Tumor volume correlated serum CEA levels in nude mice after primary xenotransplantation of human colorectal carcinoma.

Six different human colorectal adenocarcinomas were xenotransplanted onto six groups of female, syngeneic BALB/c nude mice, 4 weeks of age, under standardized pathogen-free conditions, and the serum CEA levels were determined by RIA. Five tumors grew positively, yielding a tumor take of nearly 90%. One tumor showed no growth macro-or microscopically. All animals were sacrificed after 12 weeks post-transplantation. Ten untreated controls showed a mean serum CEA concentration of 0.62 +/- 0.14 ng/ml. All tumor-bearing animals, including the negative tumor take group, exhibited increased CEA levels (1.0-60.0 ng/ml), which were positively correlated to tumor volume, measured in all tumor-bearing animal groups. However, no correlation was observed between patients' serum CEA levels, measured preoperatively, and CEA concentrations in nude mice. These findings suggest that further immunohistologic studies are necessary to evaluate the difference of CEA synthesis by microscopically identical original human and transplanted tumor tissue.