Taking too many antioxidants like vitamin C may promote cancer tumor growth

A few percent of the oxygen taken into the body becomes ' active oxygen ,' which reacts with various components in the body's metabolic processes, and when in excess, it causes cell damage that poses a risk of aging and cancer. Substances that weaken the effects of active oxygen or remove active oxygen are ' antioxidants ,' and vitamin C, vitamin A, selenium, zinc, etc. are known as antioxidants. A research team at the Karolinska Institute in Sweden has announced research results that show that excessive intake of these antioxidants may promote the growth of cancer tumors.

JCI - Antioxidants stimulate BACH1-dependent tumor angiogenesis
https://www.jci.org/articles/view/169671

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Angiogenesis is the formation of new blood vessels from existing blood vessels to build a vascular network. Blood is a pipe that supplies nutrients to cells, and angiogenesis plays an important role in the growth of cancer tumors. It is thought that when oxygen supply is insufficient in a part of the body, a protein called ``hypoxia-inducible factor (HIF)'' becomes stabilized, and angiogenesis begins by starting transcription of genes that generate blood vessels.

The research team has newly reported that angiogenic gene expression is regulated not only by HIF but also by a protein called ``BACH1.'' BACH1 is called a 'redox-sensitive transcription factor' and is known to stabilize when active oxygen levels decrease, causing oxidative stress .

The research team prepared cells that overexpressed BACH1 and cells that did not express BACH1 and investigated the expression of angiogenic genes in each. As a result, angiogenic gene expression increased in cells that overexpressed BACH1 and decreased in cells that did not express BACH1.

The research team also found that when cells that do not express HIF and normal cells were subjected to hypoxia and administered a HIF-PH inhibitor that activates the hypoxic response, BACH1 was stabilized in both. The research team argued that BACH1 also has the effect of promoting angiogenic gene expression independently of HIF.

Furthermore, when the research team administered antioxidants such as vitamin C, vitamin E, and N-acetylcysteine to lung cancer tumor cells, an increase in the expression of angiogenic genes derived from BACH1 was confirmed. They also reported that administration of angiogenesis inhibitors to newly formed blood vessels showed high sensitivity.

Professor Martin Bergo from Karolinska Institutet, who led the study, said: ``We found that antioxidants activate mechanisms that form new blood vessels that lead to cancer tumors.'' It was thought that it would have the effect of doing so, but this is surprising.'

Ting Wang, a member of the research team, said, ``The effectiveness of angiogenesis inhibitors has been evaluated in many clinical trials, but in some cases angiogenesis inhibitors work well, while in others they have little effect. In some cases, the results were not good enough to be considered effective. Our study reveals a more effective way to prevent angiogenesis in cancer tumors: reducing BACH1 in tumors. Patients with high BACH1 levels may benefit more from angiogenesis inhibitors than those with low BACH1 levels.'