Scientists Find Molecular Switch That Helps Cancer Cells Defy Death

Researchers have identified a stress-activated control mechanism that helps breast cancer cells reshape gene activity to survive and grow.

Cells often encounter environmental pressures that can harm or even kill them. To stay alive, they rapidly shift which genes are active so they can mount a protective response. Cancer cells face this challenge even more intensely because they grow within a microenvironment that is naturally difficult to survive in. Despite this, they manage to flourish, activating genes that support the formation of larger tumors or allow them to spread elsewhere in the body.

Exactly how cancer cells turn harsh conditions into an advantage has remained unclear. Researchers at Rockefeller University suspected the answer involved the way transcription machinery detects stress and adjusts its activity. Their work has now identified a molecular switch in breast cancer cells that redirects gene expression toward growth and stress tolerance.

The study, published in Nature Chemical Biology, highlights a promising new direction for developing cancer treatments.

“This previously unknown transcription-level mechanism helps the cancer cells survive stressful conditions, so targeting it could disrupt a key survival mechanism that some cancers rely on,” says first author Ran Lin, a research associate from the Laboratory of Biochemistry and Molecular Biology at The Rockefeller University. “It’s another example of how basic research can open promising therapeutic avenues.”

“We found that this molecular switch is mediated by a generic transcription complex normally required for all protein-coding genes,” says Robert Roeder, head of the lab. “But what was most unexpected is that its individual subunits can be repurposed for several physiological functions—including a function that allows cancer cells to survive and grow in high-stress environments.”

Transcription services

RNA polymerase II, also known as Pol II, is the enzyme responsible for transcribing protein-coding genes in eukaryotic cells. Roeder identified Pol II decades ago, and it often works alongside the Mediator complex, a large transcriptional coactivator made up of 30 subunits, to begin the transcription process that leads to mature RNA. Additional adjustments can occur through post-transcriptional modifications, which further influence how genes are expressed.

Within the Mediator complex, one important subunit is MED1. This component is required for Pol II to function properly in many cell types, including estrogen receptor–positive breast cancer (ER+ BC), which is among the most common forms of breast cancer.

Previous research on ER+ BC from Roeder’s lab has shown that estrogen receptor interactions with MED1 drive gene activation—so much so that they can render otherwise promising cancer drugs ineffective. These findings made Lin wonder whether MED1 played a role in helping cancer cells stay alive, and even thrive, in stressful conditions.

Lin decided to explore whether MED1 is acetylated. Acetylation is a biochemical modification that involves adding an acetyl group to a protein, which can alter its function, and is increasingly being recognized for its seemingly influential role in tumor development, metastasis, and drug resistance.

After determining that MED1 is indeed acetylated, he next aimed to understand how this modification influences its function, especially under cellular stress. They subjected the cells to different types of stress conditions, including hypoxia (lack of oxygen), oxidative stress, and thermal stress.

Altering the acetyls

They discovered that under stress, a protein called SIRT1 removes acetyl groups from normal MED1. This “deacetylation” enables MED1 to interact more efficiently with Pol II, leading to the elevated potential for activation of protective genes.

They also created a mutant form of MED1 that lacked six specific acetylation sites, making it unable to be acetylated. They then introduced this mutant protein into ER+ breast cancer cells in which the endogenous MED1 had been removed using CRISPR.

They found that regardless of how the MED1 became deacetylated—either through stressful conditions or by removing its ability to become acetylated—the breast cancer cells with deacetylated MED1 formed faster-growing and more stress-resistant tumors.

“Our work reveals that the acetylation and deacetylation of MED1 act as a regulatory switch that helps cancer cells reprogram transcription in response to stress, supporting both survival and growth,” Lin says. “In cancer—particularly in ER+ breast cancer—this pathway may be co-opted or intensified to support abnormal growth and survival. We hope these insights will inform future drug development, especially for breast cancers and possibly other malignancies that rely on stress-induced gene reprogramming.”

“This MED1 regulatory pathway appears to be part of a wider paradigm in which acetylation regulates transcription factors,” Roeder adds. “Our earlier work on p53 helped establish that principle. Continuing to probe these basic mechanisms is what allows us to identify pathways that may eventually be leveraged for therapeutic purposes.”

Reference: “MED1 IDR deacetylation controls stress responsive genes through RNA Pol II recruitment” by Ran Lin, Yan Mo, Douglas Barrows, Wenbin Mei, Takashi Onikubo, Jianfeng Sun, Zhiguo Zhang, Effie Apostolou, Sohail F. Tavazoie and Robert G. Roeder, 23 October 2025, Nature Chemical Biology.
DOI: 10.1038/s41589-025-02035-7

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