Figure 3.

Cells derived from MMTV-Neu/WC/R26 tumors contribute to a functional mammary gland when mixed with normal mammary epithelium. (A) When inoculated on their own, MMTV-Neu/WC/R26 tumor cells give rise to tumors in cleared mammary fat pads. (B) When mixed with normal mammary epithelium in a 1:50 ratio and inoculated into an epithelial divested fat pad, the β-Gal-marked tumor cells contribute to the resulting normal mammary outgrowth and did not produce tumors. (C) Cross section of a chimeric gland demonstrating presence of β-Gal⁺ cells. (D) β-Gal and casein coexpression (white) in mammary epithelium in a lactating chimeric gland demonstrates tumor-derived cells capable of differentiating to producing milk proteins.