Subcutaneous injection of the hybrids. At 7 days after subcutaneous injection in BALB/c nude mice, no mass was observed in those injected with GES-1 (panel A) or CM-MSCs (panel B), but masses were observed in mice injected with hybrids (panel C). With prolonged observation time, GES-1 and CM-MSCs remained negative for subcutaneous masses, while the size of the masses decreased in mice injected with hybrids (panel D). H&E staining (panel E) and CK-18 IHC (panel F) results show that the masses were of epithelial origin and gastric gland structures were observed, but not show characteristics of malignant tumor. Magnification: 40×, Scale bar 200 μm. Data are representative of three experiments.