The Journal of Steroid Biochemistry and Molecular Biology
Regulation of steroid sulphatase expression and activity in breast cancer
Introduction
The hydrolysis of oestrone sulphate (E1S) to oestrone (E1) by steroid sulphatase (STS) is thought to make a major contribution to the production of oestrogens within breast tumours [1], [2]. The activity of this enzyme in breast tumours is considerably higher than that of the aromatase enzyme complex, which can also contribute to tumour oestrogen synthesis [3]. STS activity is also higher in malignant and benign breast tumours than in adjacent non-involved tissues [4], [5]. Evidence for the potential importance of STS in regulating oestrogen synthesis within breast tumours has recently been obtained. Patients with tumours containing high levels of STS mRNA were found to have a significantly shorter disease free survival as compared with those with low levels of STS mRNA [6]. Furthermore, STS mRNA levels are significantly higher in malignant than non-malignant breast tissues [7].
The highest incidence of breast cancer occurs in post-menopausal women. There is evidence that STS activity is increased in breast tumours from post-menopausal women compared with the activity in tumours from pre-menopausal women [8]. It is well established that peripheral aromatase activity is related to age and body weight [9]. Cytokines, such as interleukin 6 (IL-6) and tumour necrosis factor α (TNFα) are thought to be responsible for the increases in peripheral aromatase activity associated with ageing and obesity [10], [11], [12].
In contrast to our understanding of the regulation of aromatase expression and activity, little is known about the control of STS expression and activity. In breast cancer cells IL-6 and TNFα are able to stimulate STS activity and act synergistically to increase enzyme activity [13]. There is also evidence that progestins may inhibit the expression and activity of E1-STS in breast cancer cells [14]. Whether this regulation occurs at the transcriptional level or post transcriptionally is not known. Studies on the promoter region of the STS gene are limited [15]. While no specific transcription binding sites in the promoter region of this gene have so far been identified the basal promoter and 5′ enhancer element activities did show tissue specificity in transient reporter gene expression studies. Both were only active in cells of placental origin where STS activity is known to be high but showed no activity in COS-1, HeLa or B82 cells. Post translationally a novel protein modification is required at the active site for full enzyme activity. An α-formylglycine residue is formed by oxidation of a cysteine residue at position 75 within the active site [16]. The regulation of, and modifying enzymes involved in this process have not so far been elucidated. It is possible that this process represents another level of regulation of STS activity.
In the present study we have employed a semi-quantitative RT-PCR technique to examine basal and cytokine stimulated STS expression in fibroblasts derived from normal and malignant breast tissues. In addition, we have also examined the ability of IL-6 and TNFα to regulate STS expression in MCF-7 breast cancer cells. We have also explored the possibility that compounds, such as 2-methoxyoestrone-3-O-sulphamate (2-MeOEMATE) may block the ability of cells to respond to cytokines such as TNFα. 2-MeOEMATE, while a potent inhibitor of STS activity [17], can also induce cells to undergo apoptosis and has been found to reduce the ability of TNFα to stimulate aromatase activity in fibroblasts [18], [19].
Section snippets
Cell culture
MCF-7 breast cancer cells and COS-1 cells were obtained from the European Collection of Cell Cultures, (Salisbury, Wilts, UK). Cells were routinely maintained in Dulbeco's minimal essential medium (DMEM) with 5% fetal calf serum (FCS) and other essential nutrients [13]. Cells were cultured at 37°C under 5% CO2 and used when 50–60% confluent. For experiments cells were cultured in DMEM with 5% charcoal stripped FCS.
Culture of breast fibroblasts
Fibroblasts were cultured from breast tissues of women undergoing lumpectomy for
Steroid sulphatase expression in breast tumour tissue-derived fibroblasts
Having developed a RT-PCR method to examine STS mRNA expression it was used to investigate the expression of this enzyme in fibroblasts derived from samples of normal and malignant breast tissue (Fig. 1). Three matched pairs of samples of breast tumour and tissue proximal to the tumour were used to culture fibroblasts and to subsequently determine their relative levels of STS mRNA expression. For subjects 1 and 3, who were pre-menopausal, no significant difference in basal STS mRNA expression
Discussion
The formation of E1 from E1S by the action of STS is a major pathway for in situ oestrogen production in breast tumours. In the present investigation a semi-quantitative RT-PCR method has been used to start to explore the regulation of STS mRNA expression. As previously reported by Evans et al. [21], using an RT-PCR technique it was possible to detect STS mRNA expression in breast tissue-derived fibroblasts and MCF-7 breast cancer cells.
Using cultured fibroblasts derived from breast tumour and
Acknowledgements
We would like to thank B. Malini for technical assistance with the sulphatase assay. This research was supported by Sterix Ltd.
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2016, Molecular and Cellular EndocrinologyCitation Excerpt :In contrast, there are an assortment of reports exist concerning potential regulators of STS activity and gene expression in other tissues and cell types. One study on MCF-7 breast cancer cells indicated that tumor necrosis factor-α and interleukin-6 may increase STS enzyme activity via a post-translational modification or by increasing substrate availability (Newman et al., 2000). In another report, treatment of human promyeloid leukemia cells with 1,25-dihydroxyvitamin D3 increased STS mRNA and activity via PI3K/Akt dependent activation of NFκB (Hughes et al., 2008).
Inflammatory regulation of steroid sulfatase: A novel mechanism to control estrogen homeostasis and inflammation in chronic liver disease
2016, Journal of HepatologyCitation Excerpt :Interleukin (IL)-1 decreased the expression and activity of STS in endometrial stromal cells [12]. However, IL-6 and tumor necrosis factor α (TNFα) were reported to increase STS activity in breast cancer cells, probably through post-translational mechanisms [13]. It is possible that the effects of cytokines on the expression of STS depend on the cellular context.