Tumor suppressor p53 functions as a transcriptional factor that regulates the cell cycle and apoptosis. A mutated p53 gene can result in decreased sequence-specific DNA binding and transcriptional activity of the p53 protein. In this study, we examined the regulatory role of the extracellular matrix components in p53 expression and nuclear localization in a Detroit 562 cell line derived from a pharyngeal carcinoma. When cultured on a polystyrene surface, type I collagen gel, or Matrigel containing basement membrane components, Detroit 562 cells showed a distinct response to extracellular matrix components morphologically. As shown by Western blotting, Detroit 562 cells cultured on Matrigel displayed an increased expression of p53 protein as well as an elevated nuclear p53 level, as compared with the cells cultured on the polystyrene surface or type I collagen gel. When cultured on Matrigel, nuclear p53-positive cells were exclusively localized to the outer surface layer of the cell clusters, whereas most of the inner cells showed no p53 expression. In Detroit 562 cell clusters on Matrigel, proliferative activities, as evaluated by proliferationcell nuclear antigen staining and bromo-deoxyuridine incorporation assay, were evenly distributed; virtually no apoptotic cells, as evaluated by the fluorescence TUNEL assay, were detected in the cell clusters, suggesting that the peculiar localization of nuclear p53-positive cells was not directly related to cell proliferation or apoptosis. These results indicate that p53 expression and its localization in Detroit cells were modulated by extracellular matrix signals, particularly by the basement membrane components in Matrigel.