P2RY4 and astrocytoma (excluding glioblastoma): Thanks to Dr. Gary A. Weisman from the Department of Biochemistry, University of Missouri-Columbia, for providing the h-1321N1 astrocytoma cell line, h-1321N1 astrocytoma cell line transfected with t-P2Y1, h-P2Y2, h-P2Y4, and r-P2Y6 receptors.