17β-hydroxysteroid dehydrogenase type 1 and type 2 in ductal carcinoma in situ and intraductal proliferative lesions of the human breast

17β-hydroxysteroid dehydrogenases (17β-HSDs) are involved in the interconversion of biologically active and inactive sex steroids and are considered to play important roles in the in situ metabolism of estrogen in various estrogen dependent tissues. 17β-HSD type 1 catalyzes primarily the reduction of estrone (E1) to estradiol (E2), whereas 17β-HSD type 2 catalyzes primarily the oxidation of E2 to E1. However, the possible biological roles of these estrogen metabolizing isozymes in human breast cancer, especially in carcinogenesis of the human breast, have not been examined in detail. Because of the potential roles of estrogens in the early stages of human breast carcinogenesis, we have examined the immunolocalization of 17β-HSD type 1 and type 2 isozymes and estrogen receptor α (ER α) in both normal human breast tissue and in breast cancers, including ductal carcinoma in situ (DCIS), proliferative disease without atypia (PDWA) or fibrocystic disease and atypical ductal hyperplasia (ADH). We also correlated these findings with clinicopathological findings, Ki67 antigen, progesterone receptor (PR), c-erbB-2, and p53. 17β-HSD type 2 immunoreactivity was sporadically detected in non-proliferative or Ki67 negative ductal epithelia of normal breast, but rarely in breast carcinoma cells. 17β-HSD type 1 immunoreactivity was detected in 12/22 (54.5%) PDWA cases, 8/26 (30.8%) ADH cases, and 25/40 (62.5%) DCIS cases, respectively. 17β-HSD type 1 immunoreactivity was not statistically correlated with the age of the patients, Ki67 labeling index (LI), and PR LI, p-53 and c-erbB-2 immunoreactivity. There was no significant correlation between ER α LI and 17β-HSD type 1 immunoreactivity. There was a positive correlation between ER α and Ki67 LI in PDWA, whereas a negative correlation was detected between ER α and Ki67 LI in DCIS. There was no correlation between ER α and Ki67 LI in ADH. These results suggest that in human breast epithelial cells, development of ADH and DCIS may be associated with the loss and/or deviation of oestrogen dependent regulation of cell proliferation.