KRAS and sarcoma: To determine whether Prosense 680 was labeling sarcomas in vivo, we used a mouse with a YFP reporter that is activated by Cre recombinase (LSL-YFP).10LSL-YFP;LSL-Kras;p53Flox/Flox mice that develop sarcomas after Adeno-Cre injection express YFP specifically in tumor cells.