11 December 2008

Cancer, antioxidants and free radicals

Alexey Levin, Voice of AmericaDoctors again did not find any evidence for the hypothesis that taking vitamin preparations serves to prevent cancer.

Malignant degeneration of normal tissues begins with mutations of certain genes that encode proteins that control the processes of reproduction and cell death.

Such mutations can be caused by many reasons, including the action of free radicals. This name unites a family of small molecules that have an increased ability to trigger oxidative reactions. To be more precise, free radicals differ from ordinary molecules in that they have an electron on the outer electron shell that does not have a counterpart in the person of another electron.

By virtue of the laws of quantum mechanics, they seek to regain the missing electron by taking it away from other molecules they encounter. Having lost their rightfully owned electrons, these molecules undergo changes that can significantly disrupt their structure. This also applies to nucleic acid molecules that encode hereditary information. Free radicals break DNA and RNA chains and thereby cause various mutations, some of which can be fatal.

Cells would have a much calmer life if there were no free radicals at all. However, these disruptor molecules are naturally born in many reactions on which cellular health depends. So it is impossible to completely get rid of them, biochemistry does not allow. Nevertheless, the cells also have considerable defensive capabilities. They synthesize various substances that help them defend themselves or even get rid of free radicals. Therefore, normally their intracellular concentration is very small, but it increases with various pathological processes.

There are many substances whose molecules neutralize free radicals – they are called antioxidants. These include some vitamins, especially C and E. Therefore, it is natural to assume that the increased intake of these vitamins reduces the frequency of mutations caused by free radicals, and thereby allows you to reduce the risk of cancer at least a little.

This hypothesis looks very convincing from the outside. Moreover, in the past, the results of examinations and clinical experiments have been published more than once, which even seemed to confirm it. However, in recent years, serious research projects have been carried out in various countries that have not revealed the anti-cancer capabilities of vitamin preparations. Therefore, the previous belief in the preventive potential of antioxidant vitamins has now been noticeably shaken - at least, if we talk about specialists.

Another blow has just been dealt to her, and by no means weak. He expressed himself in the appearance of two articles, which he published on December 9 in the electronic express issue of the Journal of the Amercican Medical Association. One of them presents the results collected during the project SELECT, Selenium and Vitamin E Cancer Prevention Trial (Testing the possibility of preventing cancer with selenium and vitamin E). It was attended by over 35 thousand healthy volunteers from the USA, Puerto Rico and Canada. These people were divided into 4 groups. The members of one selection for five and a half years regularly took selenium, which is also considered an antioxidant. The people who were included in the second group took vitamin E, in the third – both selenium and vitamin, and in the fourth – dummy pills (as it should be in such cases, the participants did not know what exactly they were given). The organizers of the experiment wanted to find out whether vitamin therapy reduces the likelihood of prostate cancer, so only men were selected for it.

The results were zero. The five-year incidence of prostate cancer in all four groups was almost the same, from four and a half to five percent. There were some differences between the groups, of course, but they did not go beyond statistical errors. Ironically, the least number of new cancer patients turned out to be in the group that received a placebo. However, the organizers of the experiment have no doubt that all the noted fluctuations are caused by purely random factors.

The second experiment was conducted by doctors from Boston. It was attended by about 15 thousand male doctors, on whom the effect of vitamins C and E was tested for more than eight years according to the same scheme. He also showed that these vitamins have no effect on the incidence of both prostate cancer and other forms of cancer.

Of course, the new results do not mean that all vitamin pills should be immediately thrown in the trash. Good vitamin complexes are most likely at least not useless – at least as a means of compensating for vitamin deficiency in food. However, cancer prevention, apparently, requires other techniques. If this conclusion is correct (and, of course, it will be checked more than once), it is better to know it and not build unrealistic hopes. This is exactly what Professor Peter Gann of the University of Illinois Medical School claims, who summed up the results of both experiments on behalf of the editorial board of the journal.

The Achilles heel of cancer proteinAn enzyme that protects tumor cells from chemotherapy drugs makes them more vulnerable to other drugs.

Fragments of hereditary information that contribute to the malignant degeneration of normal cells are called oncogenes. They encode the synthesis of molecules, which by analogy are called cancer proteins. Among them is the enzyme Akt, which contributes to the survival of cancer cells in various ways. In particular, it helps such cells to withstand the attacks of anti-cancer chemotherapy drugs. It is worth noting that the activity of this enzyme increases under the action of nicotine. This is probably one of the reasons why smokers are more likely to suffer from cancer, especially lung cancer.

However, now Akt also has a vulnerable spot. It was discovered by a group of researchers from the University of Illinois, headed by Professor Nissim Hay. It turned out that the excessive activity of this enzyme causes the cell to increase the production of reactive oxygen species, which is a danger to its own structures. They intensively tear off and steal electrons that are part of various biomolecules, and thereby reduce their chemical stability. Moreover, an excess of the Akt enzyme simultaneously prevents the cell from neutralizing free radicals on its own. It turns out that Akt not only protects tumor cells, but also creates hidden threats for them. It is worth noting that such situations are by no means uncommon.

Chicago scientists believe that this discovery indicates new opportunities to combat malignant neoplasms. In their opinion, tumors with hypertrophied activity of the Akt enzyme can be affected by chemicals that, like it, stimulate the appearance of free radicals. Experiments have shown that in this way it is possible to increase the concentration of free radicals so much that genetic programs are launched in the cell, leading to its death. This is stated in an article published on December 9 in the journal Cancer Cell.

Portal "Eternal youth" www.vechnayamolodost.ru11.12.2008

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