I never thought this Hallmarks of Cancer would take me 9 months to get through! If you are new to this blog (welcome and thanks for stopping by), you can find my explanations of Hallmarks 1-8 by clicking on the word cloud on the right hand side of the page for “Hallmarks of Cancer” or using the search function if you are on a mobile device
Hallmark #9 is “Deregulating Cellular Energetics.”
We have discussed many times that cancer is defined by out of control growth and replication. This wild growth requires energy, and a lot of it. It’s easy to imagine that you would become very fatigued and ill if you just got up and tried to run a marathon without training. Likewise, even the most elite athletes need rest; they are unable to sustain high performance activity without some sort of recovery. So how can cancer cells just go go go and not get sick. Well, like every other thing I have discussed in the previous Hallmarks, cancer cells have found a way to tweak their metabolism to sustain this mad pace.
Let’s get down to the nitty gritty of what biologic energy is and where it comes from. You may have heard about aerobic and anaerobic metabolism. This is the stuff elite athletes and gym rats LOVE to talk about over protein shakes. Energy in our body is stored as little molecules called ATP.
Aerobic metabolism results in 32 molecules of ATP for every molecule of glucose broken down and the by-product is carbon dioxide (which we breath out). This process requires a lot of oxygen, hence the name aerobic metabolism. When cells run low on oxygen as we discussed here, they flip to a type of metabolism called anaerobic metabolism and for every molecule glucose that is broken down, a mere 2 molecules of ATP is made and the by product is lactic acid. You know lactic acid, it’s that stuff that builds up in your muscles and makes you sore.
Anaerobic metabolism is highly inefficient, but cancer cells LOVE it. First, cancer cells have learned how to flip the switch to anaerobic metabolism quite quickly. How they do this is a very active area of study and much more complex than just sensing low oxygen. Second, they have learned how to produce ATP from anaerobic metabolism approximately 100 times faster than normal cells which essentiall overcomes the inefficiency of this process. Lastly, the cancer cells use this process because it results in a lot of intermediate molecules that they need for building blocks of proteins, fats, and DNA to make the copies of themselves.
Cancer cells utilize 20 times more glucose than healthy cells. Share on XI just told you above both processes are the result of the body is breaking down glucose. In fact, cancer cells use 20 times more glucose than normal cells. We exploit this fact and can perform a test that takes a picture of where the glucose is going in the body. This is called a PET scan. In the image below you can see the brain is very dark because it constantly uses glucose and then there is a dark spot in the leg. That’s a glucose greedy bone tumor. The other spots are urine in the kidneys and bladder and are normal excretion of the tracer we use.
So how do cancer cells guzzle all of this glucose? Well, they increase the glucose doors on the surface of their cells. These glucose doors are proteins called glucose transporters and cancer cells have figured out a way to increase the number of these so that the glucose is shunted to them to satiate their appetite.
For an answer to the question of whether you can starve a cancer, please read this blog.
