Neuropilin-1 and neuropilin-2 expression in the adenoma-carcinoma sequence of colorectal cancer.

AIMS: Neuropilin-1 (NRP1) and neuropilin-2 (NRP2) are transmembrane glycoproteins which interact with vascular endothelial growth factor (VEGF) to prevent tumour cell apoptosis and regulate angiogenesis. However, the precise role of NRP1 and NRP2 in the adenoma-carcinoma sequence (ACS) of colorectal cancer remains unclear, and we aimed to determine this in surgical specimens comprising the ACS. METHODS AND RESULTS: Histological analysis demonstrated that epithelial NRP1 expression increased significantly across the ACS (P = 0.0007), and correlated with microvessel density (MVD; r = 0.505, P = 0.0003) and weakly with VEGF (r = 0.251, P = 0.001). In contrast, although NRP2 epithelial expression was increased significantly in all carcinomas (P < 0.002), there was no correlation with MVD, VEGF or NRP1. Furthermore, patients showing coexpression of NRP1 and NRP2 had a potentially worse prognosis than those expressing a single neuropilin or neither one. Although vascular expression of NRP1 increased significantly across the ACS (P = 0.0004) and correlated with MVD (r = 0.361, P = 0.0006), NRP2 vascular expression decreased significantly (P = 0.0001) and showed an inverse correlation with MVD (r=-0.506, P = 0.0001), suggesting differential roles for neuropilins in the angiogenic process during colorectal cancer development. CONCLUSIONS: These data suggest that an increase in NRP1 and NRP2 epithelial/tumour expression, as well as in NRP1 vascular expression, may be associated with disease progression in colorectal cancer.