['We have used commercially available cDNA arrays to identify EphB4 as a gene that is up-regulated in colon cancer tissue when compared with matched normal tissue from the same patient.', 'Quantitative RT-PCR analysis of the expression of the EphB4 gene has shown that its expression is increased in 82% of tumour samples when compared with the matched normal tissue from the same patient. Using immunohistochemistry and Western analysis techniques with an EphB4-specific antibody, we also show that this receptor is expressed in the epithelial cells of the tumour tissue and either not at all, or in only low levels, in the normal tissue.'] Is receptor protein tyrosine kinase EphB4 up-regulated in colon cancer?