HMOX1 and neoplasm: At the 28th week of treatment the average tumor volume was 8.62 ± 1.91 mm3 in HO-1+/+, 25.52 ± 9.38 mm3 in HO-1+/− (P < 0.01, Student's t test), and 63.12 ± 42.55 mm3 in HO-1−/− mice (P < 0.05, Student's t test).