Cancer treatments that stop tumors from growing may also leave behind a potentially dangerous population of “undead” cells, according to a new study from researchers at The Rockefeller University. These cells have entered cellular senescence: a permanent state in which they no longer divide, but remain metabolically active and continue releasing powerful signaling molecules into their surroundings. Some of these molecules help the immune system identify and remove damaged cells. Others can generate chronic inflammation, remodel nearby tissue, and create conditions that may eventually support tumor progression. The new findings, published in Life Science Alliance, suggest that senescence is not a single, fixed condition but a changing biological process that develops over time. The study also identifies a possible way to preserve the tumor-suppressive benefits of senescence while blocking its harmful inflammatory effects.
Cellular senescence is a natural response to severe stress, including DNA damage, oncogene activation, and treatment with certain anticancer drugs. When a cell becomes senescent, molecular brakes lock the cell cycle, preventing further division. This arrest is often considered beneficial because it stops damaged or malignant cells from multiplying. However, senescent cells do not simply shut down. They can continue producing proteins, reorganizing their internal structure, and secreting a collection of cytokines, growth factors, enzymes, and other molecules known collectively as the senescence-associated secretory phenotype, or SASP. The SASP can influence immune cells and neighboring tissues, sometimes promoting repair and clearance, but persistent SASP activity can also drive inflammation and alter the tumor microenvironment.
The Rockefeller team, led by Viviana I. Risca, compared two cancer therapies that induce senescence through substantially different mechanisms. The researchers used laboratory models of liposarcoma and estrogen receptor-positive breast cancer. One treatment was doxorubicin, a chemotherapy drug that damages DNA and triggers a well-established DNA damage response. The other was palbociclib, a CDK4/6 inhibitor used clinically against several cancers. Palbociclib blocks the activity of cyclin-dependent kinases 4 and 6, enzymes that help cells pass through the cell cycle. By preventing this transition, the drug can impose prolonged growth arrest without directly producing the extensive DNA damage associated with doxorubicin.
The researchers tracked the treated cancer cells for nearly a month, combining genomic, epigenomic, and imaging methods to observe how their behavior changed over time. This extended analysis revealed that senescence develops along a trajectory rather than appearing instantaneously. The cells first activated signals associated with tissue remodeling, followed weeks later by a stronger inflammatory program. The timing was particularly important for cells exposed to palbociclib. Earlier studies that examined only short treatment windows had largely missed the delayed inflammatory phase, creating the impression that the response to CDK4/6 inhibition was either weaker or fundamentally different from the response to DNA-damaging chemotherapy.
Although doxorubicin and palbociclib initiated senescence by different routes, the two treatments eventually converged on a common inflammatory pathway controlled by the transcription factor NF-κB. NF-κB regulates the expression of numerous genes involved in inflammation, immune signaling, cell survival, and tissue remodeling. In doxorubicin-treated cells, DNA damage activated sensors that rapidly stimulated NF-κB. Palbociclib-treated cells, by contrast, did not require a major DNA damage response. Their early tissue-remodeling signals appeared to activate receptors at the cell surface, which gradually transmitted signals inward and ultimately engaged NF-κB. In this way, the two therapies followed separate molecular paths before reaching a similar inflammatory destination.
The distinction was confirmed experimentally by blocking the cells’ DNA damage sensors. This intervention reduced inflammatory signaling in doxorubicin-treated cells, consistent with the drug’s direct effects on DNA. It did not suppress the corresponding response in palbociclib-treated cells, demonstrating that the CDK4/6 inhibitor uses a different signaling route. The observation challenges the assumption that DNA damage is always the central trigger of the inflammatory SASP. Instead, the findings indicate that senescent cells can assemble overlapping features through distinct molecular mechanisms, with the final inflammatory response shaped by the treatment’s initial effects and the time elapsed after exposure.
The study also provided a detailed view of the epigenetic changes that accompany senescence. Epigenetics refers to the molecular systems that control gene activity without altering the underlying DNA sequence. The researchers found that inflammatory genes became accessible through changes in regulatory regions called enhancers, which act as switches that increase gene transcription. They also observed the loss of macroH2A, a chromatin-associated protein that helps organize DNA and regulate access to genetic information. When chromatin structure changes, previously restricted genes can become active. These alterations help explain how senescent cells maintain long-term growth arrest while simultaneously acquiring the ability to produce an increasingly complex set of inflammatory signals.
A crucial result was that the researchers could inhibit NF-κB and reduce inflammatory signaling without restoring the cancer cells’ ability to divide. This suggests that growth arrest and inflammatory activity, although both associated with senescence, are separable biological programs. In practical terms, a therapy designed to suppress the SASP might limit the harmful effects of treatment-induced senescence without “waking up” the arrested tumor cells. Such an approach could be especially valuable in cancers treated with CDK4/6 inhibitors, where senescence may persist for extended periods and continue influencing the surrounding tissue after the initial drug exposure.
The findings offer a framework for developing combination therapies that target both tumor growth and the consequences of cellular senescence. Rather than treating senescence as a binary state—either present or absent—clinicians and researchers may eventually need to consider its timing, molecular route, and secretory profile. Blocking inflammatory signals too early could interfere with beneficial immune responses, while allowing them to persist could contribute to tumor-supportive inflammation. The researchers emphasize that further studies will be needed to determine whether the same sequence occurs in patients and whether NF-κB-targeting strategies can be safely combined with existing cancer treatments. Even so, the work provides a detailed molecular map of how therapy-induced senescence unfolds and identifies a potential route to retain the anti-cancer effects of cellular arrest while limiting the signals that could promote disease later.
Subject of Research: Cellular senescence, therapy-induced inflammation, cancer treatment, the senescence-associated secretory phenotype, and NF-κB signaling in liposarcoma and estrogen receptor-positive breast cancer.
Article Title: The specific article title was not provided in the source content.
Web References: Life Science Alliance article; Viviana I. Risca laboratory profile; Laboratory of Genome Architecture and Dynamics.
References: Life Science Alliance, DOI: 10.26508/lsa.202603790.
Image Credits: Lori Chertoff/The Rockefeller University.
Keywords: Cancer, cellular senescence, senescence-associated secretory phenotype, SASP, inflammation, NF-κB, CDK4/6 inhibitors, palbociclib, doxorubicin, DNA damage, liposarcoma, breast cancer, epigenetics, tumor microenvironment.
