Figure 2.

Preclinical hAMSC tumorigenicity assessments in vitro and in vivo. (A–C) The soft agar colony experiment was performed to investigate the tumorigenicity of hAMSCs cultured for 21 days in vitro (magnification, 40×). (A) Human normal embryo lung fibroblasts (MRC-5, 3.0 × 10³ cells/well) were negative controls. (B) hAMSCs (6.0 × 10³ cells/well) showed no tumorigenic effect. (C) Human cervical cancer cells (Hela, 3.0 × 10³ cells/well) were used as positive controls. (D−H) Subcutaneous tests in nude mice (Balbc-nu) were performed to investigate the tumorigenicity of hAMSCs in vivo. The negative control group (D) and hAMSC group (E) did not show tumor formation after 16 weeks. In the positive control group (NCI-H460), the mice were sacrificed when tumor arose and grew to 3000 mm³ at Day 26 (F), Day 30 (G), and Day 33 (H), respectively.