Antioxidants help cancer cells?
Antioxidants, often credited with an ability to protect cells from the damage that makes them turn cancerous, may actually help cancerous cells survive, says linkurl:a study;http://www.nature.com/nature/journal/vaop/ncurrent/full/nature08268.html published online in Nature today (August 19).
Multiplying tumor cells Image: Wikipedia"The study was certainly intriguing, but how generally applicable the results are remains to be seen," linkurl:Harold Seifried;http://prevention.cancer.gov/program
Antioxidants, often credited with an ability to protect cells from the damage that makes them turn cancerous, may actually help cancerous cells survive, says linkurl:a study;http://www.nature.com/nature/journal/vaop/ncurrent/full/nature08268.html published online in Nature
today (August 19).
| Multiplying tumor cells |
"The study was certainly intriguing, but how generally applicable the results are remains to be seen," linkurl:Harold Seifried;http://prevention.cancer.gov/programs-resources/groups/ns/about of the Division of Cancer Prevention at the National Cancer Institute in Bethesda, Md., who was not involved in the study, told The Scientist
Healthy mammary epithelial cells undergo programmed cell death when they stray from their normal cellular environment. Tumor cells, however, receive survival signals from oncogenes, which keep the cells alive when they migrate to different parts of the body. linkurl:Joan Brugge;https://brugge.med.harvard.edu/ at Harvard University and her colleagues hypothesized that oncogenes support tumor cells by blocking apoptosis, but when they prevented apoptosis in cell culture, cells still died when they were transplanted outside a supportive extracellular matrix.
In addition to apoptosis, the researchers found what was killing those cells was an inability to produce glucose. When they expressed a breast cancer oncogene in detached tumor cells, glucose metabolism in the cells was restored, fueling the production of ATP. Surprisingly, though, adding two types of antioxidants also prevented the tumor cells from dying by restoring ATP production -- not by increasing glucose, but via another metabolic pathway called fatty acid oxidation. "We got as good if not better rescue of the ATP with antioxidants," Brugge said.
The scientists found the same results in a cell culture system that more closely resembled living tissue: Blocking apoptosis was not enough to allow tumor cells to survive, but neutralizing oxidative stress with antioxidants kept them alive. "The antioxidants we used were able to restore normal cellular energy levels to cancerous cells," said linkurl:Zachary Schafer;http://www.nd.edu/%7Ebiology/schafer.shtml at the University of Notre Dame in Indiana, the study's first author.
linkurl:Balz Frei,;http://lpi.oregonstate.edu/staff/freibio.html director of the Linus Pauling Institute at Oregon State University, cautioned that the results were a long way from showing that antioxidants actually increase the survival of pre-cancerous and cancerous cells in living organisms.
"It's important to be careful about how we interpret the results of the study," said Frei, who did not participate in the research. Frei questioned why the authors chose to use one of the antioxidants, Trolox (a water-soluble vitamin E derivative), instead of a more powerful one such as vitamin C.
Not all antioxidants, treatments, or tumor cells are the same, added Seifried. In future research, for example, "it would be good to use different cell types to test [the findings] on a more general level," he said.
Brugge said her group plans to repeat the experiment using different antioxidants and in living tissue. She agreed, though, that "it is too early to extrapolate because we have no in vivo data yet."
**__Related stories:__***linkurl:A new epigenetic cancer;http://www.the-scientist.com/blog/display/55684/
[May 2009]*linkurl:Silenced genes drive viral cancers?;http://www.the-scientist.com/blog/display/55410/
[9th February 2009]*linkurl:Energetic senescence;http://www.the-scientist.com/article/display/55303/