Polyploidization induced by acridine orange in mouse osteosarcoma cells

This study was under-taken to clarify the in vitro effect of acridine orang e (AO) on the cell kinetics of mouse osteosarcoma cells, as well as the mec hanism of cell growth inhibition induced by AO. A mouse osteosarcoma cell l ine (MOS), established from a radiation-induced mouse osteosarcoma, was cul tured under exposure to 0.05, 0.5, 5, and 50 mu g/ml of AO,either continuou sly or for 10 minutes. The cell kinetic analysis was performed using the fo llowing parameters: tumor cell growth by trypan blue exclusion test, mitoti c activity, DNA synthetic activity by BrdU labeling and DNA ploidy by cytof luorometry. The results showed that continuous exposure to 5 and 50 mu g/ml of AO or 10 minute exposure to 50 mu g/ml of AO quickly killed the tumor c ells within 12 hours whereas continuous exposure to 0.5 mu g/ml of AO ol 10 minute exposure to 5 mu g/ml of AO gradually inhibited tumor cell growth. Under the latter conditions, mitotic activity was rapidly and completely in hibited within 48 hours but DNA synthetic activity was not completely inhib ited even after 96 hours. DNA ploidy analysis demonstrated that most of the tumor cells arrested at the S-G2 phase after 12 hours, followed by G2 phas e nn est after 24 hours and progressive DNA synthesis to a higher DNA ploid y class after 48 to 96 hours. We therefore concluded that a high concentrat ion of AO has a strong cytocidal effect due to cytotoxicity whilst a modera te concentration of AO induces progressive and synchronous polyploidization by mitotic inhibition without DNA damage in MOS cells. We presume that thi s in vitro, effect on MOS cells may be caused by protein synthetic inhibiti on after transfer RNA inactivation caused AO binding.