Glycolysis, as an altered cancer cell-intrinsic metabolism, is an essential hallmark of cancer. Phosphofructokinase (PFK) is a metabolic sensor in the glycolytic pathway, and restricting the substrate availability for this enzyme has been researched extensively as a target for chemotherapy. In the present study, we investigated that the effects of epigallocatechin-3-gallate (EGCG), an active component of green tea, on inhibiting cell growth and inducing apoptosis by promoting a metabolic shift away from glycolysis in aerobic glycolytic hepatocellular carcinoma (HCC) cells. EGCG modulated the oligomeric structure of PFK, potentially leading to metabolic stress associated apoptosis and suggesting that EGCG acts by directly suppressing PFK activity. A PFK activity inhibitor enhanced the effect, while the allosteric activator reversed EGCG-induced HCC cell death. PFK siRNA knockdown-induced apoptosis was not reversed by the activator. EGCG enhanced the effect of sorafenib on cell growth inhibition in both aerobic glycolytic HCC cells and in a xenograft mouse model. The present study suggests a potential role for EGCG as an adjuvant in cancer therapy, which merits further investigation at the clinical level.

The importance of the tumor microenvironment in targeted anticancer therapies has been well recognized. Various protein factors participate in the cross-talk between tumor cells and non-malignant cells. Anterior gradient-2 (AGR2) is overexpressed in diverse human adenocarcinomas and it exists in both intracellular and extracellular spaces. Although intracellular AGR2 has been intensively investigated, the function of secreted AGR2, especially its exact mechanism of action is still poorly understood. Here we report that the secreted AGR2 promotes the angiogenesis and the invasion of vascular endothelial cells and fibroblasts by enhancing the activities of vascular endothelial growth factor (VEGF) and fibroblast growth factor 2 (FGF2). Further study indicated that AGR2 directly binds to these extracellular signaling molecules, and enhances their homodimerization. The extracellular AGR2 activity can be blocked to reduce angiogenesis and inhibit tumor growth in vitro and in vivo by a monoclonal antibody targeting the AGR2 self-dimerization region, and combined treatment with bevacizumab produced maximum inhibition effect. In conclusion, our investigation reveals a mechanism that directly links the secreted AGR2 with extracellular signaling networks, and we propose that the secreted AGR2 is a blockable molecular target, which acts as a chaperon-like enhancer to VEGF and FGF2.