BACKGROUND: Eph receptors and their ligands, the ephrins, represent a large 
class of cell-cell communication molecules with well-defined developmental 
functions. Their role in healthy adult tissues and in human disease is still 
largely unknown, although diverse roles in carcinogenesis have been postulated.
METHODS: We established a set of fluorescent PCR probes and primers for the 
definition of individual gene expression profiles of 12 different Eph receptors 
and 8 ephrins in 13 different healthy tissues. The mRNA expression profiles were 
studied in human lung, colorectal, kidney, liver, and brain cancers.
RESULTS: The family of Eph receptors/ephrins was widely expressed in adult 
tissues with organ-site-specific patterns: EphB6 was highest in the thymus, 
compatible with an involvement in T-cell maturation. Brain and testis shared a 
unique pattern with EphA6, EphA8, and EphB1 being the most prominent. EphA7 had 
a high abundance in the kidney vasculature. Ephrin-A3 was up-regulated 26-fold 
in lung cancer, and EphB2 was up-regulated 9-fold in hepatocellular carcinoma. 
EphA8 was down-regulated in colon cancer, and EphA1/EphA8 was down-regulated in 
glioblastomas.
CONCLUSION: Eph/Ephrin genes are widely expressed in all adult organs with 
certain organ-site-specific patterns. Because their function in adult tissues 
remains unknown, further analysis of their role in disease may disclose new 
insights beyond their well-defined meaning in development.