Multiple Myeloma • Research Paper Clinical significance of chemokine receptor (CCR1, CCR2 and CXCR4) expression in human myeloma cells: the association with disease activity and survival Isabelle Van de Broek Background and Objectives. The capacity of multiple myeloma (MM) cells to home to Xavier Leleu and reside in the bone marrow implies that they must be equipped with appropriate Rik Schots adhesion molecules and chemokine receptors to allow transendothelial migration. We Thiery Facon and others have previously shown that human MM cells express at least three differ- Karin Vanderkerken ent chemokine receptors that are functionally involved in MM cell migration, i.e. CCR1, Ben Van Camp CCR2 and CXCR4. In this study, we analyzed the surface expression of these Ivan Van Riet chemokine receptors on primary MM cells from bone marrow samples. Design and Methods. Chemokine receptor expression was analyzed on bone marrow samples from a large population of patients (n=80) by flow cytometric analysis. The chemokine receptor expression profile was compared with clinical characteristics. Statistical significance was evaluated by Fisher’s exact test. Survival curves were con- structed using the Kaplan-Meier method. Cox regression analysis was used to deter- mine the effect of chemokine receptor expression on survival. Results. A heterogeneous expression pattern was observed for the three receptors tested. The chemokine receptor status (CRS) (i.e. no expression versus expression of at least one chemokine receptor), as well as expression of individual chemokine recep- tors was analyzed in relation to clinical and laboratory features and evaluated for prog- nostic significance. Chemokine receptor expression was significantly inversely correlat- ed with disease activity: patients with active disease showed a significantly lower expression of CCR1, CCR2, as well as CXCR4 as compared to patients with non-active disease. Furthermore, the chemokine receptor expression profile correlated with serum b2-microglobulin, C-reactive protein and hemoglobin. CRS, and the individual expressions of CCR1, CCR2 and CXCR4 in diagnostic bone marrow samples (n=70) correlated with survival. Multivariate analysis, using the Cox proportional hazard regression model, identified CRS, along with serum b2 microglobulin, as an independ- ent prognostic factor. Interpretation and Conclusions. This study indicates that the chemokine receptor expression profile of MM cells correlates with disease status and survival of MM patients. This observation might reflect impaired chemoattraction and retention of MM cells within the bone marrow microenvironment, resulting in disease progression. Key words: multiple myeloma, homing, chemokine receptor expression, survival. Haematologica 2006; 91:200-206 ©2006 Ferrata Storti Foundation From the Department of Hematology 5,6 and Immunology, Vrije Universiteit ultiple myeloma (MM) is a mono- spreading. Brussel Belgium (IVB, RS, KV, IVR); clonal B cell malignancy, arising from The capacity of MM cells to home to and Service des Maladies du Sang, Ma late stage differentiated B cell, shar- reside in the bone marrow implies that these Hôpital Huriez, CHRU, Lille, ing many characteristics with immunoglobu- cells must be equipped with appropriate adhe- France (XL, TF). lin (Ig)-secreting plasma cells. A striking fea- sion molecules and chemokine receptors that ture of this disease is the accumulation of plas- allow their migration across the vascular Correspondence: ma cells, with a low proliferative index and an endothelium and the subsequent interaction Ivan Van Riet, Department extended life span, in the bone marrow, in with different stromal elements of the bone Hematology-Immunology, Vrije close contact with stromal cells.1 The bone marrow. Trafficking and homing of leukocytes Universiteit Brussel, aarbeeklaan marrow microenvironment plays a crucial role occurs by a multistep cascade, involving the 101, 1090 Brussels, Belgium E-mail: [email protected] in the pathogenesis of MM by influencing sequential and coordinated activation of tumor growth, survival, and drug resistance.2-4 numerous adhesion and signal molecules.7,8 Although MM cells are mainly localized in the The expression of chemokines and the pres- bone marrow during the early stages of the ence of specific chemokine receptors on differ- disease, extramedullary growth can be ent leukocyte subsets control selective recruit- observed in more advanced stages. Several ment of immune effector cells from the reports also describe the presence of small peripheral circulation and homing of lympho- amounts of MM cells in the peripheral blood cytes to the secondary lymphoid organs.9,10 The of many patients, suggesting that these circu- homing process is initiated by a tethering and lating MM cells are responsible for tumor rolling phase, during which lymphocytes in | 200 | haematologica/the hematology journal | 2006; 91(2) Chemokine receptor expression in MM the blood transiently and reversibly interact with vascular Table 1. Patients’ characteristics. adhesion receptors (including selectins and integrins) and sample the endothelium for activating factors (often Parameter n=80 chemokines). On activation, a combination of additional adhesion molecules, chemokines, and other signals will Age, mean (range) 64 (35-94) lead to an arrest of the lymphocyte, followed by transmi- Male/female ratio 1.3/1 gration across the endothelium and further migration Immunoglobulin type directed by tissue-associated chemokine gradients.11 IgG 46 Chemokines are a subgroup of cytokines with selective IgA 26 chemoattractant properties and are classified into four Bence Jones 7 Non-secretory 1 subfamilies, depending on the position of their NH2-termi- Bone marrow plasmacytosis (%), mean (range) 19 (2-95) nal cysteine residues (CXC, CC, CX, CX3C). They bind to Durie and Salmon stage G-protein-coupled receptors, whose two major subfami- Stage I 20 lies are designated CCR and CXCR. Although many stud- Stage II 23 ies have been performed to elucidate the pathophysiology Stage III 31 of MM, the homing mechanisms of MM cells are not fully Plasma cell leukemia 6 understood. In accordance with the mechanisms used by normal lymphocytes for trafficking and homing between the blood and the lymphoid tissues, one can hypothesize anti-human CCR2 (clone LS132.1D6) (IgG2a), a kind gift that MM cells also use a chemokine-mediated mechanism from Dr. C. Clement (Millenium Pharmaceuticals, for homing to the bone marrow and for remaining within Cambridge, MA, USA); phycoerythrin-conjugated the marrow stroma. mouse anti-human CCR1 MoAb (clone 53504.111) Chemokine receptor expression in MM cells has already (IgG2b) and anti-human CXCR4 (clone 12G5) (IgG2a), been analyzed in some previous reports. MM cell lines obtained from R&D systems (Abingdon, UK); Cy-5 con- show a heterogeneous expression of transcripts and sur- jugated mouse anti-human CD38 (clone HIT2) (IgG1), face protein for CCR1, CCR2, CCR3, CCR5, CCR6, from Pharmingen (Becton Dickinson, Erembodegem, CCR10, CXCR3, CXCR4 and CXCR6.12-14 So far, surface Belgium). Chemokine receptor expression on the surface expression on primary MM cells from patients’ bone mar- of primary MM cells was evaluated by a double-staining row samples has been confirmed for CCR1, CCR2, and procedure as described previously.12 Briefly, mononuclear CXCR4.12, 13, 14 These last three receptors were also found to cells isolated from bone marrow samples by Ficoll gradi- be functional since they mediate the in vitro migration of ent centrifugation, were incubated for 30 min. at 4°C human MM cells to their specific ligands, ie. MCP-1 (for with the Cy-5 conjugated CD38 specific antibody in 12,13 CCR2), MIP-1α (for CCR1) and SDF-1 (for CXCR4). combination with mouse anti-human CCR2, CXCR4, In the present study, we studied the expression of the CCR1, control mouse IgG2a or control mouse IgG2b mon- chemokine receptors CCR1, CCR2 and CXCR4 on pri- oclonal antibody (all at 10 µg/mL). In the second step, mary MM cells of a large panel of MM patients and ana- cells were incubated with phycoerythrin-conjugated goat lyzed the clinical significance of this expression. anti-mouse IgG2a/IgG2b antiserum (Southern Biotechnology ImTec, Antwerpen, Belgium) for 30 min at 4°C. After washing, cells were resuspended in phos- Design and Methods phate-buffered saline and analyzed on an EPICS XL flow cytometer (Coulter Electronics, Analis, Namur, Belgium). Patients’ samples and clinical details The presence of monoclonal plasma cells among the + Eighty patients with MM were included in this study. CD38 gated cells was checked by intracytoplasmic κ/λ Patients were staged according to the criteria of Salmon immunofluorescence using a three-color staining proce- 15 and Durie. These patients’ characteristics are shown in dure (human Igκ-fluorescein isothiocyanate and Igλ-phy- Table 1. Bone marrow aspirates were obtained for routine coerythrin (Fab)2 fragments (both from Dako diagnostics, diagnostic or evaluation purposes after informed consent. Heverlee, Belgium). Data were analyzed using WinMDI Parameters recorded at diagnosis were age, sex, Durie- 2.8 FACS software. To compare the fluorescence-staining Salmon stage, percentage of plasma cells in the bone mar- intensities of MM cells from different patients, we calcu- row, immunoglobulin (Ig) class, blood hemoglobin, serum lated the fluorescence intensity ratio (FIR). The FIR for a albumin, serum β2-microglobulin, serum C-reactive pro- given antigen is defined as the