Up-regulation of EphB and Ephrin-B Expression in Rhabdomyosarcoma

Background: Increased expression of Eph receptors and their ephrin ligands has been implicated in promoting angiogenesis and tumour progression in several malignancies. Here the expression of mRNA for ephrin-B and EphB receptors in rhabdomyosarcoma (RMS) cell lines and primary tumours was investigated. Materials and Methods: Expression of mRNA for ephrin-B and EphB receptors in RMS cell lines and primary tumours was measured by real-time RT-PCR and compared with the expression in normal striated muscle. Results: A dysregulation of both ligands and receptors was found in all cell lines. In embryonal tumours, overexpression of ephrin-B1 correlated with overexpression of EphB1 (r=0.97, p<0.01) and EphB3 (r=0.94, p<0.05); overexpression of ephrin-B2 correlated with overexpression of EphB1 (r=0.94, p<0.05), EphB2 (r=0.88, p<0.01) and EphB4 (r=0.76, p<0.01). In alveolar tumours, no similar correlations were found. A correlation between EphB2 and EphB4 receptors was demonstrated in both tumour types, being positive in embryonal cases (r=0.81, p<0.01) and negative in alveolar (r= _ 1.00, p<0.01). Conclusion: A global up-regulation of ephrin-B and EphB receptors in RMS tumours was found. The correlation between EphB2 and EphB4 receptors suggests a possible role for ephrin-B and EphB receptors in RMS development.