Chemotactic cytokines play a critical role in recruiting leukocytes to sites of tissue injury. Interleukin-8 (IL-8) is a chemotactic cytokine secreted by a variety of cells (eg, monocytes, endothelial cells, fibroblasts) during the inflammatory response. In this report, the authors demonstrate that human transitional cell carcinomas and renal cell carcinomas have the capacity to elaborate IL-8 in response to the inflammatory mediators IL-1 beta and tumor necrosis factor (TNF)-alpha. All cell lines expressed high levels of IL-8 mRNA on stimulation with either IL-1 beta or TNF-alpha, but not lipopolysaccharide; one expressed the gene constitutively. The authors selected one transitional cell carcinoma cell line (UM-UC-9) and one renal cell carcinoma cell line (UM-RC-5) for further study. Both displayed a time- and dose-dependent increase in steady-state levels of IL-8 mRNA in response to IL-1 beta and TNF-alpha. Specific mRNA was detectable by 1 hour after stimulation. Secretion of antigenic IL-8 measured by enzyme-linked immunosorbent assay into culture supernatants reflected the kinetics of mRNA expression. Because heat-inactivated TNF-alpha failed to induce synthesis of IL-8 mRNA, and cycloheximide augmented TNF-alpha-induced synthesis, IL-8 expression appears to be a stimulus-specific primary induction phenomenon. As with other inflammatory mediators whose mRNA contains a 3' AU-rich sequence (eg, IL-2, TNF-alpha), the half-life of IL-8 mRNA was short, less than 1 hour. Our data suggest that secretion of IL-8 by malignant cells may partly account for the inflammatory infiltrates associated with some malignant neoplasms.