In brief
An Australian study examined over 400 estrogen‑receptor‑positive breast cancer samples and discovered that higher activity of the protein CDK1 is linked to more aggressive tumors and poorer outcomes. The findings suggest CDK1 could serve as a biomarker for tailoring CDK4/6 inhibitor treatment, though larger trials are needed.
On October 31, 2026, the news agency Xinhua reported that scientists at the Garvan Institute of Medical Research in Australia have identified the protein CDK1 as a potential marker for predicting which estrogen‑receptor‑positive breast cancers will respond to the common class of drugs known as CDK4/6 inhibitors.
The study examined more than 400 biopsy samples from patients with ER+ breast cancer, the most common type of breast cancer that is driven by the hormone estrogen.
Researchers found that the level of activity of CDK1 increased as the tumors became more aggressive. Higher CDK1 activity also correlated with worse patient outcomes, suggesting it may reflect a tumor’s capacity to grow quickly.
Because CDK4/6 inhibitors can stop cancer cells from dividing, doctors sometimes give them together with hormone therapy. However, many patients eventually do not respond to these drugs, especially in advanced stages of the disease.
By measuring CDK1 activity, clinicians might be able to identify which patients are more likely to benefit from CDK4/6 inhibitors and which patients are at risk of early resistance.
TheGarvan Institute says that the findings must be confirmed in larger groups of patients who are actually receiving CDK4/6 inhibitors before the marker can be used in everyday care.
In addition to guiding therapy, the discovery could open the door to new drugs that directly target CDK1, offering an alternative treatment path for patients whose cancers show high CDK1 activity.
