BOA25
Expression of inflammatory chemokine receptor CXCR4 plays an active role in metastatic malignant melanoma and is a viable therapeutic target
Darryl Dunn1, Rebecca Price2, Maxine Emmett1, Howard Rigby2, Françoise Cailler4, Jean-Phillippe Girard3, David Bates1
1Microvascular Research Laboratories, Bristol Heart Institute, University of Bristol, UK, 2Frenchay Hospital, North Bristol NHS Trust, Bristol, UK, 3Institut de Pharmacologie et de Biologie Structurale, Université de Toulouse, France, 4Endocube SAS, Prologue Biotech, Labège, France
Background
Chemokines (chemoattractant cytokines) attract immune cells to areas of inflammation and secondary immune organs. CXCL12 is widely secreted where metastasis form (lymphatics, lung, liver) in malignant melanoma (MM). Its receptor CXCR4 is upregulated in primary metastaitc MM. Chemotraps are broad spectrum, chemokine binding proteins that prevent chemokine-chemokine receptor interactions. Our aims are to show increased expression of CXCR4 in metastatic MM; to give mechanistic evidence that CXCR4 causes active migration of MM in vitro and in vivo towards both lymphatic endothelial cells (LEC) and Blood endothelial cells (BEC) and treating of MM with chemotrap will attenuated therapeutically this migration.
Method
71 primary melanomas of known metastatic outcome were immunohistochemically stained with a CXCR4 specific antibody (ab2074 Abcam) and scored by 3 blinded assessors.
MM cell lines of differing metastatic potential (A375P non-metastatic(CXCR4-); A375SM metastatic(CXCR4+)) were grown. Further more A375P and A375SM cell lines were transfected to express CXCR4 and secrete chemotraps respectively
In vitro migration assays were carried out on the cell lines in response to LEC and BEC conditioned media (CM). In vivo directional growth assay for each cell line was carried out in nude mice injecting 106 melanoma cells 1cm rostrally to 105 LEC/BEC and measuring the direction of tumour growth macroscopically in relation to endothelial cell injection site.
Results
CXCR4 expression in Metastatic MM (1.9±0.15) was significantly greater than Non metastatic MM (1.2±0.12, p<0.001).
In vitro only A375SM and A375-CXCR4 cells migrated towards endothelial cell CM (p<0.05). A375P and A375SM-Chemotrap cells did not migrate. In vivo A375SM and A375P-CXCR4 tumours grew towards endothelial cells(p<0.01). A375P and A375SM-Chemotrap tumours remained at injection sites only.
Conclusion
CXCR4 plays an important role in the active migration of melanoma cells, it is an independent marker of disease progression and can be targeted for anti-metastatic therapy with chemotraps.
