Friday, December 18, 2015

Cancer and Cellular Respiration

When they are healthy, your cells -- and those of all other animals and plants -- power themselves using cellular respiration, which requires oxygen. But cancer cells, like many bacteria, use a completely different process called fermentation. Fermentation is much less efficient at extracting energy from fuel like sugar molecules; so why do cancer cells do it?

Back in 2009, a team of Dutch biologists suggested a possible explanation. Respiration is more efficient, but it requires a more elaborate set of enzymes and other factors to make it work. So a cell using fermentation can be built more simply and cheaply. Therefore, cells using fermentation can make copies of themselves more easily and thus divide more rapidly. So if cells "want" to divide very quickly, switching to fermentation might make sense.

Now some experimental biologists have confirmed that this is the case:
although oxygen-based metabolism is a more efficient means of energy production, the costs required to produce the molecular machinery that drives respiration are twice those needed to ferment the sugar glucose.
This provides more evidence for the theory that cancer may be at its heart a crisis of cellular respiration and therefore mainly a disease of mitochondria:
Thomas Seyfried, a biologist at Boston College who was not part of this study, feels that cancer is a metabolic disorder, citing the large body of evidence implicating mitochondrial dysfunction in cancer. Mitochondria—or the “powerhouses” of our cells—are where cellular energy production takes place. “There is now substantial evidence from a broad range of disciplines showing some degree of defect in the number, structure or function of mitochondria in all types of tumor cells. These mitochondrial defects cause the enhanced glucose uptake and the fermentation seen in tumor cells,” Seyfried explains.
There is, says Seyfried,
ample evidence to support his claim, including showing that a cell’s tumor potential is suppressed if it is transplanted with normal mitochondria; and conversely that transferring mitochondria from tumor cells into the cytoplasm of normal cells increases the chances that those once normal cells will become cancerous. He also points out the large body of work connecting the etiological dots: Many of the mutated genes associated with cancer seem to exert their effects by impairing cellular respiration. It is also possible, Seyfried strongly feels, that transitioning from respiration to fermentation produces free radicals that cause genetic mutations associated with cancer.
All very interesting, although who knows where it will lead.

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