Thomas Strömberg

Expression and function of chemokine receptors in human multiple myeloma

Multiple myeloma (MM) is a B cell tumor characterized by its selective localization in the bone marrow. The mechanisms that contribute to the multiple myeloma cell recruitment to the bone marrow microenvironment are not well understood. Chemokines play a central role for lymphocyte trafficking and homing. In this study we have investigated expression and functional importance of chemokine receptors in MM-derived cell lines and primary MM cells. We found that MM cell lines express functional CCR1, CXCR3 and CXCR4 receptors, and some also CCR6. Although only a minority of the cell lines responded by calcium mobilization after agonist stimulation, a migratory response to the CCR1 ligands RANTES and MIP-1α was obtained in 5/6 and 4/6, respectively, of the cell lines tested. Five out of six cell lines showed a response to the CXCR4 ligand SDF-1. In addition, 3/6 cell lines migrated in response to MIP-3α and IP-10, ligands for CCR6 and CXCR3, respectively. The expression of CXCR4 and CCR1 and the migration to their ligands, SDF-1, and RANTES and MIP-1α, respectively, were also demonstrated in primary MM cells. These findings suggest that chemokine receptor expression and the migratory capacity of MM cells to their ligands are relevant for the compartmentalization of MM cells in the bone marrow.

Expression of the bcl-2 family of pro- and anti-apoptotic genes in multiple myeloma and normal plasma cells : regulation during interleukin-6(IL-6)-induced growth and survival.

Abstract: Aberrant expression of genes regulating apoptosis/survival seems to be essential in the stepwise development of human multiple myeloma (MM). In this paper we have compared the expression of bcl‐2 family pro‐ and anti‐apoptotic genes in MM cell lines, primary MM cells and normal plasma cells. The Bcl‐2, Mcl‐1, Bcl‐xL/S, Bcl‐w, Bax, Bak, and Bad were shown to be expressed in both malignant and non‐neoplastic, normal plasma cells. Quantitative analysis revealed that the malignant phenotype seemed to correlate with an elevated expression of Mcl‐1, a decreased expression of Bax and, to a lesser extent, an increased Bcl‐2/Bax expression ratio. The possible influence of interleukin‐6 (IL‐6) in regulating the expression of the bcl‐2‐related genes was also examined. Using the IL‐6‐dependent MM cell lines U‐1958 and U‐266–1970 it was clearly shown that IL‐6 deprivation induced cell cycle arrest in both cell lines, whereas apoptosis was only detected in the U‐1958 cells. Furthermore, the anti‐apoptotic proteins Bcl‐2, Mcl‐1 and Bcl‐xL were down‐regulated, while the expression of the pro‐apoptotic Bax protein was increased. To conclude, we suggest that the expression pattern of the Bcl‐2 family of proteins separates the malignant phenotype of MM from normal plasma cells, and that the protecting effect of IL‐6 may be conducted via an altered balance between these proteins.

Targeting the insulin-like growth factor-1 receptor by picropodophyllin as a treatment option for glioblastoma

Glioblastoma (GB) is the most common malignant brain tumor in adults. It has limited treatment opportunities and is almost exclusively fatal. Owing to the central role the insulin-like growth factor-1 receptor (IGF-1R) plays in malignant cells, it has been suggested as a target for anticancer therapy including GB. The cyclolignan picropodophyllin (PPP) inhibits IGF-1R without affecting the highly homologous insulin receptor. Here, we show that PPP inhibits growth of human GB cell lines along with reduced phosphorylation of IGF-1R and AKT. In vivo, PPP-treatment causes dramatic tumor regression not only in subcutaneous xenografts but also in intracerebral xenografts, indicating passage of PPP across the blood-brain barrier.

Multiple myeloma cells are killed by syndecan-1-directed superantigen-activated T cells

Abstract. Multiple myeloma (MM) is an incurable plasma cell/plasmablast malignancy with a great need for innovative treatment strategies. Since experimental immunotherapy with targeted superantigens (SAg) proved to be effective in other haematopoietic tumours, we investigated whether this would also hold true for MM. We used the bacterial SAg Staphylococcus enterotoxin A (SEA), a potent activator of T cell cytotoxicity by means of its binding to particular T cell receptor Vß sequences on effector cells and MHC class II molecules on target cells. To eliminate potentially unspecific binding via MHC class II, SEA was point mutated (SEAm). In a second step SEAm was genetically fused to protein A (PA), resulting in a fusion protein (PA-SEAm). This fusion protein was used together with four different plasma-cell-specific/associated mAbs to direct T cells towards 10 MM target cell lines. Three of these mAbs were directed against syndecan-1/CD138, known to be highly expressed on MM and plasma cells, but absent on other haematopoietic cells. All MM cell lines proved to be sensitive to SAg-activated T cell killing (15–50% lysis), as measured in a 51Cr-release assay. This effect was clearly mediated via the plasma-cell-reactive antibodies, as control antibodies only conferred a low background lysis. MM therapy based on targeted SAgs could in theory be hampered by dysfunctional T cells in MM patients. However, we show that T cells from MM patients and healthy controls responded equally well to activation by SAg.