Hidden Metabolism in the Nucleus: A New Understanding of Cancer

In a surprising discovery, researchers have found that hundreds of metabolic enzymes, traditionally associated with energy production in the mitochondria, are as well located within the nucleus of human cells, directly interacting with DNA. This finding, published in Nature Communications, reveals a previously unknown “nuclear metabolic fingerprint” that varies between cell types and may hold crucial clues to understanding cancer development and treatment resistance.

The Discovery of Nuclear Metabolism

For decades, metabolism and genome regulation were considered largely separate processes. Metabolism, the set of chemical reactions that sustain life, primarily occurs in the cytoplasm and mitochondria. The nucleus, houses the genome and controls gene expression. However, this new research demonstrates a significant overlap, with approximately 7% of all proteins attached to chromatin being metabolic enzymes.

The research team, led by Dr. Sara Sdelci at the Centre for Genomic Regulation, used a method to isolate proteins physically attached to chromatin in 44 cancer cell lines and 10 healthy cell types from ten different tissues.¹ This revealed a surprising abundance of metabolic enzymes within the nucleus, suggesting the presence of a “mini-metabolism” operating directly on DNA.

Implications for Cancer Research

The presence of metabolic enzymes in the nucleus has significant implications for cancer research. These enzymes are involved in essential processes like DNA synthesis and repair. Their location within the nucleus suggests they may directly influence how cancer cells respond to genotoxic stress, a common characteristic of chemotherapy and radiotherapy.¹

“It could help explain why tumors of different origins, even when carrying the same mutations, often respond very differently to chemotherapy, radiotherapy, or targeted inhibitors,” says Dr. Sdelci.¹

The study also found that the specific metabolic enzymes present in the nucleus differed depending on the cancer type. For example, enzymes involved in oxidative phosphorylation were common in breast cancer cells but largely absent in lung cancer cells. This tissue-specific pattern suggests that nuclear metabolism could serve as a biomarker for diagnosis or a target for new anti-cancer drugs.

Enzyme Location and Function

Researchers are now working to determine the precise function of each enzyme within the nucleus. Experiments have shown that the location of an enzyme can dramatically alter its behavior. For instance, the enzyme IMPDH2 helped maintain genome stability when confined to the nucleus but affected other pathways when located in the cytoplasm.¹

Unanswered Questions and Future Research

Several questions remain unanswered. Researchers are investigating how these relatively large enzymes bypass the nuclear pore, a gateway between the nucleus and cytoplasm, and how the cell regulates this transport. Understanding these mechanisms could lead to the development of precise therapeutic targets for controlling nuclear metabolic activity in diseased cells.

“We’ve been treating metabolism and genome regulation as two separate universes, but our work suggests they’re talking to each other, and cancer cells might be exploiting these conversations to survive,” says Dr. Savvas Kourtis, first author of the study.¹

Further research is needed to map the location and function of all the enzymes found in the nucleus and to determine whether they are all actively catalyzing reactions or playing other roles. This groundbreaking discovery opens up a new frontier in cellular biology and promises to reshape our understanding of cancer.