Fig. 2.

Human osteosarcoma cell lines exhibit different cell cycle profiles. SaOS-2, G292, MG63, U2OS, HOS, and 143B osteosarcoma cells were synchronized by incubation for 24 h with mimosine to generate a G₁ phase block. Then, cells were released from G₁ phase arrest by the addition of fresh culture medium without mimosine and harvested after 0, 3, 6, 9, 12, 15, 18, 24, 30, and 36 h (A–F). Progression through successive cell cycle phases (G₁, S, and G₂/M) was monitored by flow cytometry (top part). Expression of cell cycle markers cyclins A, B, D, and E mRNA (middle part) and cyclin D1 protein (bottom part) were analyzed by Western blot and RT-PCR, respectively.