Scientists Find a New Way To Stop Aggressive Breast Cancer From Spreading

Triple-negative breast cancer is a tough disease. It lacks the common markers that many targeted treatments use. This makes it harder to treat and more likely to spread.

Now, Australian researchers have found a new way to potentially stop this aggressive cancer from spreading. They identified a molecular weakness that could help doctors decide which patients might benefit from an existing cancer drug.

A New Weakness in Triple-Negative Breast Cancer

The research, led by teams at Adelaide University and the Olivia Newton-John Cancer Research Institute, focuses on a molecular switch. This switch plays a role in how triple-negative breast cancer (TNBC) progresses.

The study found that patients with low levels of a molecule called miR-342, combined with high activity in the E2F pathway, were more likely to develop metastatic disease. Metastasis is when cancer spreads to other parts of the body.

In lab tests, increasing miR-342 significantly reduced how much breast cancer spread to distant organs like the lungs and bones.

The researchers also tested palbociclib. This drug is a CDK4/6 inhibitor already used for advanced hormone receptor-positive breast cancer. In models with low miR-342, palbociclib greatly slowed the growth of metastatic tumors.

These findings suggest that checking miR-342 levels could help identify women with triple-negative breast cancer who might benefit from CDK4/6 inhibitors. This could mean using an existing drug for a very aggressive type of breast cancer.

Associate Professor Philip Gregory, a senior author from Adelaide University, explained that most breast cancer deaths happen because the cancer spreads, not from the original tumor.

"Triple-negative breast cancer is especially hard to treat," Gregory said. "It doesn't have the hormone receptors and HER2 proteins that many targeted therapies rely on." While new treatments like immunotherapy are helping some patients, options are still limited if the cancer returns.

"Our research found a group of patients whose tumors seem to depend on a specific molecular pathway to spread," Gregory noted. "By targeting that pathway, we dramatically reduced metastatic growth in our lab models."

How miR-342 Controls Cancer Spread

Associate Professor Gregory explained that miR-342 acts as a main controller for many genes involved in cancer growth.

"When miR-342 levels drop, the E2F pathway becomes too active," he said. This allows dormant cancer cells that have already traveled through the body to grow into dangerous secondary tumors.

"The exciting part of this discovery is that drugs targeting this pathway already exist," Gregory added. CDK4/6 inhibitors are commonly used for patients with advanced hormone receptor-positive breast cancer. These findings suggest they could also help a specific group of patients with triple-negative disease.

Professor Robin Anderson, a co-senior author from the Olivia Newton-John Cancer Research Institute, stressed the importance of understanding how cancer spreads. Metastatic disease causes most breast cancer deaths.

"Primary tumors can often be treated with surgery or local therapies," Professor Anderson said. "But once cancer spreads throughout the body, it becomes much harder to control."

Triple-negative breast cancer is very diverse, which makes it challenging to develop targeted treatments.

Palbociclib's Role in Stopping Spread

One key finding was that palbociclib worked even after cancer cells had already spread. In these models, the drug was very good at stopping tiny metastatic tumors from growing larger.

"Instead of shrinking the main tumor, this treatment might be most valuable by stopping small metastatic deposits from turning into life-threatening secondary cancers," Professor Anderson explained.

"Our study identifies a clear group of patients whose cancers share a common biological weakness. This opens the door to a much more personalized treatment approach."

Before this approach can be tested in people, researchers plan to confirm their findings in other lab models. Clinical trials would follow.

Triple-negative breast cancer makes up about 10-15% of Australia's 21,000 breast cancer diagnoses each year. However, it causes a higher share of breast cancer deaths because it's aggressive and can spread quickly.

Deep Dive & References

Metastasis of triple negative breast cancer is regulated by a targetable miR-342-E2F network - EMBO Molecular Medicine, 2026