High doses of vitamin C delivered through injection may slow down the growth of many types of cancers and boost the anticancer efficacy of some immuno-therapies, according to a new animal study published in the February 26 issue of Science Translational Medicine.
Vitamin C has been studied as an anticancer treatment. And early findings suggest that vitamin C may be used together with immuno-therapies known as checkpoint inhibitors, which likely become ineffective after drug resistance develops in cancer patients.
In the current study, vitamin C was injected in mice in very high doses in order to achieve certain therapeutic effectiveness. This vitamin should be in an amount equivalent to what is found in more than 2,000 oranges per day.
In 1970s, research showed that administering high amounts of vitamin C both orally and intravenously helped 100 terminal cancer patients survive longer.
Some studies later failed to duplicate the good outcome when vitamin C was used. But soon it became public that in such studies, vitamin C was administered orally in forms of pills.
One study reported in 2004 showed that vitamin C ingested can’t be absorbed through the gut in high doses to achieve anticancer therapeutic effects. This prompted some researchers to believe that only the IV administered vitamin C can elicit some therapeutic effects against cancer.
The current study is one of the few that demonstrated that IV administered vitamin C is effective against tumors or cancers in mice, which suggests that vitamin C can also be effective in humans with cancers.
The study found that mice with colorectal cancer, breast cancer, melanoma,or pancreatic cancer that received high doses of vitamin C through abdominal injections experienced a delayed growth of the tumors. The study also found that vitamin C provides an anticancer therapeutic effect by boosting the activity of anticancer T cells.
Vitamin C also shows its anticancer activity when used together with checkpoint antibodies. Checkpoint antibodies do not provide treatment efficacy to all cancer patients, they have toxic adverse effects and even if they help some cancer patients initially, they lose potency soon later due to the drug resistance developed in cancer patients.
The combo therapy with vitamin C and checkpoint antibodies were very effective in mice with cancers. Many animals with breast cancer had their tumors regressed. The combination treatment was well tolerated and did not cause any autoimmune responses that have been found earlier with use of anti-CTLA-4 checkpoint antibodies.