Objective: To investigate the expression and significance of heme oxyenase-1(HO-1) in benign and malignant breast tissue.Methods: HO-1 mRNA

HO-1 protein and enzyme activity of HO-1 in 10 cases of normal breast tissue

18 of hyperplasia

20 of adenoma and 25 of carcinoma were evaluated by RT-PCR

immunohistochemistry and Western blot respectively

and the significance of HO-1 in breast tissue was discussed.Results: The expression of HO-1 mRNA in breast carcinoma tissue(0.3755±0.0628) was higher than those in normal breast tissue(0.1199±0.0810)

breast hyperplasia(0.1502±0.0479) and breast adenoma(0.1834±0.0541)(t=2.2992

P<0.01)

HO-1 protein expression in benign and malignant breast tumor tissue(23.4617±7.0136

34.2712±4.3423) were higher than those in normal(4.2742±0.8216) and hyperplasia breast tissue(6.2525±1.0032)(P<0.05)

and at the same time

HO-1 enzyme activity in benign and malignant breast tumor tissue(1.1458±0.0458

1.4646±0.0489)were higher than those in normal(0.8935±0.0271) and hyperplasia(0.9375±0.0302)(P<0.01) too and that of carcinoma tissue was higher than that in breast adenoma(t= 3.7546

P<0.01)?Conclusions:HO-1mRNA?protein expression and HO-1 enzyme activity were associated with benign and malignant breast tissue

which indicates that HO-1 can protect carcinoma cell in breast.