Background/aims: Lactate is one of the products of glycolysis and is a hallmark of the Warburg effect. Glycolysis is found in tumor as well as immune cells. However, the effects of lactate on the function of tumor-infiltrating T cells (TILs) are rarely reported.
Methods: In the present study, we investigated lactate and other glycolysis-related metabolites within TILs of human gastric cancer (GC). Lactate concentration was determined by liquid chromatography-mass spectrometry. The functional effects and clinical relevance of excessive lactate on T cells were investigated in clinical samples, and the mechanism of increased lactate was explored.
Results: Lactate was significantly increased in GC TILs and related to decreased T helper (Th)1 cells and cytotoxic T lymphocytes (CTLs). Increased lactate within GC TILs was positively correlated with increased lactate dehydrogenase A (LDH)A. Expression of LDHA in GC TILs was also negatively correlated with percentages of Th1 cells and CTLs. Decreased miR-34a expression in GC TILs was responsible for increased expression of LDHA. A hypoxic tumor environment was responsible for decreased miR-34a and lactate-induced impaired immune function.
Conclusion: We found that hypoxia decreases miR-34a expression and lose miR-34a regulation on LDHA, thus increasing lactate level within GC TILs and impairing immune function in GC.
Keywords: Cytotoxic T lymphocytes; Lactate; Lactate dehydrogenase A; Th1 cells; miR-34a.
© 2018 The Author(s). Published by S. Karger AG, Basel.