Curio, S. | bioRxiv Science

bioRxiv2023

Tyramine promotes colon cancer risk and development by inducing DNA damage and inflammation

High dietary consumption of processed meat is associated with increased colorectal cancer (CRC) risk, but mechanistic links remain largely unknown. Tyramine is a biogenic amine found in processed food and a gut bacterial product from tyrosine. However, the impact of tyramine on gut health has not been studied. We found that tyramine induced necrosis and promoted cell proliferation and DNA damage in HCT116 cells. Ingestion of tyramine increased colonic tumor size, intestinal cell proliferation and inflammation (e.g., increased mRNA expression of IL-17A and a higher number of Ly6G+ neutrophils) in ApcMin/+ mice. Furthermore, tyramine-treated wild-type mice exhibited visible adenomas and significantly enhanced intestinal tissue DNA damage, together with altered gene pathways involved in epithelial barrier function. In addition, natural killer cell numbers were lower and polymorphonuclear-myeloid derived suppressor cells were higher in tumors from tyramine-treated ApcMin/+ mice, suggesting a suppressive anti-tumor immune response. Thus, tyramine not only increases CRC risk, but also facilitates tumor development. Modulating the levels of tyramine in food and monitoring high-risk individuals could aid in better prognosis and management of CRC.

cancer biology↗

bioRxiv2021

NKG2D signaling regulates IL-17A-producing γδT cells to promote cancer progression

{gamma}{delta}T cells are unconventional T cells particularly abundant in mucosal tissues that play an important role in tissue surveillance and homeostasis. {gamma}{delta}T cell activation is mediated by the T cell receptor composed of {gamma} and {delta} chains, as well as activating receptors for stress-induced ligands, such as NKG2D. Contrary to the well-established anti-tumor function of {gamma}{delta}T cells, recent studies have shown that {gamma}{delta}T cells can promote tumor development in certain contexts. However, the mechanisms leading to this diseasepromoting role remain poorly understood. Here, we show that mice lacking {gamma}{delta}T cells survive longer in a mouse model of intestinal cancer, further supporting their pro-tumoral role. In a surprising conceptual twist, we found that these pro-tumor {gamma}{delta}T cells are regulated by NKG2D signaling, a receptor normally associated with cancer cell killing. Germline deletion of Klrk1, the gene encoding NKG2D, reduced the frequency of {gamma}{delta}T cells in the tumor microenvironment and delayed tumor progression. We further show that blocking NKG2D reduces the capability of {gamma}{delta}T cells to produce IL-17A in the pre-metastatic lung and that co-culture of lung T cells with NKG2D ligand-expressing tumor cells specifically increases the frequency of {gamma}{delta}T cells. Together, these data support the hypothesis that in a tumor microenvironment where NKG2D ligands are constitutively expressed, {gamma}{delta}T cells accumulate in an NKG2D-dependent manner and drive tumor progression by secreting pro-inflammatory cytokines, such as IL-17A.

immunology↗