Effect of NP-1 expressed on ECs and non-ECs on the proliferation of ECs.

The proliferation of ECs expressing NP-1 together with VEGFR-2 (B) is enhanced compared with that of ECs expressing VEGFR-2 alone (A). Soluble clustered NP-1 effectively enhances the signaling of VEGFR-2 (C). These findings suggest that hematopoietic cells expressing NP-1 also enhance the signaling of VEGFR-2 on ECs (D).