Free radicals also block cancer growth

Free radicals also inhibit growth of cancerous tumors

07/07/2011

Free radicals have always been considered a risk factor for the development of cancer. However, David Tuveson of the Cancer Research Institute of Cambridge and colleagues found in a comprehensive study with mice that free radicals reduce the growth of certain cancers rather than increase cancer risk. The intake of antioxidants via food, which was previously classified as cancer-preventive, might even increase the risk of cancer.

The consumption of fruit and vegetables is attributed to a cancer-preventing effect, not least because of the relatively high content of antioxidants in the form of vitamins and trace elements. Because the antioxidants absorb the free radicals in our body and prevent them from causing further damage. So far, the free radicals have been considered a major risk factor for the development of tumors and the occurrence of other diseases, such as Parkinson's or arteriosclerosis. But researchers at the Cancer Research Institute at Cambridge have now found that free radicals can inhibit the development of tumors in certain cancers, thereby reducing cancer risk. Thus, the positive effect of the antioxidants in terms of cancer prevention is at least questioned.

Free radicals previously known as harmful
Contrary to previous scientific findings, the researchers of the Cancer Research Institute come to the conclusion in their current study that free radicals do not necessarily increase the risk of cancer, but can certainly inhibit the growth of tumors. The free radicals, also known as reactive oxygen species (ROS), are constantly being formed in the human body as intermediates of metabolism in the mitochondria (tiny cell power plants). Tobacco smoking, UV radiation and ionizing radiation also contribute to the formation of free radicals in the body. In their molecular structure, the free radicals are characterized by the fact that they have at least one unpaired electron on their outer electron shell. To compensate for the electron deficit, the electrons of other molecules of the organism are bound, which then turn these molecules into free radicals and in turn bind electrons of other molecules. In this way, for example, components of the cell membrane can be disrupted in a veritable chain reaction and permanently damaged, the researchers report. Since even electrons from proteins or at worst the DNA can be bound by the free radicals, long-term significant health impairments.

Reactive oxygen species block tumor growth
The human organism therefore defends itself against the free radicals with the help of the so-called antioxidants. The antioxidants are part of a sophisticated defense system, with which the body prevents the chain reactions of the free radicals. As so-called radical scavengers, the antioxidants such as vitamin A, vitamin C, vitamin E, certain flavonoids and other trace elements stabilize the free radicals and prevent them from reacting with other molecules in the organism. Subsequently, the free radicals are eliminated from the body before they can start their chain reaction. The antioxidants are therefore given a significant importance for the health and are for example due to a lack of vitamin C too few antioxidants available, threatens the body's defense mechanism against the free radicals collapse. Cell damage and serious health problems can be the result, so the current state of research. But David Tuveson of the Cancer Research Institute in Cambridge and colleagues have now found that free radicals in the body can also have a positive effect. The scientists found that the reactive oxygen species can block the growth of tumors in the pancreas.

Cancer cells do not like free radicals
In their studies on mice, the researchers of the Cancer Research Institute could prove, „that cancer cells do not like reactive oxygen species“, explained David Tuveson. An increased concentration of free radicals has killed the cancer cells in the pancreas of the mice, Tuveson continued. In the animals, the antioxidant defense system had already become active at the beginning of cancer growth and had induced the binding of the reactive oxygen species (ROS) with the help of the protein Nrf2, explained Tuveson and colleagues. If the protein Nrf2 was missing, the growth of the cancer cells was blocked by the high ROS values ​​and only after antioxidants were added, the tumor continued to grow, report the researchers of the Cancer Research Institute.

Increase antioxidants the cancer risk?
This suggests that, contrary to all previous findings, antioxidants could definitely increase the risk of cancer. The situation is not that easy, however, according to the British researchers. Their study does not prove a general cancer-promoting effect of the antioxidants and should not be misunderstood as an appeal, „that people should eat unhealthily“, emphasized David Tuveson and colleagues. Because overall clearly outweigh the positive health effects of antioxidants. According to the experts, these also have a cytoprotective and anti-inflammatory function whose importance for health should not be underestimated. Tuveson said that the current findings do not speak against the consumption of fruit and vegetables, but rather the interesting question is how to turn off the antioxidant protection system of cancer cells. Because this mechanism could be switched off, the cancer cells would be vulnerable to the attacks of free radicals, which would open up opportunities for new treatment approaches and therapeutic procedures, explained Tuveson.

Positive health effect of the antioxidants
The consumption of antioxidants is due to the many positive health effects, regardless of the current study results continue to be recommended, the British researchers said. Also in natural medicine, antioxidants are considered to be an essential part of the diet, not least because of their cell-protecting and anti-inflammatory effects. For example, onions, turmeric and cranberries have always been considered as naturopathic treatments because of their high antioxidant content „natural antibiotic“ used. Other fruits and vegetables, which due to their high natural antioxidant content, a positive health effect is attributed to, for example, broccoli, ginger, coffee, garlic, mangoes, parsley, asparagus, tea, tomatoes, wholegrain rice and grapes. (Fp)

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Picture: Gerd Altmann