Lactate is an end product of glycolysis. Owing to the lactate shuttle concept introduced in the early 1980s

increasing researchers indicate lactate as a critical energy source for mitochondrial respiration and as a precursor of gluconeogenesis. Lactate also acts as a multifunctional signaling molecule through receptors expressed in various cells

resulting in diverse biological consequences including decreased lipolysis

immune regulation

and anti-inflammation wound healing

and enhanced exercise performance in association with the gut microbiome. Furthermore

increasing evidence reveals that lactate contributes to epigenetic gene regulation by lactylating lysine residues of histones

which accounts for its key role in immune modulation and maintenance of homeostasis. Here

we summarize the function and mechanism of lactate and lactylation in tumor metabolism and microenvironment.