CASP3 and melanoma: Compared to NTP, NTPO produced approximately 3-fold more cleaved-caspase 3 (Figure 1A) and 2-fold more TUNEL positive (Figure 1B) cells in A549 and SK-MEL2 (melanoma) human cancer cells, indicating that the addition of oxygen gas during NTP treatment could increase the apoptotic efficiency, presumably due to accelerated oxyradical production.