Vitamin C reduces the risk of leukemia, and may also be useful as chemotherapy for the blood cancer, according to two recent studies.
Both studies examined how vitamin C affects the metabolism and genetics of blood-forming, or hematopoietic stem cells. Mutations in these cells can give rise to various blood cancers.
A study released Monday found that human and mouse hematopoietic stem cells absorb unusually large amounts of vitamin C. When the cells were depleted of vitamin C, they were more likely to turn into leukemia cells.
The results indicate the importance of taking 100 percent of the recommended amount of ascorbate, or vitamin C, especially for older people, said senior study author Sean Morrison, director of the Children's Medical Center Research Institute at UT Southwestern. The study was published in Nature.
The other study found that high doses of vitamin C can cause leukemic cells to die, potentially making it a useful and safe chemotherapy agent. That study was led by scientists at NYU Langone Health and published Aug. 17 in Cell.
Morrison said the studies complement each other, in particular by showing how vitamin C interacts with a gene called Tet2 that safeguards against leukemia. When the gene is damaged, the risk of leukemia increases.
The Cell study showed that high doses of vitamin C can compensate for Tet2 mutations, restoring normal function, Morrison said. Usually, transformation of normal cells into leukemic cells is irreversible, but the study demonstrated that's not true when the leukemia is driven by Tet2 mutations.
The Nature study demonstrated that vitamin C is a limiting factor in the proper function of Tet2, Morrison said. People have two copies of the gene, one from each parent. When one of the genes is disabled, it's important to take the full recommended dose of vitamin C so the remaining gene can exert its full tumor-suppressing effect.
The danger of leukemia is especially great in people with a preleukemic condition called clonal hematopoiesis. These people have partially mutated hematopoietic stem cells that produce great numbers of genetically identical clones of themselves, crowding out normal cells.
"We found that when we depleted ascorbate from mice that it accelerated the development of leukemia from partially mutated cells," Morrison said.
"And it's known epidemiologically that people with lower levels of vitamin C are at higher risk of cancer," Morrison said. "But it's not been known what the molecular mechanism for that is. So our data begin to explain the molecular mechanism."
"Our data also suggest that probably not all cancers are increased by vitamin C depletion," Morrison said. "We particularly would predict that certain leukemias would be increased in the absence of vitamin C.
"We're collaborating with the Centers for Disease Control right now to look more carefully at the epidemiological data that have been collected over decades, to understand more precisely which cancers are at increased risk in people that have lower levels of vitamin C."
Morrison said that while it's important to get the full recommended intake of vitamin C to reduce leukemia risk, the Nature study found no benefit in megadoses.
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