ROLES OF NRP-1 IN BREAST CANCER DEVELOPMENT

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Angiogenic switch is a prerequisite for the tumor progression and presumably for the acquisition of an invasive property. Mobilization of vascular smooth muscle cells (SMCs) is the key event for new blood vessel formation. Studies have demonstrated that PDGF, secreted by various tumor cells including breast, is an important regulator of vascular smooth muscle cells motility. Recently, we have shown that NRP-1 expressed differentially in Vascular SMCs. However, the role of NRP-1 in regulation of vascular SMCs motility has not yet been fully established. We anticipate that NRP-1 may contribute in the mobilization of vascular SMCs that could be mediated through tumor cell-derived-PDGF. To test the hypothesis, we determined if PDGF physically interacts with NRP-1 to potentiate the migration of vascular SMCs. PDGF secretion level was determined by western blot analysis in different tumor cell-derived media. To determine the stimulatory effect of PDGF, cells were grown in basal media with or without PDGF in the Boyden chamber and migration was determined by counting the Giemsa stained cells. NRP-1 expression in vascular SMCs with or without PDGF was established by RT-PCR and western blot analysis. The importance of NRP-1 in PDGF-induced migration was established by silencing of NRP-1 using shRNA. Interaction of PDGF and NRP-1 was determined by immunoprecipitation/immunobloting. The studies indicate that breast tumor cells-secreted B-forms of PDGF augments the migration and NRP-1 expression in vascular SMCs. Silencing of NRP-1 by shRNA blocks the PDGF-induced migration of SMCs. B-forms of PDGF physically interacts with NRP-1 of SMCs to exert the migratory response. NRP-1 is a major component in PDGF signaling pathway in vascular SMCs migration. Next, we will determine the down-stream signaling molecules associated with this event. In particular, we will determine the role of PDGF receptors in PDGF-NRP-1 mediated vascular SMCs migration.