A modular and synthetic biosynthesis platform for de novo production of diverse halogenated tryptophan-derived molecules.

Halogen-containing molecules are ubiquitous in modern society and present unique chemical possibilities. As a whole, de novo fermentation and synthetic pathway construction for these molecules remain relatively underexplored and could unlock molecules with exciting new applications in industries ranging from textiles to agrochemicals to pharmaceuticals. Here, we report a mix-and-match co-culture platform to de novo generate a large array of halogenated tryptophan derivatives in Escherichia coli from glucose. First, we engineer E. coli to produce between 300 and 700 mg/L of six different halogenated tryptophan precursors. Second, we harness the native promiscuity of multiple downstream enzymes to access unexplored regions of metabolism. Finally, through modular co-culture fermentations, we demonstrate a plug-and-play bioproduction platform, culminating in the generation of 26 distinct halogenated molecules produced de novo including precursors to prodrugs 4-chloro- and 4-bromo-kynurenine and new-to-nature halogenated beta carbolines.

Fluorescence-Based Screens for Engineering Enzymes Linked to Halogenated Tryptophan.

Directed evolution is often limited by the throughput of accurate screening methods. Here we demonstrate the feasibility of utilizing a singular transcription factor (TF)-system that can be refactored in two ways (both as an activator and repressor). Specifically, we showcase the use of previously evolved 5-halo- or 6-halo-tryptophan-specific TF biosensors suitable for the detection of a halogenated tryptophan molecule in vivo. We subsequently validate the biosensor's utility for two halogenase-specific halo-tryptophan accumulation screens. First, we isolated 5-tryptophan-halogenase, XsHal, from a mixed pool of halogenases with 100% efficiency. Thereafter, we generated a targeted library of the catalytic residue of 6-tryptophan halogenase, Th-Hal, and isolated functioning halogenases with 100% efficiency. Lastly, we refactor the TF circuit to respond to the depletion of halogenated tryptophan and prototype a high-throughput biosensor-directed evolution scheme to screen for downstream enzyme variants capable of promiscuously converting halogenated tryptophan. Altogether, this work takes a significant step toward the rapid and higher throughput screening of halogenases and halo-tryptophan converting enzymes to further reinforce efforts to enable high-level bioproduction of halogenated chemicals.

CDK4/6i enhances the antitumor effect of PD1 antibody by promoting TLS formation in ovarian cancer.

Ovarian cancer is insensitive to immunotherapy and has a high mortality rate. CDK4/6 inhibitors (CDK4/6i) regulate the tumor microenvironment and play an antitumor role. Our previous research demonstrated that lymphocyte aggregation (tertiary lymphoid structures, TLSs) was observed after CDK4/6i treatment. This may explain the synergistic action of CDK4/6i with the anti-PD1 antibody. However, the key mechanism by which CDK4/6i promotes TLS formation has not been elucidated. We examine the link between TLS and prognosis. Animal models and high-throughput sequencing were used to explore the potential mechanism by which CDK4/6i promotes TLS formation. Our results showed the presence of TLSs was associated with a favorable prognosis for ovarian cancer. CDK4/6i promoted TLS formation and enhanced the immunotherapeutic effect of the anti-PD1 antibody. The potential mechanism of CDK4/6i affecting the formation of TLS may be through modulating SCD1 and its regulatory molecules ATF3 and CCL4. Our findings provide a theoretical basis for the application of CDK4/6i in ovarian cancer.