“…Originally identified as a secreted product of tumour cells (Senger et al, 1983(Senger et al, , 1986, it is now apparent that VEGF is part of an emerging group of related molecules having approximately 15-25% homology at the amino acid level with the platelet-derived growth factor family. Other recently identified members include VEGF-related factor (VRF) or VEGF-B, VEGFReceived 27 November 1996 Revised 5 August 1997 Accepted 5 August 1997 Correspondence to: RE Banks C (Grimmond et al, 1996;Joukov et al, 1996;Olofsson et al, 1996;Paavonen et al, 1996) and placenta growth factor (Maglione et al, 1991;Hauser and Weich, 1993;Maglione et al, 1993). The active form of VEGF is a homodimeric cytokine of molecular weight 34-46 kDa, the variation in size being due to alternative exon splicing producing four different isoforms of 121, 165, 189 and 206 amino acids (monomeric size), the last three of which have heparin binding activity (Houck et al, 1991;Tischer et al, 1991).…”