Hematopoietic stem cell function and survival depend on c-Myc and N-Myc activity.

Myc activity is emerging as a key element in acquisition and maintenance of stem cell properties. We have previously shown that c-Myc deficiency results in accumulation of defective hematopoietic stem cells (HSCs) due to niche-dependent differentiation defects. Here we report that immature HSCs coexpress c-myc and N-myc mRNA at similar levels. Although conditional deletion of N-myc in the bone marrow does not affect hematopoiesis, combined deficiency of c-Myc and N-Myc (dKO) results in pancytopenia and rapid lethality. Interestingly, proliferation of HSCs depends on both myc genes during homeostasis, but is c-Myc/N-Myc independent during bone marrow repair after injury. Strikingly, while most dKO hematopoietic cells undergo apoptosis, only self-renewing HSCs accumulate the cytotoxic molecule Granzyme B, normally employed by the innate immune system, thereby revealing an unexpected mechanism of stem cell apoptosis. Collectively, Myc activity (c-Myc and N-Myc) controls crucial aspects of HSC function including proliferation, differentiation, and survival.

A circuit-based gatekeeper for adult neural stem cell proliferation: Parvalbumin-expressing interneurons of the dentate gyrus control the activation and proliferation of quiescent adult neural stem cells.

Newborn neurons are generated in the adult hippocampus from a pool of self-renewing stem cells located in the subgranular zone (SGZ) of the dentate gyrus. Their activation, proliferation, and maturation depend on a host of environmental and cellular factors but, until recently, the contribution of local neuronal circuitry to this process was relatively unknown. In their recent publication, Song and colleagues have uncovered a novel circuit-based mechanism by which release of the neurotransmitter, γ-aminobutyric acid (GABA), from parvalbumin-expressing (PV) interneurons, can hold radial glia-like (RGL) stem cells of the adult SGZ in a quiescent state. This tonic GABAergic signal, dependent upon the activation of γ(2) subunit-containing GABA(A) receptors of RGL stem cells, can thus prevent their proliferation and subsequent maturation or return them to quiescence if previously activated. PV interneurons are thus capable of suppressing neurogenesis during periods of high network activity and facilitating neurogenesis when network activity is low.

Jagged1-dependent Notch signaling is dispensable for hematopoietic stem cell self-renewal and differentiation.

Jagged1-mediated Notch signaling has been suggested to be critically involved in hematopoietic stem cell (HSC) self-renewal. Unexpectedly, we report here that inducible Cre-loxP-mediated inactivation of the Jagged1 gene in bone marrow progenitors and/or bone marrow (BM) stromal cells does not impair HSC self-renewal or differentiation in all blood lineages. Mice with simultaneous inactivation of Jagged1 and Notch1 in the BM compartment survived normally following a 5FU-based in vivo challenge. In addition, Notch1-deficient HSCs were able to reconstitute mice with inactivated Jagged1 in the BM stroma even under competitive conditions. In contrast to earlier reports, these data exclude an essential role for Jagged1-mediated Notch signaling during hematopoiesis.

High dose chemotherapy with autologous hematopoietic stem cell support for solid tumors other than breast cancer in adults.

Since the early 1980s high dose chemotherapy with autologous hematopoietic stem cell support was adopted by many oncologists as a potentially curative option for solid tumors, supported by a strong rationale from laboratory studies and apparently convincing results of early phase II studies. As a result, the number and size of randomized trials comparing this approach with conventional chemotherapy initiated (and often abandoned before completion) to prove or disprove its value was largely insufficient. In fact, with the possible exception of breast carcinoma, the benefit of a greater escalation of dose of chemotherapy with stem cell support in solid tumors is still unsettled and many oncologists believe that this approach should cease. In this article, we critically review and comment on the data from studies of high dose chemotherapy so far reported in adult patients with small cell lung cancer, ovarian cancer, germ cell tumors and sarcomas.

A dynamic model of keratinocyte stem cell renewal and differentiation: role of the p21WAF1/Cip1 and Notch1 signaling pathways.

We present here a dynamic model of functional equilibrium between keratinocyte stem cells, transit amplifying populations and cells that are reversibly versus irreversibly committed to differentiation. According to this model, the size of keratinocyte stem cell populations can be controlled at multiple levels, including relative late steps in the sequence of events leading to terminal differentiation and by the influences of a heterogeneous extra-cellular environment. We discuss how work in our laboratory, on the interconnection between the cyclin/CDK inhibitor p21WAF1/Cip1 and the Notch1 signaling pathways, provides strong support to this dynamic model of stem cell versus committed and/or differentiated keratinocyte populations.

European guidelines for antifungal management in leukemia and hematopoietic stem cell transplant recipients: summary of the ECIL 3--2009 update.

In 2005, several groups, including the European Group for Blood and Marrow Transplantation, the European Organization for Treatment and Research of Cancer, the European Leukemia Net and the Immunocompromised Host Society created the European Conference on Infections in Leukemia (ECIL). The main goal of ECIL is to elaborate guidelines, or recommendations, for the management of infections in leukemia and stem cell transplant patients. The first sets of ECIL slides about the management of invasive fungal disease were made available on the web in 2006 and the papers were published in 2007. The third meeting of the group (ECIL 3) was held in September 2009 and the group updated its previous recommendations. The goal of this paper is to summarize the new proposals from ECIL 3, based on the results of studies published after the ECIL 2 meeting: (1) the prophylactic recommendations for hematopoietic stem cell transplant recipients were formulated differently, by splitting the neutropenic and the GVHD phases and taking into account recent data on voriconazole; (2) micafungin was introduced as an alternative drug for empirical antifungal therapy; (3) although several studies were published on preemptive antifungal approaches in neutropenic patients, the group decided not to propose any recommendation, as the only randomized study comparing an empirical versus a preemptive approach showed a significant excess of fungal disease in the preemptive group.

EWS-FLI-1 modulates miRNA145 and SOX2 expression to initiate mesenchymal stem cell reprogramming toward Ewing sarcoma cancer stem cells

Introduction: Cancer stem cells (CSC) display plasticity and self renewal properties reminiscent of normal tissue stem cells but the events responsible for their emergence remain obscure. We have recently identified CSC in Ewing sarcoma family tumors (ESFT) and shown that they arise from mesenchymal stem cells from the bone marrow. Objective of the study: To analyze the mechanisms underlying cancer stem cell development in ESFT. Methods: Primary human mesenchymal stem cells (MSC) isolation from adult and pediatric bone marrow. Retroviral delivery of fusion protein (EWS-FLI1) to primary MSC, and transcriptional and phenotypical analysis. Results: We show that the EWS-FLI-1 fusion gene, associated wit 85-90% of ESFT and believed to initiate their pathogenesis, induces expression of the embryonic stem cell (ESC) genes OCT4, SOX2 and NANOG in human pediatric MSC (hpMSC) but not in their adult counterparts. Moreover, under appropriate culture conditions, hpMSC expressing EWS-FLI-1 generate a cell subpopulation displaying ESFT CSC features in vitro. We further demonstrate that induction of the ESFT CSC phenotype is the result of the combined effect of EWSFLI- 1 on its target gene expression and repression of microRNA-145 (miRNA145) promoter activity. Finally, we provide evidence that EWS-FLI-1 and miRNA-145 function in a mutually repressive feedback loop and identify their common target gene SOX2, in addition to miRNA145 itself, as key players in ESFT cell differentiation and tumorigenicity. Conclusion: Our observations provide insight for the first time into the mechanisms whereby a single oncogene can reprogram primary cells to display a cancer stem cell phenotype.

Pegfilgrastim after high-dose chemotherapy and autologous peripheral blood stem cell transplant: phase II study.

Pegfilgrastim is equivalent to daily filgrastim after standard dose chemotherapy in decreasing the duration of neutropenia. Daily filgrastim started within 1-4 days after autologous stem cell transplant (ASCT) leads to significant decrease in time to neutrophil engraftment. We undertook a study of pegfilgrastim after high-dose chemotherapy (HDC) and ASCT. In all, 38 patients with multiple myeloma or lymphoma, eligible to undergo HDC and ASCT, were enrolled. Patients received a single dose of 6 mg pegfilgrastim subcutaneously 24 h after ASCT. There were no adverse events secondary to pegfilgrastim. All patients engrafted neutrophils and platelets with a median of 10 and 18 days, respectively. The incidence of febrile neutropenia was 49% (18/37). Neutrophil engraftment results were compared to a historical cohort of patients who received no growth factors or prophylactic filgrastim after ASCT. Time to neutrophil engraftment using pegfilgrastim was comparable to daily filgrastim and was shorter than in a historical group receiving no filgrastim (10 vs 13.7 days, P<0.001). Pegfilgrastim given as a single fixed dose of 6 mg appears to be safe after HDC and ASCT. It accelerates neutrophil engraftment comparable to daily filgrastim after ASCT. Pegfilgrastim may be convenient to use in outpatient transplant units.

Pegfilgrastim to accelerate neutrophil engraftment following peripheral blood stem cell transplant and reduce the duration of neutropenia, hospitalization, and use of intravenous antibiotics: a phase II study in multiple myeloma and lymphoma and comparison with filgrastim-treated matched controls.

This trial was aimed to explore the efficacy of pegfilgrastim to accelerate neutrophil engraftment after stem cell autotransplant. Twenty patients with multiple myeloma and 20 with lymphoma received pegfilgrastim 6 mg on day +1. Forty cases treated with daily filgrastim starting at median day +7 (5-7), matched by age, sex, diagnosis, high-dose chemotherapy schedule, CD34 +  cell-dose, and prior therapy lines, were used for comparison. Median time to neutrophil engraftment was 9.5 vs. 11 days for pegfilgrastim and filgrastim, respectively (p < 0.0001). Likewise, duration of neutropenia, intravenous antibiotic use, and hospitalization favored pegfilgrastim, while platelet engraftment, transfusion requirement, and fever duration were equivalent in both groups. No grade  ≥ 3 toxicities were observed. Patients with lymphoma performed similarly to the entire cohort, while patients with myeloma showed faster neutrophil engraftment and shorter neutropenia but not shorter hospitalization and antibiotic use. The possibility of different outcomes for lymphoma and myeloma suggests that stratification by diagnosis may be useful in future phase III studies.

Early intensification and autologous stem cell transplantation in patients with systemic AL amyloidosis: a single-centre experience.

Primary systemic amyloidosis (AL amyloidosis) continues to have a very poor prognosis. Most therapeutic strategies remain unsatisfactory. Conventional chemotherapy is known to offer at best only moderate efficacy. Several studies have yielded higher complete response rates after high-dose chemotherapy and autologous stem cell transplantation (ASCT) in addition to improving outcomes in a subgroup of patients. However, the superiority of an intensive approach in AL amyloidosis has not been confirmed in a randomised trial. The precise role of ASCT remains unclear. We report our experience in 16 patients diagnosed with AL amyloidosis and treated in a multidisciplinary approach with high-dose melphalan and ASCT. Median age was 59 (39-71) years. The kidneys were predominantly affected in 75% of cases; two or more organs were affected in 38%. Median time from diagnosis to transplantation was 2 (1-4) months. Three patients (19%) developed acute renal failure and required transient dialysis. Transplant-related mortality was 6% after 100 days. Haematological complete response (CR) was obtained in nine (56%) and organ response in six (38%) patients. Nine out of 12 patients (75%) with kidney involvement exhibited a sustained clinical benefit at 12 months. Half of all the patients (n = 8) were alive after a median follow-up of 33 months, including two in continuous CR. This suggests that high-dose chemotherapy and ASCT are still valid treatment options in AL amyloidosis and that a significant number of patients with renal involvement might benefit from this approach.

Recent advances in the epidermal growth factor receptor/ligand system biology on skin homeostasis and keratinocyte stem cell regulation.

The epidermal growth factor (EGF) receptor/ligand system stimulates multiple pathways of signal transduction, and is activated by various extracellular stimuli and inter-receptor crosstalk signaling. Aberrant activation of EGF receptor (EGFR) signaling is found in many tumor cells, and humanized neutralizing antibodies and synthetic small compounds against EGFR are in clinical use today. However, these drugs are known to cause a variety of skin toxicities such as inflammatory rash, skin dryness, and hair abnormalities. These side effects demonstrate the multiple EGFR-dependent homeostatic functions in human skin. The epidermis and hair follicles are self-renewing tissues, and keratinocyte stem cells are crucial for maintaining these homeostasis. A variety of molecules associated with the EGF receptor/ligand system are involved in epidermal homeostasis and hair follicle development, and the modulation of EGFR signaling impacts the behavior of keratinocyte stem cells. Understanding the roles of the EGF receptor/ligand system in skin homeostasis is an emerging issue in dermatology to improve the current therapy for skin disorders, and the EGFR inhibitor-associated skin toxicities. Besides, controlling of keratinocyte stem cells by modulating the EGF receptor/ligand system assures advances in regenerative medicine of the skin. We present an overview of the recent progress in the field of the EGF receptor/ligand system on skin homeostasis and regulation of keratinocyte stem cells.

Magnetic resonance imaging overestimates ferumoxide-labeled stem cell survival after transplantation in the heart.

BACKGROUND: Stem cell labeling with iron oxide (ferumoxide) particles allows labeled cells to be detected by magnetic resonance imaging (MRI) and is commonly used to track stem cell engraftment. However, the validity of MRI for distinguishing surviving ferumoxide-labeled cells from other sources of MRI signal, for example, macrophages containing ferumoxides released from nonsurviving cells, has not been thoroughly investigated. We sought to determine the relationship between the persistence of iron-dependent MRI signals and cell survival 3 weeks after injection of syngeneic or xenogeneic ferumoxides-labeled stem cells (cardiac-derived stem cells) in rats. METHODS AND RESULTS: We studied nonimmunoprivileged human and rat cardiac-derived stem cells and human mesenchymal stem cells doubly labeled with ferumoxides and beta-galactosidase and injected intramyocardially into immunocompetent Wistar-Kyoto rats. Animals were imaged at 2 days and 3 weeks after stem cell injection in a clinical 3-T MRI scanner. At 2 days, injection sites of xenogeneic and syngeneic cells (cardiac-derived stem cells and mesenchymal stem cells) were identified by MRI as large intramyocardial signal voids that persisted at 3 weeks (50% to 90% of initial signal). Histology (at 3 weeks) revealed the presence of iron-containing macrophages at the injection site, identified by CD68 staining, but very few or no beta-galactosidase-positive stem cells in the animals transplanted with syngeneic or xenogeneic cells, respectively. CONCLUSIONS: The persistence of significant iron-dependent MRI signal derived from ferumoxide-containing macrophages despite few or no viable stem cells 3 weeks after transplantation indicates that MRI of ferumoxide-labeled cells does not reliably report long-term stem cell engraftment in the heart.

Long-term follow-up of high-dose chemotherapy with autologous stem-cell transplantation and response-adapted whole-brain radiotherapy for newly diagnosed primary CNS lymphoma: results of the multicenter Ostdeutsche Studiengruppe Hamatologie und Onkologie OSHO-53 phase II study.

Background We previously reported the results of a phase II study for patients with newly diagnosed primary central nervous system lymphoma treated with autologous peripheral blood stem-cell transplantation (aPBSCT) and response-adapted whole-brain radiotherapy (WBRT). Now, we update the initial results. Patients and methods From 1999 to 2004, 23 patients received high-dose methotrexate. In case of at least partial remission, high-dose busulfan/thiotepa (HD-BuTT) followed by aPBSCT was carried out. Patients refractory to induction or without complete remission after HD-BuTT received WBRT. Eight patients still alive in 2011 were contacted and Mini-Mental State Examination (MMSE) and the European Organisation for Research and Treatment of Cancer quality-of-life questionnaire (QLQ)-C30 were carried out. Results Of eight patients still alive, median follow-up is 116.9 months. Only one of nine irradiated patients is still alive with a severe neurologic deficit. In seven of eight patients treated with HD-BuTT, health condition and quality of life are excellent. MMSE and QLQ-C30 showed remarkably good results in patients who did not receive WBRT. All of them have a Karnofsky score of 90%-100%. Conclusions Follow-up shows an overall survival of 35%. In six of seven patients where WBRT could be avoided, no long-term neurotoxicity has been observed and all patients have an excellent quality of life.

Caspofungin first-line therapy for invasive aspergillosis in allogeneic hematopoietic stem cell transplant patients: an European Organisation for Research and Treatment of Cancer study.

Caspofungin at standard dose was evaluated as first-line monotherapy of mycologically documented probable/proven invasive aspergillosis (IA) (unmodified European Organisation for Research and Treatment of Cancer/Mycosis Study Group criteria) in allogeneic hematopoietic SCT patients. The primary efficacy end point was complete or partial response at end of caspofungin treatment. Response at week 12, survival and safety were additional end points. Enrollment was stopped prematurely because of low accrual, with 42 enrolled and 24 eligible, giving the study a power of 85%. Transplant was from unrelated donors in 16 patients; acute or chronic GVHD was present in 15. In all, 12 patients were neutropenic (<500/microl) at baseline, 10 received steroids and 16 calcineurin inhibitors or sirolimus. Median duration of caspofungin treatment was 24 days. At the end of caspofungin therapy, 10 (42%) patients had complete or partial response (95% confidence interval: 22-63%); 1 (4%) and 12 (50%) had stable and progressing disease, respectively; one was not evaluable. At week 12, eight patients (33%) had complete or partial response. Survival rates at week 6 and 12 were 79 and 50%, respectively. No patient had a drug-related serious adverse event or discontinued because of toxicity. Caspofungin first-line therapy was effective and well tolerated in allogeneic hematopoietic SCT patients with mycologically documented IA.