Figure 2.

Schematic representation of solid tumor generated by cancer cells (red) surrounded by the normal tissue cells (light and dark blue) releasing extracellular adenosine triphosphate in surrounding environment (in yellow). Adenosine triphosphate (ATP) acts through three different ways: (1) binding P2X7 receptors, ATP facilitates tumor growth; (2) binding the P2X2, P2X3, P2X2/3 receptors expressed by neuronal cells (in green), ATP triggers pain perception; and (3) binding P2X4 and P2X7 receptors expressed by immune cells (in yellow), ATP causes inflammation and pain.