Pleiotropic role of chemokines in multiple myeloma, study in the 5TMM model

Student thesis: Doctoral Thesis

Abstract

Multiple myeloma (MM) is an incurable plasma cell malignancy, characterized by the accumulation of the malignant cells in the bone marrow (BM). As MM cells most likely develop from post switch B cells, the cells need to enter the BM from the blood circulation or at least spread over the BM. Once they have reached the BM, they start to modulate the microenvironment to their needs, inducing osteolysis and angiogenesis. The process of migration from the vascular to the extravascular compartment of a tissue is called ¡§homing¡¨ and has been described as a multistep process. Chemokines play an important role in this process as they attract the MM cells to the BM. Moreover, chemokines have also been implicated in processes such as osteolysis and angiogenesis.In this work we wanted to identify and investigate several chemokines and their pleiotropic role in the development of MM in the murine 5TMM model. 5TMM models initially originated spontaneously in aging C57BL/KaLwRij mice and have since been propagated in young syngeneic mice by intravenous transfer of the diseased BM. The models closely represent the human disease.We demonstrated that F-actin quantification is an attractive alternative tool to analyse chemotactic responses of MM cells compared to Transwell systems.The first chemokine we investigated was the ¡¥insulin like growth factor 1¡¦ (IGF-1). By measuring F-actin quantity, we demonstrated that IGF-1 was able to induce chemotaxis of 5T33MM cells through the PI3K/Akt pathway. Furthermore, IGF-1 stimulated proliferation of the 5TMM cells through a PI3K/Akt-MEK/ERK pathway and induced MEK/ERK mediated VEGF secretion by the MM cells, contributing thus to MM associated angiogenesis.We identified the role of IGF-1 in vivo by targeting the IGF-1R with the IGF-1R tyrosine kinase inhibitor picropodophyllin (PPP). 5T33MM mice were treated with PPP or vehicle until development of the disease. Treated 5T33MM mice showed a 77% reduction in tumor load and a 60% reduction in microvessel density (MVD). PPP was also able to inhibit IGF-1 induced proliferation and VEGF secretion in vitro. These data confirm the role of IGF-1 in MM development and MM associated angiogenesis.The second chemokine we studied was ¡¥stromal derived factor 1ƒÑ¡¦ (SDF1ƒÑƒw. SDF1ƒÑ was able to induce migration, invasion and proliferation of 5TMM cells in vitro. These effects could be blocked by the CXCR4 inhibitor 4F-benzoyl-TN14003. When 5T33MM mice were treated with this inhibitor in vivo, a 20% reduction in BM homing and tumor load could be seen. These data demonstrate the multiple roles of SDF1ƒÑ in MM.Finally, the third chemokine we investigated was ¡¥macrophage inflammatory protein 1ƒÑ¡¦ MIP1ƒÑ. MIP1ƒÑ is a known osteoclast stimulating factor in MM, which signals through CCR1 and CCR5. We demonstrated that CCR5 but not CCR1 was also involved in migration of 5TMM cells towards MIP1ƒÑ, and was involved in the in vivo BM homing of the MM cells. Both receptors were found to be involved in MM associated osteolysis in vitro and in vivo. Furthermore, we found that both receptors were also used for MM associated angiogenesis. These data indicate the important role of the receptors CCR1 and CCR5 in MM homing and development.In conclusion, we demonstrate in this study that IGF-1, SDF1ƒÑ and MIP1ƒÑ are chemotactic proteins for MM cells. Furthermore, they not only induce chemotaxis but also have pleiotropic roles in the development of MM as well. Targeting these chemokines could prove to have therapeutic value in the future.
Date of Award8 May 2006
Original languageEnglish
Awarding Institution
  • Vrije Universiteit Brussel
SupervisorKarin Vanderkerken (Promotor), Kris Thielemans (Jury), Benjamin Van Camp (Co-promotor), Jacques De Grève (Jury), C. Munaut (Jury), M. Delforge (Jury), P. De Batselier (Jury) & Christian Demanet (Jury)

Keywords

  • Multiple myeloma
  • plasma cell malignancy
  • bone marrow

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