Growth inhibition of synchronized trigeminal neurinoma cells by nerve growth factor

Nerve growth factor (NGF) reduces the development of trigeminal neurinomas in vivo. To characterize the action of NGF on these tumors, clonal cells (476-16) isolated from a rat trigeminal neurinoma cell line were synchronized at early S phase by aphidicolin, a reversible inhibitor of DNA polymerase alpha, and effects of NGF on DNA replication were examined in vitro. While NGF did not inhibit DNA replication in the ongoing S phase, it reduced the level of DNA synthesis in the succeeding S phase without altering its timing and duration. The inhibitory action was elicited by a brief exposure to NGF during progression through the preceding S to G1 phases with decreasing effectiveness in the later stage of G1.