Abstract
Rare sugars are monosaccharides with low natural abundance. They are structural isomers of dietary sugars, but hardly be metabolized. Here, we report that rare sugar L-sorbose induces apoptosis in various cancer cells. As a C-3 epimer of D-fructose, L-sorbose is internalized via the transporter GLUT5 and phosphorylated by ketohexokinase (KHK) to produce L-sorbose-1-phosphate (S-1-P). Cellular S-1-P inactivates the glycolytic enzyme hexokinase resulting in attenuated glycolysis. Consequently, mitochondrial function is impaired and reactive oxygen species are produced. Moreover, L-sorbose downregulates the transcription of KHK-A, a splicing variant of KHK. Since KHK-A is a positive inducer of antioxidation genes, the antioxidant defense mechanism in cancer cells can be attenuated by L-sorbose-treatment. Thus, L-sorbose performs multiple anticancer activities to induce cell apoptosis. In mouse xenograft models, L-sorbose enhances the effect of tumor chemotherapy in combination with other anticancer drugs. These results demonstrate L-sorbose as an attractive therapeutic reagent for cancer treatment.