Isoform-specific expression of VEGF-B in normal tissues and tumors

Vascular endothelial growth factor B (VEGF-B), a member of the VEGF/PDGF fa mily, is highly expressed in many tissues with two differentially spliced t ranscripts generating two secreted isoforms, VEGF-B-167 and VEGF-B-186. In this work, we have investigated the expression of VEGF-B in tissues and cel l lines using techniques that can distinguish the two isoforms. The results showed that the VEGF-B-167 isoform was predominantly expressed in most tis sues, accounting for more than 80% of the total VEGF-B transcripts. The VEG F-B-186 isoform was expressed at lower levels and only in a limited number of tissues. Moreover, the VEGF-B-186 isoform was up-regulated in mouse and human tumor cell lines and primary tumors compared with their corresponding normal tissues. Taken together, our data suggest a fine genetic control of the expression of the two isoforms of VEGF-B, implying tissue- and cell-sp ecific roles of the two VEGF-B isoforms.