27161

AGO2

argonaute RISC catalytic component 2;AGO2;argonaute RISC catalytic component 2

CTA-204B4.6|PAZ Piwi domain protein|PPD|argonaute 2|argonaute2|eIF-2C 2|eIF2C 2|eukaryotic translation initiation factor 2C, 2|hAgo2|protein argonaute-2|protein slicer

8q24

protein-coding

BACKGROUND: Although Argonaute proteins are considered to play important roles in stem cell self-renewal, RNA interference (RNAi) and translational regulation, relatively little is known about their functions in human disease. In this study, we investigated the expression of eight members of human Argonaute family in colon cancer and identified their potential roles in tumor development and progression. METHODS: Antibodies against human Argonaute proteins were prepared by immunizing rabbits with synthetic peptides derived from the sequences of Argonaute members. Then we constructed a tissue microarray containing 75 specimens from colon cancer and 75 specimens from adjacent non-cancer tissue, and assayed eight different proteins (EIF2C1, EIF2C2, EIF2C3, EIF2C4, PIWIL1, PIWIL2, PIWIL3 and PIWIL4) by immunohistochemistry on consecutive formalin-fixed tissue microarray sections. RESULTS: The expression of EIF2C1-4 and PIWIL1-4 was significantly higher in tumorous tissue than in adjacent tissue. Notably, a significant correlation was observed between the positive expression of EIF2C2, EIF2C3, EIF2C4, PIWIL4 and the presence of distant metastasis. Logistic regression analysis revealed that an increased expression of EIF2C1 and PIWIL2 was significantly associated with occurrence of colon cancer tissue compared with non-cancer tissue. CONCLUSIONS: Argonaute proteins are overexpressed in colon cancer relative to adjacent non-cancer tissue. The expression of EIF2C2-4 and PIWIL4 appears increased in advanced tumors with distant metastasis, suggesting it may promote tumor invasion. Furthermore, EIF2C1 and PIWIL2 might represent novel colon cancer markers with early diagnostic significance.

Hepatocellular carcinoma (HCC) is one of the most common cancers and shows a propensity to metastasize and infiltrate adjacent and more distant tissues. However, the mechanisms that contribute to tumor metastasis remain unclear. Here we evaluate the effect of Argonaute2 (Ago2), a member of the Ago gene family that plays a role in short interfering RNA-mediated gene silencing, on HCC tumorigenesis, and metastasis. We found that Ago2 was frequently up-regulated in HCC specimens compared to that in corresponding adjacent nontumor liver. Interestingly, Ago2 overexpression can promote proliferation, colony formation in an anchor-independent manner, migration, tumorigenicity, and metastasis of HCC cells in vivo; in contrast, Ago2 knockdown can restrict anchor-independent colony formation, migration, and tumor metastasis of HCC cells in vivo. However, known microRNAs related to tumor metastasis appeared not be deregulated with Ago2 overexpression in HCC cells; even the knockdown of Dicer, which is responsible for microRNA biosynthesis, did not abolish the actions of Ago2 in HCC cells. Significantly, focal adhesion kinase (FAK), a well-known molecule associated with tumor metastasis, was up-regulated as a result of Ago2 overexpression. Chromatin immunoprecipitation assay showed that Ago2 can bind to the FAK promoter and then trigger its transcription. Moreover, an increased DNA copy number of Ago2 on chromosome 8q24, one of the most frequent DNA amplified regions, was validated and shown by way of fluorescence in situ hybridization. CONCLUSION: Our data demonstrate that Ago2 overexpression, as a result of genomic DNA amplification, promotes HCC tumorigenesis and metastasis by way of up-regulation of FAK transcription, thereby providing new insight into HCC progression and Ago2 function.

MicroRNAs are posttranscriptional regulators of messenger RNA synthesis that are intracellularly processed and transferred by the microRNA-regulating machinery consisting of Drosha, Dicer, and Argonaute. The present study analyzed the expression and clinical role of the microRNA-regulating machinery in advanced-stage ovarian carcinoma. Drosha, Dicer, Argonaute 1, and Argonaute 2 messenger RNA levels were analyzed in 144 specimens (82 effusions, 33 primary carcinomas, and 29 solid metastases) using quantitative polymerase chain reaction. Dicer, Argonaute 1, and Argonaute 2 protein levels were analyzed in 103 of the above specimens by Western blotting. Argonaute 1, Argonaute 2, and Drosha messenger RNAs were overexpressed in effusions compared with primary carcinomas and solid metastases (P<.001), whereas Argonaute 1 protein expression was highest in solid metastases (P=.004). Significantly higher expression of all 4 messenger RNAs was found in effusions compared with primary carcinomas (P<.001 to P=.006), whereas Argonaute 2 messenger RNA (P=.002), Drosha messenger RNA (P=.009), and Dicer protein (P=.006) were overexpressed in solid metastases compared with primary carcinomas. Drosha, Dicer, Argonaute 1, and Argonaute 2 messenger RNAs and protein levels in effusions were unrelated to clinicopathologic parameters. In primary carcinomas, higher levels of 3 messenger RNAs were significantly associated with high-grade histology (P=.003 for Dicer and P=.01 for Drosha and Argonaute 1). Higher Argonaute 2 messenger RNA levels in prechemotherapy effusions were related to shorter progression-free survival (P=.049), a finding that retained its significance in multivariate Cox analysis (P=.046). In conclusion, Drosha, Dicer, Argonaute 1, and Argonaute 2 are differentially expressed at different metastatic sites in ovarian carcinoma compared with primary carcinomas, suggesting a role for these molecules in tumor progression. Their clinical role in metastatic ovarian carcinoma merits further research.