P2RX7 and melanoma: Using the B16 melanoma cells stably expressing the ATP reporter pmeLUC implanted into P2X7 WT or null mice, we showed that tumor growth in p2x7−/− mice (Fig. 1a–c) is accompanied by a strikingly reduced quantity of ATP, especially at days 5, 7, and 9 following cancer cell injection (Fig. 3a, b).