Type 2 3α/Type 5 17β-HSD (AKR1C3) Is a Negative Regulator of Breast Cancer Proliferation: An Immunohistochemical and In Vitro Study
Paari Murugan, Hsueh-Kung Lin, Weijuan Wu, Valerie Miller, Qing Yang, Kar-Ming Fung. University of Oklahoma Health Sciences Center, Oklahoma City
Background: Hormone dependent malignancies require local (paracrine and intracrine) concentrations of steroid hormones that can be regulated by hydroxysteroid dehydrogenases (HSDs) in the target tissue. HSDs, members of the aldo-keto reductase superfamily (AKR1), convert potent steroid hormones into cognate inactive metabolites and vice versa. AKR1C3, or type 2 3α/type 5 17β-HSD, is an isoenzyme that can alter the local concentration of androgens and estrogens. Its role may be particularly important in hormone dependent malignancies of the aging populace where the gonadal–pituitary axis is compromised. We investigated the expression of AKR1C3 in normal and neoplastic breast tissue.
Design: Immunohistochemistry for AKR1C3 was performed on formalin-fixed, paraffin embedded sections [47 breast specimens including 35 with normal lobules, 38 with normal ducts, 9 lactating adenomas, 19 ductal carcinomas in-situ (DCIS) and 18 infiltrating ductal carcinomas (IDC)]. Immunoreactivity was scored as negative (<5%), 1+ (6-25%), 2+ (26-75%) and 3+ (76-100%). In addition, stable transfection for expression of AKR1C3 was performed on T47D ductal breast carcinoma cells with a pLNCX-AKR1C3 expression construct and cell growth was quantified using a colorimetric XTT cell proliferation assay kit. Appropriate controls were employed.
Results: We demonstrated a uniform, diffuse, and strong expression of AKR1C3 in lactating adenomas. In general, other breast tissue demonstrated focal, but definite, immunoreactivity. The majority of normal ducts showed positive staining (92.1%, 35/38). Normal lobular staining (97.1%, 34/35) was more prominent than ductal expression. In contrast, the expression of AKR1C3 was reduced in DCIS (52.6%, 10/19) and more so in IDC (16.6%, 3/18). In addition, the T47D-AKR1C3 transfectants exhibited significantly suppressed cell growth (8-10 folds) as compared to T47D-mock transfectants.
Conclusions: These findings suggest that AKR1C3 may play an important role in the physiology and pathology of mammary epithelium. Suppressed AKR1C3 expression may represent one of the features that promotes tumorigenesis. The mechanism is unclear but may be influenced by loss of androgen mediated inhibitory effect on breast cancer cells as a result of AKR1C3 deprivation. The influence of AKR1C3 on mammary epithelium requires further investigation.
Wednesday, March 21, 2012 9:30 AM
Poster Session V # 40, Wednesday Morning