Tumor formation after subcutaneous inoculation of ES or in vitro differentiated cells into various hosts.

ES cells and cells differentiated in vitro for 14 days were injected subcutaneously into the flank of syngeneic or allogeneic mice or xenogeneic rats (1×106 cells in PBS/animal). Some recipients received an immunosuppressive treatment with CsA (10 mg/kg/day). The percentage and number of animals in which tumors were found during autopsy or in which tumors were palpable (at least during 3 consecutive observations) at the side of injection before day 100 after injection is indicated.1in 2 mice (8%) a tumor regression was observed before day 100.2in 2 mice (9%) a tumor regression was observed before day 100.3in 1 mouse (7%) a tumor regression was observed before day 100.4in 2 mice (11%) a tumor regression was observed before day 100.5in 8 female mice (47%) a tumor regression was observed before day 100.6in 2 rats (11%) a tumor regression was observed before day 100.