Hallmarks of Cancer 7: Reprogramming of Energy Metabolism
The seventh Hallmark of Cancer is the cell’s ability to reprogram its energy metabolism. This means that cancer cells have a different way of obtaining energy. Cells need energy in order to carry out functions such as the absorption of nutrients, reactions to changes in their environment, maintaining a stable internal environment know as homeostasis, and to grow and divide.
This energy is acquired from breaking down molecules such as sugar through metabolic processes known as cellular respiration. Often times, the energy obtain through cellular respiration is stored in molecules known as ATP, or adenosine triphosphate. Healthy cells that have access to oxygen go through the metabolic process of aerobic respiration. These cells break down glucose, which is a sugar molecule obtained from food. Approximately 32 ATP is synthesized and carbon dioxide is released as a waste product. When healthy cells do not have access to oxygen, they go through the metabolic process of anaerobic respiration. These cells break down glucose from food as well. However, the cells only produce 2 ATP, much fewer than aerobic respiration, as well as lactic acid instead of carbon dioxide.
Cancer cells have a faster metabolic rate than normal healthy cells and consume approximately 20 times more glucose than healthy cells. Cancer cells have a mutation to produce more glucose transporters on the cellular membrane that can assist in the large intake of glucose. However, cancer cells also produce lactic acid instead of completing the process of respiration to carbon dioxide. This is known as the Warburg Effect. Through this inefficient process, cancer cells obtain much less energy per molecule of glucose than healthy cells would through normal cellular respiration. Cancer cells produce far less energy than healthy cells, but they produce it at a rate approximately 100 times faster than healthy cells. Having a faster metabolic rate is more beneficial for cancer cells than synthesizing a large amount of ATP per glucose molecule. During aerobic respiration, cancer cells also produce several other biosynthetic precursors that are used as building materials to make proteins, lipids, and DNA for new cells.
An example of this Hallmark of Cancer can be seen with liver cancer. These cancer cells do not proceed with normal cellular respiration. Instead they follow the process of aerobic glycolysis that although prevents the cell from producing a large amount of ATP, allows the cell to produce a small amount of ATP very quickly. Through this process, cancer cells are also able to synthesize molecules that can be used to make proteins, lipids, DNA, etc., that will then be used to make new cells from proliferation. It is clear that there is an important connection between metabolism and cancer. Research in this area is continuously preformed to try and find a method to interfere with the cancer cell’s ability to use this metabolic process and to prevent uncontrolled proliferation. 1
1 Heiden, M.G.V., Cantley, L.C., Thompson, C.B. Understanding the Warburg Effect: The Metabolic Requirements of Cell Proliferation. Science. 2009;324(5930):1029-1033. May 22, 2009.