Emergence of Differentiated Subclones from a Human Salivary Adenocarcinoma Cell Clone in Culture after Treatment with Sodium Butyrate1

A human salivary gland adenocarcinoma cell line, which has ultrastructure and biological markers specific to the intercalated duct cells of human salivary glands, was cultured in 5 mw sodium butyrate for 12 days; then the cells were trypsinized, subcultured for an additional 16 days, and then transferred to growth medium without sodium butyrate. Morphological changes appeared about 1 wk after return to growth medium without sodium butyrate; cells being spindle or stellate in shape appeared in the treated cells, whereas the untreated cells were polygonal in shape. This morphologically altered phenotype persists after more than 14 mo of culture in growth medium without sodium butyrate. Of 40 subclones isolated, 2 clonal cell lines were established from the subculture and characterized. The other 38 subclones were accompanied by cell death during the subcul tures. The clonal lines exhibited a phenotype similar to myoepithelial cells such as myosin, /3-chain of S-100 protein, myofilaments, and oxytocin receptor in addition to decreased tumorigenicity and anchorage-independent growth. These findings in dicate that commitment to differentiation into myoepithelial cells and conversion from malignant to normal phenotype occur in a human salivary gland adenocarcinoma cell line following the sodium butyrate treatment.