BCL2 and cancer: Moreover, while ATP inhibited proliferation or induced cell death via P2X7R in human cervix and breast cancer cells as well as in murine melanoma and colon cancer cells (76, 82–85), high levels of extracellular ATP promoted survival of A549 and H23 lung cancer cells as compared to normal cells (86); here, the authors attributed the differential effects on tumor and normal tissue cells to the decreased expression of P2X7R and an enhanced Bcl-2/Bax ratio in the cancer cells (86).