Induction of other differentiation stages in neoplastic epithelial duct and myoepithelial cells from the human salivary gland grown in athymic nude mice.

The interaction between two cell lines derived from the human salivary gland (HSG), neoplastic epithelial duct HSG cells and myoepithelial human pleomorphic adenoma (HPA) cells, was studied morphologically and immunohistochemically in nude mice tumors produced by inoculation of HSG and HPA cells. Transplantation of HSG cells into nude mice resulted in the production of adenocarcinoma which contained carcinoembryonic antigen (CEA). The nude mice tumors induced by HPA cells were interpreted as myoepithelioma in which the presence of S-100 protein and myosin were identified. On the other hand, the occurrence of squamous cell nests was frequently noted in the nude mice tumors produced by inoculation of a mixture of HSG and HPA cells. The tumor cells present in the squamous cell nests had abundant tonofilaments in the cytoplasm and were attached with tight junction and distinct desmosomes. In addition, the presence of keratin in the tumor cells composing squamous cell nests was demonstrated. When the mixture of HSG and HPA cells treated with polyethylene glycol (PEG) was transplanted into the nude mice, the tumors produced consisted almost entirely of areas showing the histologic features of anaplastic carcinoma, and did not contain all of the specific cell markers observed in the HSG or HPA tumors. The nude mice tumors induced by PEG-treated HSG or HPA cells were interpreted as adenocarcinoma and myoepithelioma, respectively, and giant cells were occasionally observed in the tumor sections. These findings indicate that neoplastic cells showing differentiation stages other than those of the original two cells can be induced in nude mice by utilizing HSG and HPA cells.