What powers growth in cancer cells

Researchers have discovered that the largest source of the fuel that cancer cells use to proliferate is amino acids which make up proteins, and not glucose, as earlier believed. Cancer cells are notorious for their ability to divide uncontrollably and generate hordes of new tumor cells.

The new findings could offer a novel way to look at cancer cell metabolism, a field of research that scientists hope will yield new drugs that cut off cancer cells' ability to grow and divide.

"If you want to successfully target cancer metabolism, you need to understand something about how different pathways are being used to actually make mass," said senior author of the study Matthew Vander Heiden, associate professor at Massachusetts Institute of Technology (MIT) in the US.

The findings appeared in the journal Developmental Cell. Human cells normally use glucose as an energy source, breaking it down through a series of complex chemical reactions that requires oxygen Since the 1920s, scientists have known that cancer cells generate energy differently than normal cells, a phenomenon dubbed the "Warburg effect" after its discoverer, German biochemist Otto Warburg.

But there has been very little research on exactly what goes into the composition of new cancer cells or any kind of rapidly dividing mammalian cells. To determine where cells, including those in tumours, were getting the building blocks they needed, the researchers grew several different types of cancer cells and normal cells in culture dishes.

They fed the cells different nutrients labeled with variant forms of carbon and nitrogen, allowing them to track where the original molecules ended up. They also weighed the cells before and after they divided, enabling them to calculate the percentage of cell mass contributed by each of the available nutrients.

Although cells consume glucose and the amino acid glutamine at very high rates, the researchers found that those two molecules contribute little to the mass of new cells glucose accounts for 10 to 15 percent of the carbon found in the cells, while glutamine contributes about 10 percent of the carbon.

Instead, the largest contributors to cell mass were amino acids, which make up proteins. As a group, amino acids (excluding glutamine) contribute the majority of the carbon atoms found in new cells and 20 to 40 percent of the total mass. Although initially surprising, the findings make sense, Vander Heiden said, because cells are made mostly of protein.