Dietary Methionine Restriction Remodels Chromatin and Extends Survival in Glioma Models
核心洞察
Researchers at Baylor College of Medicine found that restricting the amino acid methionine in diet extended survival and slowed tumor growth in mouse models of high-grade glioma (搜索).
Methionine restriction destabilized chromatin organization in glioma (搜索) cells, leading to altered gene expression, cancer cell death, and increased animal survival.
The chromatin organizer protein Hp1bp3 (搜索) was identified as a key mediator; tumors lacking Hp1bp3 became more sensitive to methionine restriction, further improving survival.
An unexpected observation under the microscope has led researchers at Baylor College of Medicine and the Duncan Neurological Research Institute at Texas Children's Hospital to uncover a striking link between dietary methionine, chromatin organization, and survival in glioma (搜索) — one of the most aggressive and deadly forms of brain cancer. Reporting in the Proceedings of the National Academy of Sciences, the team demonstrated that restricting a single amino acid in the diet can destabilize DNA packaging in tumor cells, ultimately slowing tumor growth and extending survival in animal models.
"Cancer cells, including gliomas, often depend on methionine. Methionine is an essential amino acid, meaning that the body does not produce it on its own, it must consume it in the diet. Glioma (搜索) cells are unusually dependent on methionine to fuel rapid growth and control gene activity," said corresponding author Dr. Benjamin Deneen, professor and Dr. Russell J. and Marian K. Blattner Chair in the Department of Neurosurgery and director of the Center for Cancer Neuroscience at Baylor.
A Serendipitous Finding Under the Microscope
The study began with a straightforward question: if glioma (搜索) tumors depend so heavily on methionine, what happens when the supply is reduced? To answer this, the team employed a mouse model of high-grade glioma, feeding one group a normal diet containing methionine and another group a methionine-restricted diet. The results were immediate and striking — mice on the low-methionine diet lived longer and had slower-growing tumors.
The mechanistic breakthrough came when first author Brittney Lozzi, a graduate student in the Deneen lab, noticed something unusual while examining glioma (搜索) cells from the methionine-restricted mice. "I was looking under the microscope at glioma cells from mice in a methionine-restricted diet when I noticed that the DNA inside the tumors looked different," Lozzi said. "Instead of its usual compact organization, it appeared partially unraveled."
This observation pointed toward chromatin — the complex of DNA and proteins that packages genetic material within the cell nucleus. Chromatin organization is known to regulate gene activity by controlling which genes are turned on or off. In this case, the chromatin unraveling triggered gene expression changes that ultimately slowed tumor growth and led to cancer cell death.
The Chromatin Organizer Hp1bp3 (搜索) Emerges as a Key Player
To understand how this chromatin rearrangement occurred, the researchers investigated proteins involved in maintaining chromatin structure. Previous work from the Deneen lab and colleagues had identified several chromatin organizing proteins linked to familial glioma (搜索) predisposition. The team focused on one in particular: Hp1bp3 (搜索), a protein that normally helps keep chromatin organized.
Hp1bp3 (搜索) maintains chromatin stability by suppressing histone demethylases — enzymes that strip away methyl chemical tags responsible for turning genes off. Without these methyl tags in place, chromatin unravels in ways that fuel cancer growth.
When the researchers removed or reduced Hp1bp3 (搜索), tumors grew faster and mice died sooner. At the cellular level, losing Hp1bp3 opened and disorganized the chromatin, promoting tumor growth. The team then asked whether methionine restriction could counteract this effect.
A Synergistic Vulnerability
The results proved surprising. Tumors lacking Hp1bp3 (搜索) became more sensitive to methionine restriction. When both conditions were present — low methionine and loss of Hp1bp3 — tumor growth was significantly reduced, and survival improved even more than anticipated.
The researchers propose a mechanistic model: without Hp1bp3 (搜索), chromatin is already unstable. When methionine — which provides methyl groups to cells — is also limited, tumor cells struggle to maintain proper methylation patterns. This dual assault pushes cancer cells beyond their ability to cope, leading to increased cellular stress and cell death, which translates to improved animal survival.
"The findings reveal a connection between diet, gene regulation and cancer growth that opens new possibilities for treating one of the most severe brain tumors," Deneen said. He is also a member of the Dan L Duncan Comprehensive Cancer Center at Baylor and a principal investigator at the Duncan NRI.
Cautious Optimism and Future Directions
While the results are promising, the researchers emphasize that more work is needed before dietary methionine restriction can be considered as part of glioma (搜索) therapy in humans. "More research is needed to determine whether restricting methionine or other dietary components is safe and effective as a part of glioma therapies," Deneen noted.
The study was supported by multiple National Institutes of Health grants, including R35-NS132230 and R01-CA284455, a National Cancer Institute Cancer Therapeutics Development and Discovery grant (U01CA281902), and Cancer Prevention Research Institute of Texas grants. Additional contributors to the work include researchers from the University of Pittsburgh and Stanford University.