Immunohistochemistry of invasion in threedimensional culture.

Phagocytosis of material from the host tissue by invading malignant cells is suspected from the presence of vacuoles containing unidentified debris. Experiments with 51Cr-labeled host tissues in vitro support the role of phagocytosis during invasion. Using the unlabeled antibody enzyme method material from embryonic chick heart inside invading MO4 cells, HeLa cells and B 16 melanoma cells in threedimensional cultures is stained with a rabbit antiserum against embryonic chick heart. These observations show that phagocytosis by invading cells in vitro is at least partly responsible for the disappearance of the host tissue.