Since 2017, the U.S. Food and Drug Administration (FDA) has approved six chimeric antigen receptor (CAR) T cell therapies for the treatment of blood cancers (1). Underlying the excitement about these therapies are concerns about patients’ transient responses to CAR T-cell infusions, limiting their chances of long-term survival. CAR T cells are even less effective against solid tumors because immunosuppressive factors in the tumor microenvironment (TME) suppress T cell activity, thereby promoting tumor development and evading treatment.
Scientists work hard to find immunosuppressive genes that contribute to T cell dysfunction in the TME, such as using CRISPR knockout genes for loss-of-function screening.In a recently published study natureResearchers at the New York Genome Center and New York University took a different approach and proposed the possibility of CAR T cells that enhance tumor killing by targeting positive regulators that enhance T cell function (2).
Geneticist Neville Sanjana and his team at the New York Genome Center screened nearly 12,000 genes to find genes that could boost T cells’ anti-tumor activity. The researchers constructed a lentiviral library containing a collection of protein-coding genes from the human genome and transduced the library into T cells. They monitored the proliferation of these T cells and captured many highly expressed genes involved in multiple immune processes, such as lymphocyte proliferation and interferon production. To the team’s surprise, the top-ranked gene was lymphotoxin-beta receptor (LTBR).
LTBR is a tumor necrosis factor receptor that mediates cytokine release and apoptosis and helps regulate lymphoid organogenesis and inflammation. Although T and B cells often express LTBR ligands, the receptor itself is usually not present in these cells (3).
To understand how exogenous LTBR affects T cell function, Sanjana and her team used single-cell sequencing to analyze the T cell transcriptome. They found that LTBR triggered the upregulation of multiple genes and enhanced multiple immune responses, including promoting cytokine secretion, promoting T cell proliferation, and reducing apoptosis.
Based on sequencing data, the authors identified nuclear factor (NF)-κB, a key immune response regulator, as the most significantly upregulated gene in LTBR-transduced T cells. NF-κB typically coordinates various transcription factors in different pathways to trigger inflammatory responses and promote immune cell development (4). In LTBR-transduced T cells, researchers demonstrated that NF-κB also upregulated several key inflammatory pathways and transcription factors, such as NF-κB p65 and p52. These data helped Sanjana and her team determine which signaling pathways LTBR acts on to stimulate T cell immune activity.
The team then co-expressed LTBRs with FDA-approved CARs and tested their antigen-specific responses and cytotoxicity in patient T cells. They found that compared with original CAR T cells, LTBR CAR T cells exhibited increased cytokine secretion and cytotoxicity against tumor cells. These results highlight the potential of using immune-enhancing genetically engineered T cells as a way to improve CAR T immunotherapy, particularly for solid cancers.
refer to
- CAR T cells: Engineering immune cells to treat cancer. National Cancer Institute. https://www.cancer.gov/about-cancer/treatment/research/car-t-cells
- Legout, M. et al. Genome-scale screening of synthetic drivers of T cell proliferation. nature 603728–735 (2022).
- Norris, PS & Ware, CF LTβR signaling pathway. Marie Curie Bioscience Database (Internet). https://www.ncbi.nlm.nih.gov/books/NBK6515/
- Sun, S.-C. The non-canonical NF-κB pathway in immunity and inflammation. natural immunology number 17545–558 (2017).