Confrontations of rings of adult human oral mucosa epithelial cells enclosing islands of similar normal epithelium, fibroblasts, and cells of three established lines of human squamous carcinoma in monolayer culture were investigated by phase and reflection microscopy and by time lapse cinematography. Measurements of the dimensions of the rings and islands of cells revealed that, while normal epithelial rings confronted with normal epithelium or fibroblasts migrated continuously inwards, similar

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... rings confronting islands of the carcinomas retreated progressively outwards from the tumor islands. The persistence of substantial cell-free space between the epithelium and tumor cells indicated that the outwards migration of the epithelial rings was not solely due to proliferation of the tumor cells. The tumor-induced migration of normal epithelium in monolayer culture may reflect the response of normal epithelium to carcinoma cells in certain in vivo situations.