S1PR1 and neoplasm: Additionally, a few studies showed that loss of VEGFR2 phosphorylation at Y951 residues (949 in mouse) blocked tumor metastasis.12 Vijay Avin et al demonstrated that S1PR1 inhibited VEGFR2 internalization by VEGF and in this case VEGF phosphorylated VEGFR2 at Y951.