Oestrogen inactivation in the colon: analysis of the expression and regulation of 17 β -hydroxysteroid dehydrogenase isozymes in normal colon and colonic cancer

Abstract

Summary Epidemiological data suggest that oestrogen contributes to the aetiology of colonic cancer. Furthermore, recent studies have suggested that local hormone metabolism may play a key role in determining colonic responsiveness to oestrogen. To further clarify this mechanism we have characterized the expression and regulation of isozymes of 17β-hydroxysteroid dehydrogenase (17β-HSD) in vitro and in situ. Immunohistochemistry was used to confirm expression of the type 2 and 4 isozymes of 17β-HSD (17β-HSD2 and 4) in normal colonic epithelial cells. Parallel studies suggested that both isozymes were abnormally expressed in colonic tumours and this was confirmed by Western blot analyses. Abnormal expression of 17β-HSD2 and 4 proteins was also observed in Caco-2, HT-29 and SW620 colonic cancer cell lines, although the overall pattern of oestrogen metabolism in these cells was similar to that seen in primary colonic mucosal tissue. The predominant activity (conversion of oestradiol to oestrone) was highest in Caco-2>SW620>HT-29, which correlated inversely with the rate of proliferation of the cell lines. Regulatory studies using SW620 cells indicated that the most potent stimulator of oestradiol to oestrone inactivation was the antiproliferative agent 1,25-dihydroxyvitamin D 3 (1,25D 3 ), whilst oestradiol itself inhibited 17β-HSD activity. Both oestradiol and 1,25D 3 decreased mRNA for 17β-HSD2 and 4. Data indicate that the high capacity for inactivation of oestrogens in the colon is associated with the presence of 17β-HSD2 and 4 in epithelial cells. MATERIALS AND METHODS Immunohistochemical studiesColonic tumour and paired normal mucosal tissue were obtained with agreement from the local ethical approval committee. Fivemicron thick, formalin-fixed tissue sections were cut and placed on coated glass slides. Sections were de-waxed and endogenous peroxidase activity quenched with 3% hydrogen peroxide. Sections were then incubated in donkey serum (Binding Site, Birmingham, UK) diluted 1/10 in PBS (15 min), followed by primary antibody diluted in PBS (1 hour). Antisera used were as follows: 17β-HSD2 monoclonal antiserum (1/500 dilution), a kind gift of Dr S Andersson (South Western Medical Center, Dallas, USA), was produced with a synthetic carboxyterminal peptide [C]RALRMP-NYKKKAT, corresponding to amino acids 375-387 in the human 17β-HSD2 protein; 17β-HSD4 monoclonal antibody (1:200 dilution), a kind gift of Dr J Adamski (GSF, Neuherberg, Germany) was prepared against the porcine 17β-HSD4 which cross-reacts with human, rat and mouse tissues. After washing, slides were incubated for 30 min with a biotinylated universal secondary antibody (Binding Site), diluted 1/100 in PBS, and binding visualised using ABC reagent (Binding Site) and 3,3′-diaminobenzidine (Sigma Chemical Co, Poole, UK). After staining, slides were washed and counterstained in Mayer's haematoxylin. Cell cultureColonic carcinoma cell lines (SW620, Caco-2 and HT-29) were routinely maintained in Dulbecco's Modified Eagles Medium (DMEM), supplemented wit...

Downregulation of estrogen‐metabolizing 17β‐hydroxysteroid dehydrogenase Type 2 expression correlates inversely with Ki67 proliferation marker in colon‐cancer development

“…Based on Northern analysis, they concluded that the decrease was due mainly to decreased expression of 17HSD type 4, another 17HSD enzyme with oxidative activity. In another report, 29 it was suggested that both 17HSD types 2 and 4 isozymes were abnormally expressed in colon tumors, as assessed by immunohistochemistry. Our previous studies with several cell lines originating from various tissues have shown, however, that the 17HSD activity of the type 4 enzyme is very low and that there is no correlation between 17HSD type 4 mRNA expression and 17HSD activity.…”

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LH-RH receptors in human colorectal cancers: Unexpected molecular targets for experimental therapy

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