Vitamin C Injections Slow Pancreatic, Ovarian and
Brain Cancer Growth in Mice
High concentrations of ascorbate had anticancer
effects in 75% of cancer cell lines, while sparing normal cells
Aug.
4, 2008 - High-dose injections of vitamin C, also known as ascorbate or
ascorbic acid, reduced tumor weight and growth rate by about 50 percent
in mouse models of brain, ovarian, and pancreatic cancers, three of the
deadliest of cancers. Researchers from the National Institutes of Health
(NIH) report results in the August 5, 2008, issue of the Proceedings of
the National Academy of Sciences.
The researchers traced ascorbates anti-cancer
effect to the formation of hydrogen peroxide in the extracellular fluid
surrounding the tumors. Normal cells were unaffected.
Natural physiologic controls precisely regulate the
amount of ascorbate absorbed by the body when it is taken orally.
"When you eat foods containing more than 200
milligrams of vitamin C a day for example, 2 oranges and a serving of
broccoli your body prevents blood levels of ascorbate from exceeding a
narrow range," says Mark Levine, M.D., the studys lead author and chief
of the Molecular and Clinical Nutrition Section of the National
Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of
the NIH.
To bypass these normal controls, NIH scientists
injected ascorbate into the veins or abdominal cavities of rodents with
aggressive brain, ovarian, and pancreatic tumors. By doing so, they were
able to deliver high doses of ascorbate, up to 4 grams per kilogram of
body weight daily.
"At these high injected doses, we hoped to see
drug-like activity that might be useful in cancer treatment," said
Levine.
Vitamin C plays a critical role in health, and a
prolonged deficiency leads to scurvy and eventually to death. Some
proteins known as enzymes, which have vital biochemical functions,
require the vitamin to work properly. Vitamin C may also act as an
antioxidant, protecting cells from the damaging effects of free
radicals.
The NIH researchers, however, tested the idea that
ascorbate, when injected at high doses, may have prooxidant instead of
antioxidant activity. Prooxidants would generate free radicals and the
formation of hydrogen peroxide, which, the scientists hypothesized,
might kill tumor cells.
In their laboratory experiments on 43 cancer and 5
normal cell lines, the researchers discovered that high concentrations
of ascorbate had anticancer effects in 75 percent of cancer cell lines
tested, while sparing normal cells.
In their paper, the researchers also showed that
these high ascorbate concentrations could be achieved in people.
The team then tested ascorbate injections in
immune-deficient mice with rapidly spreading ovarian, pancreatic, and
glioblastoma (brain) tumors. The ascorbate injections reduced tumor
growth and weight by 41 to 53 percent. In 30 percent of glioblastoma
controls, the cancer had spread to other organs, but the ascorbate-treated
animals had no signs of disseminated cancer.
"These pre-clinical data provide the first firm
basis for advancing pharmacologic ascorbate in cancer treatment in
humans," the researchers conclude.
Interest in vitamin C as a potential cancer therapy
peaked about 30 years ago when case series data showed a possible
benefit. In 1979 and 1985, however, other researchers reported no
benefit for cancer patients taking high oral doses of vitamin C in two
double-blind, placebo-controlled clinical trials.
Several observations led the NIH researchers to
revisit ascorbate as a cancer therapy. "Clinical and pharmacokinetic
studies conducted in the past 12 years showed that oral ascorbate levels
in plasma and tissue are tightly controlled. In the case series,
ascorbate was given orally and intravenously, but in the trials
ascorbate was just given orally. It was not realized at the time that
only injected ascorbate might deliver the concentrations needed to see
an anti-tumor effect," said Levine, who noted that new clinical trials
of ascorbate as a cancer treatment are in the planning stages.
Data from Levines earlier studies of the
regulation and absorption of dietary vitamin C were used in the revision
of the Institute of Medicines Recommended Dietary Allowance for the
vitamin in 2000. In the current study, Levine led a team of scientists
from the NIDDK and the National Cancer Institute (NCI), both components
of the NIH, as well as the University of Kansas. "NIHs unique
translational environment, where researchers can pursue intellectual
high-risk, out-of-the-box thinking with high potential payoff, enabled
us to pursue this work," he said.
Editors Notes:
For more information about cancer, visit the NCI
website at
www.cancer.gov, or call NCI's Cancer Information Service at
1-800-4-CANCER (1-800-422-6237).
The NIDDK conducts and supports research in
diabetes and other endocrine and metabolic diseases; digestive diseases,
nutrition, and obesity; and kidney, urologic, and hematologic diseases.
Spanning the full spectrum of medicine and afflicting people of all ages
and ethnic groups, these diseases encompass some of the most common,
severe, and disabling conditions affecting Americans. For more
information about NIDDK and its programs, see
www.niddk.nih.gov.
The National Institutes of Health (NIH) The
Nation's Medical Research Agency includes 27 Institutes and Centers
and is a component of the U.S. Department of Health and Human Services.
It is the primary federal agency for conducting and supporting basic,
clinical and translational medical research, and it investigates the
causes, treatments, and cures for both common and rare diseases. For
more information about NIH and its programs, visit
www.nih.gov.
Aug.
4, 2008 - High-dose injections of vitamin C, also known as ascorbate or
ascorbic acid, reduced tumor weight and growth rate by about 50 percent
in mouse models of brain, ovarian, and pancreatic cancers, three of the
deadliest of cancers. Researchers from the National Institutes of Health
(NIH) report results in the August 5, 2008, issue of the Proceedings of
the National Academy of Sciences.