P2RX4 and lung carcinoma: The nonselective gap junctional blocker carbenoxolone (CBX) completely abolished the Ca2+ transients (Supplemental Figure 2B), however, this turned out to be the consequence of its off-target inhibition of purinergic receptors, as evidenced by direct instillation of ATP into the lung (Supplemental Figure 2C) and the Ca2+ response of A549 lung cancer cells to different concentrations of extracellular ATP (Supplemental Figure 2D).