche. Recently, we and others described a positive regulatory role for prostaglandin E2 (PGE2) on HSC function ex vivo. Here we show that inhibition of endogenous PGE2 by non-steroidal anti-inflammatory drug (NSAID) treatment in mice results in modest HSC egress from the bone marrow. Surprisingly, this was independent of the SDF-1-CXCR4 axis implicated in stem-cell migration. Stem and progenitor cells were found to have differing mechanisms of egress, with HSC transit to the periphery dependent on niche attenuation and reduction in the retentive molecule osteopontin. Haematopoietic grafts mobilized with NSAIDs had superior repopulating ability and long-term engraftment. Treatment of non-human primates and healthy human volunteers confirmed NSAID-mediated egress in other species. PGE2 receptor knockout mice demonstrated that progenitor expansion and stem/progenitor egress resulted from reduced E-prostanoid 4 (EP4) receptor signalling. These results not only uncover unique regulatory roles for EP4 signalling in HSC retention in the niche, but also define a rapidly translatable strategy to enhance transplantation therapeutically. [ABSTRACT FROM AUTHOR]

ENMD-2076 is a novel, orally-active molecule that has been shown to have significant activity against aurora and multiple receptor tyrosine kinases. We investigated the activity of ENMD-2076 against multiple myeloma (MM) cells in vitro and in vivo. ENMD-2076 showed significant cytotoxicity against MM cell lines and primary cells, with minimal cytotoxicity to haematopoietic progenitors. ENMD-2076 inhibited the phosphoinositide 3-kinase/AKT pathway and downregulated survivin and X-linked inhibitor of apoptosis as early as 6 h after treatment. With longer treatment (24–48 h), ENMD-2076 also inhibited aurora A and B kinases, and induced G2/M cell cycle arrest. In non-obese diabetic/severe combined immunodeficient mice implanted with H929 human plasmacytoma xenografts, oral treatment with ENMD-2076 (50, 100, 200 mg/kg per day) resulted in a dose-dependent inhibition of tumour growth. Immunohistochemical staining of excised tumours showed significant reduction in phospho-Histone 3 (pH3), Ki-67, and angiogenesis, and also a significant increase in cleaved caspase-3 at all dose levels compared to tumours from vehicle-treated mice. In addition, a significant reduction in p-FGFR3 was observed on Western blot. ENMD-2076 shows significant activity against MM cells in vitro and in vivo, and acts on several pathways important for myeloma cell growth and survival. These results provide preclinical rationale for clinical investigation of ENMD-2076 in MM. [ABSTRACT FROM AUTHOR]

Tandem autologous stem cell transplantation (ASCT) improves long-term survival of platinum-refractory germ cell tumors (GCT) patients. Studies, predominantly in lymphoma, showed that CD34 + cell doses > 5.0 × 10 6 /kg/single transplant led to decreased resource utilization. Because most GCT patients have received prior cisplatin-based treatment, collecting >10 × 10 6 CD34 + cells/kg is challenging. We analyzed the effect of CD34 +  cell dose on resource utilization and outcome in 131 GCT patients, median age 29.5 years (range, 16 to 58), undergoing tandem ASCT. Of 262 individual transplants performed, 120 were performed as inpatient and 142 as planned outpatient. Overall, median CD34 + dose per transplant was 3.1 × 10 6 /kg (range, 0.8 to 16.0), with no significant difference between inpatient and outpatient transplants. Patients were divided into quartiles based on the CD34 cell dose infused: Q1, 0.8 to 1.9 × 10 6 /kg; Q2, 2.0 to 2.9 × 10 6 /kg; Q3, 3.0 to 4.1 × 10 6 /kg; and Q4, 4.2 to 16.0 × 10 6 /kg. For all patients higher CD34 + cell doses were associated with significantly shorter times to neutrophil ( P  <   .001) and platelet recovery ( P  <   .001). For inpatient transplants higher CD34 + doses were significantly associated with shorter length of hospital stay ( P  <   .001), fewer days of filgrastim ( P  <   .001), i.v. antibiotic ( P  = .012) and antifungal ( P  = .03) usage; and fewer RBC ( P  = .001) and platelet units transfused ( P  <   .001), resulting in overall lower cost of care ( P  < .001). Of the 142 planned outpatient transplants, 100 admissions were required for a median length of hospital stay of 7.0 days (range, 1 to 18). Although there was no significant difference in the rates of hospitalization between patients in different CD34 +  cell dose quartiles, a significant trend was observed for shorter hospitalization ( P  = .01) and fewer RBC ( P  = .002) and platelet ( P  = .005) transfusions with higher CD34 + cell dose quartile. Patients receiving CD34 +  cell doses in the lowest dose quartile (Q1) had significantly worse progression-free survival and overall survival compared with patients receiving higher CD34 +  cell doses. Overall, resource utilization, including cost of care, is significantly reduced when patients receive higher CD34 +  cell doses, indicating greater efforts to improve peripheral blood stem cell collection in this population are needed. [ABSTRACT FROM AUTHOR]

To maintain lifelong production of blood cells, haematopoietic stem cells (HSCs) are tightly regulated by inherent programs and extrinsic regulatory signals received from their microenvironmental niche. Long-term repopulating HSCs reside in several, perhaps overlapping, niches that produce regulatory molecules and signals necessary for homeostasis and for increased output after stress or injury. Despite considerable advances in the specific cellular or molecular mechanisms governing HSC-niche interactions, little is known about the regulatory function in the intact mammalian haematopoietic niche. Recently, we and others described a positive regulatory role for prostaglandin E2 (PGE2) on HSC function ex vivo. Here we show that inhibition of endogenous PGE2 by non-steroidal anti-inflammatory drug (NSAID) treatment in mice results in modest HSC egress from the bone marrow. Surprisingly, this was independent of the SDF-1-CXCR4 axis implicated in stem-cell migration. Stem and progenitor cells were found to have differing mechanisms of egress, with HSC transit to the periphery dependent on niche attenuation and reduction in the retentive molecule osteopontin. Haematopoietic grafts mobilized with NSAIDs had superior repopulating ability and long-term engraftment. Treatment of non-human primates and healthy human volunteers confirmed NSAID-mediated egress in other species. PGE2 receptor knockout mice demonstrated that progenitor expansion and stem/progenitor egress resulted from reduced E-prostanoid 4 (EP4) receptor signalling. These results not only uncover unique regulatory roles for EP4 signalling in HSC retention in the niche, but also define a rapidly translatable strategy to enhance transplantation therapeutically. [ABSTRACT FROM AUTHOR]

Introduction: Multiple myeloma (MM) remains an incurable malignancy indicating a need for continued investigation of novel therapies. Recent studies have highlighted the role of cyclin-dependent kinases (CDK) in the pathogenesis of MM. PD0332991 (Palbociclib) is an orally bioavailable, highly selective inhibitor of the CDK4/6-cyclin complex and downstream retinoblastoma protein (Rb) activation pathway that induces cell cycle arrest in the G1 phase., Areas Covered: In this review, the authors summarize the role of the CDK4/6 signaling pathway in MM. They also summarize the development of PD0332991 as a specific inhibitor of CDK4/6, and the reported preclinical and clinical data supporting the potential role of PD0332991 in MM., Expert Opinion: While PD0332991 is essentially cytostatic, inducing prolonged G1 arrest, it enhances the cytotoxic effect of other agents effective in MM, including bortezomib and lenalidomide, as confirmed in early phase clinical trials. However, with a plethora of other drugs of different classes being tested in MM, further development of PD0332991 will depend on defining the most efficacious combination with least toxicity. An unexplored opportunity remains the potential protective effect of PD0332991 against lytic bone lesions of MM. The next few years are likely to better define the place of PD0332991 in the treatment of MM.

Multiple myeloma and non-Hodgkin's lymphoma remain the most common indications for high-dose chemotherapy and autologous peripheral blood stem cell rescue. While a CD34+ cell dose of 1 × 10(6)/kg is considered the minimum required for engraftment, higher CD34+ doses correlate with improved outcome. Numerous studies, however, support targeting a minimum CD34+ cell dose of 2.0 × 10(6)/kg, and an "optimal" dose of 4 to 6 × 10(6)/kg for a single transplant. Unfortunately, up to 40% of patients fail to mobilize an optimal CD34+ cell dose using myeloid growth factors alone. Plerixafor is a novel reversible inhibitor of CXCR4 that significantly increases the mobilization and collection of higher numbers of hematopoietic progenitor cells. Two randomized multi-center clinical trials in patients with non-Hodgkin's lymphoma and multiple myeloma have demonstrated that the addition of plerixafor to granulocyte-colony stimulating factor increases the mobilization and yield of CD34+ cells in fewer apheresis days, which results in durable engraftment. This review summarizes the pharmacology and evidence for the clinical efficacy of plerixafor in mobilizing hematopoietic stem and progenitor cells, and discusses potential ways to utilize plerixafor in a cost-effective manner in patients with these diseases.

Secondary cytogenetic abnormalities at diagnosis of Philadelphia chromosome-positive (Ph+) chronic myelogenous leukemia (CML) have been associated with an inferior outcome in reported series of largely chemotherapy-treated patients. To date, no study has specifically focused on the prognostic significance of secondary karyotypic abnormalities, detected at the time of diagnosis, in interferon (IFN)-alpha treated patients. We compared the outcome of 29 newly diagnosed Ph+ CML patients with additional abnormalities to that of 234 sole Ph+ patients, treated on CALGB protocols with IFN-alpha alone or together with IFN-gamma or low-dose cytarabine. Complete and partial cytogenetic responses were achieved in 20 and 19% of sole Ph+ patients, compared to 23 and 18%, respectively, of patients with additional abnormalities (P=1.00). None of 4 patients with 'high-risk' secondary abnormalities [+8, +Ph and i(17)(q10)], for whom follow-up cytogenetic samples were available, achieved a cytogenetic response. With a median follow-up of 11.3 years, the median overall survival (OS) was 6.0 years for sole Ph+ patients compared to 7.5 years for patients with additional abnormalities (P=0.70), with corresponding 8-year OS of 36 and 38%, respectively. On multivariable analysis, only age (P<0.001) and white blood cell count (P=0.02) were associated with outcome. We conclude that, with the possible exception of +8, +Ph and i(17)(q10), additional chromosomal abnormalities at diagnosis are not associated with inferior outcome in Ph+ CML patients treated with IFN-alpha-based therapy.

Isolated trisomy is a relatively common cytogenetic abnormality in acute myeloid leukemia (AML), but with uncertain prognostic significance. We studied a large cohort of newly diagnosed de novo AML patients karyotyped on CALGB 8461 from 1984-1999, where trisomy was the sole abnormality. The common isolated trisomies (IT(C)), +8, +11, +13 and +21, comprised 90% of all sole trisomies. The outcome of 101 IT(C) patients was compared to that of 976 with normal and "poor risk" cytogenetics. The overall survival (OS) for IT(C) patients was unsatisfactory with 10% [95% confidence interval (CI), 3-17%] alive at 5 years. Repeated cycles of I/HDAC intensification did not improve outcome. However, SCT significantly improved relapse-free survival (RFS). Among IT(C) patients <60 years in first remission, only 1 of 7 receiving SCT relapsed, compared to 16 of 19 patients treated with chemotherapy only. The prognosis of IT(C) was dependent on SCT. For non-transplanted patients, the 5-year OS for IT(C) was 5% (95% CI, 0-11%), compared to 20% (95% CI, 16-23%) for 640 normal cytogenetics patients. IT(C) was an independent adverse prognostic factor for OS in non-transplanted patients. In those receiving SCT, however, the 5-year OS for IT(C) patients (69%, 95% CI, 32-100%) was not different to that of transplanted normal cytogenetics patients (60%, 95% CI, 38-81%). We conclude that in de novo adult AML patients not receiving SCT, IT(C) appears to independently predict a poor outcome that may be improved with SCT in first remission. Prospective studies are required to confirm this hypothesis.

Purpose: The purpose of the study is to investigate the tolerability of interleukin 2 (IL-2) after intensive chemotherapy in elderly acute myeloid leukemia (AML) patients in first complete remission (CR)., Experimental Design: AML patients > or =60 years in CR after induction and consolidation chemotherapy on Cancer and Leukemia Group B study 9420 were eligible if they had neutrophils > or =1 x 10(9)/liters and platelets > or =75 x 10(9)/liters. Patients received low-dose IL-2 (1 x 10(6) IU/m(2)/day s.c. for 90 days) or low-dose IL-2 with intermediate pulse doses (6-12 x 10(6) IU/m(2)/day s.c. for 3 days) every 14 days (maximum five pulses). In a subset of patients, we investigated the expression of NKG2D ligands by leukemic cells because they are likely important mediators of natural killer cytotoxicity., Results: Of 35 CR patients receiving IL-2, 34 were evaluable for toxicity. Median age was 67 (range, 60-76) years. Thirteen of 16 patients receiving low-dose IL-2 completed the planned therapy, and 11 of 18 who also received intermediate pulse dose IL-2 therapy completed all five pulses. The spectrum of toxicity in both groups was similar, with predominantly grade 1-2 fatigue, fever, injection site reactions, nausea, anemia, and thrombocytopenia. Grade 3-4 hematological and nonhematological toxicity were more frequent in patients also receiving intermediate pulse dose IL-2 therapy. Grade 3-4 fatigue and hematological toxicity, although uncommon, were the major causes for discontinuing or attenuating therapy. In 8 cases, mRNA for one or more NKG2D ligands was detected in leukemic cells obtained at diagnosis before treatment., Conclusions: Low-dose IL-2, with or without intermediate pulse dose therapy, given immediately after chemotherapy in first CR to elderly AML patients is well tolerated. Expression of NKG2D ligands by leukemic cells was detected in the majority of cases tested and should be assessed for correlation with response to IL-2 in future studies.