PHGDH-Driven Epigenetic Silencing Creates Immune-Scarce Sanctuary for Metastatic Seeds
核心洞察
Researchers from Fudan University and collaborators identified that transient PHGDH (搜索) elevation in disseminated tumor cells suppresses immune signaling genes via histone methylation, enabling survival in the lung.
Spatial transcriptomic analysis in mice revealed that rare surviving metastatic cells enter a quiescent state, evading immune clearance despite the rapid amassing of immune cells.
Lineage tracing confirmed that most lung metastases descend from cells that briefly upregulated PHGDH (搜索), a rate-limiting enzyme in single-carbon metabolism.
A single tumor cell's journey from a primary site to a distant organ is fraught with peril—most disseminated cells perish before they can establish a foothold. Now, researchers from Zhongshan Hospital, ShanghaiTech University, Fudan University, and BGI Research have uncovered the metabolic and epigenetic trick that allows a tiny fraction of these cells to survive, revealing a transient state that could be exploited therapeutically.
Using spatial transcriptomic analysis in mouse models, the team tracked tumor cells injected into mice and observed metastasis formation in the lungs over more than a month. They found that while tumor cells rapidly seeded the lung, a swarm of immune cells amassed within hours to clear them out. The vanishingly rare survivors were the ones that captured the researchers' attention.
A Metabolic Enzyme with an Epigenetic Twist
Among the many genes up- and downregulated in surviving tumor cells, one stood out: the gene encoding phosphoglycerate dehydrogenase (搜索) (PHGDH (搜索)), a rate-limiting enzyme in single-carbon metabolism. PHGDH touches numerous cellular processes, but the team identified a specific histone methylation that appeared more frequently in high-PHGDH cells. This epigenetic mark clustered on immune signaling genes, suppressing their expression.
As a result, disseminated cells "effectively prevent the recruitment of cytotoxic . . . cells, creating an 'immune-scarce' sanctuary that allows them to survive initial host clearance," writes co-corresponding author Yunfan Sun, a physician-scientist focused on liver cancer at Fudan University, in an email to C&EN.
"What makes this finding surprising is the transient and non-proliferative nature of PHGDH (搜索) elevation," writes Wenkai Ren, a professor at South China Agricultural University who studies the interaction between metabolism and immunity, in an email to C&EN. Because PHGDH also supplies metabolites for DNA synthesis, one might expect fast growth from cells with high PHGDH. Instead, these cells were quiescent—like a submarine seeking to evade detection, they had gone silent.
Immune Evasion Through Quiescence
Analysis of the cellular neighborhoods surrounding these quiescent cells confirmed the strategy's effectiveness: they were surrounded by fewer immune cells. Even though PHGDH (搜索) expression dropped away as the stealthy survivor cells began to proliferate, Sun and colleagues demonstrated using lineage tracing that most metastases descended from cells that had briefly experienced high PHGDH expression. The researchers also explored the contribution of macrophages to building a welcoming niche for these secondary tumors to grow.
"Our goal was to preserve the structural architecture and local microenvironment niches of the tissue," writes Sun, explaining the rationale behind using spatial transcriptomic analysis rather than bulk or dissociated single-cell methods.
According to Ren, the study's strength lies in its demonstration that "distant tumor colonization is not a single event, but rather a complex and dynamic process." That process involves many genes expressed in numerous cell types. But with a clearer understanding of the critical windows in the formation of secondary tumors, the researchers say they hope to find points where medicine can intervene.
The study was published in Science (2026, DOI: 10.1126/science.adz7928).