Effect of the novel prostaglandin A(1) derivative TEI-6363 on ROS17/2.8 cell differentiation in vitro

The effect of TEI-6363 (5-[E-4-N,N-dimethylaminophenylmethylene]-4-hydroxy- 2-[1-methyl imidazole-2-ilthio]-4-[4-phenylbutyl]-2-cyclopentenone), a chem ically synthesized prostaglandin A(1) derivative, on cell proliferation and osteoblastic differentiation was investigated concurrently. ROS17/2.8 cell s (a rat osteosarcoma-derived cell line) were treated with TEI-6363 at two concentrations, 10(-7) and 10(-6) M, and viable cells were counted to asses s cytotoxic effects and determine the growth curve. After 96 h of treatment , there was no evidence of any effect of TEI-6363 on cell viability at eith er concentration. However, a clear inhibitory effect on cell proliferation was observed after treatment with 10(-6) M TEI-6363 for 24 h or longer. A p ulse-treatment experiment showed that TEI-6363 induced the inhibition of pr oliferating ROS17/2.8 cells 24 h after addition. The inhibition of prolifer ation was associated with G1-arrest demonstrated by flow cytometric analysi s, and incorporation of [H-3]thymidine by ROS17/2.8 cells was decreased. Os teoblastic differentiation (assessed on the basis of increased alkaline pho sphatase activity and collagen synthesis) was induced by TEI-6363 treatment at 10(-6) M following G1-arrest and inhibition of cell proliferation. Thes e results suggest that TEI-6363 arrested the cell cycle of ROS17/2.8 cells at the G1 phase and induced osteoblastic differentiation. These results did not appear to be dependent on a marked cytotoxic effect.