Structural and behavioral anomalies of highly malignant respiratory tract epithelial cells

These studies were designed to determine whether cytostructural changes and characteristics of in vitro behavior were related to malignancy and the loss of growth control in epithelial cells. Three highly malignant cell lines were derived from transplantable carcinomas of the respiratory tract and compared with 3 respiratory tract epithelial lines of negligible malignancy.

Keratin cytoskeletons were visualized by indirect immunofluorescence staining, and sample photomicrographs representing each line were prepared. Observers naive to the immunofluorescent images were asked to classify the encoded photomicrographs into 6 groups, corresponding to the cell lines, and then into 2 major classes, each containing 3 of the original groups. We recorded and analyzed the criteria used in making the classifications to identify the features common to the highly malignant lines. These included the nonuniform spacing of cells in the field of view, the cell shape, and the presence of nonfluorescent areas in the lamellar cytoplasm. The criteria that were not useful for discriminating between images from the malignant lines and those of negligible malignancy were cell size, the prominence and structure of the filaments and their integration into desmosomes, and the appearance of the nucleus. Since the nonuniformity of keratin distribution in the periphery of the malignant cells suggested a structural anomaly, the cell lines were also examined by scanning electron microscopy. Unlike cells from the lines of negligible malignancy, cells from 2 of the highly malignant lines showed thickenings in the subterminal portions of the lamellar cytoplasm.

In vitro behavior was analyzed by growing cells in a specially designed chamber that allowed continuous microscopic observation for Video image intensification microscopy in conjunction with time-lapse video recording was used to obtain permanent records Visual analysis of these recordings revealed that each of the highly malignant cell lines displayed up to 5 days. of cell behavior for all of the lines. dramatic differences in growth behavior when cultured on either a glass or plastic substrate. Cells from the malignant lines appeared to lose substrate adhesiveness and to grow primarily as spheriod aggregates