The receptor for advanced glycation end-products (RAGE) is only present in mammals, and belongs to a family of cell adhesion molecules (CAMs)

RAGE controls leukocyte adhesion in preterm and term infants

BACKGROUND

Insufficient leukocyte recruitment may be one reason for the high incidence of life-threatening infections in preterm infants. Since the receptor of advanced glycation end products (RAGE) is a known leukocyte adhesion molecule and highly expressed during early development, we asked whether RAGE plays a role for leukocyte recruitment in preterm and term infants.

METHODS

Leukocyte adhesion was analyzed in dynamic flow chamber experiments using isolated leukocytes of cord blood from extremely premature (<30 weeks of gestation), moderately premature (30-35 weeks of gestation) and mature neonates (>35 weeks of gestation) and compared to the results of adults. For fluorescent microscopy leukocytes were labeled with rhodamine 6G. In the respective age groups we also measured the plasma concentration of soluble RAGE (sRAGE) by ELISA and Mac-1 and LFA-1 expression on neutrophils by flow cytometry.

RESULTS

The adhesive functions of fetal leukocytes significantly increase with gestational age. In all age groups, leukocyte adhesion was crucially dependent on RAGE. In particular, RAGE was equally effective to mediate leukocyte adhesion when compared to ICAM-1. The plasma levels of sRAGE were high in extremely premature infants and decreased with increasing gestational age. In contrast, expression of β2-Integrins Mac-1 and LFA-1 which are known ligands for RAGE and ICAM-1 did not change during fetal development.

CONCLUSION

We conclude that RAGE is a crucial leukocyte adhesion molecule in both preterm and term infants.

RAGE expression in tumor-associated macrophages promotes angiogenesis in glioma

Interaction of RAGE (the receptor for advanced glycation endproducts) with its ligands can promote tumor progression, invasion, and angiogenesis. Although blocking RAGE signaling has been proposed as a potential anticancer strategy, functional contributions of RAGE expression in the tumor microenvironment (TME) have not been investigated in detail. Here, we evaluated the effect of genetic depletion of RAGE in TME on the growth of gliomas. In both invasive and noninvasive glioma models, animal survival was prolonged in RAGE knockout (Ager(-/-)) mice. However, the improvement in survival in Ager(-/-) mice was not due to changes in tumor growth rate but rather to a reduction in tumor-associated inflammation. Furthermore, RAGE ablation in the TME abrogated angiogenesis by downregulating the expression of proangiogenic factors, which prevented normal vessel formation, thereby generating a leaky vasculature. These alterations were most prominent in noninvasive gliomas, in which the expression of VEGF and proinflammatory cytokines were also lower in tumor-associated macrophages (TAM) in Ager(-/-) mice. Interestingly, reconstitution of Ager(-/-) TAM with wild-type microglia or macrophages normalized tumor vascularity. Our results establish that RAGE signaling in glioma-associated microglia and TAM drives angiogenesis, underscoring the complex role of RAGE and its ligands in gliomagenesis.

Defective RAGE activity in embryonal rhabdomyosarcoma cells results in high PAX7 levels that sustain migration and invasiveness

Rhabdomyosarcoma is a muscle-derived malignant tumor mainly affecting children. The most frequent variant, embryonal rhabdomyosarcoma (ERMS) is characterized by overexpression of the transcription factor, PAX7 which prevents ERMS cells from exiting the cell cycle and terminally differentiating. However, a role for PAX7 in the invasive properties of ERMS cells has not been investigated in detail thus far. Here we show that ectopic expression of receptor for advanced glycation end-products (RAGE) in human ERMS cells results in the activation of a RAGE/myogenin axis which downregulates PAX7 by transcriptional and post-translational mechanisms, as in normal myoblasts, and reduces metastasis formation. High PAX7 sustains migration and invasiveness in ERMS cells by upregulating EPHA3 and EFNA1 and downregulating NCAM1 thus decreasing the neural cell adhesion molecule (NCAM)/polysialylated-NCAM ratio. Microarray gene expression analysis shows that compared with the RAGE(-ve) TE671/WT cells and similarly to primary human myoblasts, TE671/RAGE cells show upregulation of genes involved in muscle differentiation and cell adhesion, and downregulation of cell migration related and major histocompatibility complex class I genes. Our data reveal a link between PAX7 and metastasis occurrence in ERMSs, and support a role for the RAGE/myogenin axis in metastasis suppression. Thus, low RAGE expression in ERMS primary tumors may be predictive of metastatic behavior.