Organ distribution of experimental metastases of a human colorectal carcinoma injected in nude mice.

The metastatic behavior of the HT-29 human colorectal carcinoma cell line was studied following injection into nude mice by different routes. After intrasplenic injection, experimental metastases formed in the livers of most mice. Variant lines were established in culture from the liver lesions and from tumors growing at the site of injection, the spleen. Cells of the HT-29 LMM line exhibited slightly enhanced ability to form liver metastases compared with cells of the non-selected parent line. When injected i.v., the HT-29 cells produced only a few small experimental metastases in the lungs, but in most of the mice macroscopic tumors were found in various lymph nodes and the interscapular fat. Analyses of the distribution of IdUrd-labeled cells did not reveal a preferential localization of the HT-29 cells in sites where metastases subsequently formed. This suggested that the growth of the human colon carcinoma cells in those sites might be the result of a stimulatory interaction between the tumor and host cells as opposed to growth in sites such as the lungs, where numerous cells arrested after i.v. injection but only a few, small metastases were seen 60 days later.