Liver metastases induced by implantation of VX2 cancer into the gastrointestine.

An experimental model with a high frequency of spontaneous liver metastases was induced by implantation of VX2 cancer cells into the gastrointestinal walls of 36 rabbits, and the developmental process of primary cancer lesions and metastases was examined histologically. Gastric and colonic cancer lesions showed similar growth patterns in both primary and metastatic lesions: the average diameter of primary lesions enlarged from 0.7-0.8 cm on Day 7 to 2.4-2.8 cm on Day 28. The frequency and average diameter of liver metastases were 25% and microscopically certificated levels on Day 14, 25% and 3 mm on Day 21, and 50% and 8 mm on Day 28 in the gastric wall-implantation group. They were, respectively, 20% and microscopically recognized levels on Day 14, 40% and 2 mm on Day 21, and 80% and 9 mm on Day 28 in the colonic wall-implantation group. Thus, the frequency and diameter of the metastases increased in parallel with the primary cancer growth. Liver metastases occurred only in animals with vascular invasion in primary lesions, though none of the animals with the invasion always showed the metastases. These results suggest that vascular invasion of cancer cells in the primary lesions may be a premise of liver metastases, and that this experimental model may be utilized as a useful tool for studying many aspects of the pathogenesis and/or therapy of the spontaneous liver metastases in gastrointestinal cancer.