Lactic Acid in Tumour Biology

Lactic acid accumulates in the tumour microenvironment (TME) at concentrations reaching up to 40 mM. Initially, lactic acid was considered merely a metabolic by-product of aerobic glycolysis, a phenomenon commonly referred to as the Warburg effect and observed in the majority of tumours. Recent evidence, however, has demonstrated that lactic acid is not merely a waste product; rather, it plays a pivotal role in tumour biology. High plasma lactic acid levels correlate with increased metastatic potential and lower survival rates. Elevated lactic acid levels in the TME have been shown to suppress antitumour immune responses, facilitate both metastasis and cellular senescence, and might modulate gene expression through novel epigenetic mechanisms such as histone lactylation. This review aims to summarize current knowledge on the multifaceted impact of elevated lactic acid in the TME on tumour progression and biology.