Cancer Feeds on Sugar to Make Tumors More Aggressive

Updated | New research done in yeast cells may shed light on the relationship between sugar and cancer cell growth.

The work, by microbiologists and molecular biologists at three institutions in Belgium, shows that one particular kind of protein can be activated by sugar. Mutations in that protein have been linked to cancer, especially pancreatic and colon cancer.

The study, published in Nature Communications on Friday, explains how cancer cells’ energy production processes are different from normal cells.

“Some people are interpreting that we have found a mechanism for how sugar causes cancer, but that is certainly not the case,” Johan Thevelein, a molecular biologist at Katholieke Universiteit Leuven (KU Leuven), in Belgium, and one of the authors of the paper, told Newsweek

Instead, Thevelein said, his work shows just how sugar is broken down differently in cancer cells.

Normal cells, cancer cells and yeast all need sugar to function. They split the sugar molecules and transform it into something they can actually use. But there are two different ways they can process the sugar. One way is far more efficient than the other.

With oxygen around, cells can produce a different kind of molecule than they would without it. You can feel the difference—it’s what causes muscles to burn during particularly strenuous workouts when blood’s oxygen supplies are depleted. Without enough oxygen available, muscles cells have to process sugar another way—through glycolysis, which produces lactic acid. This process is also what makes beer happen. Instead of producing lactic acid, yeast using this process produces ethanol.

In normal human cells, this process is the last resort to keep up with energy demands because it’s far less efficient than the alternative. But in cancer cells, this alternative process, which is similar to what happens in organisms like yeast, is just what is done.

This phenomenon has a name: the Warburg effect.

Yeast also has the same class of proteins that is linked to many cancers. Mutations in the genes that code for these proteins, called Ras, can often contribute to cancer cells’ ability to grow unchecked. In cancer, these Ras proteins can be far more active than they ought to be.

Thevelein, who is not a clinician, said his work might mean that cancer patients should eat a low-sugar diet. (However, he stressed that his work does not mean that eating a low-sugar diet before a cancer diagnosis might lower a person’s risk.)

Some human studies do show a link between lower-sugar diets and a lower rate of cancer recurrence, especially for people who are obese, said Dr. Juan Manuel Schvartzman, a medical oncology fellow at Memorial Sloan Kettering Cancer Center.

However, there are two things to keep in mind. "Firstly, for normal healthy individuals it is actually very hard to change the blood sugar level significantly by eating less or more sugar," he said. "Secondly, we now know that in vivo, cancer cells that make up a tumor are not all the same. Some may take up a lot of sugar and some may not and still grow." 

"My advice for patients is usually the following: try to eat a healthy prudent diet, rich in fresh fruits and vegetables (not juices), low in animal fats, low in red meat and high in fish protein. There is some evidence that this can decrease the risk of recurrence in patients with cancer."

One study that followed more than 300,000 people found that sugars were not associated with a higher chance of developing most major types of cancer, including colorectal, breast, prostate or pancreatic cancer. But high sugar levels may be associated with an increased risk of some rarer forms of cancer, including types of lung or esophageal cancer.

And even Thevelein said that his work will not be the last word on the Warburg effect. “What we have demonstrated is that the enhanced breakdown of sugar in the cancer cells stimulates cancer. But why cancer cells have a faster, enhanced breakdown of sugar compared to normal cells—this is still a mystery.” 

This story has been updated to add additional comment from Dr. Juan Manuel Schvartzman.

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