In the present paper, while treatment of NRP1-expressing carcinoma cells with exogenous VEGF had no effects on growth and migration, the effects of VEGF on migration in A549 cells were unmasked by siRNA-mediated inhibition of endogenous VEGF production, most likely because endogenous VEGF production limits the formation of a chemoattractant gradient. The gene discussed is NRP1; the disease is carcinoma.