Abstract
Five gastric carcinomas, induced in inbred Wistar rats by oral administration of NβmethylβN'βnitroβNβnitrosoguanidine (MNNG) dissolved in drinking water, were successfully transplanted to isologous rats. The transplants grew to a size of 10 to 35 mm in diameter within 8 to 25 weeks of implantation. In one case, serial transplantations were maintained up to the 11th generation, with occurrence of distant metastasis in the 3rd generation. Histological, histochemical, and electron microscopical comparison of the original and transplanted tumors revealed thet (1) the original tumors were quite well differentiated, forming either papillary or tubular structures, whereas the transplants were more anaplastic and pleomorphic showing often solid nests; and (2) tumor cells with gastrointestinal differentiation and cells with neuroendocrine differentiation were present and evenly distributed in both the original and the serially transplanted tumors. As it is unlikely that the normal and neoβplastic neuroendocrine cells are growing sideβbyβside with and independently of the epithelial neoplastic components in the present series of transplants, the findings strongly suggest (1) the multidirectional potency of the inbred rat stomach carcinoma cells and (2) the common neoplastic origin of the epithelial and neuroendocrine components.