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Protein That Controls CAR T-Cell Longevity Identified

Protein structure.
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CAR T cell therapy has revolutionized the way certain types of cancer are treated, and the longer those CAR T cells live in a patient’s body, the more effectively they respond to cancer. Now, in a new study, researchers at Children’s Hospital of Philadelphia (CHOP) and Stanford Medicine have found that a protein called FOXO1 improves the survival and function of CAR T cells, which may lead to more effective CAR T cell therapies and could potentially expand its use in difficult-to-treat cancers. The findings were published online today by the journal Nature.

T cells are a type of immune cell that recognize and kill pathogens in order to protect the host. Cancer is often able to evade the body’s immune system, but as a result of CAR T cell therapy, a patient’s own T cells can be reprogrammed to recognize and kill these cancer cells, which has led to FDA-approved treatments for certain types of lymphomas and leukemias.

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However, fewer than 50% of patients who receive CAR T cell therapy remain cured after a year. One of the reasons for this is that CAR T cells often don’t survive long enough in patients to completely eradicate their cancer. Prior research has demonstrated that patients who are cured through CAR T cell therapy often have CAR T cells that live longer and can more successfully fight cancerous cells.

To determine what helps CAR T cells live longer, researchers wanted to understand the underlying biology behind memory T cells, which are a type of natural T cell whose purpose is to persist and retain function. One protein of interest, FOXO1, which activates genes associated with T cell memory, has previously been studied in mice but remains under-researched in human T cells or CAR T cells.

To learn more about the role of FOXO1 in human CAR T cells, the researchers in this study used CRISPR to delete FOXO1. They found that in the absence of FOXO1, human CAR T cells lose their ability to form a healthy memory cell or protect against cancer in an animal model, supporting the notion that FOXO1 controls memory and antitumor activity.

Researchers then applied methods to force CAR T cells to overexpress FOXO1, which turned on memory genes and enhanced their ability to persist and fight cancer in animal models. In contrast, when the researchers overexpressed a different memory-promoting factor, there was no improvement in CAR T cell activity, suggesting that FOXO1 plays a more unique role in promoting T cell longevity.

Importantly, researchers also found evidence that FOXO1 activity in patient samples correlates with persistence and long-term disease control, thereby implicating FOXO1 in clinical CAR T cell responses.

“These findings may help improve the design of CAR T cell therapies and potentially benefit a wider range of patients,” Weber said. “We are now collaborating with labs at CHOP to analyze CAR T cells from patients with exceptional persistence to identify other proteins like FOXO1 that could be leveraged to improve durability and therapeutic efficacy.”

Reference: Doan AE, Mueller KP, Chen AY, et al. FOXO1 is a master regulator of memory programming in CAR T cells. Nature. 2024. doi: 10.1038/s41586-024-07300-8

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