Scientists at Wake Forest University School of Medicine may have found a way to tackle one of the deadliest complications of lung cancer: when the disease spreads to the brain. Their research, published in Nature Biomedical Engineering, shows that specially engineered immune cells can cross the brain’s protective barrier and attack tumours — something current treatments struggle to do.

Why Brain Metastases Are So Hard to Treat

About one in three people with advanced lung cancer develop brain metastases. Once cancer reaches the brain, options become limited. Surgery and radiation are often used, but most chemotherapy drugs fail because they can’t get past the blood-brain barrier—a natural shield that protects the brain from harmful substances. Unfortunately, this barrier also blocks many cancer medicines.

“Brain metastases are incredibly difficult to treat because most therapies simply can’t get inside the brain,” said Dr Shih-Ying Wu, one of the study’s authors. “Macrophages, however, naturally know how to cross into the brain. So we asked, "What if we could train them to recognise and destroy cancer cells once they get there?”

Turning the Body’s “Clean-Up Crew” Into Cancer Fighters

Macrophages are white blood cells that act like the body’s clean-up crew — they move through tissues, find harmful cells, and swallow them. Because they can already enter the brain, the researchers used them as a delivery system.

They reprogrammed macrophages with a special receptor that helps them spot lung cancer cells. They also added a molecule to make the cells more aggressive against tumours. These engineered cells are called CAR macrophages (CARMA).

What the Study Found

In lab and animal tests, CARMA cells successfully crossed the blood-brain barrier and gathered at tumour sites. The enhanced version slowed tumour growth and helped animals live longer.

Even more encouraging, the cells triggered a “bystander effect". They not only killed cancer cells directly but also released signals that rallied other immune cells to join the fight. This created a stronger, longer-lasting defence inside the brain.

“These macrophages didn’t just find the tumours; they reshaped the entire immune environment,” said Dr Kounosuke Watabe, another author of the study. “That’s something we haven’t been able to achieve before.”

Safer Than Other Approaches

The therapy also appeared less toxic than similar treatments using CAR-T cells, which can cause severe side effects. That’s an important step toward making the approach safe for patients.

What’s Next?

So far, the work has only been tested in the lab and in animals. The next step is refining the design and moving toward early human trials. If successful, this strategy could open the door to a new class of treatments that use the body’s own cells to bypass the blood-brain barrier.

A Reason for Hope

For patients with brain metastases—where survival rates are low and treatments are limited—the idea of a therapy that can reach the brain and rally its immune defences offers caution but real hope.