Australian researchers have identified a promising new approach that could help stop one of the most aggressive forms of breast cancer from spreading.
Triple-negative breast cancer becomes especially dangerous once tumor cells escape the breast and establish themselves elsewhere in the body. Australian researchers have now identified a molecular weakness that could eventually help determine which patients might benefit from an existing cancer drug aimed at slowing that spread.
The work, led by Adelaide University and the Olivia Newton-John Cancer Research Institute, centers on a molecular switch involved in the progression of triple-negative breast cancer (TNBC). This aggressive subtype lacks the hormone receptors targeted by many existing breast cancer therapies, contributing to poorer outcomes and fewer treatment options.
Low miR-342 marked higher metastatic risk
The research, published on August 21, 2026, in EMBO Molecular Medicine, found that patients with low levels of a naturally occurring molecule called miR-342, combined with high activity in the cancer-promoting E2F pathway, were more likely to develop metastatic disease.
In pre-clinical models, restoring miR-342 substantially reduced the spread of breast cancer to distant organs, including the lungs and bones.
The researchers also tested palbociclib, a CDK4/6 inhibitor already used for advanced hormone receptor-positive breast cancer. In models with low miR-342, the drug significantly reduced the growth of metastatic tumors.
Together, the results suggest that miR-342 levels might eventually help identify women with triple-negative breast cancer who are more likely to benefit from CDK4/6 inhibitors. That could provide a way to repurpose an existing therapy for a particularly aggressive form of breast cancer.
Co-senior author Associate Professor Philip Gregory, from Adelaide University’s Center for Cancer Biology and SA Pathology, said metastasis remains the central challenge in treating triple-negative breast cancer.
“Most deaths from breast cancer occur because the cancer spreads to other parts of the body, rather than being caused by the primary tumor itself,” Associate Professor Gregory said.
“Triple-negative breast cancer is particularly difficult to treat because it lacks the hormone receptors and HER2 proteins upon which many targeted therapies rely. While immunotherapy is improving outcomes for some patients, treatment options remain very limited once the cancer returns.
“Our research identified a subgroup of patients whose tumors appear to rely on a specific molecular pathway to spread. By targeting that pathway, we were able to dramatically reduce metastatic growth in our laboratory models.”
miR-342 controls a pathway cancer exploits
According to Associate Professor Gregory, miR-342 functions as a master regulator for a broad network of genes involved in cancer progression.
“When miR-342 levels fall, the E2F pathway becomes overactive, allowing dormant cancer cells that have already traveled through the body to grow into dangerous secondary tumors.
“The exciting aspect of this discovery is that drugs targeting this pathway already exist. CDK4/6 inhibitors are routinely used for patients with advanced hormone receptor-positive breast cancer, and our findings suggest they could also benefit a carefully selected group of patients with triple-negative disease.”
Co-senior author Professor Robin Anderson, from the Olivia Newton-John Cancer Research Institute, said understanding what allows cancer to move beyond the original tumor is critical because metastatic disease accounts for most breast cancer deaths.
“Primary tumors can often be treated successfully with surgery or local therapies, but once cancer spreads throughout the body it becomes far more difficult to control,” Professor Anderson said.
“Triple-negative breast cancer is incredibly diverse, and that’s one of the reasons it has been so challenging to develop targeted treatments.”
Palbociclib worked after cancer had spread
One of the most important findings emerged when palbociclib was given after cancer cells had already dispersed. In those models, the drug was particularly effective at preventing microscopic metastatic tumors from expanding.
“Rather than shrinking the primary tumor, this treatment may prove most valuable by stopping tiny metastatic deposits from developing into life-threatening secondary cancers.
“Our study identifies a distinct subgroup of patients whose cancers share a common biological weakness, opening the door to a much more personalized treatment approach.”
Before the approach can move toward clinical testing, the researchers plan to confirm the findings in patient-derived pre-clinical models. Clinical trials would come afterward.
Triple-negative breast cancer represents about 10–15% of Australia’s roughly 21,000 breast cancer diagnoses each year, yet it accounts for a disproportionate share of breast cancer deaths because it is aggressive and can spread rapidly to distant organs.
Reference: “Metastasis of triple negative breast cancer is regulated by a targetable miR-342-E2F network” by Victoria K Arnet, Cameron N Johnstone, Richard P Redvers, Caroline A Chambers, Katherine A Pillman, John Toubia, Rachael Lumb, B Kate Dredge, Andrew G Bert, Emily Hackett-Jones, Pannapa Pinweha, Julie M Bracken, Shruti Deshpande, Zoe K Price, Michael Ortiz, Kaitlin G Scheer, Jasleen Rajpal, Ashleigh B Geiger, Suraya Roslan, Xiaochun Li, Sandra O’Toole, Traude H Beilharz, Cameron P Bracken, Yeesim Khew-Goodall, Gregory J Goodall, Robin L Anderson and Philip A Gregory, 21 August 2026, EMBO Molecular Medicine.
DOI: 10.1038/s44321-026-00496-4
Funding: National Breast Cancer Foundation, National Health and Medical Research Council
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