Scientists Discover Hidden 'Brake' on Immune Cells — And How to Release It to Fight Cancer

Cancer researchers in Montreal have identified a previously unrecognized molecule that acts as an internal brake on our immune system — and they've developed antibodies that can release it, offering new hope to patients who don't respond to existing treatments.

The Hidden Brake: SLAMF6

The discovery, published in the journal Nature, centers on a molecule called SLAMF6 that sits on the surface of T cells — the immune system's cancer-fighting soldiers. Unlike other inhibitory molecules, SLAMF6 doesn't need to interact with tumors to weaken the immune response. It self-activates directly on T cells, sending a stop signal that:

• Weakens their attack capacity against cancer
• Reduces the production of healthy, long-lasting T cells
• Accelerates "immune exhaustion" — a state where T cells become ineffective

Led by Dr. André Veillette of the Université de Montréal and the Montreal Clinical Research Institute (IRCM), the team developed new monoclonal antibodies that prevent SLAMF6 from activating itself.

Why This Is a Big Deal

Current immunotherapies like PD-1 and PD-L1 inhibitors work by "releasing the brakes" that tumors impose on the immune system. These treatments have revolutionized cancer care — but a large number of patients either don't respond or eventually stop responding.

SLAMF6 represents a completely different mechanism. Because it's an internal brake that doesn't depend on tumor interaction, blocking it could help precisely those patients who've run out of options with existing treatments.

The antibodies could be used alone or combined with other immune-stimulating therapies, potentially opening up treatment options for patients with solid tumors or blood cancers.

What's Next

Dr. Veillette's team plans to move these antibodies into early-phase clinical trials to test their safety and effectiveness in humans.

"By identifying an internal brake that had until now gone unrecognized and by developing antibodies capable of neutralizing it, our researchers are offering an innovative solution to the limitations of current treatments," said Dr. Jean-François Côté, IRCM president and scientific director.