Monocarboxylate transporter 4 (MCT4)

Monocarboxylate transporter 4 (MCT4 or SLC16A3) is a membrane-bound proton-coupled symporter responsible primarily for the export of lactate and protons from cells, especially in settings of high glycolytic activity such as hypoxic tissue, rapidly proliferating cells, and metastatic tumors. It distinguishes itself from other monocarboxylate transporters (MCT1–MCT3) by its elevated affinity for lactate and relevance in environments where extracellular lactate is high. MCT4 supports vital adaptations during the Warburg effect by enabling cancer cells and inflammatory cells to maintain their metabolic flux. Overexpression of MCT4 is correlated with poor prognosis in various cancers and serves as a promising target for therapeutic intervention. Inhibiting MCT4 disrupts glycolytic metabolism leading to intracellular acidification and cell death, making it an attractive target but with safety challenges and resistance mechanisms, notably metabolic heterogeneity within malignancies. It is also emerging as a predictive biomarker (when combined with routine lab parameters) for therapy response, especially in cancers treated with immunotherapy.

Other names

SLC16A3Monocarboxylic acid transporter 4Lactate transporter 4MCT-IV

Inhibition of lactate export, leading to intracellular lactic acid accumulation and metabolic crisis/apoptosis (ROS-dependent). Disruption of glycolysis and oxidative phosphorylation when MCT4 activity is inhibited. Synergistic killing with concurrent inhibitors of glycolysis and mitochondrial complex I.