PTAFR and melanoma: As multiple GPC species can act as PAF-R agonists, we quantified total PAF-R biochemical activity in lipid extracts from murine B16F10 melanoma cells following treatment with 5 Gy of IR as measured by intracellular calcium mobilization responses in Fura-2-loaded PAF-R-expressing KBP cells [7-8, 25].