Bold claim: A new CAR T-cell approach shows promise by delivering a gentler, more durable attack on cancer in mice, potentially transforming how blood cancers are treated. But here's where it gets controversial... Could a safer, longer-lasting therapy truly reduce relapse without triggering severe immune reactions? And this is the part most people miss: the leap from mouse models to humans is huge, with many therapies fading in translation. Here’s a rewritten, easy-to-understand version of the original content that preserves all key information and adds clarity and context.
A new type of CAR T-cell therapy has been developed by researchers at the Keck School of Medicine of USC. This approach reengineers the internal signaling of CAR T cells, aiming to produce a controlled and sustained immune response against cancer. In mouse studies, these engineered T cells not only killed cancer cells more effectively—including cells that usually escape detection—but also caused fewer toxic side effects. The researchers hope STEM-engineered CAR T cells could eventually offer safer, more durable treatment for blood cancers and lower relapse rates.
What CAR T-cell therapy is and why it matters
CAR T-cell therapy modifies a patient’s own immune cells to hunt down cancer. It has shown strong promise for blood cancers like leukemia and lymphoma. However, it faces major challenges: many patients relapse within a year, and some experience dangerous immune reactions known as cytokine storms. These problems arise when CAR T cells don’t endure long enough in the body, cancer cells evolve to evade detection, or treatment triggers excessive immune responses.
The STEM redesign: targeting the signaling, not just the surface receptor
All approved CAR T therapies use a common signaling protein on the T cell surface called CD3 zeta (CD3ζ) to activate cancer-killing activity. While effective, these cells can lose strength quickly and fail to persist, increasing relapse risk. To improve safety and durability, the USC team focused on the early signaling events inside the T cell—proteins that determine how strongly and how long T cells stay active.
A standout molecule: ZAP70 and the ZAP327 variant
Among the signaling components tested, ZAP70 stood out for providing strong activation without driving excessive stimulation. The researchers tested several forms of ZAP70 and identified a fragment named ZAP327 as the best balance of safety and potency. They then substituted CD3ζ with ZAP327 to create the next-generationCAR T cells, called STEM-engineered CAR T cells.
What the STEM cells did in mice
In head-to-head experiments, STEM-engineered CAR T cells matched or exceeded the performance of conventional FDA-approved CAR T cells. They showed longer persistence, maintained a healthier memory-like state that supports long-term cancer defense, and were able to eradicate cancer cells that typically evade current therapies. Importantly, STEM cells also performed well against low-antigen cancer cells, which often fly under the radar of the immune system.
Safety signals: fewer cytokines, potentially fewer toxic side effects
The STEM approach produced fewer cytokines in mouse models. Since cytokines drive inflammatory responses, this reduction suggests the therapy could be safer and more tolerable for patients, potentially lowering the risk of dangerous immune reactions.
Lead investigator insights
Rongfu Wang, PhD, a professor of medicine and pediatrics at the Keck School of Medicine and senior study author, emphasized that toxicity is a major hurdle in CAR T immunotherapy. The significant drop in cytokine release observed with STEM-engineered CAR T cells could translate into safer treatment for patients.
Next steps toward clinical use
With these promising preclinical results, the team plans to move toward clinical trials to test STEM-engineered CAR T cells in patients. They are also exploring combining this approach with CAR T cells that recognize multiple cancer-associated proteins, which could enhance detection and reduce misidentification of healthy cells.
Additionally, researchers are investigating applying the STEM concept to T-cell receptor (TCR) T-cell therapy, a related immunotherapy that may be more effective against solid tumors.
Reference and publication
Liu X, Zhang J, Chu J, et al. ZAP327 signaling domain–driven chimeric antigen receptor generates robust and long-term antitumor immunity in mouse models. Science Translational Medicine. 2025;17(828):eadz0529. doi:10.1126/scitranslmed.adz0529
Note: This article is republished from USC Keck News and has been edited for length and clarity. For original information, consult the linked sources in the publication.
