Neuropilin-1 and VEGF correlate with somatostatin expression and microvessel density in ovarian tumours

Vascular endothelial growth factor (VEGF), is an angiogenic growth factor, expressed more highly in malignant than benign ovarian tumours. Neuropilin-1, which can act as a VEGF receptor has been shown to be associated with tumour angiogenesis in some cancer systems. Somatostatin (SST), a potentially anti-angiogenic factor, acts via somatostatin receptors that are expressed in ovarian cancer. We used immunohistochemistry to demonstrate expression of Neuropilin-1 in 63 malignant and 35 benign ovarian tumours and compared it to VEGF, Flt, Flk, SST expression and tumour microvessel density (MVD). Neuropilin-1 was expressed in 34/63 malignant and 22/35 benign lesions. VEGF, Flt, Flk and SST were expressed more highly in the epithelium of malignant and the vessels of benign lesions. VEGF expression correlated with SST expression in the epithelium (p<0.001) and the vessels (p<0.001), this co-expression was confirmed by dual immunostaining. The MVD for malignant lesions was higher than benign (p<0.001) and positively correlated to epithelial VEGF expression (p=0.001) and negatively correlated to vascular VEGF expression (p=0.025). These results show that Neuropilin-1 is expressed in ovarian tumours and also show that VEGF and SST are co-expressed in the same tissue compartments raising the intriguing possibility that SST may be important in angiogenesis in ovarian cancer.