Richard E. Moore*, Thomas H. Corbett, Gregory M. L. Patterson and Frederick A. Valeriote Pages 317 - 330 ( 14 )
Six to ten percent of the extracts of laboratory-cultured blue-green algae are significantly cytotoxic against human tumor cell lines. Structurally-unique cytotoxins have been isolated from most of the active extracts. Of the extracts of >2000 cyanophytes examined to date, approximately 0.8% showed solid tumor selective cytotoxicity in the Corbett assay. The lipophilic extract of Nostoc sp. GSV 224 was by far the most cytotoxic and one of the few extracts that were both solid tumor and tumor selective. Cyclic depsipeptides called cryptophycins were found to be the solid tumor and tumor selective agents. In vivo studies on naturally-occurring cryptophycin-1 and semi-synthetic cryptophycin-8 indicate that these compounds are very active against a broad spectrrum of tumors implanted in mice, including multidrug-resistant tumors, and that a cryptophycin analog may eventually be evaluated in the clinic. Several cytotoxins from terrestrial cyanophytes have•structures that resemble those of some antineoplastic agents from marine invertebrates, suggesting that a more extensive cultivation and screening effort on marine cyanophytes could lead to more discoveries of new antitumor drugs.