In a twist worthy of molecular drama, scientists at Karolinska Institutet have uncovered a surprising new role for a well-known cellular guardian, and it could reshape how we target cancer.
Published in Nature Communications, the study reveals that cyclin-dependent kinases (CDKs), specifically CDK4/6, do not just push cells to divide. They also help prep the cell’s DNA for copying, a process called replication licensing. And they do it by quieting the inhibitory signals from the RB tumor suppressor, a gene long known as the cell cycle’s gatekeeper.
The RB gene made its debut in the scientific spotlight through childhood retinoblastoma, earning its title as the world’s first tumor suppressor. For decades, it’s been seen as the bouncer at the cell cycle club, keeping rogue cells from dividing unchecked. But this new research shows RB has a second job: making sure the genome is ready to be duplicated.
“Phosphorylation of RB by CDK4/6 doesn’t just commit the cell to divide—it also ensures the genome is properly licensed for replication,” explains Dr. Bennie Lemmens, senior author of the study. “This dual role may be why CDK4/6 inhibitors are so effective in cancer treatment.”
The team didn’t stop there. They tested what happens when CDK4/6 inhibitors are combined with drugs that block DNA licensing. The result? Cancer cells tried to divide without copying their DNA correctly, a fatal error, especially in cells missing p53, another key protective gene often lost in cancer.
The unexpected nature of the findings struck lead author Michael Hawgood. “CDKs were traditionally thought to inhibit DNA licensing. But our data, from biochemical assays to single-cell imaging, consistently showed the opposite.”
To crack this cellular mystery, the researchers developed rapid protein degradation technologies and teamed up with the Halazonetis lab in Switzerland. Together, they performed ultra-sensitive DNA sequencing across thousands of genomic sites, offering unprecedented control and clarity over replication dynamics.
“This study builds on years of work exploring RB’s role in preventing replication stress—a major driver of genomic instability and cancer progression,” adds co-author Jiri Bartek.
The Lemmens and Bartek labs credit their breakthrough to support from The Mark Foundation for Cancer Research, Cancerfonden, the Swedish Research Council, KI, and SciLifeLab. Their findings not only deepen our understanding of cell division but also open new doors for precision cancer therapies that strike at the heart of genomic chaos.
Journal Reference:
- Sosenko Piscitello, A., Nilsson, AS., Hawgood, M. et al. Temporal control of human DNA replication licensing by CDK4/6-RB signalling and chemical genetics. Nat Commun 16, 8268 (2025). DOI: 10.1038/s41467-025-63669-8
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