Scientists at UCLA have found a hidden weak point in some of the toughest cancers. This discovery may lead to fresh ways to fight tumors that have avoided treatment for many years.
What Are Small‑Cell Neuroendocrine Cancers?
These cancers can start in the lungs, prostate, or ovaries. They grow very quickly and tend to spread early, which makes them especially hard to cure.
Why The RB Gene Matters
A common feature of these tumors is the loss of a gene called RB. In healthy cells, RB acts like a brake, slowing down cell growth. When RB is missing, cells divide unchecked and many medicines stop working.
Finding a New Achilles’ Heel
Recent research published in the Proceedings of the National Academy of Sciences shows that losing RB also creates an unexpected vulnerability. The UCLA team discovered that cells without RB become heavily reliant on another protein named E2F3 to stay alive.
When researchers blocked E2F3 in the lab, the cancer cells stopped growing. This effect, called “synthetic lethality,” means the cells can survive without RB, but they cannot survive when both RB and E2F3 are gone.
Better Lab Models for Small‑Cell Cancer
Studying these cancers has been difficult because realistic lab models were missing. To fix this, the UCLA scientists edited normal human prostate cells, adding five common cancer‑causing changes, including the loss of RB and TP53. The edited cells formed tiny organ‑like structures called organoids, which were then implanted into mice. The resulting tumors look a lot like human small‑cell prostate cancer.
CRISPR Screens Spot a Shared Weakness
Using the new models, the researchers performed a genome‑wide CRISPR screen, testing thousands of genes to see which ones the cancer cells needed. They found nearly 1,400 important genes, and one pattern stood out: cancers from different organs all depended strongly on E2F3.
When the team lowered E2F3 levels in RB‑deficient cells, the tumors stopped dividing, could not form clusters, and sometimes died completely.
Can Existing Drugs Fill the Gap?
Because no current medicine directly targets E2F3, the scientists looked for another way to hit the cancer’s weakness. They discovered that blocking a metabolic pathway that makes DNA building blocks—by inhibiting an enzyme called DHODH—also reduces E2F3 and slows tumor growth.
Drugs that block DHODH, such as leflunomide and teriflunomide, are already approved by the FDA for autoimmune disorders. Using these approved medicines for cancer could speed up the move from lab to patient.
While the work is still early, it gives a clear picture of how aggressive small‑cell cancers stay alive and points to a promising new direction for future treatments.