The chemokine CXCL12 regulates monocyte-macrophage differentiation and RUNX3 expression

7 Figures. The online version of this article contains a data supplement.Monocytes are versatile cells that can express different functional programs in response to microenvironmental signals. We show that primary blood monocytes secrete the CXCL12 chemokine, and express the CXCR4 and CXCR7 receptors, leading to an autocrine/paracrine loop that contribute to shape monocyte differentiation to a distinct type of macrophages, with an enhanced expression of CD4, CD14, and CD163, or dendritic cells, with a reduced functional ability to stimulate antigen-specific T-lymphocyte responses. The in vivo relevance of CXCL12 production by mononuclear phagocytes was studied in metastatic melanoma tissues by a thoroughly immunofluorescence phenotyping of CXCL12high expressing cells, which were CD45+, coexpressed the macrophage antigens CD68, CD163, and CD209 and constituted the 60%-90% of tumor-associated macrophages. Microarray analysis of primary monocytes revealed that the vascular endothelial growth factor and the angiogenic chemokine CCL1 mRNA levels were up-regulated in response to CXCL12, leading to enhanced expression of both proteins. In addition, we found that CXCL12 autocrine/paracrine signaling down-regulates the expression of the transcription factor RUNX3 and contributes to maintain the long-term CD4 and CD14 expression in monocytes/macrophages. Together, these results suggest that autocrine CXCL12 production modulates differentiation of monocytes toward a distinct program with proangiogenic and immunosuppressive functions.The authors thank Dr J. L. Rodríguez-Fernández and Dr C. Cabanas for the valuable contribution to this work; Dr F. Sánchez-Madridmand Dr M. Penfold for antibodies and reactives; Dr M. Ortega, Dr E. Fernández-Ruiz, and Dr M. Alonso (UCAM) for assistance with qPCRs, and J. Villarejo and I. Trevino for expert technical assistance. This work was supported by grants from the Ministerio de Educación y Ciencia (SAF 2006-08615, 2010-16102, and GEN 2003-20, 649-C06-04 to P.S.-M.) and Ayuda a la investigación científica y técnica 2006 from Fundación Ramón Areces (P.S.-M.), Contrato Juan de la Cierva from Ministerio de Educación y Ciencia and Contrato RETICS RD08/0075 from Ministerio de Ciencia e Innovación to L.S.-M, Contrato de Investigación from Fondo de Investigación Sanitaria/Comunidad de Madrid to R.S and A.E.Peer reviewe