2.9. Human Xenograft HT29 Colorectal Cancer Model

All experimental procedures involving animals were reviewed, approved, and conducted in accordance with established guidelines of the Animal Care and Use Committee at China Medical University. All efforts were also made to minimize animal suffering and to reduce the number of animals used according to the 3Rs principles (replacement, reduction, and refinement). To establish peritoneal colorectal cancer mice models, eight-week-old male athymic Balb/c mice were s.c. injected with 1 × 10⁶ HT29 colon carcinoma cells. After 14 days, the mice were randomly divided into three groups of 9 mice each and IV injected once with 1 × 10⁶ control primed MSCs (MSC), CRAdNTR-loaded primed MSCs (MSC^CRAdNTR), or 1 × 10⁹ CRAdNTR suspended in the 1:10 diluted NAbs-containing human serum (50 μL serum in 500 μL PBS). Two days later, all mice were i.p. administrated with 25 mg/kg CB1954 (Sigma-Aldrich, St. Louis, MO, USA) for 5 consecutive days per week for 2 cycles. After 14 days of last cycle of CB1954 administration, all mice were given third cycles of 25 mg/kg CB1954. The mice were sacrificed for harvest of tumor and vital organ tissues 7 days later. Tumors from all groups of mice were measured every week with calipers after treatment. The volume was estimated by the formula: volume = width² × length/2.