Can Vitamin C help fight cancer?

Vitamin C and the war on cancer

From Jocelyn Kaiser, Science 

Maybe Linus Pauling was on to something after all. Decades ago the Nobel Prize–winning chemist was relegated to the fringes of medicine after championing the idea that vitamin C could combat a host of illnesses, including cancer.

Now, a study published online today in Science reports that vitamin C can kill tumor cells that carry a common cancer-causing mutation and—in mice—can curb the growth of tumors with the mutation.

If the findings hold up in people, researchers may have found a way to treat a large swath of tumors that has lacked effective drugs. 

"This [could] be one answer to the question everybody's striving for," says molecular biologist Channing Der of the University of North Carolina, Chapel Hill, one of many researchers trying to target cancers with the mutation.

The study is also gratifying for the handful of researchers pursuing vitamin C, or ascorbic acid, as a cancer drug. "I'm encouraged. Maybe people will finally pay attention," says vitamin C researcher Mark Levine of the National Institute of Diabetes and Digestive and Kidney Diseases.

 In 1971, Pauling began collaborating with a Scottish physician who had reported success treating cancer patients with vitamin C. But the failure of two clinical trials of vitamin C pills, conducted in the late 1970s and early 1980s at the Mayo Clinic in Rochester, Minnesota, dampened enthusiasm for Pauling’s idea.

Studies by Levine’s group later suggested that the vitamin must be given intravenously to reach doses high enough to kill cancer cells. A few small trials in the past 5 years—for pancreatic and ovarian cancer—hinted that IV vitamin C treatment combined with chemotherapy can extend cancer survival.

But doubters were not swayed. "The atmosphere was poisoned" by the earlier failures, Levine says.

A few years ago, Jihye Yun, then a graduate student at Johns Hopkins University in Baltimore, Maryland, found that colon cancer cells whose growth is driven by mutations in the gene KRAS or a less commonly mutated gene, BRAF, make unusually large amounts of a protein that transports glucose across the cell membrane.

The transporter, GLUT1, supplies the cells with the high levels of glucose they need to survive. GLUT1 also transports the oxidized form of vitamin C, dehydroascorbic acid (DHA), into the cell, bad news for cancer cells, because Yun found that DHA can deplete a cell’s supply of a chemical that sops up free radicals.

Because free radicals can harm a cell in various ways, the finding suggested “a vulnerability” if the cells were flooded with DHA, says Lewis Cantley at Weill Cornell Medicine in New York City, where Yun is now a postdoc.

Read more at Science.