Estrogen metabolism in human colorectal cancer cells

Abstract

Epidemiological and “in vitro” studies support a direct role of estrogens in the pathogenesis and/or progression of colorectal cancer (CRC). Recent observations suggest a local synthesis of 17β-estradiol (E 2). In the present study, the CRC estrogen receptor β (ERβ) positive HCT8, HCT116, DLD-1 and LoVo cell lines were evaluated for expression of functional 17β-hydroxysteroid dehydrogenase (17βHSD) types 1, 2, 3, and 4. RT-PCR analysis revealed that while 17βHSD1 and 17βHSD4 were expressed in all the four cell lines, 17βHSD2 and 17βHSD3 were expressed in a cell-specific manner. The interconversion of tritiated estrone (E 1) or E 2 evaluated by thin layer chromatography of conditioned media revealed that in HCT8, HCT116, and DLD-1 cells both reductive and oxidative activities were present, the latter showing K m values (∼10 μM) 40-fold higher than the former (∼250 nM). On the contrary, in LoVo cells, estrogens were almost (∼90%) completely metabolized to hydrophile compounds. Charcoal-dextrane (DC) stripped fetal calf serum (FCS) (10%), E 2 (10 nM), Vitamin D 3 (100 nM) and the combined E 2 and Vitamin D 3 treatment were evaluated for modulation of 17βHSD isoenzymes gene expression and activity. Gene expression and activity of 17βHSD reductive and oxidative isoenzymes were respectively inhibited and enhanced by Vitamin D 3 in HCT8 and LoVo cells. Surprisingly, DC-FCS induced a marked increase of estrogen metabolism toward hydrophile metabolites in all four cell lines. In conclusion, our results clearly show that metabolism of estrogens by 17βHSD isoenzymes is functional and modulated by external stimuli in continuous neoplastic colonic epithelial cell lines.