miR-122 affects the viability and apoptosis of hepatocellular carcinoma cells

Abstract

Objective. miR-122 is highly abundant in liver and a hepato-specific microRNA. There is evidence to show that miR-122 expression is down-regulated in human hepatocellular carcinoma (HCC). It is not known whether miR-122 affects the cellular behavior of hepatoma cells. The aim of this study was to investigate the effects of miR-122 on the viability and apoptosis of hepatoma cells. Material and methods. The viability and apoptosis of Huh-7 and HepG2 cells treated with miR-122 or miR-122 antisense RNA (anti-miR-122) were analyzed by adenosine triphosphate (ATP)-based luminescent assay, annexin V-based flow cytometry, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) detection. The miR-122 coding genes in both cell lines were sequenced. Results. Although two putative promoter sequences for the miR-122 gene at 18q21.31 were detected, the miR-122 coding sequence was missing in HepG2 cells, which might be the reason for the absence of miR-122 expression. There was no significant difference between the viabilities of HepG2 cells transfected with miR-122 and mock HepG2 cells (p >0.05). However, the viability of Huh-7 transfected with anti-miR-122 was significantly elevated at 24, 36, and 48 h posttransfection compared with that of mock cells (p <0.01). Both the flow cytometry and TUNEL assay showed that the apoptotic level of Huh-7 transfected with anti-miR-122 was significantly decreased at 48 h posttransfection (p <0.01). Conclusions. miR-122 down-regulated the viability but up-regulated the apoptosis of hepatoma cell Huh-7. The absence of miR-122 expression in HepG2 cells was due to the loss of the miR-122 coding sequence in chromosome 18. These results imply that aberrant expression of miR-122 may contribute to hepatocarcinogenesis.

Key Words::

• Apoptosis
• cell viability
• hepatocellular carcinoma
• miR-122

Acknowledgements

This study was supported by a grant from the Heilongjiang Science and Technology Foundation (No. 2006G1416-00) to Dr. Xia Wu and partly by a grant from the Natural Science Foundation of China (No. 30872231) to Zhaohua Zhong. We express our thanks to Dr. Shi Shuang, Department of Microbiology, Beijing University Medical School and Dr. Stefan Wieland, The Scripps Research Institute, La Jolla, for generously offering the Huh-7 cells. Dr. Xia Wu and Dr. Shuaiqin Wu contributed equally to this study.

Declaration of interests:The authors declare that they have no conflict of interest.