Basal and stimulated expression of IL-6 mRNA and protein in human colon carcinoma cell clones. Additions to the culture medium were: 10-6 M indomethacin, 10-7 M PGE2, 10-8 M 1,25-(OH)2D3, 10-7 M 17β-E2, 5 ng/ml IL-1β. Upper part: Representative RT-PCR amplifications of mRNA transcripts specific for IL-6 (culture time 4 h). Expression of epithelial cell marker CK8 is shown for comparison. Lower part: IL-6 release into medium during 24 h culture period. Data are means ± SD, n ≥ 4. Note that changes in IL-6 secretion by COGA-13 cells are given on a logarithmic scale. Statistically significant differences: *, P < 0.05; **, P < 0.01; ***, P < 0.001 (Student's t-test).