Scanning electron microscopic observations on cells grown in vitro. VII. HeLa cells can penetrate Wi38 fibroblasts

When HeLa cells are seeded on a preexisting monolayer of Wi38 fibroblasts, the HeLa cells "try" to get into direct contact with the glass substrate. Once on top of a flat fibroblast the HeLa cell can either migrate from the fibroblast to settle between two fibroblasts on glass or somehow stimulate the underlying cells to retract. In a few cases the HeLa cell directly penetrates the fibroblast, "melting" its way through the underlying cell. The mechanism of this phenomenon which has never been described before in this combination is discussed.