MKI67 and sarcoma: Of note, immunostaining of sarcomas with an antibody directed against Ki-67, which is a marker of cellular proliferation because it is expressed during interphase (G1, S, G2) and mitosis (M), but not in resting G0 cells (Scholzen and Gerdes, 2000), showed no difference between the two groups suggesting that miR-16 deletion had no significant impact on proliferation of sarcoma cells in vivo (Fig. 4C,D).