KB cell culture I. Role in discovery of antitumor agents from higher plants.

KB (Eagle) cell culture has played a powerful role in discovery of antitumor agents from higher plants. Had KB alone been used as a preliminary screen, with in vivo screening limited to KB-active extracts, fractions, or compounds, KB activity of crude products would have led to discovery of vinblastine, vincristine, podophyllotoxin (from which the semisynthetics VM-26 and VP-16 were derived), and all but one of the antitumor agents now under development toward or in clinical evaluation, including bouvardin, bruceantin, camptothecin, ellipticine, homoharringtonine, maytansine, taxol, thalicarpine, and tripdiolide. Indicine N-oxide is the only important antitumor agent which would have been discovered only by in vivo screening of crude plant products. A substantial number of compounds effective against lymphoid leukemia L1210 and B16 melanoma were isolated from plants, extracts of which were active against KB.