A new study by scientists at the Massachusetts Institute of Technology (MIT) has found how cancer cells use an unusual process of multiplication. The study, which answers a long-standing mystery about the proliferation of unhealthy cells in the human body, will be published in Molecular cell newspaper.
The study was conducted by MIT biologists Matthew Vander Heiden, lead author of the new study, and lead authors, former MIT graduate student and postdoc Alba Luengo (PhD ’18) and graduate student Zhaoqi Li. Their research have shown that the metabolic process, known as fermentation, helps cancer cells regenerate large amounts of a molecule called NAD +, which they need to synthesize DNA and other important molecules. Speaking to MIT News, Heiden said that according to their study under certain circumstances cells have to perform more electron transfer reactions, which requires NAD + to make molecules such as DNA.
Fermentation is a way for cells to convert the energy in sugar into adenosine triphosphate (ATP). ATP is a chemical that cells use to store energy for their needs. Humans use a process called aerobic respiration where cells break down sugar to access more ATP. However, the cells switch to a less efficient method called fermentation when there is a lack of oxygen in the cells.
German chemist Otto Warburg discovered that it is usually cancer cells that metabolize sugar using the fermentation process. Scientists have since come up with various theories to justify why cancer cells switch to a more lethargic way of breaking down cells, but with little success.
To understand this reason, scientists at MIT have blocked cancer cells from carrying out the fermentation process. With this, they observed that the growth of cancer cells was hampered. The researchers then introduced another method of cell growth by stimulating cells to produce NAD +, a molecule that helps cells get rid of extra electrons that are left behind when cells make molecules such as DNA and the proteins.
With this experiment, the researchers found that the cells started to proliferate again, despite their inability to perform fermentation. The results produced by this study led the researchers to conclude that when cells are growing rapidly, they need NAD + more than ATP. And just like in aerobic respiration, the cells produce a lot of ATP and a little NAD +, they go through fermentation. Scientists have found that if cells accumulate more ATP than they can consume, their respiration calms down and NAD + production also decreases.