Theses Doctoral

A pathogenic function of regulatory T cells in chronic liver disease and Chemokines expressed by engineered bacteria recruit and orchestrate anti-tumor immunity

Savage, Thomas M.

In my dissertation, I have worked on two distinct projects related to the immune system. The abstracts for the two projects that make up my dissertation work are below.

In the first project (presented in Chapter 2), we study regulatory T (Treg) cells in chronic liver disease. Current dogma holds that Treg cells preserve tissue function in settings of inflammation and damage. Consistent with this, herein we observe that Treg cells – in particular those producing the epidermal growth factor receptor (EGFR)-ligand amphiregulin (Areg) – are enriched in the livers of mice and humans with non-alcoholic steatohepatitis (NASH). Mouse and human Treg cells undergo substantial transcriptional changes in chronic liver damage, reflecting their increased activation; however, rather than playing a protective role, we find that Treg cell–derived Areg promotes NASH-induced liver fibrosis, the key prognostic factor for patients – through the direct activation of EGFR on hepatic stellate cells.

Clinically, NASH is closely linked to insulin resistance, but the mechanistic contributions of NASH-induced disease processes to insulin resistance has hitherto been unclear. We further observe that Treg cell–derived Areg promotes glucose intolerance in a NASH-dependent manner, also mediated through EGFR signaling on hepatic stellate cells. Mechanistically, in the setting of NASH, we find that Areg from Treg cells promotes hepatocyte gluconeogenesis – through hepatocyte detection of fibrosis development and soluble mediators, including IL-6, produced by activated hepatic stellate cells – offering new insight into the cellular interplay of how chronic liver disease promotes insulin resistance. Taken together, we provide the first evidence that Treg cells mediate a maladaptive role in tissue injury, finding that their production of a growth factor plays a central role in liver disease and promotes liver fibrosis and glucose intolerance in NASH.

In the second project (presented in Chapter 3), we use engineered bacteria to produce chemokines in the tumor to promote anti-tumor immunity. Tumors employ multiple mechanisms to actively exclude immune cells involved in anti-tumor immunity. Strategies to overcome these exclusion signals remain limited due to an inability to target therapeutics specifically to the tumor. Synthetic biology enables engineering of cells and microbes for tumor-localized delivery of therapeutic candidates previously unavailable using conventional systemic administration techniques. Here, we engineer bacteria to intratumorally release chemokines to attract adaptive immune cells into the tumor environment.

Bacteria expressing an activating mutant of the human chemokine CXCL16 (hCXCL16K42A) offer therapeutic benefit in multiple mouse tumor models – an effect mediated via recruitment of CD8+ T cells. Furthermore, we target the presentation of tumor-derived antigens by dendritic cells – using a second engineered bacterial strain expressing CCL20. This led to type 1 conventional dendritic cell recruitment and synergized with hCXCL16K42A-induced T cell recruitment to provide additional therapeutic benefit. In summary, we engineer bacteria to recruit and activate innate and adaptive anti-tumor immune responses, offering a new cancer immunotherapy strategy.


This item is currently under embargo. It will be available starting 2025-03-24.

More About This Work

Academic Units
Microbiology, Immunology, and Infection
Thesis Advisors
Arpaia, Nicholas
Ph.D., Columbia University
Published Here
March 29, 2023