ABSTRACT
Chronic inflammation is known to promote carcinogenesis; Dicer heterozygous mice are more likely to develop colitis-associated tumors. This study investigates whether Dicer is downregulated in inflamed colon tissues before malignancy occurs and whether increasing Dicer expression in inflamed colon tissues can alleviate colitis and prevent colitis-associated tumorigenesis. Methods: Gene expression in colon tissues was analyzed by immunohistochemistry, immunoblots, and real-time RT-PCR. Hydrogen peroxide or N-acetyl-L-cysteine was used to induce or alleviate oxidative stress, respectively. Mice were given azoxymethane followed by dextran sulfate sodium to induce colitis and colon tumors. Berberine, anastrozole, or pranoprofen was used to rescue Dicer expression in inflammatory colon tissues. Results: Oxidative stress repressed Dicer expression in inflamed colon tissues by inducing miR-215 expression. Decreased Dicer expression increased DNA damage and cytosolic DNA and promoted interleukin-6 expression upon hydrogen peroxide treatment. Dicer overexpression in inflamed colon tissues alleviated inflammation and repressed colitis-associated carcinogenesis. Furthermore, we found that anastrozole, berberine, and pranoprofen could promote Dicer expression and protect cells from hydrogen peroxide-induced DNA damage, thereby reducing cytosolic DNA and partially repressing interleukin-6 expression upon hydrogen peroxide treatment. Rescuing Dicer expression using anastrozole, berberine, or pranoprofen in inflamed colon tissues alleviated colitis and prevented colitis-associated tumorigenesis. Conclusions: Dicer was downregulated in inflamed colon tissues before malignancy occurred. Decreased Dicer expression further exaggerated inflammation, which may promote carcinogenesis. Anastrozole, berberine, and pranoprofen alleviated colitis and colitis-associated tumorigenesis by promoting Dicer expression. Our study provides insight into potential colitis treatment and colitis-associated colon cancer prevention strategies.
Subject(s)
Colon/pathology , DEAD-box RNA Helicases/genetics , DEAD-box RNA Helicases/metabolism , Ribonuclease III/genetics , Ribonuclease III/metabolism , Anastrozole/pharmacology , Animals , Berberine/pharmacology , Carcinogenesis/genetics , Carcinogenesis/metabolism , Cell Line, Tumor , Cell Transformation, Neoplastic/genetics , Colitis/metabolism , Colon/metabolism , Gene Expression/genetics , Gene Expression Regulation/genetics , Humans , Inflammation/genetics , Intestinal Mucosa/drug effects , Male , Mice , Mice, Inbred C57BL , MicroRNAs/genetics , MicroRNAs/metabolism , Oxidative Stress/physiology , Signal Transduction/drug effectsABSTRACT
OBJECTIVE: To investigate the effect of hepatitis B virus (HBV) and hepatitis B virus surface antigen (HBsAg) on microRNA-31 (miR-31) expression in HBV-related hepatocellular carcinoma using HepG2 hepatoma cells. METHODS: Stable HBsAg-overexpressing cell lines were established by transfecting HepG2 cells with an HBsAg-bearing mammalian expression vector, and the clones (designated as HepG2-H2 cells) were validated by enzyme-linked immunosorbent assay and immunohistochemistry. Effects on expression of miR-31 were determined by measuring the mRNA level by real-time PCR and performing statistical comparisons with levels detected in HepG2-H0 cells (stably transfected with empty vector) and HepG2.2.15 cells (stably transfected with the HBV genome). RESULTS: The HepG2-H2 HBsAg-overexpressing transfectant cell line was successfully established. The expression level of miR-31 was significantly higher in the HepG2-H0 cells than in the HepG2.2.15 cells (t = 583.8, P less than 0.001). In contrast, the expression level of miR-31 was significantly higher in the HBsAg-overexpressing HepG2-H2 cells than in the HepG2-H0 cells (F = 24.9, P less than 0.05). CONCLUSION: Intact HBV leads to down-regulation of miR-31 expression and HBsAg overexpression leads to up-regulation of miR-31 expression in hepatocarcinoma cells.
