Regulation of steroid sulphatase expression and activity in breast cancer.
Steroid sulphatase (STS) catalyzes the conversion of oestrone sulphate (E1S) to oestrone (E1) and its action in breast tumours makes a major contribution to in situ oestrogen production in this tissue. Although expression of STS mRNA and STS activity are increased in malignant breast tissues compared with that in non-malignant tissues, little is known about the regulation of its expression or activity. In the present study we have used a RT-PCR technique to investigate the regulation of STS mRNA expression in cultured breast tissue fibroblasts and MCF-7 cells. STS mRNA expression was readily detectable in fibroblasts derived from breast tissue proximal to tumours, breast tumour tissue and reduction mammoplasty tissue. For two pre-menopausal subjects, STS mRNA expression was similar in proximal and tumour fibroblasts whereas for a third, post-menopausal subject, expression in breast tumour fibroblasts was 2.4-fold that in proximal fibroblasts. The cytokine tumour necrosis factor alpha (TNFalpha) or the STS inhibitor, 2-methoxyoestrone-3-O-sulphamate, had no effect on STS mRNA expression in fibroblasts. STS mRNA was detectable in MCF-7 cells but neither TNFalpha nor interleukin 6 (IL-6) affected its expression. Transient transfection of COS-1 and MCF-7 cells with a STS cDNA lacking STS 5' and 3' sequences increased activity 17-fold and 2-fold, respectively. TNFalpha plus IL-6 increased STS activity in mock transfected MCF-7 cells and further increased STS activity in transfected MCF-7 cells. This indicates that activation can occur independently of STS promoter and enhancer elements. In conjunction with the lack of regulation of STS mRNA it suggest that TNFalpha and IL-6 may increase STS activity via a post-translational modification of the enzyme or by increasing substrate availability.
Newman
S P
SP
Endocrinology and Metabolic Medicine, Imperial College School of Medicine, St. Mary's Hospital, W2 1NY, London, UK. simon.newman@ic.ac.uk
Purohit
A
A
Ghilchik
M W
MW
Potter
B V
BV
Reed
M J
MJ
D000818:Animals; D001192:Arylsulfatases / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D001943:Breast Neoplasms / Q000201:enzymology* / Q000235:genetics*; D019556:COS Cells; D017931:DNA Primers / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D043266:Steryl-Sulfatase; D014162:Transfection; D014407:Tumor Cells, Cultured
D017931:DNA Primers; D018076:DNA, Complementary; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D001192:Arylsulfatases; D043266:Steryl-Sulfatase