The Molecular Mechanisms of Serotonin in the Regulation of Megakaryocytopoiesis and TPO Production

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 3347-3347
Author(s):  
Mo Yang ◽  
Fanyi Meng ◽  
Jie Yu Ye ◽  
Yue Xu ◽  
Bin Xiao ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Molecular Mechanisms ◽  
Conflicts Of Interest ◽  
Promoting Effect ◽  
Actin Reorganization ◽  
Cord Blood Cd34 ◽  
5Ht2 Receptors ◽  
Proplatelet Formation ◽  
Subsequent Activation

Abstract Abstract 3347 We have reported that serotonin (5-HT) show a promoting effect on cord blood CD34+ stem/progenitor cells (Yang et al, Stem Cells 2007). We also demonstrated that serotonin enhances murine megakaryopoiesis via 5-HT2 receptors (Yang et al. Blood Coagul Fibrinol 1996). In this present study, we explored how serotonin regulated human megakaryocytopoiesis, proplatelet formation, and thrombopoietin (TPO) production. Our results indicated that serotonin significantly promoted human CFU-MK formation and reduced apoptosis in megakaryocytes through phosphorylation of Akt. These effects were attenuated by addition of ketanserin, a 5-HT2 receptor inhibitor. In addition, serotonin was able to stimulate the F-actin reorganization in megakaryocytes through activating the p-Erk1/2 expression. Bone marrow mesenchymal stromal cells (MSCs) are important in regulating megakaryocytopoiesis through stimulating release of thrombopoietic growth factor, such as TPO. Our studies suggested that when activated by serotonin, bone marrow MSCs were induced to release significant amount of TPO by q-PCR, ELISA and cytokine-array assays. Our findings demonstrated an important role of serotonin played on megakaryocytopoiesis. This effect was likely mediated via 5HT2 receptors with subsequent activation of Akt and Erk 1/2 phosphorylation, which led to survival of megakaryocytes and proplatelet formation. Serotonin also stimulated TPO released from MSCs, which indirectly promoted megakaryopoiesis. In present studies, we have demonstrated a positive “feed-back” control loop between MK-derived granule- serotonin and megakaryocytopoiesis. These findings improved our knowledge on megakaryocytopoiesis regulation and provided new clues on identifying novel thrombopoietic agents. It also deepened our understandings on how TPO production is regulated. Disclosures: No relevant conflicts of interest to declare.

Actin reorganization and proplatelet formation in murine megakaryocytes: the role of protein kinase Cα

Blood ◽  
2001 ◽  
Vol 97 (1) ◽  
pp. 154-161 ◽  
Author(s):  
Ponlapat Rojnuckarin ◽  
Kenneth Kaushansky
Keyword(s):  
Protein Kinase ◽  
Actin Polymerization ◽  
Map Kinases ◽  
Molecular Mechanisms ◽  
Marrow Cell ◽  
Actin Dynamics ◽  
Actin Reorganization ◽  
Murine Bone Marrow ◽  
Proplatelet Formation

Abstract With the recent cloning and characterization of thrombopoietin, appreciation of the molecular events surrounding megakaryocyte (MK) development is growing. However, the final stages of platelet formation are less well understood. Platelet production occurs after the formation of MK proplatelet processes. In a study to explore the molecular mechanisms underlying this process, mature MKs isolated from suspension murine bone marrow cell cultures were induced to form proplatelets by exposure to plasma, and the role of various cell-signaling pathways was assessed. The results showed that (1) bis-indolylmaleimide I, which blocks protein kinase C (PKC) activation; (2) down-modulation of conventional or novel classes of PKC by phorbol myristate acetate; and (3) ribozymes specific for PKCα each inhibited proplatelet formation. Inhibition of several MAP kinases, PI3 kinase, or protein kinase A failed to affect MK proplatelet formation. To gain further insights into the function of PKCα in proplatelet formation, its subcellular localization was investigated. In cultures containing active proplatelet formation, cytoplasmic polymerized actin was highly aggregated, its subcellular distribution was reorganized, and PKCα colocalized with the cellular actin aggregates. A number of MK manipulations, including blockade of integrin signaling with a disintegrin or inhibition of actin polymerization with cytochalasin D, interrupted actin reorganization, PKC relocalization, and proplatelet formation. These findings suggest an important role for PKCα in proplatelet development and suggest that it acts by altering actin dynamics in proplatelet-forming MKs. Identification of the upstream and downstream pathways involved in proplatelet formation should provide greater insights into thrombopoiesis, potentially allowing pharmacologic manipulation of the process.

scholarly journals Elevated FANCA Expression Marks a Worse Prognosis in Chronic Lymphocytic Leukemia. Evidence of a New Role of FANCA in the Stability of p53 By a Neddylation-Related Mechanism

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 5541-5541
Author(s):  
Carlos Pipaon ◽  
Sara Bravo Navas ◽  
Iñigo Romon ◽  
Eulogio Conde ◽  
Lucrecia Yanez San Segundo
Keyword(s):  
Cell Cycle ◽  
Bone Marrow ◽  
Chronic Lymphocytic Leukemia ◽  
Molecular Mechanisms ◽  
Target Genes ◽  
Conflicts Of Interest ◽  
Clinical Manifestations ◽  
Lymphocytic Leukemia ◽  
Worse Prognosis

Abstract Background: Chronic lymphocytic leukemia (CLL) is the most common hematological malignancy in western countries. It is characterized by a failure in the mechanisms of apoptosis that leads to an accumulation of mature B cells in peripheral blood, bone marrow and lymphoid organs. With exceptions, CLL is considered incurable and some patients show a worse prognosis related to the expression of certain cytogenetic or molecular markers such as p53 dysfunction (17p13 deletion or TP53 inactivation), 11q23 deletion, unmutated IgVH and the presence of a complex karyotype. FANC proteins have been related to chromosomal instability and alterations in the mechanisms of p53 activation, control of cell cycle and apoptosis. Germline mutations in any of the 20 FANC genes known so far generates Fanconi Anemia, a syndrome characterized by a extraordinary proneness to cell apoptosis leading to a progressive bone marrow aplasia and pancytopenia. Some FANCA proteins aggregate in response to DNA damage forming the FANCcore complex that mediates the monoubiquitination of FANCD2 and FANCI, thus activating the mechanism to repair stalled replication forks. In addition, individual FANC proteins have been involved in functions out of the FANCcore. This is the case of FANCA, that has recently been involved in the neddylation of CXCR5 and beta-2-microglobulin, processes reported to be altered in CLL. Hypothesis: Given the fragmentary information connecting FANC proteins with cellular processes altered in CLL, like apoptosis, cell cycle or neddylation, we hypothesize a role of these proteins in the diagnosis or prognosis of CLL. Methods: We analyzed the expression of 5 FANC genes in a cohort of 160 patients of CLL by quantitative RT-PCR. Statistical analysis were carried out to establish relations between FANC genes deregulation and clinical manifestations. We also investigated the role of the FANCA gene in primary circulating B-lymphocytes from CLL patients by either gain- or loss-of-function approaches. Results: Our data identified a group of CLL patients with high expression of FANCA in peripheral B-CLL cells, and we stablished its relationship with the deletion of 11q23 and a worse prognosis. When we investigated the molecular mechanisms of this bad prognosis, we observed a reduction in the mRNA expression of two p53 target genes, p21 and ∆Np73, in CLL primary cells transfected with FANCA. Luciferase studies demonstrated an impairment of p53 function by FANCA. Moreover, we obtained evidence of a cooperation between FANCA and the NEDD8-interacting protein NUB1L in the destabilization of p53. Conclusion: These results point to FANCA as a bad prognosis marker in CLL and unveils a new role of this protein aside from its role in the FA-BRCA DNA repair pathway. Disclosures No relevant conflicts of interest to declare.

Serotonin and Its Metabolism Enhances Megakaryopoiesis and Proplatelet Formation

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 4753-4753
Author(s):  
Jie yu Ye ◽  
Fan yi Meng ◽  
Qianli Jiang ◽  
Su yi Li ◽  
En yu Liang ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Conflicts Of Interest ◽  
Signal Pathway ◽  
Mice Model ◽  
Actin Reorganization ◽  
Cytoskeleton Reorganization ◽  
Colony Forming Units ◽  
Proplatelet Formation ◽  
5Ht2 Receptor ◽  
Receptor Inhibitor

Serotonin (5-HT) has been recently identified as a novel growth factor. We previously demonstrated that 5-HT enhances murine megakaryopoiesis via 5-HT2 receptors and has promotor effect on hematopoiesis(Yang M et al, Stem Cells, 2007). However, the molecular mechanism remains under explored. In the terminal stage of mammalian megakaryocyte development, platelets are released from proplatelet protruding from megakaryocytes via cytoskeleton reorganization. 5-HT is shown to modulate cell migration and remolding by activating cytoskeleton reorganization, but the effects of 5-HT on proplatelet formation have not been investigated. Our results showed that 5-HT significantly promoted human CFU-MK formation and reduced apoptosis on human megakaryocytes through phosphorylation of Akt. These effects were attenuated by addition of ketanserin, a 5HT2 receptor inhibitor. 5-HT also stimulated proplatelet formation through activating the p-Erk1/2 expression and F-actin reorganization. Melatonin, the metabolism of 5-HT, promoted the recovery of platelets and the formation of bone marrow colony forming units in irradiated mice. Our findings suggested that 5-HT and melatonin plays an important role in human megakaryopoiesis. Interaction of 5-HT and 5-HTR2B induced downstream activation of PI3-k/Akt signal pathway leading to human MK cell proliferation. In addition, activation of 5-HTR2B also induced Erk1/2 phosphorylation, which then promoted cytoskeleton reorganization and subsequent proplatelet formation. We also proved that melatonin exerts a protective effect on MK and platelets in the irradiation mice model. Disclosures: No relevant conflicts of interest to declare.

Aberrant Bone Marrow Perivascular Niches are Involved in Multiple Myeloma Progression: Role of Notch–Delta Pathway.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 2800-2800
Author(s):  
Sara Lamorte ◽  
Marta Costa ◽  
Giovanni Camussi ◽  
Sergio Dias
Keyword(s):  
Multiple Myeloma ◽  
Bone Marrow ◽  
Conflicts Of Interest ◽  
Annexin V ◽  
Pcr Analysis ◽  
Adherent Cells ◽  
Feeder Layer ◽  
Hematopoietic Stem ◽  
Lower Chamber

Abstract Abstract 2800 Poster Board II-776 Bone marrow (BM) angiogenesis is implicated in Multiple Myeloma (MM) progression. In this study, we tested the hypothesis that MM progression occurs when aberrant BM perivascular niches are established. We isolated BM endothelial cells derived from MM patients (MM-BMECs) from BM aspirates using anti-CD31Ab coupled to magnetic beads. FACS analysis showed that of all the cell lines isolated were endothelial: more than 95% expressed Ulex Europaeus Agglutinin-1 and Factor VIII and were negative for monocyte-macrophage (CD14) and plasma cell markers (CD38). To test the hypothesis that in MM patients BM perivascular niches are aberrant we analyzed how MM-BMECs modulate hematopoietic stem cells (HSCs) properties using a BM microvascular endothelial cell line isolated from a healthy donor (BMECs) as control. We co-cultured cord blood cells CD34+ HSCs in the presence of MM-BMECs or BMECs feeder layer and we analyzed the ability of MM-BMECs compared with BMECs to modulate HSCs adhesion, chemotaxis and apoptosis. The results show that MM-BMECs promote CD34+ HSCs adhesion, recruitment and protect them from apoptosis. In detail, we showed that after 24h of co-culture there was a significant increase in the number of adherent HSCs on MM-BMECs than on BMECs: 43±9% versus 25±6%. Moreover, when HSCs were cultured for 48 hours in 1% of serum in the presence of MM-BMECs they were less sensitive to apoptosis (9±11% of Annexin V+ cells) than HSCs cultured in the presence of BMECs (14±1% of Annexin V+ cells) or without a feeder layer, as control (17±3% of Annexin V+ cells). For the migration assay a transwell chamber system, in which the upper and the lower chambers were separated by 5-μm pore-size filter, was used. BMECs, MM-BMECs or nothing was plated in the lower chamber, while HSCs were seeded into the upper chamber. Both chambers were loaded with unsupplemented EBM-2 plus 2% of serum. Cell migration was studied over a 6-8 hours period and evaluated as number of cells migrated into the lower chamber. The results showed a significantly greater migration of HSCs in the presence of MM-BMECs than BMECs: 12±2% versus 5±1% of migrated cells. Taken together, these data showed that MM-BMECs promoted HSCs migration, adhesion and survival. Next we evaluated how MM-BMECs modulate the hemopoiesis recovery after irradiation in a NOD-SCID mouse model. When injected into sub-lethally irradiated (3 Grey) NOD-SCID mice MM-BMECs were detected in the BM integrated within the murine BM vessels and promoted hematopoietic recovery. In detail, MM-BMECs provided signals favoring the commitment towards lymphoid lineage. In fact, 7 days after injection, the BM of mice injected with MM-BMECs showed an increase in the percentage of lymphoblast (2.7%), compared with mice injected with BMECs or PBS, as control (respectively, 1.5% and 1.4%); followed, 14 days after injection, by a significant increase in the percentage of peripheral blood lymphocytes in mice injected with MM-BMECs (75±6%) versus mice injected with BMECS and PBS (respectively 60±0.5% and 47±7%). Since MM is a plasma cells disorder and the Notch-Delta pathway has been shown to play a central role in regulating HSCs properties, including the decisions of HSCs to undergo T- or B-cell differentiation, we investigated the involvement of this pathway in MM-BMECs and HSCs interaction. As determined by FACS and RT-PCR analysis, MM-BMECs, compared to BMECs, over expressed Delta-like Notch ligand 4 (DII4). Thus, we investigated the role of DII4 in the MM-BMECs/BMECs-HSCs adhesion. The first results showed that the expression of DII4 by MM-BMECs is necessary to promote HSCs adhesion. In fact, using a blocking antibody against DII4 (AbαDII4) at 50ug/ml there was an impairment in HSCs adhesion to MM-BMECs (43±9% versus 24±2% of adherent cells without and with AbαDII4 treatment), but not on BMECs (25±6% versus 26±1.4% of adherent cells without and with AbαDII4 treatment). Ongoing experiments are focusing on the role of DII4 in the modulation of HSCs proliferation, protection against apoptosis and in vitro-in vivo B commitment by MM-BMECs. Taken together, all these data suggest that BMECs in MM may function as “aberrant perivascular niches”, modulating HSCs properties. This aberrant phenotype could be due to an alteration of the Notch-Delta pathway in BMECs that favors malignant clonal growth by protecting it from apoptosis, favoring migration, adhesion and providing self-renewing and/or proliferative cues. Disclosures: No relevant conflicts of interest to declare.

Desialylated Platelets Are Cleared From the Circulation by the Hepatic Asialoglycoprotein Receptor,

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 3257-3257
Author(s):  
Renata Grozovsky ◽  
Silvia Giannini ◽  
Karin M. Hoffmeister
Keyword(s):  
Bone Marrow ◽  
Conflicts Of Interest ◽  
Fold Increase ◽  
Asialoglycoprotein Receptor ◽  
Regulatory Mechanisms ◽  
Wild Type ◽  
Cell Counts ◽  
Blood Cell Counts ◽  
Terminal Galactose

Abstract Abstract 3257 The regulatory mechanisms of platelet homeostasis remain elusive. We investigated here the role of hepatic asialoglycoprotein receptor (a.k.a. Ashwell-Morell receptor) in platelet clearance. Mice lacking the hepatic asialoglycoprotein receptor Asgpr2 subunit had increased platelet survivals (T1/2 = 49.5±2h) when compared to wild type (WT, T1/2 = 31±4h) mice. Consequently, Asgpr2−/− mice had platelet counts increased by ∼20%, compared to WT, with increased terminal galactose exposure, as demonstrated using the galactose specific lectin RCA1. Bone marrow and spleen megakaryocyte numbers were reduced by ∼15% and ∼20% in Asgpr2−/− mice, compared to WT mice. Sialidase (NA, Clostidium perfringens, 50mU/mice) maximally desialylated circulating platelets when injected intravenously, as evidenced by increased RCA1 binding. Sialidase injection resulted in a ∼60% depletion of circulating platelets after 24h in Asgpr2−/− mice, compared to >90% in WT mice, indicating that desialylated platelets were partially removed by Asgpr1/2. In contrast to platelets, red blood cell counts were unaffected by sialidase treatment. Sialidase injection for 72h resulted in a 2.3-fold and 1.2-fold increase in megakaryocyte numbers in the spleen and bone marrow of WT mice, respectively, but not in Asgpr2−/− mice. In contrast to sialidase treatment, injections of rabbit anti-mouse platelet serum (RAMPS) depleted >95% of circulating platelets and increased by 70% bone marrow, but not spleen MK numbers in both WT and Asgpr2−/− mice. The data shows that removal of desialylated, i.e, senescent, platelets by the hepatic Ashwell-Morell receptor differs to that of antibody-mediated platelet clearance. Disclosures: No relevant conflicts of interest to declare.

Non-Canonical NF-Kb Signaling Regulates Hematopoietic Stem Cell Self-Renewal and Microenvironment Interactions

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 859-859 ◽  
Author(s):  
Chen Zhao ◽  
Yan Xiu ◽  
John M Ashton ◽  
Lianping Xing ◽  
Yoshikazu Morita ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Bone Marrow Cells ◽  
Conflicts Of Interest ◽  
Wild Type ◽  
Double Knockout ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Physiological Processes ◽  
Marrow Cells

Abstract Abstract 859 RelB and NF-kB2 are the main effectors of NF-kB non-canonical signaling and play critical roles in many physiological processes. However, their role in hematopoietic stem/progenitor cell (HSPC) maintenance has not been characterized. To investigate this, we generated RelB/NF-kB2 double-knockout (dKO) mice and found that dKO HSPCs have profoundly impaired engraftment and self-renewal activity after transplantation into wild-type recipients. Transplantation of wild-type bone marrow cells into dKO mice to assess the role of the dKO microenvironment showed that wild-type HSPCs cycled more rapidly, were more abundant, and had developmental aberrancies: increased myeloid and decreased lymphoid lineages, similar to dKO HSPCs. Notably, when these wild-type cells were returned to normal hosts, these phenotypic changes were reversed, indicating a potent but transient phenotype conferred by the dKO microenvironment. However, dKO bone marrow stromal cell numbers were reduced, and bone-lining niche cells supported less HSPC expansion than controls. Further, increased dKO HSPC proliferation was associated with impaired expression of niche adhesion molecules by bone-lining cells and increased inflammatory cytokine expression by bone marrow cells. Thus, RelB/NF-kB2 signaling positively and intrinsically regulates HSPC self-renewal and maintains stromal/osteoblastic niches and negatively and extrinsically regulates HSPC expansion and lineage commitment through the marrow microenvironment. Disclosures: No relevant conflicts of interest to declare.

PU.1 and p53 Double Mutant Mice Develop Aggressive AML with Dysplastic Features

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 769-769
Author(s):  
Petra Vlckova ◽  
Libor Stanek ◽  
Pavel Burda ◽  
Karin Vargova ◽  
Filipp Savvulidi ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Transcription Factor ◽  
Progenitor Cells ◽  
Double Mutant ◽  
Molecular Mechanisms ◽  
Conflicts Of Interest ◽  
Regulatory Element ◽  
Tumour Suppressor ◽  
Mutant Mice ◽  
Stem And Progenitor Cells

Abstract Abstract 769 Introduction: Downregulation of tumour suppressor transcription factor PU.1 in haematopoietic stem and progenitor cells represents primary underlying mechanism for the development of acute myeloid leukaemia (AML) in mice with homozygous deletion of the upstream regulatory element (URE) of PU.1 gene. Human AML often display differences in aggressiveness that are associated with mutations of a well known tumour suppressor p53. We produced murine model carrying mutations of p53 and URE that develops highly aggressive AML and focused on molecular mechanisms that are responsible for AML aggressiveness. Mouse models: PU.1ure/ure (Rosenbauer F, et al. 2004) and p53−/− (Jacks T, et al. 1994) mice were used. Conditional deletion of the URE leads to downregulation of PU.1 and is marked by clonal accumulation of myeloid c-Kit+Mac-1low Gr-1low blast cells within bone marrow, spleen, and peripheral blood mirrored by lower numbers of lymphoid and erythroid cells. AML development in PU.1ure/ure mice involves a preleukaemic phase (at 2–3 months) marked by proliferation of myeloid c-Kit+Gr-1+ cells and splenomegaly. Interestingly, p53−/−mice do not develop AML, instead loss of p53 predisposes mice to solid tumours, mostly lymphomas, by 6 months of age. Results: Deletion of TP53 in the PU.1ure/ure mice (PU.1ure/ure p53−/−) results in more aggressive AML with significantly shortened overall survival, prominent hepatosplenomegaly and cachexia (wasting syndrome). Mild differences in cell surface phenotype of bone marrow derived cells were observed between PU.1ure/ure and PU.1ure/ure p53−/− mice by flow cytometry (these included: blasts expansion and lymphopenia). Next, the PU.1 expression was determined in all genotypes at progenitor and stem cell levels. PU.1 mRNA level in more aggressive PU.1ure/ure p53−/− murine AML is decreased in the entire c-Kit+tumour cell population compared to AML in PU.1ure/ure mice including haematopoietic stem and progenitor cells (HSPCs). Correspondingly to RNA level, in the PU.1ure/ure progenitors the PU.1 protein was decreased compared to p53−/− progenitors and is yet further reduced in the PU.1ure/ure p53−/− c-Kit+ Mac1+progenitors. p53−/− progenitors express similar level of PU.1 as wild type progenitors indicating that despite p53 can bind DNA as a transcription factor, it does not regulate PU.1 level directly. In addition to URE deletion we searched for other mechanisms that control PU.1 levels and found that PU.1-inhibiting microRNA miR-155 gene display altered chromatin structure and expression of both pri-miR-155 as well as its spliced mature form in the AML of PU.1ure/ure and (to higher extent in) PU.1ure/ure p53−/− murine progenitors. Upregulation of miR-155 coincides with upregulation of the Mir155hg activators: Myc and Myb. Finally, upon inhibition of either Myb or miR-155 in vitro the AML progenitors restore PU.1 levels and lose leukaemic cell growth. Conclusion: In summary, PU.1 and p53 double mutant mice develop aggressive AML with dysplastic features. Defective control of PU.1 levels in PU.1ure/ure and PU.1ure/ure p53−/−AML involves miR-155. Lastly, restored PU.1 level and cell differentiation capacity are achieved by inhibiting either Myb or miR-155 in the PU.1ure/ure p53−/− progenitors. (Grant support: P305/12/1033, UNCE 204021, PRVOUK-P24/LF1/3, SVV-2012-264507, P301/12/P380. MK was sponsored by GAUK 251070 45410, 251135 82210) Disclosures: No relevant conflicts of interest to declare.

Role Of Long Pentraxin 3 (PTX3) In Wound Closure Induced By Bone Marrow-Derived Mesenchymal Stromal Cells

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 1220-1220
Author(s):  
Claudia Cappuzzello ◽  
Andrea Doni ◽  
Erica Dander ◽  
Fabio Pasqualini ◽  
Manuela Nebuloni ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Mesenchymal Stromal Cells ◽  
Stromal Cells ◽  
Wound Closure ◽  
Conflicts Of Interest ◽  
Histological Evaluation ◽  
Pentraxin 3 ◽  
Alizarin Red ◽  
Matrix Deposition

Abstract Although several studies have shown the capacity of mesenchymal stromal cells (MSCs) to repair and regenerate different tissues, the mechanisms underlying these processes are not understood. Long Pentraxin 3 (PTX3) is a multifunctional protein produced by MSCs and other cell subsets upon activation with inflammatory cytokines. PTX3 is involved in innate immunity, inflammation and extracellular matrix deposition. In the present study we analyzed the potential role of PTX3 in wound repair process induced by MSCs. PTX3 knockout MSCs (PTX3-/-MSCs) were collected from bone marrow of PTX3-/- mice. After 3-5 culture passages the expression of surface markers was analyzed by flow cytometry and their osteogenic and adipogenic differentiation capacity was detected by alizarin red O and oil red S staining, respectively. The ability of PTX3-/-MSCs to abrogate T cell proliferation was evaluated by co-culturing MSCs and PBMCs previously activated with Phytohaemagglutinin. Finally, equal number of both PTX3-/-MSCs and wild type (WT) MSCs were implanted into excisional wounds created by a biopsy punch on the back of allogenic WT and PTX3-/- mice. Wound area was measured up to 14 day and calculated using an image analysis program. The wound specimens were collected at 2, 7 and 14 days and processed for histological analysis. We demonstrated that PTX3-/-MSCs, similarly to WT MSCs, displayed typical fibroblastoid morphology, they expressed common MSC markers and were able to differentiate into adipocytes and osteoblasts. In addition, they drastically decreased the mitogen-induced proliferation of lymphocyte. Importantly, in a mouse model of wound healing, PTX3-/- MSCs showed a highly significant defect in wound closure compared to WT MSCs at each time point. Histological evaluation of skin samples treated with PTX3-/- MSCs showed a reduction of the granulation tissue and a significant increase of neutrophils (GR-1+) in the wound bed. Moreover, wounds treated with PTX3-/- MSCs were characterized by an excessive accumulation of fibrin at the 2nd day after injury. Accordingly, PTX3-/- MSCs showed a defective ability to degrade the fibrin matrix in vitro. Finally, PTX3-/- MSCs failed to close the ulcers in PTX3-/- mice. In conclusion, we demonstrated that PTX3 deficiency does not alter the phenotype and the capacity of MSCs to differentiate into mesengetic lineages; however, the production of PTX3 represents an essential requirement for MSC ability of enhancing tissue repair. Disclosures: No relevant conflicts of interest to declare.

CD44v6 Is Required For In Vivo Tumorigenesis Of Human AML and MM Cells: Role Of Microenvironmental Signals and Therapeutic Implications

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 605-605 ◽  
Author(s):  
Benedetta Nicolis di Robilant ◽  
Monica Casucci ◽  
Laura Falcone ◽  
Barbara Camisa ◽  
Bernhard Gentner ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Tumor Cells ◽  
Conflicts Of Interest ◽  
Human Leukemia ◽  
Vegf Receptor ◽  
Durable Response ◽  
Wide Range ◽  
Cd44v6 Expression

Abstract Background Targeting the interactions between tumor cells and their microenvironment is an exciting new frontier in cancer therapy. The biology of acute myeloid leukemia (AML) and multiple myeloma (MM) is characterized by addiction to specific signals uniquely provided within the bone marrow (BM), where tumor cells preferentially home and locally thrive. The hyaluronate receptor CD44 was shown to be required for retroviral-induced leukemogeneis in syngeneic mouse models. Conversely, CD44 mAbs interfere with human leukemia initiation in immunocompromised mice by inhibiting leukemia stem cell homing to the bone marrow (BM). The therapeutic potential of CD44 mAbs is also under clinical investigation in humans. Much less is known on the role of the differently spliced CD44 variant isoforms. The expression of exon 6 (CD44v6) conveys additional properties to standard CD44, like binding to osteopontin and cooperation with different tyrosine kinase receptors (RTKs), like VEGF receptor type II and c-Met. Interestingly, CD44v6 is the most abundantly expressed CD44 isoform in both AML and MM, where it correlates with a bad prognosis. Since CD44v6 expression is much more tumor-restricted than CD44, targeting this isoform may have a better efficacy/toxicity profile than targeting the standard molecule. Aim To preclinically validate CD44v6 as a therapeutic target in AML and MM Results By FACS analysis and RT-qPCR, we established CD44v6 over expression in a relevant fraction of leukemic blasts from AML pts (15/25, 60%) with preference for the M4-5 FAB subtypes, and in the majority of malignant plasmacells from MM pts (13/15, 87%). CD44v6 was also over expressed on THP-1, Kasumi and U937 human AML cells, and on MM.1S, XG-6 and XG-7 MM cells. To address the specific role of CD44v6 in BM homing, we pretreated MM1.S cells with either a CD44 mAb (SFF-2) or a CD44v6 mAb (VFF-18) and infused them i.v. in NSG mice. Unexpectedly, while SFF-2 almost completely inhibited early (18hrs) homing to the BM compared with an irrelevant mAb, VFF-18 had no effect. To rule out confounding variables associated with specific mAb clones, we silenced CD44v6 expression in MM1.S cells by lentiviral-mediated shRNA transduction and confirmed no difference in BM homing compared with control LV-transduced cells. Longer follow-ups (4-6 weeks) however revealed that, despite unaltered rates of in vitro proliferation, CD44v6-silenced MM1.S cells were severely hampered in their tumorigenic capacity in vivo (P<0.001). These results were confirmed by using THP-1 cells (P<0.001) and primary leukemic blasts (P<0.01). Hypothesizing that CD44v6 may be crucial for in vivo tumorigenesis by cooperating with RTKs, we set-up a co-culture system with BM-derived mesenchymal stromal cells (MSCs), which are producers of VEGF and the c-Met ligand HGF. MSCs protected a wide range of tumor cells, including primary leukemic blasts, from spontaneous apoptosis (P<0.05) and from apoptosis induced by Ara-C or daunorubicin (P<0.01), or bortezomib in the case of MM cells (P<0.001). Comparable results were obtained by using MSC supernatants, hinting to a causative soluble factor, which was neither VEGF nor HGF, as demonstrated by inhibition experiments with bevacizumab and crizotinib, respectively. Noteworthy, MSCs or their supernatants prompted a significant up-regulation of CD44v6 expression levels (P<0.01). Most importantly, preventing CD44v6 up-regulation on tumor cells by shRNA silencing restored their sensitivity to spontaneous and drug-induced apoptosis (P<0.01). Conclusions These results clearly indicate that CD44v6 is dispensable for BM homing, but responsible for AML and MM addiction to microenvironmental signals. Combining CD44v6 targeting with cytotoxic chemotherapy might interfere with this vicious circle and result in higher and/or more durable response rates. Disclosures: No relevant conflicts of interest to declare.

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