In vitro evaluation of the antineoplastic activity of combretastatin A-4, a natural product from Combretum caffrum (arid shrub).

Combretastatin A-4 is a natural product which was isolated from the South African tree Combretum caffrum. In this study, the cytotoxic activity of combretastatin A-4 was tested in radiometric and human tumor cloning assays against eight different tumor cell lines and against 15 patient tumors in the human tumor cloning assay. To test the preferential cytotoxicity of combretastatin A-4 against tumor cells versus non-tumor cells, it was also tested in the radiometric assay against both normal human diploid fibroblasts and human bone marrow cells. Of the eight cell lines used, combretastatin A-4 showed preferential cytotoxicity for six of them. In addition, combretastatin A-4 showed a concentration-dependent cytotoxicity against a variety of human tumors. Based on the data generated in this study, combretastatin A-4 should be further tested in in vivo preclinical models.