(A) Frozen sections of lungs of Luc-RFP-231 tumor-bearing and tumor-free nude micesacrificed 24 hours after CD-MSC, N-MSC, DPBS, or MRCS-CD infusion were stained with anti-annexin V (green) and DAPI (blue). RFP signal (red) indicates the presence of lung metastasis. Scale bars, 100 μm. Representative images of frozen section samples of tumor-bearing lungs and tumor-free lungs from nude mice treated with CD-MSC, MRCS-CD, N-MSC, or DPBS before and after 5-FC injections by TUNEL assays are shown. Horseradish peroxidase signals (brown) indicate damaged nuclei, and green signals are methyl green counterstain of normal nuclei. Scale bars, 100 μm. (B) Quantification of TUNEL assay data measuring lung tissue damage in vivo. Ten representative images were used per group for quantification. *P < 0.05, **P < 0.01, and ****P < 0.0001. Data are means ± SD.