Characterization of steroid sulfatase in human and mouse tissues and in the mouse MC3T3-E1 pre-osteoblastic cell line

Steroid sulfatase cleaves the sulfate group from 3beta-hydroxysteroid sulfates. This enzyme is widely distributed among mammalian tissues, and it has been suggested to play a role in the in situ conversion of inactive steroids to active forms in a variety of tissues. Two tissues in which steroid sulfatase may be particularly important are breast cancer and bone. Our laboratory is interested in the role of steroid sulfatase; consequently, I worked on four projects characterizing steroid sulfatase in human and mouse tissues and investigating the role of this enzyme in mouse bone cells. Recent evidence indicates that steroid sulfatase could be a prognostic indicator in breast cancer. Our lab generated a steroid sulfatase antibody to examine the presence of steroid sulfatase in a variety of tissues, including breast carcinomas. I performed immunohistochemical analyses on human tissue slides and a human tissue microarray. The findings confirm previous reports that steroid sulfatase is higher in hormone-dependent breast cancers, suggesting that this enzyme could serve as a useful prognostic indicator of breast cancer. I next sought to determine activity and presence of steroid sulfatase and the presence of steroid sulfatase mRNA in a variety of mouse tissues. Using enzyme assays, Western blotting and RT-PCR, it was determined to each of six mouse tissues (liver, lung, kidney, muscle, ovary and uterus) contained steroid sulfatase protein and mRNA. Our results show that mouse tissues have the ability to convert inactive steroids into active steroids. The mouse model may prove useful in future studies of steroid sulfatase physiology. Steroid sulfatase may provide a local mechanism for 17beta-estradiol needed to maintain bone health, as estrogens play a central role in the regulation of bone density. I characterized steroid sulfatase in the MC3T3-E1 mouse pre-osteoblastic cell line, as these cells are a model for bone differentiation. I then developed a 21-day protocol to measure steroid sulfatase throughout differentiation. Steroid sulfatase showed changes in activity during development, depending on the treatment; however steroid sulfatase mRNA was constant throughout development. These data provide a baseline for future studies of the role of steroid sulfatase in bone development.