Optimal conditions for the growth of malignant human and animal cell populations in immunosuppressed mice.

Immunosuppressed mice have been used to support the growth of xenogeneic human and animal malignant cell populations. The optimal conditions for tumor growth are neonatal thymectomy coupled with antithymocyte serum or thymectomy, followed by whole-body irradiation and bone marrow reconstitution. When mice are inoculated with a mixture of normal and malignant cells, the malignant cells have a selective advantage. No such selectivity is found when the mixed populations are grown in vitro. Human tumors may also be grown in immunosuppressed mice. These tumors retain the organization of the original tumor in the human host. The advantages of this system to cancer researchers are discussed.