NRP-1 interacts with GIPC1 and alpha 6/beta 4-integrins to increase YAP1/Delta Np63 alpha-dependent epidermal cancer stem cell survival

We have identified an epidermal cancer stem (ECS) cell population that drives formation of rapidly growing and highly invasive and vascularized tumors. VEGF-A and neuropilin-1 (NRP-1) are highly expressed in ECS cell tumors and VEGF-A/NRP-1 interaction is required for ECS cell survival and tumor vascularization. We now identify a novel signaling cascade that is triggered by VEGF-A/NRP-1. We show that NRP-1 forms a complex with GIPC1 and alpha 6/beta 4-integrin to activate FAK/Src signaling, which leads to stabilization of a YAP1/Delta Np63 alpha to enhance ECS cell survival, invasion, and angiogenesis. Loss of NRP-1, GIPC1, alpha 6/beta 4-integrins, YAP1, or Delta Np63 alpha reduces these responses. Moreover, restoration of constituently active YAP1 or Delta Np63 alpha in NRP-1 null cells restores the ECS cell phenotype. Tumor xenograft experiments show that NRP-1 knockout ECS cells form small tumors characterized by reduced vascularization as compared to wild-type cells. The NRP-1 knockout tumors display signaling changes consistent with a role for the proposed signaling cascade. These studies suggest that VEGF-A interacts with NRP-1 and GIPC1 to regulate alpha 6/beta 4-integrin, FAK, Src, PI3K/PDK1, LATS1 signaling to increase YAP1/Delta Np63 alpha accumulation to drive ECS cell survival, angiogenesis, and tumor formation.