New Treatment Target Identified for Aggressive Small Cell Neuroendocrine Cancers

Understanding the Discovery

Small cell neuroendocrine cancers, which can develop in the lung, prostate, and ovary, are known for their rapid growth and early spread. A key factor in their aggressiveness is the loss of the RB gene, which normally regulates cell growth. When RB is missing, cancer cells multiply uncontrollably and become resistant to many therapies.

The UCLA team found that these RB-deficient cancer cells become heavily dependent on a protein called E2F3. By blocking E2F3, researchers observed “synthetic lethality,” a process where the combined loss of RB and E2F3 halts tumor growth. “Discovering a vulnerability like this opens the door to thinking about entirely new treatment strategies,” said Dr. Owen N. Witte, senior author of the study.

Building Better Models to Study the Disease

Progress in treating small cell prostate cancer has been hindered by the lack of realistic laboratory models. To address this, UCLA researchers engineered human prostate cells with genetic mutations, including RB and TP53 loss, to create organoids and mouse tumor models that mimic human disease. These models enabled genome-wide CRISPR screens, identifying nearly 1,400 genes critical to cancer cell survival.

“These new model systems allowed us to uncover a genetic vulnerability that would have been very difficult to find otherwise,” said Dr. Evan Abt, the study’s first author. “This could lead to therapies targeting this pathway.”

Existing Drugs Offer a Potential Shortcut

While no drugs directly target E2F3, the team found that inhibiting the DHODH enzyme—a component of a metabolic pathway for DNA building blocks—reduced E2F3 levels and slowed tumor growth. DHODH inhibitors like leflunomide and teriflunomide, already approved for autoimmune diseases, could be repurposed for cancer treatment.

“What’s exciting is that our findings open the door to applying existing drugs in a new way,” Abt said. “By understanding how these cancers depend on E2F3, we can start to think about strategies that might work much more quickly in patients.”

Challenges and Next Steps

The research is in early stages, but the findings highlight a critical genetic dependency in these cancers. Further studies are needed to validate E2F3 as a therapeutic target and explore DHODH inhibition in clinical trials. Witte emphasized the urgency: “There has not been a major change in how we treat these cancers for decades. When I first encountered these tumors as a medical student more than 50 years ago, the survival statistics were essentially the same as they are today.”

Why This Matters

Small cell neuroendocrine cancers have historically had poor survival rates, with limited treatment options. The identification of E2F3 as a vulnerability and the potential for drug repurposing represent a significant step forward. If validated, these findings could lead to therapies that address the root causes of resistance in these aggressive tumors.