Berberine exerts its antineoplastic effects by reversing the Warburg effect via downregulation of the Akt/mTOR/GLUT1 signaling pathway.

Glucose transporter 1 (GLUT1) plays a primary role in the glucose metabolism of cancer cells. However, to the best of our knowledge, there are currently no anticancer drugs that inhibit GLUT1 function. The present study aimed to investigate the antineoplastic activity of berberine (BBR), the main active ingredient in numerous Traditional Chinese medicinal herbs, on HepG2 and MCF7 cells. The results of Cell Counting Kit­8 assay, colony formation assay and flow cytometry revealed that BBR effectively inhibited the proliferation of tumor cells, and induced G2/M cell cycle arrest and apoptosis. Notably, the results of luminescence ATP detection assay and glucose uptake assay showed that BBR also significantly inhibited ATP synthesis and markedly decreased the glucose uptake ability, which suggested that the antitumor effect of BBR may occur via reversal of the Warburg effect. In addition, the results of reverse transcription­quantitative PCR, western blotting and immunofluorescence staining indicated that BBR downregulated the protein expression levels of GLUT1, maintained the cytoplasmic internalization of GLUT1 and suppressed the Akt/mTOR signaling pathway in both HepG2 and MCF7 cell lines. Augmentation of Akt phosphorylation levels by the Akt activator, SC79, abolished the BBR­induced decrease in ATP synthesis, glucose uptake, GLUT1 expression and cell proliferation, and reversed the proapoptotic effect of BBR. These findings indicated that the antineoplastic effect of BBR may involve the reversal of the Warburg effect by downregulating the Akt/mTOR/GLUT1 signaling pathway. Furthermore, the results of the co­immunoprecipitation assay demonstrated that BBR increased the interaction between ubiquitin conjugating enzyme E2 I (Ubc9) and GLUT1, which suggested that Ubc9 may mediate the proteasomal degradation of GLUT1. On the other hand, BBR decreased the interaction between Gα­interacting protein­interacting protein at the C­terminus (GIPC) and GLUT1, which suggested that the retention of GLUT1 in the cytoplasm may be achieved by inhibiting the interaction between GLUT1 and GIPC, thereby suppressing the glucose transporter function of GLUT1. The results of the present study provided a theoretical basis for the application of the Traditional Chinese medicine component, BBR, for cancer treatment.

Vitexin, an inhibitor of hypoxia-inducible factor-1α, enhances the radiotherapy sensitization of hyperbaric oxygen on glioma.

PURPOSE: Vitexin, an inhibitor of hypoxia-inducible factor (HIF)-1α, has anti-tumor effect. However, whether it can enhance the radiotherapy sensitization of hyperbaric oxygen (HBO) on glioma is unclear. This study aimed to investigate the effect of vitexin. METHODS: The nude mice with paw-transplanted glioma were divided into four groups: control group, HBO + radiation group, HBO + vitexin group, and HBO + vitexin + radiation group. The mice of last two groups were daily given vitexin 75 mg/kg by intraperitoneal injection. 30 min after administration of vitexin, the HBO-treated mice were daily placed in HBO chamber for 60 min. The radiation-treated mice were given local tumor irradiation once every week during the HBO treatment, and the dose of irradiation was 10 Gy/time. The experimental treatment lasted for 21 days. RESULTS: Compared with the HBO + radiation group, the tumor volume, tumor weight, and tumor weight coefficient in the HBO + vitexin + radiation group were lower (p < 0.05). Importantly, the contents of reduced glutathione and glutathione peroxidase as well as expressions of HIF-1α, vascular endothelial growth factor, glucose transporter (GLUT)-1, and GLUT-3 proteins in tumor tissues were also lower in the HBO + vitexin + radiation group than in the HBO + radiation group (p < 0.01). CONCLUSIONS: Vitexin can cooperate with HBO to sensitize the glioma radiotherapy, and its mechanisms may be correlated to the inhibition of HIF-1α protein expression and subsequent decrements of its downstream protein expressions, which finally cause the reduction of antioxidant capacity.

The alternative medicine pawpaw and its acetogenin constituents suppress tumor angiogenesis via the HIF-1/VEGF pathway.

Products that contain twig extracts of pawpaw (Asimina triloba) are widely consumed anticancer alternative medicines. Pawpaw crude extract (CE) and purified acetogenins inhibited hypoxia-inducible factor-1 (HIF-1)-mediated hypoxic signaling pathways in tumor cells. In T47D cells, pawpaw CE and the acetogenins 10-hydroxyglaucanetin (1), annonacin (2), and annonacin A (3) inhibited hypoxia-induced HIF-1 activation with IC(50) values of 0.02 microg/mL, 12 nM, 13 nM, and 31 nM, respectively. This inhibition correlates with the suppression of the hypoxic induction of HIF-1 target genes VEGF and GLUT-1. The induction of secreted VEGF protein represents a key event in hypoxia-induced tumor angiogenesis. Both the extract and the purified acetogenins blocked the angiogenesis-stimulating activity of hypoxic T47D cells in vitro. Pawpaw extract and acetogenins inhibited HIF-1 activation by blocking the hypoxic induction of nuclear HIF-1alpha protein. The inhibition of HIF-1 activation was associated with the suppression of mitochondrial respiration at complex I. Thus, the inhibition of HIF-1 activation and hypoxic tumor angiogenesis constitutes a novel mechanism of action for these anticancer alternative medicines.