OncoTargets and Therapy (Feb 2019)
RRAD suppresses the Warburg effect by downregulating ACTG1 in hepatocellular carcinoma
Abstract
Yingcai Yan,1,2,* Hao Xu,1,2,* Linshi Zhang,1,2 Xiaohu Zhou,1,2 Xiaohui Qian,1,2 Jiarong Zhou,1,2 Yu Huang,1,2 Wenhao Ge,1,2 Weilin Wang1–4 1Division of Hepatobiliary and Pancreatic Surgery, Department of Surgery, The First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China; 2Key Laboratory of Precision Diagnosis and Treatment for Hepatobiliary and Pancreatic Tumor of Zhejiang Province, The First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China; 3Clinical Research Center of Hepatobiliary and Pancreatic Diseases of Zhejiang Province, The First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China; 4State Key Laboratory and Collaborative Innovation Center for Diagnosis and Treatment of Infectious Disease, Zhejiang University, Hangzhou, China *These authors contributed equally to this work Purpose: Hepatocellular carcinoma (HCC) is a common malignancy with poor prognosis and limited therapeutic options. Ras-related associated with diabetes (RRAD) belongs to the subfamily of Ras-related GTPases and is associated with several types of cancer, including HCC, although the mechanisms involving RRAD in HCC remains unknown. Patients and methods: We aimed to elucidate the role of RRAD and whether it affects glucose metabolism in HCC by immunohistochemically examining tissue samples from HCC patients and assessing the effect of RRAD overexpression and knockdown on the glucose metabolism, proliferation, cell cycle, and apoptosis of HCC cell lines SK-Hep-1 and Huh7, as well as on tumor progression in vivo. Results: We demonstrated that RRAD binds to actin gamma 1 (ACTG1). RRAD suppressed aerobic glycolysis in HCC by downregulating ACTG1. On the other hand, ACTG1 promoted HCC proliferation by regulating the cell cycle via downregulation of cyclins and cyclin-dependent kinases and inhibited apoptosis through the mitochondrial apoptosis pathway in vitro. In addition, RRAD retarded tumor growth by downregulating ACTG1 in vivo. ACTG1 was overexpressed in HCC tissues compared with adjacent normal tissues, whereas the expression of RRAD was low in tumor tissues. Low RRAD levels were significantly correlated with large tumor size and advanced tumor stage; high ACTG1 levels were significantly correlated with advanced tumor stage. Furthermore, Kaplan–Meier survival curves showed that HCC patients with high RRAD and low ACTG1 expression may have a better prognosis. Conclusion: We have shown that RRAD exhibits a tumor-suppressing role in HCC by downregulating glucose metabolism and ACTG1 expression, thus lowering cell proliferation, arresting the cell cycle, and increasing apoptosis. These findings indicate that ACTG1 may act as a downstream effector of RRAD and open a new avenue for potential HCC treatment. Keywords: hepatocellular carcinoma, Ras-related associated with diabetes, actin gamma 1, the Warburg effect, tumorigenicity
