Natural products as leads to antitumor drugs

The discussion in this short review emphasizes that the main and future source of novel natural products as leads to antitumor agents is probably in the areas of biology that cannot be seen, i.e. the microbial world. The review discusses the role of microbes in the production of secondary metabolites that were initially thought to be from marine invertebrates and goes on to discuss the potential for a number of well-known anticancer agents isolated from plant sources to actually be the products of a microbe-plant interaction and finishes with a discussion of the potential of microbial “cryptic clusters” as sources of novel agents/leads to anti-tumor treatments.