These and other findings pose the problem of the mechanism through which VEGF acts in tumour cells, since the present study together with previous work shows that NRP1 is expressed in diverse tumour cells in the absence of significant expression of the major signalling VEGF receptor, VEGFR-2 (Soker et al, 1998; Bachelder et al, 2003; Simiantonaki et al, 2008). This evidence concerns the gene KDR and neoplasm.