At the Li lab, we are interested in engineering cellular and molecular systems to address a range of diseases, including gastrointestinal disorders, cancer, and infectious diseases. Examples are shown below:
1. Nonpathogenic E. coli engineered to surface display cytokines as a new platform for immunotherapy
Given the safety, tumor tropism, and ease of genetic manipulation in non-pathogenic Escherichia coli (E. coli), we designed a novel approach to deliver biologics to overcome poor trafficking and exhaustion of immune cells in the tumor microenvironment, via the surface display of key immune-activating cytokines on the outer membrane of E. coli K-12 DH5α. Bacteria expressing murine decoy-resistant IL18 mutein (DR18) induced robust CD8+ T and NK cell-dependent immune responses leading to dramatic tumor control, extending survival, and curing a significant proportion of immune-competent mice with colorectal carcinoma and melanoma. The engineered bacteria demonstrated tumor tropism, while the abscopal and recall responses suggested epitope spreading and induction of immunologic memory. E. coli K-12 DH5α engineered to display human DR18 potently activated mesothelin-targeting CAR NK cells and safely enhanced their trafficking into the tumors, leading to improved control and survival in xenograft mice bearing mesothelioma tumor cells, otherwise resistant to NK cells. Gene expression analysis of the bacteria-primed CAR NK cells showed enhanced TNFα signaling via NFkB and upregulation of multiple activation markers. Our novel live bacteria-based immunotherapeutic platform safely and effectively induces potent anti-tumor responses in otherwise hard-to-treat solid tumors, motivating further evaluation of this approach in the clinic.
2. Developing a new class of chemically modified small RNA inhibitors to modulate the oral microbiome
The oral microbiome represents an exciting frontier in medicine, and early successes in the field have demonstrated the dynamic interactions among individual microbial species and highlighted the crosstalk between oral microbiota and their hosts at the mucosal interface. Recent studies uncovered the roles of host-derived small RNAs (sRNAs) in the growth inhibition of pathogenic bacteria. However, it remains unclear about the spectra and mechanistic functions of host sRNAs as defense molecules in the context of host-microbiome interaction. Moreover, considering the success of RNA medicines in recent years, it presents an exciting opportunity to make use of the host sRNAs to target pathogenic bacteria. Building on the profiling of sRNAs in human saliva, we will engineer host-derived sRNAs to target specific bacteria in a complex environment consisting of bacterial pathogens, the commensal bacteria, and the host.
3. Engineering commensal bacteria to sense and respond to the intracellular redox imbalance toward mitochondrial dysfunction
Mitochondrial dysfunction is associated with many diseases including, but not limited to, aging, cancer, neurodegeneration, and diabetes. The dysfunction of the mitochondrial electron transport chain (ETC) is one of the hallmarks of mitochondrial diseases and emerging studies show that the elevated NADH/NAD+ ratio resulting from ETC dysfunction can lead to reductive stress. The second project will enable a smart bio-robot to ameliorate mitochondrial dysfunctions by coupling a common mitochondrial disease marker, lactate, to the redox levels inside host cells.
4. Engineering Bacillus subtilis spores as a versatile and stable platform for the production of therapeutics
The ability to manufacture biologics from engineered cells has revolutionized biotechnology research and therapeutic biologic production. In most cases, the designed protein product is freeze-dried to mitigate cold chain requirements. However, lyophilization has traditionally been plagued by complications. A better approach would be a viable cell that can remain dormant for prolonged periods of time until activated with a specific biological cue to produce desired proteins. In this project, we will develop a highly stable and integrated platform based on Bacillus subtilis spores, to streamline the production and storage of temperature-sensitive biomolecules for various applications.
