Reinier Raymakers

Acquired mutations in TET2 are common in myelodysplastic syndromes

Myelodysplastic syndromes (MDS) represent a heterogeneous group of neoplastic hematopoietic disorders. Several recurrent chromosomal aberrations have been associated with MDS, but the genes affected have remained largely unknown. To identify relevant genetic lesions involved in the pathogenesis of MDS, we conducted SNP array–based genomic profiling and genomic sequencing in 102 individuals with MDS and identified acquired deletions and missense and nonsense mutations in the TET2 gene in 26% of these individuals. Using allele-specific assays, we detected TET2 mutations in most of the bone marrow cells (median 96%). In addition, the mutations were encountered in various lineages of differentiation including CD34+ progenitor cells, suggesting that TET2 mutations occur early during disease evolution. In healthy tissues, TET2 expression was shown to be elevated in hematopoietic cells with highest expression in granulocytes, in line with a function in myelopoiesis. We conclude that TET2 is the most frequently mutated gene in MDS known so far.

Bortezomib Induction and Maintenance Treatment in Patients With Newly Diagnosed Multiple Myeloma: Results of the Randomized Phase III HOVON-65/ GMMG-HD4 Trial

PURPOSE We investigated whether bortezomib during induction and maintenance improves survival in newly diagnosed multiple myeloma (MM). PATIENTS AND METHODS In all, 827 eligible patients with newly diagnosed symptomatic MM were randomly assigned to receive induction therapy with vincristine, doxorubicin, and dexamethasone (VAD) or bortezomib, doxorubicin, and dexamethasone (PAD) followed by high-dose melphalan and autologous stem-cell transplantation. Maintenance consisted of thalidomide 50 mg (VAD) once per day or bortezomib 1.3 mg/m(2) (PAD) once every 2 weeks for 2 years. The primary analysis was progression-free survival (PFS) adjusted for International Staging System (ISS) stage. RESULTS Complete response (CR), including near CR, was superior after PAD induction (15% v 31%; P < .001) and bortezomib maintenance (34% v 49%; P < .001). After a median follow-up of 41 months, PFS was superior in the PAD arm (median of 28 months v 35 months; hazard ratio [HR], 0.75; 95% CI, 0.62 to 0.90; P = .002). In multivariate analysis, overall survival (OS) was better in the PAD arm (HR, 0.77; 95% CI, 0.60 to 1.00; P = .049). In high-risk patients presenting with increased creatinine more than 2 mg/dL, bortezomib significantly improved PFS from a median of 13 months to 30 months (HR, 0.45; 95% CI, 0.26 to 0.78; P = .004) and OS from a median of 21 months to 54 months (HR, 0.33; 95% CI, 0.16 to 0.65; P < .001). A benefit was also observed in patients with deletion 17p13 (median PFS, 12 v 22 months; HR, 0.47; 95% CI, 0.26 to 0.86; P = .01; median OS, 24 months v not reached at 54 months; HR, 0.36; 95% CI, 0.18 to 0.74; P = .003). CONCLUSION Bortezomib during induction and maintenance improves CR and achieves superior PFS and OS.

A critical role for prostaglandin E2 in podosome dissolution and induction of high-speed migration during dendritic cell maturation.

Dendritic cells (DCs) are professional APCs of the immune system that play a key role in regulating T cell-based immunity. The capacity of DCs to activate T cells depends on their maturation state as well as their ability to migrate to the T cell areas of draining lymph nodes. In this study, we investigated the effects of DC maturation stimuli on the actin cytoskeleton and β1 integrin-dependent adhesion and migration. Podosomes, specialized adhesion structures found in immature monocyte-derived DCs as well as myeloid DCs, rapidly dissolve in response to maturation stimuli such as TNF-α and PGE2, whereas the TLR agonist LPS induces podosome dissolution only after a long lag time. We demonstrate that LPS-mediated podosome disassembly as well as the onset of high-speed DC migration are dependent on the production of PGs by the DCs. Moreover, both of these processes are inhibited by Ab-induced activation of β1 integrins. Together, these results show that maturation-induced podosome dissolution and loss of α5β1 integrin activity allow human DCs to undergo the transition from an adhesive to a highly migratory phenotype.

Functional differences between mesenchymal stem cell populations are reflected by their transcriptome.

Stem cells are widely studied to enable their use in tissue repair. However, differences in function and differentiation potential exist between distinct stem cell populations. Whether those differences are due to donor variation, cell culture, or intrinsic properties remains elusive. Therefore, we compared 3 cell lines isolated from 3 different niches using the Affymetrix Exon Array platform: the cord blood-derived neonatal unrestricted somatic stem cell (USSC), adult bone marrow-derived mesenchymal stem cells (BM-MSC), and adult adipose tissue-derived stem cells (AdAS). While donor variation was minimal, large differences between stem cells of different origin were detected. BM-MSC and AdAS, outwardly similar, are more closely related to each other than to USSC. Interestingly, USSC expressed genes involved in the cell cycle and in neurogenesis, consistent with their reported neuronal differentiation capacity. The BM-MSC signature indicates that they are primed toward developmental processes of tissues and organs derived from the mesoderm and endoderm. Remarkably, AdAS appear to be highly enriched in immune-related genes. Together, the data suggest that the different mesenchymal stem cell types have distinct gene expression profiles, reflecting their origin and differentiation potential. Furthermore, these differences indicate a demand for effective differentiation protocols tailored to each stem cell type.

Comparison of modern and conventional imaging techniques in establishing multiple myeloma-related bone disease: a systematic review

This systematic review of studies compared magnetic resonance imaging (MRI), 18F‐fluorodeoxyglucose positron emission tomography (FDG‐PET), FDG‐PET with computerized tomography (PET‐CT) and CT with whole body X‐Ray (WBXR) or (whole body) CT in order to provide evidence‐based diagnostic guidelines in multiple myeloma bone disease. A comprehensive search of 3 bibliographic databases was performed; methodological quality was assessed using Quality Assessment of Diagnostic Accuracy Studies (QUADAS) criteria (score 1–14). Data from 32 directly comparative studies were extracted. The mean QUADAS score was 7·1 (3–11), with quality hampered mainly by a poor description of selection and execution criteria. All index tests had a higher detection rate when compared to WBXR, with up to 80% more lesions detected by the newer imaging techniques; MRI (1·12–1·82) CT (1·04–1·33), PET (1·00–1·58) and PET‐CT (1·27–1·45). However, the modern imaging techniques detected fewer lesions in the skull and ribs. In a direct comparison CT and MRI performed equally with respect to detection rate and sensitivity. This systematic review supports the International Myeloma Working Group guidelines, which recommend that WBCT can replace WBXR. In our opinion, the equal performance of MRI also indicates that it is a valuable alternative. As lesions of the skull and ribs are underdiagnosed by modern imaging techniques we advise additional X‐rays of these regions. The consequences of this approach are discussed.

Partially T-Cell–Depleted Allogeneic Stem-Cell Transplantation for First-Line Treatment of Multiple Myeloma: A Prospective Evaluation of Patients Treated in the Phase III Study HOVON 24 MM

PURPOSE To determine in a prospective study the efficacy, toxicity, and long-term outcome of up-front allogeneic stem-cell transplantation (allo-SCT) in multiple myeloma (MM). PATIENTS AND METHODS In the prospective phase III study by the Dutch-Belgian Hemato-Oncology Cooperative Group (HOVON), HOVON 24 MM, 53 patients with an HLA-identical sibling (median age at transplantation, 48 years; range, 31 to 56 years) were allocated to a partial T-cell-depleted allo-SCT after induction therapy. RESULTS The overall response rate after allo-SCT was 89% (47 of 53 patients), including the 19% of patients (10 of 53 patients) with a complete remission (CR). Five patients achieved a CR only after allo-SCT. Five (71%) of seven primary refractory patients obtained a response to allo-SCT, all of whom had a partial remission. With a median follow-up of 38 months (range, 25 to 61 months), 20 patients are alive since allo-SCT and 33 patients have died (14 from progressive disease, 18 from treatment-related mortality [TRM], and one from another cause). Occurrence of acute graft-versus-host disease grades 2 to 4 predicted for higher TRM in a time-dependent analysis. The median progression-free survival time after allo-SCT was 17 months. Median overall survival time after allo-SCT was 25 months, or 29 months from the start of therapy. Only three patients are in continuing CR, indicating that the potential cure rate of this approach is, at best, 6%. CONCLUSION This first prospective evaluation of up-front allo-SCT of MM in a multicenter setting does not support the use of T-cell-depleted myeloablative allo-SCT as part of first-line therapy.

Reconstructing the human hematopoietic niche in immunodeficient mice: opportunities for studying primary multiple myeloma

Interactions within the hematopoietic niche in the BM microenvironment are essential for maintenance of the stem cell pool. In addition, this niche is thought to serve as a sanctuary site for malignant progenitors during chemotherapy. Therapy resistance induced by interactions with the BM microenvironment is a major drawback in the treatment of hematologic malignancies and bone-metastasizing solid tumors. To date, studying these interactions was hampered by the lack of adequate in vivo models that simulate the human situation. In the present study, we describe a unique human-mouse hybrid model that allows engraftment and outgrowth of normal and malignant hematopoietic progenitors by implementing a technology for generating a human bone environment. Using luciferase gene marking of patient-derived multiple myeloma cells and bioluminescent imaging, we were able to follow pMM cells outgrowth and to visualize the effect of treatment. Therapeutic interventions in this model resulted in equivalent drug responses as observed in the corresponding patients. This novel human-mouse hybrid model creates unprecedented opportunities to investigate species-specific microenvironmental influences on normal and malignant hematopoietic development, and to develop and personalize cancer treatment strategies.

Molecular analysis of the hematopoiesis supporting osteoblastic cell line U2-OS.

OBJECTIVE Osteoblasts play an important role in regulating hematopoiesis in the bone marrow. Here we show that U2-OS, a widely used osteoblastic cell line derived from an osteosarcoma, has the capacity to support proliferation of human hematopoietic progenitor cells in vitro. In this study, U2-OS cells are characterized at the molecular level to unravel the molecular mechanisms underlying the support of hematopoiesis. MATERIALS AND METHODS U2-OS was analyzed in great detail using RT-PCR and flow cytometry. In addition, a cDNA library was constructed and randomly sequenced to obtain insight in the repertoire of expressed molecules. RESULTS A broad panel of growth factors and cytokines is expressed by U2-OS. TGF-beta, GM-CSF, c-kit ligand, and IL-7 are produced constitutively and IL-1beta, IL-6, IL-8, TNF-alpha, IFN-gamma, and MIP1-alpha are upregulated upon stimulation. In addition to those, mRNAs of the CC chemokine LARC and leukemia inhibitory factor were identified. U2-OS cells express high levels of beta1-integrins at the cell surface: VLA-2, VLA-3, VLA-4, VLA-5, VLA-6, and the integrin alphavbeta3. Besides integrins, ALCAM and NCAM are detected on the cell surface of U2-OS. Interestingly, we show that CD34(+) progenitor cells expressing ALCAM are highly proliferative when compared with CD34(+) ALCAM(low) cells, hinting at a role for ALCAM in anchoring progenitor cells to the bone marrow stroma. Interestingly, random sequencing of an U2-OS cDNA library yielded almost 10% of novel cDNAs with a potential role in hematopoiesis. The involvement of these novel molecules in hematopoiesis is an interesting target for future investigations. CONCLUSIONS We conclude that U2-OS supports outgrowth of hematopoietic progenitor cells and accordingly expresses adhesion molecules and growth factors and a number of novel, as yet uncharacterized potentially interesting genes.

Breast Cancer Resistance Protein in Drug Resistance of Primitive CD34+38− Cells in Acute Myeloid Leukemia

Purpose: Acute myeloid leukemia (AML) is considered a stem cell disease. Incomplete chemotherapeutic eradication of leukemic CD34+38− stem cells is likely to result in disease relapse. The purpose of this study was to investigate the role of the breast cancer resistance protein (BCRP/ATP-binding cassette, subfamily G, member 2) in drug resistance of leukemic stem cells and the effect of its modulation on stem cell eradication in AML. Experimental Design: BCRP expression (measured flow-cytometrically using the BXP21 monoclonal antibody) and the effect of its modulation (using the novel fumitremorgin C analogue KO143) on intracellular mitoxantrone accumulation and in vitro chemosensitivity were assessed in leukemic CD34+38− cells. Results: BCRP was preferentially expressed in leukemic CD34+38− cells and blockage of BCRP-mediated drug extrusion by the novel fumitremorgin C analogue KO143 resulted in increased intracellular mitoxantrone accumulation in these cells in the majority of patients. This increase, however, was much lower than in the mitoxantrone-resistant breast cancer cell line MCF7-MR and significant drug extrusion occurred in the presence of BCRP blockage due to the presence of additional drug transport mechanisms, among which ABCB1 and multiple drug resistance protein. In line with these findings, selective blockage of BCRP by KO143 did not enhance in vitro chemosensitivity of leukemic CD34+38− cells. Conclusions: These results show that drug extrusion from leukemic stem cells is mediated by the promiscuous action of BCRP and additional transporters. Broad-spectrum inhibition, rather than modulation of single mechanisms, is therefore likely to be required to circumvent drug resistance and eradicate leukemic stem cells in AML.

Donor versus no-donor comparison of newly diagnosed myeloma patients included in the HOVON-50 multiple myeloma study.

To prospectively evaluate allogeneic stem cell transplantation (allo-SCT) for myeloma as part of first-line therapy, a donor versus no-donor analysis was performed of patients treated in the HOVON-50 study, a study that was originally designed to examine thalidomide combined with intensive therapy. Two hundred sixty patients having received an autologous-SCT fulfilled the criteria to be included, 138 patients without an HLA-identical sibling donor and 122 patients with a donor. After a median follow-up of 77 months, complete remission, progression-free survival (PFS), and overall survival were not significantly different between the 2 groups. PFS at 6 years was 28% for patients with a donor versus 22% for patients without a donor (P = .19) and overall survival at 6 years from high-dose melphalan was 55%, irrespective of having a donor (P = .68). Cumulative incidence of nonrelapse mortality at 6 years after autologous-SCT was 16% in the donor group versus 3% in the no-donor group (P < .001). However, PFS was significantly prolonged in the 99 patients who actually proceeded to allo-SCT compared with the 115 patients who continued maintenance or received a second high-dose melphalan, but the difference did not translate into a prolonged survival benefit. These results do not support a general application of allo-SCT in all myeloma patients as part of first-line therapy.