Keratin subtypes of small cell lung cancer.

The molecular forms of keratin in small cell lung cancer (SCLC) cell lines and tumors were examined with antikeratin monoclonal antibodies. Immunostaining of SCLC by antikeratin antibody and examination by fluorescence microscopy indicates population heterogeneity in keratin content. Intensity of immunostaining is often weak. However, polyacrylamide gel electrophoresis and immunoblotting reproducibly demonstrate the presence of keratin and allow analysis of the keratin subtypes. The finding of keratin subtypes closely associated with the development of keratinizing epithelium (the 68 kDa basic keratin) in SCLC was unexpected in a tumor that is regarded as poorly differentiated. The cytoskeletal composition of SCLC suggests the presence of a heterogeneous population with a significant proportion of cells expressing highly differentiated epithelial properties.