The genetic elimination of TOX factors improves the eradication of solid tumors in the CAR T model

Ten years ago, researchers announced the development of an anti-cancer immunotherapy called CAR (for chimeric antigenic receptor) -T, in which a patient is reinjected with his own genetically modified T cells, equipped to mount a powerful anti-tumor attack. Since then, CAR T approaches (one of several strategies known collectively as "adoptive T cell transfer") have made headlines as a new tool for cellular immunotherapy, with the most success against "liquid cancers" such as leukemias and lymphomas.

Sarcomas and carcinomas have been shown to be more resistant to these approaches, in part because the modified T cells progressively lose their ability to fight tumors once they have infiltrated a tumor. Immunologists call these cells T cell fatigue "exhaustion" or "dysfunction".

To try to understand why, investigators Anjana Rao, Ph.D. and Patrick Hogan, Ph.D. of the La Jolla Institute for Immunology (LJI), have published in recent years a series of articles stating that a transcription factor regulating the gene expression, called NFAT, activates the "downstream" genes that weaken T cell responses to tumors and thereby induce the disease. depletion of T lymphocytes. A set of these genes downstream codes transcription factors known as NR4A, and a former graduate student, Joyce Chen, has shown that the genetic elimination of NR4A proteins in CAR T cells infiltrators in the tumor improved the rejection of the tumor. However, the identity of additional actors cooperating with NFAT and NR4A in this sector remains unknown.

Now, an article published in this week's online edition of the Proceedings of the National Academy of Sciences (PNAS) Rao and Hogan Laboratories provides a more comprehensive list of participants in a vast network of gene expression that establishes and maintains depletion of T-lymphocytes. The study uses a mouse model to show that the patient's blood pressure is high. Genetically eliminating two new factors, TOX and TOX2, also improves the eradication of "solid" melanoma tumors in the CAR T model. These studies suggest that comparable interventions aimed at targeting NR4A and TOX factors in patients could extend the use of T CAR based immunotherapy to solid tumors.

The group began by comparing gene expression profiles in normal and "depleted" T cell samples, looking for positively regulated factors in parallel with NR4A as co-conspirators in T-cell dysfunction.

We found that two DNA binding proteins called TOX and TOX2 were consistently strongly expressed with NR4A transcription factors. This discovery suggests that factors such as NFAT or NR4A may control the expression of TOX. "

Hyungseok Seo, Ph.D., postdoctoral researcher at Rao Lab and first author of the study

The group then recapitulated a CAR T protocol in mice by inoculating animals with melanoma tumor cells to establish a tumor, and then a week later by infusing mice with one of two collections of T cells: a control sample "from a normal mouse, versus a sample derived from a mouse genetically engineered to not express the expression of TOX and TOX2 in T cells."

Remarkably, mice infused with TOX-deficient CAR T cells showed a more robust regression of melanoma tumors than mice infused with normal cells. In addition, mice treated with TOX deficient CAR T cells showed significantly increased survival, suggesting that TOX factor loss fights T cell depletion and allows T cells to destroy more tumor cells. effectively.

An additional badysis led the investigators into a path ending in a well-known immune opponent. The researchers showed that TOX factors join forces with both NFAT and NR4A to promote the expression of an inhibitory receptor called PD-1, which decorates the surface of depleted T cells and sends immunosuppressive signals.

PD-1 is blocked by many monoclonal antibodies called control point inhibitors, which fight immunosuppression and activate an innate anti-cancer immune response. The convergence of TOX, NFAT and NR4A on PD-1 has a molecular and immunological meaning and the place to convergence of both cellular and anti-antibody immunotherapy approaches.

"Currently, CAR T cell therapy is showing amazing effects in patients with" liquid tumors "such as leukemia and lymphoma," says Seo. "But they still do not work well in patients with solid tumors due to T-cell depletion. If we could inhibit TOX or NR4A by treating T-CAR cells with a small molecule, this strategy could have an effect potent therapeutic on solid cancers such as melanoma. "