Cloning of plasmacytoma micrometastases from spleen

Soft agarose cloning of tumor cells in spleens from mice bearing 4T00.1 plasmacytomas reveals the ubiquitous presence of micrometastases. The latter can be found in spleens of mice splenectomized as early as 4 h post subcutaneous inoculation of 4T00.1 tumor cells. The total number of potentially proliferating 4T00.1 cells in the spleen is low (approximately 100) and constant for the first 18 days, after which the number increases and reaches 7000 at 27 days post inoculation, when the tumor is greater than 20 mm in diameter. The soft agarose cloning technique detects small numbers of micrometastases in spleen, which cannot be detected by other methods.