Absence of intermediate filaments in a human adrenal cortex carcinoma-derived cell line

Subclones of a human adrenal cortex carcinoma-derived cell line (SW13) are described which by immunofluorescence lack detectable expression of any of the five known classes of intermediate filament (IF) proteins. Further investigation for vimentin and keratins in these subclones by two-dimensional gel analysis and by immunoblotting gave results consistent with the immunofluorescence results. Despite the apparent absence of IFs, SW13 subclones have organized actin and microtubule cytoskeletal networks, maintain an epithelial shape and colony pattern, and grow well in culture. Although a rat hepatoma cell line which similarly appears to have ceased IF expression has been reported [1], this is the first such report of a human cell line. Although rare, these cases provide evidence that IFs in general are not essential to growth in culture, nor are the keratin-containing IFs in particular necessarily responsible for the ‘cobblestone’ morphology or colony-type growth pattern characteristic of cultured epithelial cells.