Figure 2

Murine hybrid cells harbor tumor-initiating capacity. (A) Mammary carcinoma cells from PyMT:RFP mice injected into GFP-expressing recipients. Resulting tumors express E-cadherin (red) and Actin:GFP (green) and were counterstained with Hoechst dye (blue). Arrowhead denotes co-positive hybrid cells. (B) Representative FACs plot of tumor-derived hybrid cells (GFP⁺/RFP⁺) and unfused tumor cells (RFP⁺/GFP⁻⁾ from dissociated tumor and injected into syngeneic wt recipient mice. (C) Twenty-five hundred FACS-isolated cells were injected into recipient mice (hybrid cells, red line) and (unfused cells, dashed black line) and temporally monitored for growth. (D) Injection of 250,000 unfused tumor cells developed tumors in recipient mice (black line), while 25,000 cells did not grow (dashed line).