In:
Journal of Gastroenterology and Hepatology, Wiley, Vol. 28, No. 9 ( 2013-09), p. 1545-1554
Abstract:
By array‐comparative genomic hybridization, we demonstrated cyclin E as one of seven genes associated with hepatocellular carcinoma ( HCC ) development in Ku70 DNA repair‐deficient mice. We therefore explored the hypothesis that during hepatocarcinogenesis, cyclin E kinase can overcome the inhibitory effects of p53 and establish whether abnormal miRNA(mi‐R)‐34, a co‐regulator of cyclin E and p53, can account for their interactions as “drivers” of HCC . Methods Dysplastic hepatocytes ( DNs ) and HCCs were generated from diethylnitrosamine ( DEN )‐injected C57BL/6 male mice at 3–12 months. Results Cyclin E/cdk2 was barely expressed in normal liver, but was readily detected in dysplastic hepatocytes, localizing to glutathione‐S transferase pi‐form positive cells dissected by laser‐dissection. Cyclin E kinase activity preceded cyclin D1 , proliferating cell nuclear antigen expression in DNs and HCCs despite maximal p53 and p21 expression. We confirmed that cyclin E , rather than cyclin D1 , is the proliferative driver in hepatocarcinogenesis by immunoprecipitation experiments demonstrating preferential binding of p21 to cyclin D1 , allowing cyclin E ‐mediated “escape” from G1/S checkpoint. We then showed cyclin E was responsible for regulating wild‐type p53 by knockdown experiments in primary HCC cells; cyclin E ‐knockdown increased p53 and p21, diminished anti‐apoptotic Bcl‐XL and reduced cell viability. Conversely, blocking p53 augmented cyclin E , Bcl‐XL expression and increased proliferation. Physiological interactions between cyclin E /p53/p21 were confirmed in primary hepatocytes. miR‐34a,c were upregulated in dysplastic murine, human liver and HCCs compared with normal liver, and appeared to be linked to cyclin E /p53. Conclusion Upregulation of functionally active cyclin E via miR34 with loss of p53 function is associated with cell‐cycle checkpoint failure increasing proliferative drive that favors hepatocarcinogenesis.
Type of Medium:
Online Resource
ISSN:
0815-9319
,
1440-1746
DOI:
10.1111/jgh.2013.28.issue-9
Language:
English
Publisher:
Wiley
Publication Date:
2013
detail.hit.zdb_id:
2006782-3
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