Drugs that provide a dose of antioxidants, such as those used to treat malaria and diabetes, might also help treat cancer, a new study suggests.
The results show a process known as oxidative stress, which damages cells, can fuel tumor growth. Specifically, oxidative stress triggers cells near the cancer to release nutrients, which feed the cancer cells.
"Cancer cells are parasites, and the way they do their business is that they use oxidative stress as a weapon to extract nutrients from adjacent normal cells," said study researcher Dr. Michael Lisanti, professor of cancer biology at Jefferson Medical College in Philadelphia.
Because antioxidant drugs ameliorate oxidative stress, they might be useful tools for fighting cancer, the researchers said.
"The oxidative stress is part of a process to make food for cancer," Lisanti said. "So the best way to then kill a cancer would be to cut off the oxidative stress."
Current cancer treatments do not use antioxidant drugs, because it is thought these drugs might interfere with chemotherapy . Some chemotherapies are thought to work in part by increasing oxidative stress on the cancer cells. "We should rethink the idea of using antioxidants" during chemotherapy, Lisanti said.
However, the new study was conducted on cells in a lab dish, not on tumors in people. And clinical trials are needed to see whether antioxidant drugs, such as the diabetes drug metformin or the malaria drug chloroquine, could benefit those with cancer, Lisanti said. But the ways these drugs reduce oxidative stress make them promising cancer treatments, he said.
Antioxidants and cancer
Previous research has suggested that oxidative stress may promote cancer, but researchers weren't sure exactly how this worked.
Lisanti and his colleagues had previously found that the presence of a protein known as Caveolin-1 is strongly tied to the survival of breast cancer patients. Patients with an aggressive form of breast cancer who had this protein in certain cells had a survival rate of 75 percent over 12 years. But among patients who did not have Caveolin-1 in their cells, the survival rate was less than 10 percent after five years.
Caveolin-1 prevents oxidative stress in cells that surround the cancer, called fibroblasts, the researchers said.
In the new study, the researchers removed the Caveolin-1 protein from these fibroblasts, and the size of the neighboring tumors increased four-fold.The researchers said the loss of Caveolin-1 in the fibroblasts increased the oxidative stress on the fibroblasts, causing them to degrade and leak nutrients, which fed the cancer cells.
And further, when the researchers inserted a gene to get the fibroblasts to make a different antioxidant protein, they found that it stopped fibroblasts from leaking nutrients, Lisanti said.
This provides genetic evidence that antioxidants could be used to treat cancer , Lisanti told MyHealthNewsDaily.
Proving the benefits
To date, evidence of the effects of antioxidants on cancer has been mixed.
For example, a recent study found that women in China who took the antioxidants vitamins E and C during the first six months after they were diagnosed with breast cancer had a reduced risk of death and recurrence of their cancer, compared with women who did not take these vitamins. The link held true regardless of whether the women were on chemotherapy. However, there was no benefit to taking the vitamins if the women were undergoing radiation treatments as well.
Other researchers, writing in the journal Breast Cancer Research and Treatment in 2009, reviewed the findings of 22 previous studies, and concluded that taking antioxidants during chemotherapy, radiation treatments or hormonal therapy for breast cancer did not benefit the patients, but didn't harm them, either.
More clinical trials are needed to determine the short- and long-term effects of consuming antioxidants during cancer treatment, the researchers of that study concluded.
Pass it on: Antioxidants may provide benefit when taken along with cancer treatments, including chemotherapy. The antioxidants prevent oxidative stress, which can fuel cancer cell growth, a new study says.
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