3-bromopyruvate and buthionine sulfoximine effectively kill anoikis-resistant hepatocellular carcinoma cells.

BACKGROUND & AIMS: Acquisition of anoikis resistance is a prerequisite for metastasis in hepatocellular carcinoma (HCC). However, little is known about how energy metabolism and antioxidant systems are altered in anoikis-resistant (AR) HCC cells. We evaluated anti-tumor effects of a combination treatment of 3-bromopyruvate (3-BP) and buthionine sulfoximine (BSO) in AR HCC cells. METHODS: We compared glycolysis, reactive oxygen species (ROS) production, and chemoresistance among Huh-BAT, HepG2 HCC cells, and the corresponding AR cells. Expression of hexokinase II, gamma-glutamylcysteine synthetase (rGCS), and epithelial-mesenchymal transition (EMT) markers in AR cells was assessed. Anti-tumor effects of a combination treatment of 3-BP and BSO were evaluated in AR cells and an HCC xenograft mouse model. RESULTS: AR HCC cells showed significantly higher chemoresistance, glycolysis and lower ROS production than attached cells. Expression of hexokinase II, rGCS, and EMT markers was higher in AR HCC cells than attached cells. A combination treatment of 3-BP/BSO effectively suppressed proliferation of AR HCC cells through apoptosis by blocking glycolysis and enhancing ROS levels. In xenograft mouse models, tumor growth derived from AR HCC cells was significantly suppressed in the group treated with 3-BP/BSO compared to the group treated with 3-BP or sorafenib. CONCLUSIONS: These results demonstrated that a combination treatment of 3-BP/BSO had a synergistic anti-tumor effect in an AR HCC model. This strategy may be an effective adjuvant therapy for patients with sorafenib-resistant HCC.

Enhancement of lipid peroxidation and of the antitumor effect of hyperthermia upon combination with oral eicosapentaenoic acid.

The present study was designed to determine the effect of eicosapentaenoic acid (EPA) on the susceptibility of tumor cells to treatments that kill the cells by lipid peroxidation. Using AH109A carcinoma, a rat liver cancer, we measured EPA content, levels of antioxidants, and degree of lipid peroxidation in tumor tissue and normal liver tissue after oral administration of EPA. In the control group treated with distilled water, EPA in tumor tissue was lower than in normal liver tissue, suggesting that its content of polyunsaturated fatty acids (the substrates for lipid peroxidation) was inherently low. Levels of antioxidants also tended to be lower in tumor tissue. EPA level increased in both tumor and normal tissues after oral administration of EPA. At the same time, glutathione peroxidase (GSH-Px) increased in normal tissue, whereas tumor tissue displayed no increase in antioxidants; instead GSH decreased. The EPA-induced change in balance between substrates for lipid peroxidation and antioxidants suggested that tumor tissue might become more susceptible to lipid peroxidation than normal liver tissue. In fact, hyperthermia treatment did enhance lipid peroxidation and antitumor action. Our results indicate that oral EPA specifically increases the susceptibility of liver tumor tissue to lipid peroxidation, and hence enhance the antitumor effect of hyperthermia and prolongs survival.