The mechanisms by which multiple myeloma (MM) cells migrate and home to the bone marrow are not well understood. In this study, we sought to determine the effect of the chemokine SDF-1 (CXCL12) and its receptor CXCR4 on the migration and homing of MM cells. We demonstrated that CXCR4 is differentially expressed at high levels in the peripheral blood and is down-regulated in the bone marrow in response to high levels of SDF-1. SDF-1 induced motility, internalization, and cytoskeletal rearrangement in MM cells evidenced by confocal microscopy. The specific CXCR4 inhibitor AMD3100 and the anti-CXCR4 antibody MAB171 inhibited the migration of MM cells in vitro. CXCR4 knockdown experiments demonstrated that SDF-1-dependent migration was regulated by the PI3K and ERK/ MAPK pathways but not by p38 MAPK. In addition, we demonstrated that AMD3100 inhibited the homing of MM cells to the bone marrow niches using in vivo flow cytometry, in vivo confocal microscopy, and whole body bioluminescence imaging. This study, therefore, demonstrates that SDF-1/CXCR4 is a critical regulator of MM homing and that it provides the framework for inhibitors of this pathway to be IntroductionMultiple myeloma (MM) is the second most prevalent hematologic malignancy; it remains incurable, and the median survival time is 3 to 5 years. 1,2 It is characterized by the presence of multiple lytic lesions and widespread involvement of the bone marrow at diagnosis, implying a continuous (re)circulation of MM cells in the peripheral blood and (re)entrance into the bone marrow. 1 Studies have demonstrated the presence of circulating malignant plasma cells in more than 70% of patients diagnosed with MM. 3,4 Migration of cells through the blood to the bone marrow niches requires active navigation, a process termed homing.Chemokines are small chemoattractant cytokines that bind to specific G-protein-coupled 7-span transmembrane receptors present on the plasma membranes of target cells. [5][6][7] Chemokines play a central role in lymphocyte trafficking and homing. [8][9][10][11] One of the most extensively studied chemokines in migration is SDF-1 and its receptor, CXCR4. 12,13 SDF-1 is primarily produced by stromal cells. CXCR4 is expressed on the surfaces of normal cells such as hematopoietic stem cells and T and B lymphocytes and on malignant cells such as breast cancer cells and lymphoid malignancies. 6,11,[14][15][16] To date, the role of CXCR4 in homing of MM cells to the bone marrow has not been fully elucidated. Inhibitors of CXCR4, such as AMD3100 (AnorMED, Toronto, ON, Canada), have been shown to induce the mobilization of stem cells. 17,18 AMD3100 (AnorMED) is a bicyclam molecule that reversibly blocks the binding of CXCR4 with SDF-1. 19 Because SDF-1/CXCR4-dependent signaling differs between cell types and between malignant and normal counterparts, 20 it is critical to investigate the unique role of CXCR4/SDF-1 in MM. In this study, we sought to determine the effect of CXCR4 and its specific inhibitor, AMD3100, on the migration and in vivo ...

SUMMARYPlasma cell disorders form a spectrum ranging from the asymptomatic presence of small monoclonal populations of plasma cells to conditions like plasma cell leukemia and multiple myeloma, in which the bone marrow can be replaced by the accumulation of neoplastic plasma cells. Immunophenotyping has become an invaluable tool in the management of hematological malignancies and is increasingly finding a role in the diagnosis and monitoring of plasma cell disorders. Multiparameter flow cytometry has evolved considerably during the past decade with an increasing ability to screen large numbers of events and to detect multiple antigens at the same time. This, along with a better understanding of the phenotypic heterogeneity of the clonal plasma cells in different disorders, has made immunophenotyping an indispensible tool in the diagnosis, prognostic classification and management of plasma cell disorders. This book chapter addresses the approaches taken to evaluate monoclonal plasma cell disorders, and the different markers and techniques that are important for the study of these diseases.

We compared the angiogenic potential of bone marrow plasma and the expression of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and their receptors on plasma cells from patients with monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM), and newly diagnosed multiple myeloma (NMM). Cytokine and cytokinereceptor expression was studied by bone marrow immunohistochemistry, quantitative reverse transcription-polymerase chain reaction (RT-PCR) on sorted plasma cells, and quantitative Western blot analysis. Bone marrow angiogenic potential was studied using a human in vitro angiogenesis assay. The expression levels of VEGF, bFGF, and their receptors were similar among MGUS, SMM, and NMM. Sixty-one percent of NMM samples stimulated angiogenesis in the in vitro angiogenesis assay compared with SMM (0%) and MGUS (7%) (P < .001). Importantly, 63% of MGUS samples inhibited angiogenesis compared with SMM (43%) and NMM (4%) (P < .001). The inhibitory activity was heat stable, not overcome by the addition of VEGF, and corresponded to a molecular weight below 10 kd by sizeexclusion chromatography. Our results suggest that increasing angiogenesis from MGUS to NMM is, at least in part, explained by increasing tumor burden rather than increased expression of VEGF/ bFGF by individual plasma cells. The active inhibition of angiogenesis in MGUS is lost with progression, and the angiogenic switch from MGUS to NMM may involve a loss of inhibitory

Molecular genetic T-cell receptor (TCR) and flow cytometric analysis using antibodies to conventional T-cell antigens and TCR beta-chain variable region families (TCR-Vbeta) were performed in 65 peripheral blood specimens evaluated for potential involvement by a T-cell lymphoproliferative disorder (TCLPD). A normal or reactive conventional T-cell immunophenotype was present in 36 cases; TCR-Vbeta flow cytometric and molecular TCR analyses were negative for clonality in 32 and 27 of these cases, respectively. In the remaining normal and reactive cases, one or both methods seemed to detect dominant cell populations in settings with limited T-cell diversity. We identified 29 TCLPDs; all studied cases had clonal molecular TCR results; 23 TCLPDs had clonal TCR-Vbeta flow cytometric results; the remaining were suggestive of (n = 3) or negative (n = 3) for clonality. TCR-Vbeta flow cytometric analysis is a powerful clinical laboratory tool that can be used to aid in the rapid diagnosis of peripheral blood involvement by T-cell malignant neoplasms.

Purpose We hypothesized that vertical blockade of VEGF signaling by combining bevacizumab with sorafenib in recurrent glioblastoma (rGBM) patients would result in a synergistic therapeutic effect. We also investigated whether VEGF, VEGFR2, and HIF-1α single nucleotide polymorphisms (SNPs), circulating biomarkers of angiogenesis and Magnetic Resonance (MR) imaging markers, such as apparent diffusion coefficient (ADC), correlated with treatment efficacy and/or toxicity. Patients/Methods Patients received bevacizumab (5 mg/kg every 2 weeks) with sorafenib (200 mg bid, weekly, days 1-5) (Group A), but due to toxicity the starting sorafenib dose was subsequently modified to 200 mg qd (Group B). Results 54 patients were enrolled: 19 patients in Group A and 35 in Group B. Objective response rate was 18.5% with median duration of 6.7 mo (range 0.5-24.1 mo). Six-month progression free survival (PFS6) was 20.4% (11/54), and median OS was 5.6 months (95% CI 4.7 – 8.2); outcome was similar between the two dose groups. We identified single nucleotide polymorphisms in the VEGF and VEGFR2 promoter regions which were associated with PFS6 (p<0.022). Among molecular markers of angiogenesis, a higher log2 baseline level of stromal cell derived factor-1 was associated with PFS6 success (p=0.04). The circulating endothelial cell log2-fold decreased during treatment with subsequent increase at disease progression (p=0.022). Imaging analysis demonstrated a trend associating ADC-L with poor outcome. Conclusions The bevacizumab/sorafenib combination did not improve outcome of recurrent GBM patients versus historic bevacizumab treated controls. Biologic markers of response and resistance to bevacizumab in gliomas were identified which merit prospective validation.