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Cancer loves sugar so much that it is willing to be sloppy in the way that it makes energy just so it can gobble up more of this stuff. Lucky for us, this flaw is exploitable; we can use a machine called a PET scanner to watch where sugar goes in the body and that can lead us right to a patient’s cancer. Better yet, as scientists learn more about why cancer cells have such a love affair with the sweet stuff, we might be able to develop new treatments too.
PET is short for Positron Emission Tomography and it can help doctors measure a whole bunch of different things, but it’s often used to show where in the body cells are turning sugar into energy. It does this by detecting a radioactive substance that has been injected into a patient’s bloodstream. One example is really similar to the sugar glucose and it gets sucked up by sugar-hungry cells. Since cancer cells have the ultimate sweet tooth, they show up as bright blotches on a PET scan.
As you may or may not know, the reason why I keep wearing hats inside your videos is that I’m currently undergoing cancer treatment. So, I go in for my PET scan and it’s a little freaky because they got like the thing they’re going to inject into your veins in like a lead-lined syringe to protect the text because they’re of course going to get exposed to tons of it working for years as radiation tax but still it’s a little weird to have something that someone can’t touch get injected into your veins. Then I get the scan back and it shows me exactly where the cancer is and I’m like, “Yeah! Radiation in the cancer. That’s great.” Then I also see that my brain is glowing like crazy because the other place that consumes a lot of glucose is up here.
So, that’s roughly how it all goes down, but if you’ve had this experience you might be wondering to yourself, like I did, why does cancer like sugar so much? And scientists would love to know that too, because on the surface this love affair doesn’t make any sense. See, cells produce and use energy mainly in the form of a molecule called ATP. Most of the time, healthy cells use oxygen to produce ATP from glucose through a series of biochemical reactions called respiration. Now, respiration actually happens in a series of steps, the first one being glycolysis where glucose is turned into two of a smaller molecule called pyruvate and two molecules of something called NADH. Pyruvate can then be broken down further to make energy in one of two ways. First, when there’s enough oxygen around, pyruvate undergoes the complex process of oxidative phosphorylation where the mitochondria convert it into energy (we’re going to refer to that one just as respiration for convenience to make things easier to follow). The alternative to respiration happens when there’s not a lot of oxygen around; you still start with glycolysis but after that pyruvate takes an alternative route called fermentation where it’s broken down less completely for less energy.
Respiration is great because cells can make a lot of energy through glycolysis plus oxidative phosphorylation. Fermentation is okay too because cells can still get the energy they need, but it is less efficient. Cells only get around six percent of the energy per unit of glucose from fermentation compared to respiration.
Cancer cells have for some strange reason switched most of their energy making to fermentation even though there is plenty of oxygen around. They’re still doing that first step glycolysis and some of that pyruvate goes through the respiration pathway, but somewhere between 56 and 63 percent of the ATP cancer cells make comes from fermentation. Researchers also call this kind of fermentation aerobic glycolysis to point out that this kind of energy making is happening with oxygen. Since fermentation is less efficient, cancer cells that take up more sugar can make more energy.