[Differentiation therapy for salivary gland tumors]

A neoplastic human salivary intercalated duct cell line, HSG and its derivative HSG-AZA1 cells with a myoepithelial cell phenotype and HSG-AZA3 cells with an acinar cell phenotype, which were induced by treatment of HSG cells with 5-azacytidine, have been used in our laboratory as models for studying mechanisms regulating cytodifferentiation in salivary glands as well as for developing differentiation therapy for salivary gland tumors. Consequently, it has been shown that the treatment of HSG, HSG-AZA1 and HSG-AZA3 cells with various differentiation agents results in cellular differentiation into myoepithelial, acinar or neuronal cells as well as keratinizing squamous cells, chondrocytes, and osteoblast, with a concomitant decrease of anchorage-independent and anchorage-dependent growths in addition to decreased tumorigenicity in nude mice. It was also found that the treatment of an adenoid cystic carcinoma of the maxillary sinus with adoptive immunotherapy involving intra-arterial injection of LAK cells and IL-2 in combination with radiotherapy, resulted in bone formation in the treated tumor, which was then replaced completely by lamellar bone tissue with myxomatous stroma. These findings may suggest the potential usefulness of differentiation therapy in human salivary gland tumors.