Steroid sulfatase activity and expression in mammary myoepithelial cells.
OBJECTIVE
This investigation examined mRNA expression and enzymatic activity of steroid sulfatase (STS) in human mammary myoepithelial cells (MMECs) and MCF-7 cells and assessed the effects of 17-beta estradiol on the activity of STS.


METHODS
The mRNA level of STS in MMECs was determined by RT-PCR analysis using specific primers for STS. STS enzymatic activity prior to and after treatment with 17-beta estradiol was determined by measuring 3H-metabolites formed after exposure to [3H]estrone 3-sulfate (E1S) and [3H]dehydroepiandrosterone-sulfate (DHEA-S).


RESULTS
Our data demonstrate the presence of STS in the MMECs. Based on RT-PCR analysis, MMECs had slightly lower levels of STS compared to MCF-7 cells. However, sulfatase activity was about 120 times greater in the MMECs than the MCF-7 cells (E1S V(max)=2640nmol/(mg DNAh) compared to 20.9nmol/(mg DNAh)). Exposure to 17-beta estradiol was associated with 70% reduction in E1S sulfatase activity in the MCF-7 cells and 9% increase in the MMECs after 6 days.


CONCLUSIONS
Our studies indicate for the first time the presence of STS in MMECs. This is suggestive of a previously undetermined role for MMECs in converting precursor hormones into active steroid hormones within mammary tissue. In addition, differential response of the MMECs and the MCF-7 cells to estrogen demonstrates differences in hormone metabolism between these two cell types, perhaps related to the absence of estrogen receptors in the MMECs and their presence in the MCF-7 cells. The MMECs may have an important role in hormonal regulation within mammary tissue.
Tobacman
Joanne K
JK
Department of Internal Medicine, University of Iowa, Iowa City, IA 52242-1081, USA. joanne-tobacman@uiowa.edu
Hinkhouse
Marilyn
M
Khalkhali-Ellis
Zhila
Z
D001192:Arylsulfatases / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001940:Breast / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D002460:Cell Line; D017931:DNA Primers; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D004958:Estradiol / Q000494:pharmacology; D006801:Humans; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D043266:Steryl-Sulfatase
D017931:DNA Primers; D012333:RNA, Messenger; D004958:Estradiol; D001192:Arylsulfatases; D043266:Steryl-Sulfatase