Sugar does not ‘construct’ cancer cells — another nutrient does. It is not the nutrient that provides the most building blocks to make the cancerous cells, according to a new study published in the journal Developmental Cell. The researchers were surprised to discover that another nutrient does the job.
The uncontrolled cell division characterising cancer proliferation is thought to be supplied by sugar, more specifically glucose. Scientists have assumed that the majority of the material making up this mass of cells (and any other cell for that matter) originates from glucose. However, recent findings generated by MIT researchers show that amino acids constitute the greatest source of the new cell material; these molecules would fuel the cells in relatively smaller amounts.
Understanding the different techniques that are being used to cause the accumulation of the aggregation of cells will help to target cancer metabolism better with the aim of getting rid of the disease, says study author Matthew Vander Heiden.
The metabolism of cancer cells is unlike that of normal cells — this difference is known as the Warburg effect. While the latter break down glucose (their energy source) in processes for which oxygen is a prerequisite, tumour cells adhere to a less efficient metabolic pathway called fermentation that needs no oxygen, thus generating much less energy. Scientists thought of this strategy as the way to make the building blocks of new cells — this has, however, remained mostly unsubstantiated. The composition of the cancer cells is not documented in detail: what is really used to construct tumour cells? This is the mystery that Heiden and his team wanted to decipher.
The researchers grew cultures of different types of normal and cancer cells. These were fed with several nutrients that were identified thanks to the labelling via varying forms of carbon and nitrogen. The percentage cell mass resulting from each nutrient was also calculated.
The results show that glucose accounts for only 10 to 15 % of the carbon that makes up the cells. On the other hand, amino acids were found to make the greatest contributions to cell mass: most of the carbon atoms incorporated into new cells came from them. This made amino acids account for 20 to 40% of the total cell mass.
These findings are in great contrast to the generally-believed concept that glucose is what mostly provides the materials needed to make new cancer cells. But, as Heiden says, their results make sense since cells are made up of protein mostly.
If amino acids are the greatest contributors of cancer cell proliferation, why do these rapidly-dividing cells consume so much glucose? Heiden and his team suggest that the fact that most of the glucose is excreted as lactate which is not otherwise useful to the cells alludes to how high glucose consumption might be important for supplying energy and not for contributing carbon to make the cells.
This updated perspective of the metabolism of cancer cells will hopefully pave the way for the production of new drugs to prevent them from dividing and propagating. Heiden now wants to address the question as to why does the conversion of glucose to lactate boost the use of amino acids to construct more cells.