Caco-2 cells express type I interleukin-1 receptors: ligand binding enhances proliferation

We examined the effect of interleukin-1 (IL-1) on the rate of proliferation of the human colon carcinoma Caco-2 and characterized the human intestinal epithelial cell IL-1 receptor (IL-1R). IL-1 dose dependently increased tritiated thymidine uptake in confluent Caco-2 monolayers fed complete growth medium. An anti-IL-1 beta completely blocked the increase in tritiated thymidine uptake, whereas an IL-1 receptor antagonist human recombinant blocked it partially. In long-term culture, IL-1 increased DNA content over control, an effect similar to that of epidermal growth factor (EGF). Unlike EGF, IL-1 did not enhance tritiated thymidine uptake in Caco-2 monolayers grown in serum-free medium, implying that IL-1 needs a cofactor(s) to elicit its proliferative effect. Cross-linking 125I-IL-1 beta to Caco-2 membranes revealed a binding protein of approximately 80 kDa with binding saturated at approximately 2.5 x 10(9) M-1 consistent with that for the type I IL-1R. cDNA transcribed from Caco-2 mRNA and amplified by polymerase chain reaction, using complementary oligonucleotides, resulted in a reaction product matching the sequence of the type I IL-1R. Our results demonstrate that IL-1 enhances proliferation of Caco-2 cells. This effect requires the presence of an unidentified cofactor(s). Also, Caco-2 cells express the type I IL-1R.