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MiRNA-99a directly regulates AGO2 through translational repression in hepatocellular carcinoma.

Zhang J, Jin H, Liu H, Lv S, Wang B, Wang R, Liu H, Ding M, Yang Y, Li L, Zhang J, Fu S, Xie D, Wu M, Zhou W, Qian Q - Oncogenesis (2014)

Bottom Line: Subsequently, Argonaute-2 (Ago2), a central component of RNA-induced silencing complex, was found to be directly regulated by miR-99a via translational repression.Overexpression of Ago2 could partly impair the inhibitory effect of miR-99a on HCC cells in vitro.In addition, this study provides potential strategies for HCC therapy by reintroduction of miRNA suppressors.

View Article: PubMed Central - PubMed

Affiliation: The Third Department of Hepatic Surgery, Eastern Hepatobiliary Surgery Hospital, Second Military Medical University, Shanghai, China.

ABSTRACT
The regulation network consisting of microRNAs (miRNAs) and their target genes remains largely elusive in hepatocellular carcinoma (HCC), especially the reciprocal loop between specific miRNAs and the miRNA processing machinery. In this study, we found that miR-99a was remarkably decreased in 111 of 152 (73.03%) primary HCC tissues and low-level expression of miR-99a was correlated with low tumor differentiation (P=0.001), liver cirrhosis (P=0.015), poor tumor-free survival (P=0.004) and overall survival (P=0.006) for HCC patients. By restoration of miR-99a, the HCC growth could be considerably inhibited both in vitro and in vivo. Subsequently, Argonaute-2 (Ago2), a central component of RNA-induced silencing complex, was found to be directly regulated by miR-99a via translational repression. Overexpression of Ago2 could partly impair the inhibitory effect of miR-99a on HCC cells in vitro. Then, we demonstrated that Ago2 was upregulated in HCC tissues at both RNA and protein levels and the expression of AGO2 protein and miR-99a was negatively correlated within detected HCC tissues (r=-0.727, P=0.004). Interestingly, the tumorigenicity of Ago2-knockdown HCC cells was severely impaired (4/10 vs 10/10, P<0.05), and this was in contrast to the miR-99a-overexpressing HCC cells. Functionally, the increased AGO2 protein could specifically facilitate oncogenic miR-21 to repress its targeted gene phosphatase and tensin homolog (Pten) in HCC, whereas leave the regulatory capacity of let-7a on its targeted oncogenes almost unaltered. In summary, our study has revealed a novel pathway for the tumor suppressor miR-99a to control tumor growth in HCC, via its downstream signaling of AGO2/miR-21/PTEN. In addition, this study provides potential strategies for HCC therapy by reintroduction of miRNA suppressors.

No MeSH data available.


Related in: MedlinePlus

Ago2 is upregulated in HCC and negatively correlated with miR-99a. (a) The correlation between relative expression of miR-99a and Ago2 mRNA in HCC tissues as determined by qRT–PCR. (b) Increased AGO2 protein as analyzed by immunohistochemistry in cancerous tissues. The patient serial number was 30 and 6, respectively. (c) Increased AGO2 protein as detected by western blotting. Expression ratio was calculated by normalizing AGO2 to total protein levels in each case. The value of relative expression of miR-99a/AGO2 protein is shown below. The patient serial number was 6, 8, 9, 11, 30, 41, 53, 68, 73, 90, 121, and 132, respectively. N, matched noncancerous control; T, HCC tissue. (d) The correlation between expression of miR-99a and AGO2 protein in 12 pairs of HCC samples mentioned above.
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fig4: Ago2 is upregulated in HCC and negatively correlated with miR-99a. (a) The correlation between relative expression of miR-99a and Ago2 mRNA in HCC tissues as determined by qRT–PCR. (b) Increased AGO2 protein as analyzed by immunohistochemistry in cancerous tissues. The patient serial number was 30 and 6, respectively. (c) Increased AGO2 protein as detected by western blotting. Expression ratio was calculated by normalizing AGO2 to total protein levels in each case. The value of relative expression of miR-99a/AGO2 protein is shown below. The patient serial number was 6, 8, 9, 11, 30, 41, 53, 68, 73, 90, 121, and 132, respectively. N, matched noncancerous control; T, HCC tissue. (d) The correlation between expression of miR-99a and AGO2 protein in 12 pairs of HCC samples mentioned above.

Mentions: Ago2 plays an important role in miRNA-mediated posttranscriptional regulation, but its expression profile in HCC remains largely unknown. Thus, the expression profile of Ago2 in HCC cell lines and primary HCC tissues was investigated by RT–PCR analysis. As a result, overexpression of Ago2 was found in 5 of 6 detected HCC cells (Supplementary Figure S4) and 105 of 152 cancerous tissues as compared with their paired noncancerous tissues. However, no distinct correlation was revealed between the expression of miR-99a and Ago2 at the RNA level (r=−0.077, P=0.117, Figure 4a).


MiRNA-99a directly regulates AGO2 through translational repression in hepatocellular carcinoma.

Zhang J, Jin H, Liu H, Lv S, Wang B, Wang R, Liu H, Ding M, Yang Y, Li L, Zhang J, Fu S, Xie D, Wu M, Zhou W, Qian Q - Oncogenesis (2014)

Ago2 is upregulated in HCC and negatively correlated with miR-99a. (a) The correlation between relative expression of miR-99a and Ago2 mRNA in HCC tissues as determined by qRT–PCR. (b) Increased AGO2 protein as analyzed by immunohistochemistry in cancerous tissues. The patient serial number was 30 and 6, respectively. (c) Increased AGO2 protein as detected by western blotting. Expression ratio was calculated by normalizing AGO2 to total protein levels in each case. The value of relative expression of miR-99a/AGO2 protein is shown below. The patient serial number was 6, 8, 9, 11, 30, 41, 53, 68, 73, 90, 121, and 132, respectively. N, matched noncancerous control; T, HCC tissue. (d) The correlation between expression of miR-99a and AGO2 protein in 12 pairs of HCC samples mentioned above.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4007193&req=5

fig4: Ago2 is upregulated in HCC and negatively correlated with miR-99a. (a) The correlation between relative expression of miR-99a and Ago2 mRNA in HCC tissues as determined by qRT–PCR. (b) Increased AGO2 protein as analyzed by immunohistochemistry in cancerous tissues. The patient serial number was 30 and 6, respectively. (c) Increased AGO2 protein as detected by western blotting. Expression ratio was calculated by normalizing AGO2 to total protein levels in each case. The value of relative expression of miR-99a/AGO2 protein is shown below. The patient serial number was 6, 8, 9, 11, 30, 41, 53, 68, 73, 90, 121, and 132, respectively. N, matched noncancerous control; T, HCC tissue. (d) The correlation between expression of miR-99a and AGO2 protein in 12 pairs of HCC samples mentioned above.
Mentions: Ago2 plays an important role in miRNA-mediated posttranscriptional regulation, but its expression profile in HCC remains largely unknown. Thus, the expression profile of Ago2 in HCC cell lines and primary HCC tissues was investigated by RT–PCR analysis. As a result, overexpression of Ago2 was found in 5 of 6 detected HCC cells (Supplementary Figure S4) and 105 of 152 cancerous tissues as compared with their paired noncancerous tissues. However, no distinct correlation was revealed between the expression of miR-99a and Ago2 at the RNA level (r=−0.077, P=0.117, Figure 4a).

Bottom Line: Subsequently, Argonaute-2 (Ago2), a central component of RNA-induced silencing complex, was found to be directly regulated by miR-99a via translational repression.Overexpression of Ago2 could partly impair the inhibitory effect of miR-99a on HCC cells in vitro.In addition, this study provides potential strategies for HCC therapy by reintroduction of miRNA suppressors.

View Article: PubMed Central - PubMed

Affiliation: The Third Department of Hepatic Surgery, Eastern Hepatobiliary Surgery Hospital, Second Military Medical University, Shanghai, China.

ABSTRACT
The regulation network consisting of microRNAs (miRNAs) and their target genes remains largely elusive in hepatocellular carcinoma (HCC), especially the reciprocal loop between specific miRNAs and the miRNA processing machinery. In this study, we found that miR-99a was remarkably decreased in 111 of 152 (73.03%) primary HCC tissues and low-level expression of miR-99a was correlated with low tumor differentiation (P=0.001), liver cirrhosis (P=0.015), poor tumor-free survival (P=0.004) and overall survival (P=0.006) for HCC patients. By restoration of miR-99a, the HCC growth could be considerably inhibited both in vitro and in vivo. Subsequently, Argonaute-2 (Ago2), a central component of RNA-induced silencing complex, was found to be directly regulated by miR-99a via translational repression. Overexpression of Ago2 could partly impair the inhibitory effect of miR-99a on HCC cells in vitro. Then, we demonstrated that Ago2 was upregulated in HCC tissues at both RNA and protein levels and the expression of AGO2 protein and miR-99a was negatively correlated within detected HCC tissues (r=-0.727, P=0.004). Interestingly, the tumorigenicity of Ago2-knockdown HCC cells was severely impaired (4/10 vs 10/10, P<0.05), and this was in contrast to the miR-99a-overexpressing HCC cells. Functionally, the increased AGO2 protein could specifically facilitate oncogenic miR-21 to repress its targeted gene phosphatase and tensin homolog (Pten) in HCC, whereas leave the regulatory capacity of let-7a on its targeted oncogenes almost unaltered. In summary, our study has revealed a novel pathway for the tumor suppressor miR-99a to control tumor growth in HCC, via its downstream signaling of AGO2/miR-21/PTEN. In addition, this study provides potential strategies for HCC therapy by reintroduction of miRNA suppressors.

No MeSH data available.


Related in: MedlinePlus