Scientific Resources

Chimeric antigen receptor (CAR) therapy targeting CD19 has yielded remarkable outcomes in patients with acute lymphoblastic leukemia. To identify potential CAR targets in acute myeloid leukemia (AML),we probed the AML surfaceome for overexpressed molecules with tolerable systemic expression. We integrated large transcriptomics and proteomics datasets from malignant and normal tissues,and developed an algorithm to identify potential targets expressed in leukemia stem cells,but not in normal CD34+CD38- hematopoietic cells,T cells,or vital tissues. As these investigations did not uncover candidate targets with a profile as favorable as CD19,we developed a generalizable combinatorial targeting strategy fulfilling stringent efficacy and safety criteria. Our findings indicate that several target pairings hold great promise for CAR therapy of AML. View Publication

Many acute and chronic anaemias,including haemolysis,sepsis and genetic bone marrow failure diseases such as Diamond-Blackfan anaemia,are not treatable with erythropoietin (Epo),because the colony-forming unit erythroid progenitors (CFU-Es) that respond to Epo are either too few in number or are not sensitive enough to Epo to maintain sufficient red blood cell production. Treatment of these anaemias requires a drug that acts at an earlier stage of red cell formation and enhances the formation of Epo-sensitive CFU-E progenitors. Recently,we showed that glucocorticoids specifically stimulate self-renewal of an early erythroid progenitor,burst-forming unit erythroid (BFU-E),and increase the production of terminally differentiated erythroid cells. Here we show that activation of the peroxisome proliferator-activated receptor α (PPAR-α) by the PPAR-α agonists GW7647 and fenofibrate synergizes with the glucocorticoid receptor (GR) to promote BFU-E self-renewal. Over time these agonists greatly increase production of mature red blood cells in cultures of both mouse fetal liver BFU-Es and mobilized human adult CD34(+) peripheral blood progenitors,with a new and effective culture system being used for the human cells that generates normal enucleated reticulocytes. Although Ppara(-/-) mice show no haematological difference from wild-type mice in both normal and phenylhydrazine (PHZ)-induced stress erythropoiesis,PPAR-α agonists facilitate recovery of wild-type but not Ppara(-/-) mice from PHZ-induced acute haemolytic anaemia. We also show that PPAR-α alleviates anaemia in a mouse model of chronic anaemia. Finally,both in control and corticosteroid-treated BFU-E cells,PPAR-α co-occupies many chromatin sites with GR; when activated by PPAR-α agonists,additional PPAR-α is recruited to GR-adjacent sites and presumably facilitates GR-dependent BFU-E self-renewal. Our discovery of the role of PPAR-α agonists in stimulating self-renewal of early erythroid progenitor cells suggests that the clinically tested PPAR-α agonists we used may improve the efficacy of corticosteroids in treating Epo-resistant anaemias. View Publication

Gaucher disease is caused by an inherited deficiency of glucocerebrosidase that manifests with storage of glycolipids in lysosomes,particularly in macrophages. Available cell lines modeling Gaucher disease do not demonstrate lysosomal storage of glycolipids; therefore,we set out to develop two macrophage models of Gaucher disease that exhibit appropriate substrate accumulation. We used these cellular models both to investigate altered macrophage biology in Gaucher disease and to evaluate candidate drugs for its treatment. We generated and characterized monocyte-derived macrophages from 20 patients carrying different Gaucher disease mutations. In addition,we created induced pluripotent stem cell (iPSC)-derived macrophages from five fibroblast lines taken from patients with type 1 or type 2 Gaucher disease. Macrophages derived from patient monocytes or iPSCs showed reduced glucocerebrosidase activity and increased storage of glucocerebroside and glucosylsphingosine in lysosomes. These macrophages showed efficient phagocytosis of bacteria but reduced production of intracellular reactive oxygen species and impaired chemotaxis. The disease phenotype was reversed with a noninhibitory small-molecule chaperone drug that enhanced glucocerebrosidase activity in the macrophages,reduced glycolipid storage,and normalized chemotaxis and production of reactive oxygen species. Macrophages differentiated from patient monocytes or patient-derived iPSCs provide cellular models that can be used to investigate disease pathogenesis and facilitate drug development. View Publication

Chemotherapy is the most common way to treat malignancies,but myelosuppression,one of its common side-effects,is a formidable problem. The present study described the protective role of dammarane sapogenins (DS),an active fraction from oriental ginseng,on myelosuppression induced by cyclophosphamide (CP) in mice. DS was orally administered at different dosages (37.5,75,and 150 mg/kg) for 10 d after CP administration (200 mg/kg intraperitoneally). The results showed that DS increased the number of white blood cells (WBC) on day 3 and day 7 (P textless 0.05),such that WBC levels were increased by 105.7 ± 29.5% at 75 mg/kg of DS on day 3 (P textless 0.05,compared with the CP group). Similar results were observed in red blood cells and platelets in DS-treated groups. The colony-forming assay demonstrated that the depressed numbers of CFU-GM (colony-forming unit-granulocyte and macrophage),CFU-E (colony-forming unit-erythroid),BFU-E (burst-forming unit-erythroid),CFU-Meg (colony-forming unit-megakaryocyte) and CFU-GEMM (colony-forming unit-granulocyte,-erythrocyte,-monocyte and -megakaryocyte) induced by CP were significantly reversed after DS treatment. Moreover,the ameliorative effect of DS on myelosuppression was also observed in the femur by hematoxylin/eosin staining. In DS-treated groups,ConA-induced splenocyte proliferation was enhanced significantly at all the doses (37.5,75,150 mg/kg) on day 3 at the rate of 50.3 ± 8.0%,77.6 ± 8.5% and 44.5 ± 8.4%,respectively,while lipopolysaccharide-induced proliferation was increased mainly on day 7 (P textless 0.01),with an increased rate of 39.8 ± 5.6%,34.9 ± 6.6% and 38.3 ± 7.3%,respectively. The thymus index was also markedly increased by 70.4% and 36.6% at 75 mg/kg on days 3 and 7,respectively,as compared with the CP group. In summary,DS has a protective function against CP-induced myelosuppression. Its mechanism might be related to stimulating hematopoiesis recovery,as well as enhancing the immunological function. View Publication

Pim kinases are Ser/Thr kinases with multiple substrates that affect survival pathways. These proteins are overexpressed in acute myeloid leukemia (AML) blasts and we hypothesized that Pim kinase inhibition would affect AML cell survival. Imidazo[1,2-b]pyridazine compound,SGI-1776 inhibits Pim-1,Pim-2 and Pim-3,and was evaluated in AML-cell line,-xenograft model,and -primary blasts. Treatment of AML cells with SGI-1776 results in a concentration-dependent induction of apoptosis and we investigated its effect on Pim kinase functions. Phosphorylation of traditional Pim kinase targets,c-Myc(Ser62) and 4E-BP1 (Thr36/Thr47),were both decreased in actively cycling AML cell lines MV-4-11,MOLM-13 and OCI-AML-3. Levels of antiapoptotic proteins Bcl-2,Bcl-x(L),XIAP,and proapoptotic Bak and Bax were unchanged; however,a significant reduction in Mcl-1 was observed. This was correlated with inhibition of global RNA and protein synthesis and MCL-1 transcript decline after SGI-1776 treatment. These data suggest that SGI-1776 mechanism in AML involves Mcl-1 protein reduction. Consistent with cell line data,xenograft model studies with mice bearing MV-4-11 tumors showed efficacy with SGI-1776. Importantly,SGI-1776 was also cytotoxic in AML primary cells,irrespective of FLT3 mutation status and resulted in Mcl-1 protein decline. Pim kinase inhibition may be a new strategy for AML treatment. View Publication

Hematopoietic stem cells (HSC) can be harmed by disease,chemotherapy,radiation,and normal aging. We show in this study that damage also occurs in mice repeatedly treated with very low doses of LPS. Overall health of the animals was good,and there were relatively minor changes in marrow hematopoietic progenitors. However,HSC were unable to maintain quiescence,and transplantation revealed them to be myeloid skewed. Moreover,HSC from treated mice were not sustained in serial transplants and produced lymphoid progenitors with low levels of the E47 transcription factor. This phenomenon was previously seen in normal aging. Screening identified mAbs that resolve HSC subsets,and relative proportions of these HSC changed with age and/or chronic LPS treatment. For example,minor CD150(Hi)CD48(-) populations lacking CD86 or CD18 expanded. Simultaneous loss of CD150(Lo/-)CD48(-) HSC and gain of the normally rare subsets,in parallel with diminished transplantation potential,would be consistent with age- or TLR-related injury. In contrast,HSC in old mice differed from those in LPS-treated animals with respect to VCAM-1 or CD41 expression and lacked proliferation abnormalities. HSC can be exposed to endogenous and pathogen-derived TLR ligands during persistent low-grade infections. This stimulation might contribute in part to HSC senescence and ultimately compromise immunity. View Publication

Erythropoietin (Epo) has been used in the treatment of anemia resulting from numerous etiologies,including renal disease and cancer. However,its effects are controversial and the expression pattern of the Epo receptor (Epo-R) is debated. Using in vivo lineage tracing,we document that within the hematopoietic and mesenchymal lineage,expression of Epo-R is essentially restricted to erythroid lineage cells. As expected,adult mice treated with a clinically relevant dose of Epo had expanded erythropoiesis because of amplification of committed erythroid precursors. Surprisingly,we also found that Epo induced a rapid 26% loss of the trabecular bone volume and impaired B-lymphopoiesis within the bone marrow microenvironment. Despite the loss of trabecular bone,hematopoietic stem cell populations were unaffected. Inhibition of the osteoclast activity with bisphosphonate therapy blocked the Epo-induced bone loss. Intriguingly,bisphosphonate treatment also reduced the magnitude of the erythroid response to Epo. These data demonstrate a previously unrecognized in vivo regulatory network coordinating erythropoiesis,B-lymphopoiesis,and skeletal homeostasis. Importantly,these findings may be relevant to the clinical application of Epo. View Publication

PURPOSE: Genz-644282 [8,9-dimethoxy-5-(2-N-methylaminoethyl)-2,3-methylenedioxy-5H-dibenzo[c,h][1,6]naphthyridin-6-one] has emerged as a promising candidate for antitumor agents. This report describes the bone marrow colony-forming unit,granulocyte macrophage (CFU-GM) and tumor cell CFU activity of topoisomerase I (Top1) inhibitors,such as Genz-644282,topotecan,irinotecan/SN-38,and ARC-111,and examines their activity in several human tumor xenograft models. EXPERIMENTAL DESIGN: Colony-forming assays were conducted with mouse and human bone marrow and eight human tumor cell lines. In addition,29 human tumor cell lines representing a range of histology and potential resistance mechanisms were assayed for sensitivity to Genz-644282 in a 72-hour exposure assay. The efficacy of Genz-644282 was compared with standard anticancer drugs (i.e.,irinotecan,docetaxel,and dacarbazine) in human tumor xenografts of colon cancer,renal cell carcinoma,non-small cell lung cancer,and melanoma. RESULTS: Human bone marrow CFU-GM was more sensitive to the Top1 inhibitors than was mouse bone marrow CFU-GM. The ratio of mouse to human IC(90) values was more than 10 for the camptothecins and less than 10 for Genz-644282,which had more potency as a cytotoxic agent toward human tumor cells in culture than the camptothecins in the colony-forming and 72-hour proliferation assays. Genz-644282 has superior or equal antitumor activity in the human tumor xenografts than the standard drug comparators. CONCLUSIONS: On the basis of preclinical activity and safety,Genz-644282 was selected for development and is currently undergoing phase 1 clinical trial. View Publication

Imatinib mesylate has shown remarkable efficacy in the treatment of patients in the chronic phase of chronic myeloid leukemia. However,despite an overall significant hematological and cytogenetic response,imatinib therapy may favor the emergence of drug-resistant clones,ultimately leading to relapse. Some imatinib resistance mechanisms had not been fully elucidated yet. In this study we used sensitive and resistant sublines from a Bcr-Abl positive cell line to investigate the putative involvement of telomerase in the promotion of imatinib resistance. We showed that sensitivity to imatinib can be partly restored in imatinib-resistant cells by targeting telomerase expression,either by the introduction of a dominant-negative form of the catalytic protein subunit of the telomerase (hTERT) or by the treatment with all-trans-retinoic acid,a clinically used drug. Furthermore,we showed that hTERT overexpression favors the development of imatinib resistance through both its antiapoptotic and telomere maintenance functions. Therefore,combining antitelomerase strategies to imatinib treatment at the beginning of the treatment should be promoted to reduce the risk of imatinib resistance development and increase the probability of eradicating the disease. View Publication

Even though myelodysplastic syndromes (MDS) are characterized by ineffective hematopoiesis,the molecular alterations that lead to marrow failure have not been well elucidated. We have previously shown that the myelosuppressive TGF-β pathway is constitutively activated in MDS progenitors. Because there is conflicting data about upregulation of extracellular TGF-β levels in MDS,we wanted to determine the molecular basis of TGF-β pathway overactivation and consequent hematopoietic suppression in this disease. We observed that SMAD7,a negative regulator of TGF-β receptor I (TBRI) kinase,is markedly decreased in a large meta-analysis of gene expression studies from MDS marrow-derived CD34(+) cells. SMAD7 protein was also found to be significantly decreased in MDS marrow progenitors when examined immunohistochemically in a bone marrow tissue microarray. Reduced expression of SMAD7 in hematopoietic cells led to increased TGF-β-mediated gene transcription and enhanced sensitivity to TGF-β-mediated suppressive effects. The increased TGF-β signaling due to SMAD7 reduction could be effectively inhibited by a novel clinically relevant TBRI (ALK5 kinase) inhibitor,LY-2157299. LY-2157299 could inhibit TGF-β-mediated SMAD2 activation and hematopoietic suppression in primary hematopoietic stem cells. Furthermore,in vivo administration of LY-2157299 ameliorated anemia in a TGF-β overexpressing transgenic mouse model of bone marrow failure. Most importantly,treatment with LY-2157199 stimulated hematopoiesis from primary MDS bone marrow specimens. These studies demonstrate that reduction in SMAD7 is a novel molecular alteration in MDS that leads to ineffective hematopoiesis by activating of TGF-β signaling in hematopoietic cells. These studies also illustrate the therapeutic potential of TBRI inhibitors in MDS. View Publication

Osteoblasts play a crucial role in the hematopoietic stem cell (HSC) niche; however,an overall increase in their number does not necessarily promote hematopoiesis. Because the activity of osteoblasts and osteoclasts is coordinately regulated,we hypothesized that active bone-resorbing osteoclasts would participate in HSC niche maintenance. Mice treated with bisphosphonates exhibited a decrease in proportion and absolute number of Lin(-)cKit(+)Sca1(+) Flk2(-) (LKS Flk2(-)) and long-term culture-initiating cells in bone marrow (BM). In competitive transplantation assays,the engraftment of treated BM cells was inferior to that of controls,confirming a decrease in HSC numbers. Accordingly,bisphosphonates abolished the HSC increment produced by parathyroid hormone. In contrast,the number of colony-forming-unit cells in BM was increased. Because a larger fraction of LKS in the BM of treated mice was found in the S/M phase of the cell cycle,osteoclast impairment makes a proportion of HSCs enter the cell cycle and differentiate. To prove that HSC impairment was a consequence of niche manipulation,a group of mice was treated with bisphosphonates and then subjected to BM transplantation from untreated donors. Treated recipient mice experienced a delayed hematopoietic recovery compared with untreated controls. Our findings demonstrate that osteoclast function is fundamental in the HSC niche. View Publication

SPARC is an extracellular matrix protein that exerts pleiotropic effects on extracellular matrix organization,growth factor availability,cell adhesion,differentiation,and immunity in cancer. Chronic myelogenous leukemia (CML) cells resistant to the BCR-ABL inhibitor imatinib (IM-R cells) were found to overexpress SPARC mRNA. In this study,we show that imatinib triggers SPARC accumulation in a variety of tyrosine kinase inhibitor (TKI)-resistant CML cell lines. SPARC silencing in IM-R cells restored imatinib sensitivity,whereas enforced SPARC expression in imatinib-sensitive cells promoted viability as well as protection against imatinib-mediated apoptosis. Notably,we found that the protective effect of SPARC required intracellular retention inside cells. Accordingly,SPARC was not secreted into the culture medium of IM-R cells. Increased SPARC expression was intimately linked to persistent activation of the Fyn/ERK kinase signaling axis. Pharmacologic inhibition of this pathway or siRNA-mediated knockdown of Fyn kinase resensitized IM-R cells to imatinib. In support of our findings,increased levels of SPARC mRNA were documented in blood cells from CML patients after 1 year of imatinib therapy compared with initial diagnosis. Taken together,our results highlight an important role for the Fyn/ERK signaling pathway in imatinib-resistant cells that is driven by accumulation of intracellular SPARC. View Publication