Tumor cells used to be thought to metabolize at high rates of glucose consumption, but a new finding, published Wednesday in the journal Nature by researchers at Vanderbilt University in the United States suggests that tumor cells themselves are not the culprits, but rather that immune cells (non-tumor cells) called macrophages have higher glucose intake levels.
The discovery that different cells in the tumor microlenses use different nutrients, according to their metabolic procedures has upended cancer metabolism models over the past century and helped develop new treatments and tumor imaging techniques.
The usual positivity emission tomography (PET) uses a radioactive tracer (FDG) of glucose to “light up” cancer cells based on their glucose metabolism. This time, the team used two different PET tracers, one to track glucose and the other to track the nutrient glutamine, to look at six different tumor models, including colorectal, kidney, and breast cancer. In each of these cancers, myelin immune cells (mainly macrophages) were found to have the highest intake of glucose, followed by T cells and tumor cells. Tumor cells have the highest intake of glutamine. They believe that this is a common phenomenon that applies to all types of cancer.
The researchers also found that differences in glucose and glutamine intake were not caused by restricted nutrients, but by specific cellular signaling pathways. This contrasts with the previous popular belief that cancer cells compete metabolically to “win” nutrients and inhibit immune cell growth in the tumor microencinal environment.
“It has long been thought that cancer cells devour all glucose, so immune cells can’t get enough glucose to get the job done.” Matthew Madden, one of the researchers, said, “Our data suggest that nutrients are not a limiting condition. Cells consume certain nutrients, and nutrients are distributed between cells: tumor cells ingest glutamine and fatty acids; ”
Understanding how cells in the tumor micro-environment use different nutrients has the hope of facilitating research into new therapies or imaging methods specifically targeting specific types of tumor cells, the researchers said.