Figure 4.

Shuttling the onco-metabolite L-lactate from the tumor stroma to epithelial cancer cells. Previously, we proposed that a “lactate shuttle” also exists in human breast cancers. More specifically, the distribution of lactate transporters is highly compartmentalized in human breast cancers. Note that MCT4 (a marker of aerobic glycolysis and L-lactate secretion) is largely confined to cancer-associated fibroblasts in the tumor stroma. Conversely, MCT1 (a marker of L-lactate uptake) is localized to epithelial cancer cells. Because of their broad specificity, the same MCT transporters can also function in the shuttling of ketone bodies from the tumor stroma to epithelial cancer cells. Arrows indicate the direction of energy transfer. Reproduced and modified with permission from reference ⁵⁷.