Leibo Xu1, Susanne Beckebaum2, Speranta Iacob3, Gang Wu4, Gernot M Kaiser5, Arnold Radtke6, Chao Liu7, Iyad Kabar8, Hartmut H Schmidt8, Xiaoyong Zhang9, Mengji Lu10, Vito R Cicinnati11. 1. Department of Transplant Medicine, University Hospital Münster, Münster, Germany; Department of Gastroenterology and Hepatology, University Hospital Essen, Essen, Germany; HPB Surgical Department, Sun Yat-sen Memorial Hospital, Guangzhou, China. 2. Department of Transplant Medicine, University Hospital Münster, Münster, Germany; Department of General, Visceral and Transplantation Surgery, University Hospital Essen, Essen, Germany. 3. Department of Transplant Medicine, University Hospital Münster, Münster, Germany; Fundeni Clinical Institute, Gastroenterology and Hepatology Center, Bucharest, Romania. 4. Department of Transplant Medicine, University Hospital Münster, Münster, Germany; Department of Gastroenterology and Hepatology, University Hospital Essen, Essen, Germany. 5. Department of General, Visceral and Transplantation Surgery, University Hospital Essen, Essen, Germany. 6. Department of General, Visceral and Transplantation Surgery, University Hospital Essen, Essen, Germany; Department of General and Visceral Surgery, University Hospital Münster, Münster, Germany. 7. HPB Surgical Department, Sun Yat-sen Memorial Hospital, Guangzhou, China. 8. Department of Transplant Medicine, University Hospital Münster, Münster, Germany. 9. Institute of Virology, University Hospital Essen, Essen, Germany; Hepatology Unit and Department of Infectious Diseases, Nanfang Hospital, Guangzhou, China. 10. Institute of Virology, University Hospital Essen, Essen, Germany. 11. Department of Transplant Medicine, University Hospital Münster, Münster, Germany; Department of Gastroenterology and Hepatology, University Hospital Essen, Essen, Germany. Electronic address: vito.cicinnati@ukmuenster.de.
Abstract
BACKGROUND & AIMS: Oncogene polycomb group protein enhancer of zeste homolog 2 (EZH2) has been proposed to be a target gene of putative tumor suppressor microRNA-101 (miR-101). The aim of our study was to investigate the functional role of both miR-101 and EZH2 in human hepatocellular carcinoma (HCC). METHODS: MiR-101 and EZH2 expressions were evaluated in tumor tissues of 99 HCC patients and 7 liver cancer cell lines by real-time PCR. Luciferase reporter assay was employed to validate whether EZH2 represents a target gene of miR-101. The effect of miR-101 on HCC growth as well as programmed cell death was studied in vitro and in vivo. RESULTS: MiR-101 expression was significantly downregulated in most of HCC tissues and all cell lines, whereas EZH2 was significantly overexpressed in most of HCC tissues and all cell lines. There was a negative correlation between expression levels of miR-101 and EZH2. Luciferase assay results confirmed EZH2 as a direct target gene of miR-101, which negatively regulates EZH2 expression in HCC. Ectopic overexpression of miR-101 dramatically repressed proliferation, invasion, colony formation as well as cell cycle progression in vitro and suppressed tumorigenicity in vivo. Furthermore, miR-101 inhibited autophagy and synergized with either doxorubicin or fluorouracil to induce apoptosis in tumor cells. CONCLUSION: Tumor suppressor miR-101 represses HCC progression through directly targeting EZH2 oncogene and sensitizes liver cancer cells to chemotherapeutic treatment. Our findings provide significant insights into molecular mechanisms of hepatocarcinogenesis and may have clinical relevance for the development of novel targeted therapies for HCC.
BACKGROUND & AIMS: Oncogene polycomb group protein enhancer of zeste homolog 2 (EZH2) has been proposed to be a target gene of putative tumor suppressor microRNA-101 (miR-101). The aim of our study was to investigate the functional role of both miR-101 and EZH2 in humanhepatocellular carcinoma (HCC). METHODS:MiR-101 and EZH2 expressions were evaluated in tumor tissues of 99 HCC patients and 7 liver cancer cell lines by real-time PCR. Luciferase reporter assay was employed to validate whether EZH2 represents a target gene of miR-101. The effect of miR-101 on HCC growth as well as programmed cell death was studied in vitro and in vivo. RESULTS:MiR-101 expression was significantly downregulated in most of HCC tissues and all cell lines, whereas EZH2 was significantly overexpressed in most of HCC tissues and all cell lines. There was a negative correlation between expression levels of miR-101 and EZH2. Luciferase assay results confirmed EZH2 as a direct target gene of miR-101, which negatively regulates EZH2 expression in HCC. Ectopic overexpression of miR-101 dramatically repressed proliferation, invasion, colony formation as well as cell cycle progression in vitro and suppressed tumorigenicity in vivo. Furthermore, miR-101 inhibited autophagy and synergized with either doxorubicin or fluorouracil to induce apoptosis in tumor cells. CONCLUSION:Tumor suppressor miR-101 represses HCC progression through directly targeting EZH2 oncogene and sensitizes liver cancer cells to chemotherapeutic treatment. Our findings provide significant insights into molecular mechanisms of hepatocarcinogenesis and may have clinical relevance for the development of novel targeted therapies for HCC.