An in vivo clonogenic assay for human tumors using plasma clot diffusion chambers implanted in mice.

A modification of the in vivo tumor clonogenic assay using plasma clot diffusion chambers has been described which allows improved study of the cytological characteristics of the colonies cultured. Seventy-five percent of the tumors derived from malignant ascites could be cultured successfully (more than 30 small and large colonies per diffusion chamber). The cloning efficiency ranged from 0.01 to 10%. The addition of 2-mercaptoethanol, horse serum and insulin to the diffusion chambers did not affect colony formation, whereas the effect of cell-free malignant ascites added to the diffusion chambers was unpredictable. Colony growth was comparable when fresh or cryopreserved tumor cells were cultured. A linear relationship between the number of tumor cells inoculated and the number of colonies cultured was apparent in the range 10(2)-10(4) cells. Colony formation was stimulated by pre-irradiation (8 Gy) of the host animal and by weekly transplantation of the diffusion chambers in new mice. Intravenously administered doxorubicin penetrated the plasma clot and caused inhibition of colony formation in two experiments with melanoma cells.