Date Published: March 31, 2017
Publisher: Public Library of Science
Author(s): Minjong Lee, Ara Jo, Seulki Lee, Jong Bin Kim, Young Chang, Joon Yeul Nam, Hyeki Cho, Young Youn Cho, Eun Ju Cho, Jeong-Hoon Lee, Su Jong Yu, Jung-Hwan Yoon, Yoon Jun Kim, Yuan-Soon Ho.
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.
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.
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.
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.
For patients with advanced Hepatocellular carcinoma (HCC), only sorafenib significantly prolonged patient survival to date. However, the long-term survival benefit from sorafenib treatment is a modest improvement of 3 months, which is far from satisfactory . Several other anti-angiogenesis drugs have been evaluated clinically for the treatment of HCC, but they were not satisfactory [2, 3]. Therefore, new strategies should be developed for patients with advanced HCC who did not respond to sorafenib or anti-angiogenesis agents.
Five important findings emerged from this study: 1) expression of key enzymes involved in glycolysis, antioxidant systems, and EMT, such as HK II, p-PDH, MCT-1, rGCS, and Snail, was upregulated upon matrix detachment; 2) compared to attached HCC cells, AR HCC cells significantly increased lactic acid production and decreased ROS generation; 3) AR HCC cells showed chemoresistance to conventional chemotherapy agents, particularly sorafenib, and had higher tumor growth rates than attached HCC cells in animals; 4) high intracellular ROS levels accelerated glycolysis rates via HK II induction; 5) although BSO did not effectively suppress cancer cell proliferation, a combination treatment of 3-BP and BSO potently suppressed the AR HCC and attached cell proliferation rates via apoptosis and inhibited tumor growth compared to 3-BP or sorafenib treatment alone in a xenograft mouse model bearing AR HCC cells: BSO played a role for a booster to 3-BP effects.