Human breast cancer cells contribute to the formation of luminal epithelial cells and secrete human milk proteins in the chimeric mammary gland.

<p>Human breast cancer cells incorporated into the mammary gland express human-specific luminal epithelial cell marker keratin 8 as indicated by the white arrows (green; Alexa Fluor 488) and secrete milk proteins in impregnated hosts (arrows, human alpha-lactalbumin, green, FITC; mouse casein, red, rhodamine). Human-specific luminal epithelial cell marker keratin 8 (arrows) is expressed in chimeric mammary gland outgrowths produced with A) MDA-MB-468 plus mammary epithelial cells transplant fragment, B) MDA-MB-231-GFP plus mammary epithelial cells transplant fragment; C) MDA-MB-231BRMS-GFP plus mammary epithelial cells transplant fragment; D) hTERT-HME1 human epithelial cells plus mammary epithelial cells transplant fragment. Anti-human alpha-lactalbumin (arrows) is expressed in chimeric mammary gland outgrowths generated using E) MDA-MB-231BRMS-GFP plus mammary epithelial cells transplant fragment; F) intact host. Anti-mouse caseins (arrows) is expressed in chimeric mammary gland outgrowths generated using G) MDA-MB-231-GFP plus mammary epithelial cells transplant fragment; H) intact host. All outgrowths are second generation chimeras (human breast cancer cells plus mouse mammary epithelial cells). Intact glands are from lactating hosts. Scale bars 10 µm.