(A) Effect of hIL-6 on growth rate of confluent Caco-2/AQ, COGA-1A, and COGA-13 cells. Cellular proliferation was evaluated from [3H]thymidine incorporation into DNA after 72 h incubation with rhIL-6 (0–100 ng/ml). Data are means ± SD (n = 4 – 16) and expressed as multiples of IL-6-free controls. Statistically significant differences from controls: **, P < 0.01; ***, P < 0.001 (Student's t-test). (B) Time-course of c-myc mRNA expression in confluent Caco-2/AQ, COGA-1A, and COGA-13 clones during incubation with 100 ng/ml rhIL-6. Expression of the epithelial cell marker CK8 is shown for comparison. (C) Densitometric evaluation of expression of c-myc in relation to CK8 as shown in (B): basal expression ratios in zero time controls were set to 1.