Evaluation of Growth and Histology of Human Tumor Xenografts Implanted under the Renal Capsule of Immunocompetent and Immunodeficient Mice1

Fresh surgical expiants of human carcinomas were implanted as first transplant generation xenografts under the kidney cap sule of mice. Immunocompetent and immune-deficient mice were compared for their ability to support the persistence and growth of these xenografts. Consistent growth of tumor xenografts could not be demonstrated following implantation under the kidney capsule of immunocompetent mice. Immunological infil tration and rejection of the xenografts began 3 days postimplan tation, and tumors were largely eliminated from the subcapsular space by 6 days postimplantation. In contrast human tumors consistently grew under the kidney capsule of nude mice. Sig nificant growth became apparent by 9 days postimplantation with most human carcinomas and continued thereafter. Growth was always accompanied by neovascularization of tumor xeno grafts which was visible by examination of tumor-bearing kidneys under a dissecting microscope (x 6). There was no histological evidence of immunological interference with the persistence and growth of xenografts in nude mice. Thymectomized, irradiated, bone marrow-reconstituted conventional mice, as well as con ventional mice, treated daily with 60 mg of cyclosporine A/kg were comparable to nude mice as hosts which supported the long-term persistence and growth of subrenal capsule implants of human tumors. Such mice could provide an alternative to nude mice as hosts in which chemosensitivity assays could be carried out against growing human tumors at a considerable saving in cost and convenience.