Lactate acidosis and simultaneous recruitment of TGF-β leads to alter plasticity of hypoxic cancer cells in tumor microenvironment.

Lactate acidosis is often observed in the tumor microenvironment (TME) of solid tumors. This is because glucose breaks down quickly via glycolysis, causing lactate acidity. Lactate is harmful to healthy cells, but is a major oncometabolite for solid cancer cells that do not receive sufficient oxygen. As an oncometabolite, it helps tumor cells perform different functions, which helps solid hypoxic tumor cells spread to other parts of the body. Studies have shown that the acidic TME contains VEGF, Matrix metalloproteinases (MMPs), cathepsins, and transforming growth factor-β (TGF-β), all of which help spread in direct and indirect ways. Although each cytokine is important in its own manner in the TME, TGF-β has received much attention for its role in metastatic transformation. Several studies have shown that lactate acidosis can cause TGF-β expression in solid hypoxic cancers. TGF-β has also been reported to increase the production of fatty acids, making cells more resistant to treatment. TGF-β has also been shown to control the expression of VEGF and MMPs, which helps solid hypoxic tumors become more aggressive by helping them spread and create new blood vessels through an unknown process. The role of TGF-β under physiological conditions has been described previously. In this study, we examined the role of TGF-β, which is induced by lactate acidosis, in the spread of solid hypoxic cancer cells. We also found that TGF-β and lactate work together to boost fatty acid production, which helps angiogenesis and invasiveness.