Levels of soluble tumor-necrosis factor alpha (sTNF-α) in the medium of MCF-7
cells on exposure to docetaxel. The ability of MCF-7 cells to produce sTNF-α was measured by using an enzyme-linked immunosorbent assay (ELISA) after selection for survival to docetaxel dose levels 8 (MCF-7TXT8), 9 (MCF-7TXT9), 10 (MCF-7TXT10), 11 (MCF-7TXT11), or 12 (MCF-7TXT12), or to the maximally tolerated dose of paclitaxel (MCF-7TAX-1 cells). After selection, the cells at the various selection doses were assessed for their production of sTNF-α in the absence (white bars) or presence (black bars) of 50 nM docetaxel (a). The results presented are the mean levels (± standard error) for five independent experiments, and the significance of differences in sTNF-α levels between MCF-7CC and MCF-7TXT cells was assessed by using a Student t test; P values of < 0.01 and < 0.001 are represented by the ** and *** symbols, respectively. (b) Expression of TNF-α and S28 transcripts measured with RTqPCR by using cDNA preparations from MCF-7CC and MCF-7TXT cells (dose level 10).