Abstract: In the experiment of induction of transformation of host stroma cells in nude mice by transplanted human colonic adenocarcinoma HT-29 cell liner, we discovered accidentally that the serial passage of the HT-29 cell line in nude mice caused the differentiation of human tumor cells. There appeared a lot of granular cavities, mucus-likem material secreted by differentiated adenocarcinoma cells and rich connective tissue in the sections of 3rd and 4th passage. Moreover, colonic villi-like structures can be seen in sections of 5th passage. We also found that the amount of carcinoembryonic antigen(CEA) per unit volume of tumor in serum of tumor bearing animals decreased as the number of passage was incerased.

Key words: Human colonic adenocarcinoma HT-29 cell line, BALB/nude mice, differentiation, carcinoembroyonic autigen(CEA)