| Aurora-A kinase,a member of the evolutionary conserved Aurora serine/threonine kinase family,plays a vital role in regulation of centrosome maturation,bipolar spindle assembly,chromosome segregation,mitotic entry and exit.However,it has been shown that overexpression of Aurora-A induces unexpected centrosome duplication and chromosomal instability,leading to aneuploidy and cell transformation.Now,Aurora-A is considered to be a bona fide oncogene related to a variety of human tumors.There is also increased evidence of significant high levels of Aurora-A mRNA and protein expression in human malignancies from different organs,including breast,pancreas, esophagus,stomach,lung and bladder.Besides,its overexpression is correlated to tumor histological grade,clinical staging and the prognosis.Some studies observed that targeted disruption of Aurora-A might induce tumor growth suppression and finally apoptosis.Hepatocellular carcinoma(HCC) is one of the most frequent malignant tumors in China with a still poor prognosis and increasing mortality for its aggressive invasion and metastasis.In spite of improvements in diagnosis and treatment methods,the efficacy remains unsatisfied.Recently,amplification of chromosome 20q was found frequently in HCC,where Aurora-A is located,indicating a close relationship between Aurora-A and HCC.In order to determine the involvement of Aurora-A in HCC and to explore the molecule mechanism of Aurora-A for the tumorigenesis of HCC,we designed this study as follows:1.Analysis of Aurora-A mRNA expression in HCC patients' tumor tissues and paired tumor-adjacent liver parenchyma by real-time PCR, as well as the clinicopathologic relation of Aurora-A expression in HCC;2.Observation of biological phenotypes in hepatocellular cancer cell lines HepG2,MHCC-97H, SMMC-7721 and Hep3B after specific knockdown of Aurora-A expression by using RNA interference(RNAi) technique;3.Exploration of the molecule mechanisms by which inhibition of Aurora-A expression exerts potent antitumor activity.We observed,among 32 HCCs,Aurora-A mRNA was overexpressed in 16(50%) patients,and the expression ratio between tumor tissue and paired tumor-adjacent liver parenchyma ranged from 1.6 to 148.Besides,Aurora-A mRNA overexpression in HCC did not correlate to age,gender,hepatitis B virus infection,serumα-fetoprotein elevation and tumor histologic grade,but was significantly associated with increasing TNM staging and worse survival rate.After specific knockdown of Aurora-A expression by RNAi,growth of cultured HepG2,MHCC-97H and SMMC-7721 cells was time-dependantly suppressed showed by MTT assay.Flow cytometry then showed a significant accumulation of cells in the G2/M phase and finally apoptosis.In addition, the failure of HepG2 cells to heal a scar or to penetrate the Matrigel detected by scratch assay and transwell assay indicated the inhibition of metastasis and invasion of HepG2 cells by specific knockdown of Aurora-A expression.Furthermore,we discovered that the expression of Cyclin B1 was downregulated by Aurora-A RNAi,which resulted in G2/M phase arrest.Meanwhile,we demonstrated for the first time in hepatoma cells that specific knockdown of Aurora-A expression by RNAi restored the tumor suppressor activity of wild type p53(wt-p53) which had been inhibited by overexpressed Aurora-A in hepatoma cells,and then resulted in apoptosis and inhibition of invasion by DNA binding and transactivation activity of released wt-p53.In conclusion,Aurora-A kinase is closely associated with the biological phenotypes of hepatoma cells,and its overexpression in HCC might represent a worse prognosis. By further understanding of its function in HCC makes Aurora-A to become a potent gene therapy target to suppress the progression of HCC.Interestingly,we suppose that the therapeutic effect by inhibition of Aurora-A in HCC patients with mutant p53 might not so good as those with wt-p53,according to the outcome that Aurora-A RNAi could only induce apoptosis in hepatoma cells with wt-p53. |
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