Figure 3
Tumorigenicity of stem-like cells derived from CMC cultures. a) Tumor-forming rates of mammosphere-derived cells from CMCs. Cells were pseudo-orthotopically injected into NOD/SCID mice, and tumor development was monitored. Tumor take rate was 100% after the 1st injection. Tumorigenicity rate was steadily up to 100% when cells recovered from primary xenografts were cultured in stem-permissive conditions and re-injected into mice fat pads. b) Cells derived from mice xenografts appearance after in vitro culture. As the original cultures derived from canine carcinomas, cells grow as partially attached or floating spheroids in stem conditions, while upon differentiation are able to attach to the substrate and grow as monolayer. Phase-contrast images, original magnification 20X. c) Canine mammary stem-like cells fully recapitulate the tumor of origin when transplanted into immunodeficient mouse. Histopathologic examination of implanted tumors: representative H&E staining reveals the typical appearance of tubulopapillary carcinomas both in the original canine tumor and the corresponding mice xenograft; immunohistochemical staining for CD44 shows the presence of rare, but observed in each tumor tissue, positive cancer cells (original magnification 40X).