This project, Defining and Targeting Novel Anti-viral and Anti-cancer T cell Immunity, investigated the role of nuclear-to-cytoplasmic (N→C NF-κB) signaling in regulating CD8+ T cell responses to infections and cancer. The researchers aimed to understand how N→C NF-κB signaling affects CD8+ cell regulation during viral infections and tumor responses. They found that inhibiting the N→C NF-κB pathway led to improved anti-tumor responses in their mouse model, NEMODK. However, in chronic viral infections, the model had reduced virus control, suggesting its importance in CD8+ T cell differentiation. The research team explored a drug that targeted the NF-κB pathway and showed promising results in tumor regression. The study has received NIH funding to further investigate the mechanisms of a NF-κB inhibitory drug.
The Challenge
CD8+ T cells play key roles in defense against intracellular pathogens and cancer. The activation of T cells requires T cell receptor engagement by specific antigens and costimulatory and inflammatory signals. These signals start outside the cell and lead to changes in the cell’s interior and are referred to as cytoplasm-to-nucleus, or C→N, signaling. By contrast, cells can also experience signaling that emanates from the nucleus to the cytoplasm, or N→C signaling, in response to DNA damage. The role of N→C signaling in T cell activation and differentiation remains unknown.
Researchers sought to explore the role of a specific nuclear-to-cytoplasmic signaling pathway, in the regulation of CD8 T cells’ responses to infections and cancer. Researchers were able to inhibit the N→C NF-κB signaling pathway throughout the bodies of a mouse model known as NEMODK. Their initial findings revealed that the N→C NF-κB signaling pathway is involved in the regulation of CD8+ T cell proliferation, differentiation and function.
Project Goals
The primary objective of this study was to define and understand the mechanism of N→C NF-κB signaling-dependent CD8+ cell regulation in order to target such mechanisms to improve CD8+ immunity against cancers and viral infections. This objective was addressed through three specific aims:
Test the hypothesis that oxidative stress causes NEMODK-dependent N→C NF-κB signaling to limit stem-like CD8+ cell generation during viral infections.
Test the hypothesis that cell-intrinsic and NEMODK-dependent N→C NF-κB signaling limited the development of stem-like CD8+ T cells capable of sustaining anti-tumor responses.
Target host N→C NF-κB signaling with chemical inhibitors to improve the generation of stem-like CD8+ T cells capable of sustaining anti-tumor responses.
Results
The researchers made significant progress toward each of their aims. First, they explored the role of N→C NF-κB signaling in anti-tumor immunity. NEMODK and wildtype mice were exposed to radiation, and researchers found that a single dose of local tumor irradiation gave rise to a strong anti-tumor response in NEMODK mice relative to their wildtype counterparts. The intratumoral immune responses were analyzed 8 and 19 days following tumor irradiation. These analyses showed that the frequency of memory precursor effector CD8+ T cells, which are important for long-term immunity against tumors, was significantly greater in NEMODK mice, and the tumors in these mice progressively regressed overtime.
To understand whether N→C NF-κB signaling inhibition promotes the development of stem-like CD8+ T cells, which are thought to be the precursor of terminally differentiated cells that attack tumor cells and virally-infected cells, researchers tested the levels of these cells in NEMODK mice following chronic viral infection. The NEMODK mice produced significantly higher levels of the stem-like CD8+ T cells compared to wildtype mice. Based on this result, researchers hypothesized that NEMODK mice will also have significantly greater virus control, but contrary to this hypothesis, virus control was reduced in NEMODK mice compared to the wildtype mice. This indicated that N→C NF-κB signaling may play an important role in the differentiation of stem-like CD8+ T cells into effector T cells to control virus spread during chronic infection.
Lastly, researchers investigated anti-tumor immunity by chemically targeting N→C NF-κB signaling with a NF-κB inhibitory drug. When tumors were treated with the drug, the tumors regressed, but when drug administration was stopped, the tumors regrow. In NEMODK mice, the tumor regression induced by the drug was dependent on CD8+ T cells. Notably, the inhibitory drug has demonstrated safety and about a 30 percent response rate against advanced tumor patients in a phase I clinical trial and is currently undergoing phase II clinical testing by research collaborators at Indiana University.
Looking to the Future
The researchers received $1,882,275 in NIH funding to expand on their WPP funded work and elucidate the cellular and molecular mechanisms of the NF-κB inhibitory drug actions.
