Susanna Fletcher Greer: New Discovery by V Foundation Grantee Reveals CD4 Cells as Bloodborne Tumor Killers

Susanna Fletcher Greer, Chief Scientific Officer of the V Foundation, shared a post on LinkedIn:

“Well friends, this is a cool finding: turns out there is a potent, underappreciated immune cell in the bloodstream of cancer patients, ready to fight, if we just release the brakes. A new discovery opens new doors for cancer immunotherapy, early detection, and more personalized treatment options.

If you’re working in oncology, immunotherapy, or translational medicine, read on.

If you are interested in helping to fund high impact, high reward research – you’ll find it at the V Foundation.

Hidden Cancer Killers in the Bloodstream: A New Way to Track, and Treat Tumors

Funded in part by the V Foundation, this research highlights a surprising immune cell that could reshape how we monitor and mobilize anti-tumor immunity. When we talk about immune cells fighting cancer, CD8 T cells, you’ve heard me refer to them as “killer” cells, usually get the spotlight. But this new study from V Grantee Dr. David Oh University of California, San Francisco shows another unexpected group of fighters: CD4 T ‘helper’ cells that don’t just help, they can also kill cancer cells.

The VERY cool part about this study is that these cancer-killing CD4 cells aren’t locked away in tumors. They are circulating in the blood. It’s like deploying an elite strike team out on patrol instead of stuck behind enemy lines.

What Dr. Oh and team found: In patients with bladder cancer, the team identified two main types of killer CD4 T cells:

The Fighters: These cells produce granzyme B and can directly kill tumor cells. Granzyme B is a weapon to destroy infected or cancerous cells, like a microscopic grenade. The ‘Fighters’ respond to immunotherapy, but their activity is also held back by a protein called KLRG1, which interacts with E-cadherin on tumors (like a brake pedal).

The Scouts: These cells produce granzyme K but don’t kill directly, but they remember what the tumor ‘looks like’ and…maybe evolve from the Fighter cells. Crucially, KLRG1 acts as a “second brake” on these killer cells. Even if you remove one block (like with PD-1 therapy), KLRG1 can still hold them back.

But when Dr. Oh and team blocked KLRG1’s interaction with tumors in the lab? These cells went back to killing. That’s incredible!

Why It Matters:

• Non-invasive immune monitoring: potential to detect and track these killer cells by drawing a patient’s blood; offers a real-time window into what’s happening inside tumors.
• Better therapies: these cells can be isolated from blood and expanded for personalized cell therapy.
• New drug targets: blocking KLRG1 (or its tumor partner E-cadherin) could boost the effectiveness of immunotherapy. (!)

Why Developmental Science Is Key

This project started with a fundamental question: Could Dr. Oh and lab track the tumor-killing activity of CD4 cells through blood? What they uncovered could help reshape how clinicians monitor and mobilize the immune system in cancer care.And it’s thanks in part to the V Foundation for supporting bold, curiosity-driven research. The coolest part.

The Takeaway

There’s a potent, underappreciated immune cell in the bloodstream of cancer patients, ready to fight, if we just release the brakes. This discovery opens new doors for cancer immunotherapy, early detection, and more personalized treatment options. If you’re working in oncology, immunotherapy, or translational medicine, this is a space to watch. If you are interested in helping to fund high impact, high reward research – the V Foundation is a place to watch as well.Find Dr. Oh and team at David Oh | UCSF Health and read this great paper.”

More posts featuring Susanna Fletcher Greer on OncoDaily.