Background: The prognostic value of circulating tumor cells remains unclear since, in principle, most tumor cells are unable to survive in the bloodstream. The aim of the study was to establish a system that can be used to investigate the metastatic process in more detail, with emphasis on circulating tumor cells.
Materials and methods: Human colon carcinoma cells (HT29) were transplanted into severe-combined-immunodeficient (scid) mice. The metastatic load in the blood was investigated using the human-specific carcinoembryonic antigen (CEA) as target for quantitative polymerase-chain-reaction (PCR).
Results: A close correlation between the weight of the primary tumor and the number of circulating tumor cells was detected (r=0.7240; p<0.0001). Moreover, the number of circulating tumor cells and the actual number of spontaneous lung metastases was related (r=0.8283; p<0.0001).
Conclusion: A tumor xenotransplantation model is presented that allows for a detailed investigation of the metastatic process in three different compartments: the primary tumor bed, the bloodstream and the target organ of metastatic residency.