Figure 1.

Stimulation by EGF + estrogen additively upregulates the release and transcription of CXCL8 in MCF-7 breast carcinoma cells. (A) CXCL8 release by the tumor cells. MCF-7 cells were grown in the presence of estrogen (72 hours), EGF (last 24 hours), EGF + estrogen (estrogen 72 hours; EGF last 24 hours), or ethanol as control (ethanol did not affect CXCL8 release compared with untreated cells) (time points were selected based on kinetics analyses, as described in Materials and Methods). CXCL8 extracellular expression was determined in the supernatants of the cells by ELISA and was analyzed in the linear range of absorbance. A representative experiment of n > 3 is presented. *P < .05, **P < .01 for the difference between treated and untreated cells. (B) CXCL8 transcription. MCF-7 cells were grown in the presence of estrogen (48 hours), EGF (last 6 hours), EGF + estrogen (estrogen: 48 hours; EGF: last 6 hours), or ethanol as control (time points were selected based on kinetics analyses, as described in Materials and Methods). The CXCL8 transcript level was determined by quantitative real-time PCR analysis. The results were standardized by rS9 levels. The figure presents the mean ($\overline{x}$) ± SD of normalized values of mRNA levels in three independent experiments, all showing similar results.