Expression of fibronectin on clonally related transformed and control sublines from an epithelial cell strain and a tumor line of mouse alveolus

The cellular expression of fibronectin and the importance of fibronectin for the morphology of cultured cells were studied in a lung epithelial cell system. The cells used were clonally related control NAL1A, spontaneously transformed NAL1AS cells of the NAL1A cell strain, and transformed clonal sublines of the cell line NAL1AM and the tumor cell line NUL1. Fibronectin was detected on the surface of NAL1A cells by surface iodination; fibronectin synthesis, secretion, and pericellular accumulation were detected in each of the control sublines by immunoblot assay, immunoprecipitation of metabolically labeled cell extracts and conditioned medium, and was confirmed by immunofluorescence microscopy. Fibronectin synthesis, secretion, or accumulation could not be detected by these methods in NAL1AS and NAL1AM sublines, or the sublines of NUL1. The control NAL1A cells showed enhanced cell spreading on culture substrata of fibronectin or extracellular matrix from bovine endothelial cells, as compared to plastic. The transformed NAL1AS and NAL1AM cells had the same cell shape when cultured on the three different substrata. For these cultured epithelial cells, cellular fibronectin expression and sensitivity to the presence of adhesive glycoproteins in the culture substrata are seen in the control, anchorage-dependent cells, but the transformed cells appear not to express fibronectin and to have a cell shape that is unaffected by the nature of the culture substratum.