The expression levels of PRG-1 and P2X7 receptor in the hippocampus were both increased on postoperative day 45 in the BCP rats by immunofluorescence and western blot (Figure 2A-E), indicating activation of hippocampal PRG-1 and P2X7 receptor may be involved in bone cancer induced pain and depression. Here, PLPPR4 is linked to depressive symptom measurement.