Normoxia recovery and different levels of oxygen on lung cancer tumor growth in rats. Effect of normoxia recovery on hypoxia-induced reduction of lung cancer tumor growth (Figure 1E): (A) Tumor growth curve. Because large tumor mass was not allowed in living animals, we sacrificed the control rats when the tumor size reached over 1.5 cm. N = Rats under normoxia for entire experiment. H+N = Rats under hypoxia for 10 days and then under normoxia for another 8 days. Effect of different levels of oxygen on lung cancer tumor growth (Figure 1C) (B & C): (B) Tumor growth curve and (C) Tumor weight. n = 5 for each group. *p < 0.05 as compared with normoxia.