Scientists Crack 'Mix and Match' Code Behind Bacterial Anti-Cancer Drug Assembly, Opening Door to Engineered HDAC Inhibitors
Key Insights
Researchers at the University of Warwick and Monash University have revealed how bacterial enzymes use 'docking domains' to assemble multiple variants of powerful anti-cancer compounds through a combinatorial biosynthesis mechanism.
The study, published in Nature Communications, identifies a conserved connection point that allows different enzyme partners to mix and match, explaining how bacteria generate structural diversity in HDAC (search) inhibitors like Romidepsin.
The team also identified the previously mysterious biosynthetic pathway for FR-901375 (search), a chemically related depsipeptide HDAC (search) inhibitor, by locating its gene cluster in Pseudomonas chlororaphis subsp. piscium.
A team of researchers at the University of Warwick and Monash University has solved a decades-old puzzle that has stymied drug developers: how bacteria naturally create multiple versions of powerful cancer therapies. Published in Nature Communications, the findings reveal the molecular "mix and match" mechanism that enables bacterial enzymes to assemble a family of related anti-cancer compounds, including the FDA-approved blood cancer treatment Romidepsin (Istodax). The breakthrough establishes a rational approach to designing new therapies for hard-to-treat cancers.
"For decades, we've known that bacteria can naturally produce multiple versions of powerful anti-cancer drugs, yet we had no idea how they achieved this," said first author Dr. Munro Passmore, Research Fellow in the Department of Chemistry at the University of Warwick. "This work finally cracks that code. We've identified how the different enzymes communicate and cooperate to produce these drug variants, something that has eluded researchers because the system is so elegantly economical. It's the breakthrough we needed to actually engineer these drugs ourselves."
Docking Domains: The Molecular Connectors
The team's analysis reveals that small molecular regions, termed "docking domains," act as connectors between the core drug assembly machinery and the variable component-building enzymes. Crucially, these docking domains use a conserved connection point that is compatible with multiple different enzyme partners — a feature that explains how bacteria generate structural diversity while maintaining drug precision and efficacy.
The compounds in question belong to the HDAC (search) inhibitor class, which block histone deacetylases — enzymes that cells use to control gene expression. These depsipeptide molecules are complex cyclic structures assembled from various amino acid building blocks and a conserved hydroxy acid pharmacophore, held together by a mix of peptide and ester bonds. Inside bacteria, they are manufactured by enormous protein machines called PKS-NRPS hybrids, which combine polyketide synthase (PKS) and nonribosomal peptide synthetase (NRPS) activities.
Unmasking FR-901375 (search)'s Biosynthetic Origins
A key achievement of the study was identifying the biosynthetic pathway for FR-901375 (search), a chemically related drug that has remained scientifically mysterious for decades. Using bioinformatic searches of public databases, the researchers located the FR-901375 biosynthetic gene cluster in Pseudomonas chlororaphis subsp. piscium, confirmed by mass spectrometry analysis of extracted metabolites.
The research employed an integrated suite of structural, biochemical, and genetic approaches. In vitro reconstitution experiments with purified protein domains demonstrated productive enzyme-enzyme interactions, validated by intact protein mass spectrometry. AlphaFold computational modeling predicted protein complex structures, and these predictions were tested experimentally using carbene footprinting mass spectrometry to map interaction interfaces. Site-directed mutagenesis confirmed the functional importance of predicted binding residues, while gene deletion experiments in bacterial strains demonstrated the essential role of the docking domains in vivo.
Evolutionary Blueprint for Drug Design
The work also traces how these drug-producing systems evolve naturally. The researchers found that the newly discovered compound likely evolved from a related drug-producing system through gene duplications and recombinations. Comparative analysis of biosynthetic gene clusters across multiple HDAC (search) inhibitor-producing bacteria revealed evolutionarily conserved parts of the system.
Prof. Greg Challis, Monash Warwick Alliance Professor of Sustainable Chemistry at the University of Warwick and Monash University, emphasized the translational potential: "This research gives us a blueprint to do what nature does, but better and faster. By reverse-engineering nature's evolutionary logic, we can now design synthetic pathways that generate new anti-cancer drug candidates with properties optimized for clinical use, such as superior potency, improved selectivity, fewer side effects."
He added: "Our immediate goal is to build an expanded library of candidates for various cancers where new treatments are urgently needed. This discovery is moving us from understanding how the systems work to building new ones."
The study, titled "Molecular basis for depsipeptide HDAC (search) inhibitor combinatorial biosynthesis," represents a significant advance for the field of combinatorial biosynthesis — a strategy that has long held promise but stalled due to an incomplete understanding of how bacterial enzymes interact. By cracking the code of enzyme communication, the researchers have laid the groundwork for engineering next-generation HDAC inhibitors with tailored therapeutic properties.