Lanthanum ions （La3＋） have been reported to exert profound effects on the proliferation of NIH 3T3 mouse embryonic fibroblasts. In the present studies, the pro-proliferative effect of La3＋ on NIH 3T3 cells was further characterized, and its impacts on the cell cycle kinetics were analyzed in detail by cell cycle arrest-and-release and pulse BrdU-labeling and chasing experiments. The results show that La3＋ promoted the proliferation of NIH 3T3 cells after 12 h and the ECs0 was 2.4 ktM after 48 h. Such effect was also confirmed by enhanced BrdU incorporation. La3＋ stimulated more cells to pass through the G1/S checkpoint into S phase, but did not change the length of cell cycle. Furthermore, La3＋-treatment increased the protein levels and nuclear localization of cyclin D 1 and c-Myc, two key regulators of G1/S checkpoint, as demonstrated by immunostaining. The pro-proliferative effects of La3＋ share striking similarity with that of Gd3＋, and provided new information regarding the cellular biological activities of lanthanides.
