Discovery and synthesis of cryptic enediynes and microbial cytotoxins

About This Grant

Project Summary & Abstract Microbial natural products have yielded remarkable anticancer agents, such as enediyne antibiotics, bleomycin, and mitomycin, that directly target DNA and induce double-strand breaks or DNA alkylation. The recent surge in microbial genome sequencing has uncovered the genetic fingerprints for thousands of molecules within these categories. However, only a tiny fraction of this potential has been harnessed, as the discovery process is hindered by the transcriptionally silent nature of the corresponding biosynthetic genes and the extremely low production levels, even when these genes are expressed. We have established methods to access metabolites encoded by transcriptionally silent or ‘cryptic’ biosynthetic gene clusters. Using a forward chemical genetics approach, termed high-throughput elicitor screening (HiTES), we have identified >150 novel, cryptic metabolites. Very recently, we have utilized the approach in conjunction with DNA cleavage assays to identify a new, cryptic enediyne that we have named clavulyne. We are therefore poised to apply this method broadly in the current proposal to discover novel enediyne natural products, thereby expanding the chemical space of this intriguing family of metabolites. We also plan to leverage creative synthetic strategies to repurpose nine-membered ring enediynes, such as clavulyne, which are otherwise too unstable for detailed biological and chemical evaluation. To further expand these efforts, we will also target a broader group of anticancer agents. Guided by bioinformatics, we will search for products of divergent bleomycin and mitomycin gene clusters as well as exploit emerging bioassays in an untargeted manner to discover completely new classes of DNA-targeting antiproliferative agents. Successful completion of the proposed studies will contribute new and difficult-to-find enediynes and DNA-targeting metabolites, thus expanding our repertoire of antiproliferative agents derived from microbial sources. They will additionally introduce new synthetic approaches to generate next-generation designer enediynes. The synthetic and natural products that result from this proposal could serve as lead compounds, payloads for antibody-drug conjugates, or chemical probes to better investigate their biological and chemical properties.