MicroRNA-21 promotes hepatocellular carcinoma HepG2 cell proliferation through repression of mitogen-activated protein kinase-kinase 3

Abstract

BackgroundmicroRNA 21 (miR-21) has been demonstrated to be significantly elevated in many types of cancers, including the hepatocellular carcinoma (HCC). In the present study, we investigated the role of miR-21 in HCC by identifying its novel targets, as well as its underlying molecular mechanism.MethodsThe expression of mitogen-activated protein kinase-kinase 3 (MAP2K3) in human HCC tumor tissues and adjacent non-tumor tissues was determined by immunohistochemistry staining (IHC) analysis. The 3’-untranslated region (3’-UTR) of MAP2K3 combined with miR-21 was experimentally verified by a miRNA luciferase reporter approach. Moreover, the role of miR-21 in regulating HCC cell proliferation was analyzed by an MTT assay infected with miR-21mimics/sponge inhibitor Adenoviral viral vectors.ResultsBy immunohistochemistry staining analysis, we found that mitogen-activated protein kinase-kinase 3 (MAP2K3) was strikingly repressed in the human HCC tumor tissues, in comparison with the adjacent non-tumor tissues in clinical settings. More importantly, the repression of MAP2K3 was inversely correlated with the expression of miR-21 in HCC. Further study demonstrated that the MAP2K3 was a novel direct target of miR-21, which was experimentally validated by a miRNA luciferase reporter approach. In HepG2 cells, inhibition of miR-21 expression with an adenoviral miR-21 sponge vector profoundly suppressed cell proliferation by up-regulating MAP2K3 expression at both mRNA and protein levels.ConclusionsThese results provide a clinical evidence that MAP2K3 may be a tumor repressor gene, and it is a direct target of miR-21 in HCC, indicating an underlying mechanism by which miR-21 is able to directly target MAP2K3 and inhibit its expression during the carcinogenesis of HCC, at both transcriptional and post-translational levels. This study also suggests that targeting miR-21-MAP2K3 pathway may be a promising strategy in the prevention and treatment of HCC.

Expression and clinical significance of microRNA-21, maspin and vascular endothelial growth factor-C in bladder cancer

“…In particular, miR-21 has been shown to be involved in various cancer-associated processes, including cell growth, invasion and apoptosis (14). miR-21 induces hepatocellular carcinoma HepG2 cell proliferation via the suppression of mitogen-activated protein kinase-kinase 3 (15). In addition, miR-21 promotes oral cancer invasion via the Wnt/β-catenin pathway by targeting DKK2 (16).…”

Anti–miR-21 Suppresses Hepatocellular Carcinoma Growth via Broad Transcriptional Network Deregulation

“…Mice homozygous for miR-21 deletion are fertile and appear phenotypically normal, indicating that miR-21 is dispensable under normal physiologic conditions, yet plays a pivotal prosurvival function during cellular oncogenic transformation (11,12). In addition, a number of studies have demonstrated antiproliferative and antimigratory effects of miR-21 inhibitors in cancer cell lines in vitro (13)(14)(15)(16).…”

Investigation of the value of miR-21 in the diagnosis of early stage HCC and its prognosis: a meta-analysis

“…Many studies have supported the hypothesis that miR-21 overexpression might promote HCC invasion and metastasis through direct or indirect mechanisms, and thus lead to poor prognosis (Liu et al, 2010;Tomimaru et al, 2010;Xu et al, 2011;Tomimaru et al, 2012;Zhu et al, 2012). Zhou et al (2013) demonstrated that miR-21 promoted side population cell migration and invasion by targeting PTEN, RECK, and PDCD4, and that it could also directly target MAP2K3 and inhibit its expression during HCC carcinogenesis (Xu et al, 2013). Therefore, patients with high tumoral miRNA-21 expression were shown to have a significantly shorter time-to-recurrence compared to those with low tumoral expression, and that patients with low plasma miRNA-21 expression tended to have a longer time-to-recurrence compared to those with high plasma miRNA-21 expression (Tomimaru et al, 2012).…”