Epigenetic silencing of TMEM176A activates ERK signaling in human hepatocellular carcinoma
- Clin Epigenetics. 2018 Nov 6;10(1):137. doi: 10.1186/s13148-018-0570-4.
- 1. College of Life Science and Bioengineering, Beijing University of Technology, Beijing, 100124, China.
- 2. Department of Gastroenterology and Hepatology, Chinese PLA General Hospital, #28 Fuxing Road, Beijing, 100853, China.
- 3. Department of Thoracic Surgery, Anyang Tumor Hospital, Anyang, 455000, China.
- 4. The Hillman Cancer Center, University of Pittsburgh Cancer Institute, 5117 Centre Avenue, Suite 2.18/Research, Pittsburgh, PA, 15213, USA.
- 5. College of Life Science and Bioengineering, Beijing University of Technology, Beijing, 100124, China. [email protected].
- 6. Department of Gastroenterology and Hepatology, Chinese PLA General Hospital, #28 Fuxing Road, Beijing, 100853, China. [email protected].
Background: The role of TMEM176A in human hepatocellular carcinoma (HCC) is unknown. This study explored the epigenetic regulation and function of TMEM176A in human HCC.
Materials and methods: Twelve HCC cell lines and 126 cases of primary Cancer were analyzed. Methylation-specific PCR, immunohistochemistry, flow cytometry, and xenograft mouse models were employed.
Results: TMEM176A was highly expressed in SNU387, SNU182, Huh1, and SNU475 cells; reduced expression was observed in HepG2 and PLC/PRF/5 cells; and no expression was found in SNU449, HBXF344, SMMC7721, Huh7, and LM3 cells. Unmethylation of the TMEM176A promoter was detected in SNU387, SNU182, Huh1, and SNU475 cells; partial methylation was observed in HepG2 and PLC/PRF/5 cells; and complete methylation was found in SNU449, HBXF344, SMMC7721, Huh7, and LM3 cells. Upon treatment with 5-Aza-2-deoxycytidine, re-expression of TMEM176A was detected in SNU449, HBXF344, SMMC7721, Huh7, and LM3 cells; increased expression of TMEM176A was observed in HepG2 and PLC/PRF/5 cells; and no expression changes were found in SNU387, SNU182, Huh1, and SNU475 cells. The TMEM176A promoter region was methylated in 75.4% (95/126) of primary human HCC. Reduced expression of TMEM176A was associated with promoter region methylation (P < 0.05). No association was found between TMEM176A promoter methylation and age, gender, HBV Infection, liver cirrhosis, tumor size, lymph node metastasis, vessel cancerous embolus, number of lesions, and TNM stage (all P > 0.05). These results demonstrated that the expression of TMEM176A is regulated by promoter region methylation. Methylation of the TMEM176A promoter was significantly associated with tumor cell differentiation (P < 0.05) and was an independent prognostic factor for poor 3-year overall survival (OS, P < 0.05). TMEM176A expression induced cell apoptosis; inhibited cell proliferation, migration, and invasion; suppressed human HCC cell xenograft growth in mice; and inhibited ERK signaling in HCC cells.
Conclusion: The promoter region of TMEM176A is frequently methylated in human HCC, and the expression of TMEM176A is regulated by promoter region methylation. Methylation of the TMEM176A promoter may serve as a diagnostic and prognostic marker in HCC. TMEM176A suppresses HCC growth by inhibiting the ERK signaling pathway.