Effect of Tumour Necrosis Factor-Alpha on Estrogen Metabolic Pathways in Breast Cancer Cells

Tumor necrosis factor-alpha (TNF-α) is a proinflammatory cytokine that has been linked to breast cancer development. Estrogen metabolic pathway is also involved in breast carcino-genesis and DNA adducts formation. In this study we investigated the effect of TNF-α on the estrogen metabolic pathway in MCF-7, a breast cancer cell line. Capillary liquid chromatog-raphy/mass spectrometry (LC/MS) and High performance liquid chromatography (HPLC) were used for analysis of estrogen metabolites and estrogen-DNA adducts levels respectively. Reporter gene assay, Real time reverse transcription polymerase chain reaction (real time RT-PCR) and Western blot were used to assess the expression of estrogen metabolizing genes and enzymes. TNF-α significantly increased the total EM and decreased the estrone (E1) / 17-β estradiol (E2) ratio. Moreover, it altered the expression of genes and enzymes involved in E2 activation and deactivation pathways e.g. Cytochrome P-450 1A1 (CYP1A1), Cyto-chrome P-450 1B1 (CYP1B1), Catechol-O-methyl transferase (COMT) and Nicotinamide adenine dinucleotide phosphate-quinone oxidoreductase 1 (NQO1). In addition, there were increased levels of some catechol estrogens e.g. 4-hydroxy-estrone (4-OHE1) and 2-hydroxyestradiol (2-OHE2) with decreased levels of methylated catechols e.g. 2-methoxy estradiol (2-MeOE2). DNA adducts especially 4-OHE1-[2]-1-N3 Adenine was significantly increased. TNF-α directs the estrogen metabolism into more hormonally active and car-cinogenic products in MCF-7. This may implicate a new possible explanation for inflammation associated breast cancer. © Ivyspring International Publisher.