miR-346 Up-regulates Argonaute 2 (AGO2) Protein Expression to Augment the Activity of Other MicroRNAs (miRNAs) and Contributes to Cervical Cancer Cell Malignancy

Abstract

MicroRNAs (miRNAs) are a class of post-transcriptional regulators of gene expression, and AGO2 is essential for miRNA activity. In this study, we focused on the regulation of AGO2 by miR-346 and the consequences in cervical cancer cells. miR-346 enhanced the expression of AGO2, resulting in the increased activity of other miRNAs and contributing to the malignancy of HeLa cells. GRSF1 participated in the regulation of AGO2 by miR-346, and the middle sequence of miR-346 was vital for the synergy effect of miR-346 and GRSF1. We determined that miR-346 promoted the migration and invasion of HeLa cells. In summary, we are the first to report that AGO2 is regulated positively by miRNA and that GRSF1 participates in the miRNA pathway.Cervical cancer is one of the most prevalent gynecological cancers worldwide, accounting for ϳ12% of all cancers globally (1). The etiology of cervical cancer varies, and high-risk human papilloma virus infection is one of the most prominent features of cervical cancer (2). Recently, the role of microRNAs (miRNAs), 2 a class of small RNAs that post-transcriptionally regulate target gene expression in a sequence-specific manner, has received widespread attention (3, 4). The dysregulation of miRNAs affects many aspects of cervical cancer, including cellular apoptosis, cell cycle progression, and cell migration and invasion (5-7). miRNAs are transcribed as long primary transcripts that are subsequently processed by the RNase III proteins Drosha and Dicer to form mature microRNAs (8). Then, a strand of mature miRNA is incorporated into an RNA-induced silencing complex (RISC), where it exerts its effects. AGO2 is a key component of the RISC and is the only AGO2 protein with intrinsic endonuclease activity (9). The expression of AGO2 is tightly regulated at both transcriptional and post-transcriptional levels (10). Dysregulation of AGO2 has been reported in many tumors, including lung cancer (11), prostate cancer (12, 13), hepatocarcinoma (14), and melanoma (15), but the role of AGO2 and how its expression is regulated in cervical cancer have not been well studied.In this study, we found that AGO2 was expressed in cervical cancers and that its expression was enhanced by miR-346 and GRSF1 independent of an increase in AGO2 stability. The increased expression of AGO2 augmented the activity of other miRNAs and promoted the malignant phenotype of cervical cancer cells. These findings could provide new insights into the regulation of AGO2 expression and the mechanisms by which miRNAs up-regulate the expression of their target genes. Materials and Methods Cell Lines and Clinical Tissue Samples-The cancer cell lines used in this study were preserved in liquid nitrogen in our laboratory, and the cells were maintained in standard culture medium as recommended by the ATCC. All transfections were performed with Lipofectamine TM 2000 reagent (Invitrogen) according to the recommendations of the manufacturer. Fourteen pairs of clinical cervical cancer tissues and respective adjacent non-cancerous tissues were...

miRNA-346 promotes proliferation, migration and invasion in liver cancer

“…Increasing data findings have indicated miRNAs to be critical regulators of cancer-related processes, but it is still unknown the molecu lar mechanisms by which miRNAs modulate the behavior of cancer cells (26,27). miR-346 has been reported as an oncomir because it facilitates cell growth and metastasis in various human cancers (16)(17)(18)(19)(20)(21). This is the first study that indicates that ectopically expressed miR-346 can promote migration, proliferation, and invasion of liver cancer cells.…”

“…Emerging evidence suggests that the abnormal expression of miRNAs is involved in the invasion and metastasis, during the progression of various human cancers (14,15). miR-346 has been reported as an oncomir in various human cancers, including cutaneous squamous cell carcinoma (16), cervical cancer (17), prostate cancer (18), nasopharyngeal carcinoma (19), lung cancer (20) and breast cancer (21).…”

MicroRNA-346 facilitates cell growth and metastasis, and suppresses cell apoptosis in human non-small cell lung cancer by regulation of XPC/ERK/Snail/E-cadherin pathway

“…Previous studies indicated that miR-346 might be an oncogenic miRNA in some cancers, including cervical cancer [21,22], cutaneous squamous cell carcinoma [23]. However, the functional role and mechanistic action of miR-346 in NSCLC remained largely unclear.…”

“…Including Graves' disease [19], rheumatoid arthritis [20], cervical cancer [21,22], cutaneous squamous cell carcinoma [23]. Wang et al also found that miR-346 regulates osteogenic differen-tiation of human bone marrow-derived mesenchymal stem cells by targeting the Wnt/β-catenin pathway [24].…”

MicroRNAs in gynecological cancers: Small molecules with big implications

“…miR-183 targets MMP3 to inhibit invasion of CC cells [185] while miR-375 inhibits invasion by targeting transcription factor SP1 [186]. miR-205 [187] promotes invasion of EC cells and miR-346 promotes migration and invasion of CC cells by positively regulating AGO2 (argonaute 2) [188]. …”