Abstract
The secretion of CEA into the blood of athymic mice was studied with 4 sublines of human colonic adenocarcinoma cell lines, HT 29 and SLu. Growth curves based on tumour volume (caliper measurements) or tumour mass (weight) correlated with a concomitant increase of serum CEA during the logarithmic growth phase, but showed a marked dissociation when the growth rate slowed down. In the logarithmic growth phase doubling times between 2 and 6 days were calculated and about 6-7 doubling times passed until the shift in the growth rate was observed, independently of the sublines transplanted. Constant increases of CEA between 0.03 and 0.45 microgram/l serum per mm3 increase of tumour volume, depending on the sublines, were recorded during the logarithmic growth phase. Sublines releasing high amounts of CEA in vitro (cell culture) retained this characteristic in vivo. Correlation between tumour volume and tumour mass or serum CEA showed correlation coefficients of 0.820-0.977 during the logarithmic growth phase.