Purpose: Epidermal growth factor (EGF) is excreted in high concentrations in the urine and stimulates urothelial cell growth. The cultured bladder cancer cell line KU-1 was used to study the molecular mechanisms by which EGF affects urothelial tumor growth and invasion activity.
Materials and methods: KU-1 cells were grown in cell culture in the presence or absence of EGF. Anchorage-independent cell growth assays and Matrigel invasion assays were performed. Expression of cytokeratins was examined by Northern and Western blot analyses. Chloramphenicol acetyltransferase assays were used to determine whether EGF stimulated matrix metalloproteinase expression.
Results: EGF enhanced anchorage-independent growth in soft agar and increased the number of cells penetrating into a Matrigel membrane. A transient transfection assay revealed that EGF increased the promoter activities of the matrix metalloproteinase 1 and 9 genes in KU-1 cells. Moreover, the morphology of KU-1 cells changed after the addition of EGF to the culture medium. Western and Northern blot analyses demonstrated that EGF decreased cytokeratin 19 expression, but did not affect expression of cytokeratin 8 or 18.
Conclusion: EGF increased the invasive activity of KU-1 bladder cancer cells in part by increasing the secretion of matrix metalloproteinases. Morphologic changes may result from altered composition of cytoskeletal proteins.