Effect of 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin on growth factor expression in the human breast cancer cell line MCF-7

The aim of this study was to examine whether changes in growth factor or cytokine expression could be responsible for the growth inhibitory effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on the human breast cancer MCF-7 cell line. Treatment of MCF-7 cells with 10 nM TCDD for 7 days reduced the cell growth to 60% of control; this effect was partly abolished by cotreatment of the cells with 100 nM 17β-estradiol (E₂). The inhibition of cell growth by TCDD was accompanied by an enhanced secretion of transforming growth factor-β (TGF-β) and the TGF-β content in cell culture supernatants was 2-fold higher than in controls. Using reverse transcription polymerase chain reaction (RT-PCR), the effect of TCDD on the expression of TGF-β isoforms, transforming growht factor-α (TGF-α), tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) was investigated. It was demonstrated that incubation with 1, 10 and 100 nM TCDD for 24 h increased mRNA levels of TGF-α, TNF-α and IL-1β. The strongest effect was found on IL-1β, the mRNA level of which was dose-dependently increased. TCDD had a minor effect on TGF-α and TNF-α mRNA. The mRNA levels were significantly increased after treatment with 10 and 100 nM TCDD. The mRNA expression of \(TGF - \beta _1 \) and \(TGF - \beta _2 \) was unchanged, whereas the \(TGF - \beta _3 \) mRNA level was enhanced 2 to 3-fold after TCDD treatment. From the results, we suggest that TCDD-induced growth inhibition in MCF-7 cells is related to the growth inhibitory action of a set of growth factors and cytokines which have a contextual action on MCF-7 cell proliferation.