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To investigate how tumors cope with high levels of ammonia, scientists used a technique to label the nitrogen on glutamine. When glutamine is broken down during cell metabolism, ammonia containing labeled nitrogen is released as a byproduct. Tracing the fate of this marked ammonia, the researchers analyzed more than 200 different cellular metabolites in breast cancer cells and in human tumors transplanted into mice.
They found cancer cells recycled ammonia with high efficiency, incorporating it into numerous components--primarily the amino acid glutamate, a fundamental building block for proteins, as well as its derivatives. Shown here: An image of a breast tumor and its local environment; tumor cells are displayed in cyan, macrophages in red and collagen fibers in green.Image credit: National Cancer Institute
