Tumours of the Ewing's sarcoma (ES) family and neuroblastoma (NBL) were examined by reverse transcriptase-PCR for expression of mRNA for endothelin (ET) receptors ET-A and ET-B, and the ligands ET-1, ET-2 and ET-3. The effect of ET-1, ET-3, an ET-1-neutralizing antibody and ET-A receptor antagonist BQ-123 on cell proliferation was examined using an ELISA. Loss of ET-B receptor mRNA occurred in 57% of ES and 42% of NBL tumours. This appeared to be associated with the presence of metastatic disease and disease progression. ET-A receptor mRNA was expressed in all ES and 85% of NBL tumours, and in all ES and NBL cell lines examined. All ET ligands were detected in NBL cell lines, but only ET-1 and ET-2 were expressed in ES cell lines. Treatment of ES and NBL cells with ET-1 increased proliferation, but ET-3 had no effect. Incubation of ES and NBL cells with an ET-1-neutralizing antibody or BQ-123 decreased proliferation. The ET-3 ligand and ET-B receptor may be associated with migration and metastasis of ES and NBL, whereas ET-1 (acting through the ET-A receptor) may regulate their proliferation.

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