DUSP4 protein identified as key to preventing CAR T cell exhaustion

Researchers have identified a protein that helps cancer-fighting immune cells maintain their ability to attack tumours, potentially offering a new approach to improving engineered T-cell therapies for colorectal cancer.

The study, led by researchers at the Yong Loo Lin School of Medicine, National University of Singapore (NUS Medicine), found that dual-specificity phosphatase 4 (DUSP4) helps CD8+ T cells retain their anti-tumour activity and resist exhaustion.

The findings indicate that by increasing DUSP4 activity, it could improve the effectiveness of chimeric antigen receptor (CAR)-T cell therapies, which involve genetically engineering a patient’s T cells to recognise and destroy cancer cells.

DUSP4 helps prevent T-cell exhaustion

CD8+ T cells are immune cells that can directly recognise and kill cancer cells. However, prolonged exposure to the tumour environment can cause them to become exhausted, gradually reducing their ability to multiply and attack cancer.

To investigate DUSP4’s role in maintaining T-cell function, the researchers combined clinical data from colorectal cancer patients with experiments using human cells and preclinical models.

They found that models lacking DUSP4 developed more and larger colorectal tumours and showed weaker CD8+ T-cell responses. These immune cells also produced fewer cancer-killing molecules and displayed more signs of exhaustion.

Analysis of tumour tissue from 105 colorectal cancer patients further revealed that lower DUSP4 levels were associated with poorer overall survival. A similar trend was observed in an independent dataset.

The researchers established that DUSP4 primarily supports immune cell activity rather than directly inhibiting cancer growth. Removing the protein from cancer cells had little effect, whereas its loss in blood-forming cells weakened CD8+ T-cell responses and increased tumour development.

The team also identified the molecular mechanism involved. DUSP4 helps regulate a signalling pathway involving ERK2 and KLF2. Without sufficient DUSP4, increased ERK2 activity raises KLF2 levels, suppressing the genetic programmes that CD8+ T cells need to kill cancer cells.

“CD8+ T cells are among the immune system’s main weapons against cancer, but prolonged exposure to tumours can gradually weaken their ability to function,” said Associate Professor Zhang Yongliang from the Department of Microbiology, Immunology and Immunology Translational Research Programme (TRP) at NUS Medicine. ”Our findings suggest that DUSP4 helps keep these cells in a state where they can continue to multiply and attack cancer cells effectively.”

Enhancing CAR T cell activity

The researchers next investigated whether increasing DUSP4 activity could improve CAR T cell performance by using CRISPR activation (CRISPRa) to increase DUSP4 activity in human CAR T cells and compared their performance with standard CAR T cells.

In laboratory experiments, the enhanced cells multiplied more readily and demonstrated greater cancer-killing activity against colorectal cancer cells. Treatment with the DUSP4-enhanced CAR T cells also produced smaller and lighter tumours in laboratory models than treatment with standard CAR T cells.

“By increasing DUSP4 activity, we were able to improve both the growth and cancer-killing capacity of CAR T cells in our experimental models,” said Professor Nicholas R.J. Gascoigne, Department of Microbiology and Immunology and Immunology TRP at NUS Medicine. ”This gives us a potential strategy for engineering T cells that are better able to maintain their function in the difficult environment of solid tumours.”

Further studies needed before clinical application

The colorectal cancer cells used in the CAR T experiments had been engineered to carry CD19, the target recognised by the CAR T cells. Further research will therefore be needed to establish whether the approach can be applied clinically.

The team now plans to investigate how DUSP4 is regulated within tumours, identify other molecules through which it influences T-cell function and explore ways to increase its activity in engineered immune cells.

Ultimately, the researchers hope their findings will support the development of improved T cell-based immunotherapies for colorectal cancer and other solid tumours.