In order for cancer to develop and unfold, it has to evade detection by our immune cells, significantly specialised “killer” T cells. Salk researchers led by Professor Susan Kaech have discovered that the setting inside tumors (the tumor microenvironment) incorporates an abundance of oxidized fats molecules, which, when ingested by the killer T cells, suppresses their means to kill cancer cells. In a vicious cycle, these T cells, in want of power, enhance the extent of a mobile fats transporter, CD36, that sadly saturates them with much more oxidized fats and additional curtails their anti-tumor features.
The discovery, revealed on-line in Immunity on June 7, 2021, suggests new pathways for safeguarding the immune system’s means to combat cancer by lowering the oxidative lipid injury in killer T cells. Identifying elements like these that trigger immune suppression within the tumor microenvironment can result in the event of novel immunotherapies for cancer.
“We know that tumors are a metabolically hostile environment for healthy cells, but elucidating which metabolic processes are altered and how this suppresses immune cell function is an important area of cancer research that is gaining a lot of attention,” says Kaech, senior creator and director of Salk’s NOMIS Center for Immunobiology and Microbial Pathogenesis. “Our findings uncovered a novel mode of immunosuppression in tumors involving the import of oxidized fats (AKA lipids) in T cells via the cellular fat transporter CD36, which impairs their anti-tumor functions locally.”
The burgeoning area of cancer immunometabolism research how immune cell metabolism is reprogrammed inside tumors and pushed by alterations in nutrient availability. While scientists know that tumors accumulate fat — and that such accumulation is related to immune dysfunction — the main points of the connection have not been clear.
Working with Joseph Witztum’s lab at UC San Diego and Antonio Pinto within the Salk Mass Spectrometry Core facility, the workforce established that tumors include elevated quantities of a number of courses of lipid, and oxidized lipids particularly, that are usually present in oxidized low-density lipoproteins (LDLs), generally thought of “bad” fats. They then noticed how killer T cells reply to the oxidized LDLs in tumors and located that killer T cells tailored to the tumor microenvironment by growing CD36 on their floor and ingesting an abundance of oxidized lipids. Working with Brinda Emu’s lab at Yale University, they discovered this course of served as a catalyst to drive even better quantities of lipid oxidation internally within the killer T cells and in the end repressed their defenses.
Next, the workforce employed numerous strategies to research how CD36 impaired killer T cell perform. They created mouse fashions missing CD36 on T cells and used antibodies to dam CD36. They confirmed that CD36 promoted T cell dysfunction in tumors by growing oxidized lipid import, which prompted better lipid oxidation and injury inside the T cells and triggered the activation of a stress response protein, p38.
“We found that when the T cells get ‘stressed out’ by oxidized lipids, they shut down their anti-tumor functions,” says Shihao Xu, a Salk postdoctoral fellow and the primary creator on the paper.
The workforce additionally discovered new therapeutic alternatives to scale back lipid oxidation and restore killer T cells’ perform in tumors via immunotherapy by blocking CD36 with an antibody remedy or by overexpressing glutathione peroxidase 4 (GPX4, a key molecule that removes oxidized lipids in cells).
Importantly, lipid oxidation would not simply occur in T cells; it additionally occurs in tumor cells, and an excessive amount of of it might trigger cell loss of life. In reality, there may be quite a lot of pleasure in cancer analysis to extend lipid oxidation in tumor cells to a deadly degree, however Kaech and her workforce urge some warning.
“Now that we’ve uncovered this vulnerability of T cells to lipid oxidation stress, we may need to find more selective approaches to inducing lipid oxidation in the tumor cells but not in the T cells,” says Kaech, who holds the NOMIS Chair at Salk. “Otherwise, we may destroy the anti-tumor T cells in the process, and our work shows a few interesting possibilities for how to do this.”
Materials offered by Salk Institute. Note: Content could also be edited for model and size.