Cytotoxicity and Cell Cycle Specificity of Homoharringtonine

Abstract
The plant alkaloid, homoharringtonine, isolated from Cephalotaxus harringtonia is cytotoxic to HeLa, KB, and L cells growing in monolayer cell cultures. This effect appears to be cell-cycle specific. In synchronized KB cells, protein synthesis was preferentially inhibited in the G(1) and G(2) phases (70 and 45% inhibition, respectively) as might be expected for a protein-synthesis inhibitor.