Distribution of EphB4 and EphrinB2 in normal and malignant urogenital tissue

Ephrin (Eph) receptors are receptor tyrosine kinases; both EphrinB2, as a ligand, and EphB4, as a receptor, are involved in angiogenesis. EphrinB2 is expressed on arteries and EphB4, a specific receptor for EphrinB2, is expressed on veins. It is unknown whether involvement of arteries and veins in tumor angiogenesis is distinctive. Here we investigated their distribution in normal and malignant tissue of the urogenital tract.

Five-micrometer-thick paraffin sections from nontumoral and tumoral tissues of kidney (n = 12), bladder (n = 33), and prostate (n = 20) were immunoreacted with antisera against EphB4 and EphrinB2 using the avidin-biotin-peroxidase complex technique. Comparisons of EphB4 and EphrinB2 stained arterial and venous vessels in the nontumoral and tumoral sections were evaluated in a semiquantitative analysis as frequency of the vessels in a predetermined tumor area counted under light microscopy.

Expression of EphrinB2 in arterial and EphB4 in venous endothelium was significantly greater in tumoral sections compared with nontumoral sections. No statistically significant correlation in comparing the labeling patterns for EphrinB2 with the labeling patterns for EphB4 was observed in nontumoral as well as tumoral sections.

The high expression of EphrinB2 in arterial and EphB4 in venous endothelium of urogenital tract tumors might contribute to their involvement in the progression of tumor angiogenesis. The relation between arteries and veins in the normal and tumor tissues is unchanged.