Figure 2.

Diagram of amino acids metabolism involved in cancer radioresistance and its radiosensitizers. In response to radiotherapy, tumor cells enhance the metabolism of amino acids such as glutamate, serine, and asparagine, which provides the biomacromolecules and other materials required for nucleotides, GSH and energy production, prolonging the cancer cell survival. Tumor cells regulate glutamine metabolism by self-balancing the activities of GLS and GS, promoting cell resistance to radiation. Abnormally activated glycolysis also indirectly allows tumor cells to enhance serine synthesis, increasing one-carbon metabolic flux. In addition, amino acids, such as arginine, asparagine and tryptophan, also play important roles in the formatino of cancer radioresistance, which have been proved to be the effective targets for radiosensitization.