Increased Expression of miR-23a Mediates a Loss of Expression in the RAF Kinase Inhibitor Protein RKIP

Abstract

RAF kinase inhibitor protein (RKIP) is a seminal regulator of intracellular signaling and exhibits both antimetastatic and antitumorigenic properties. Decreased expression of RKIP has been described in several human malignancies, including acute myelogenous leukemia (AML). As the mechanisms leading to RKIP loss in AML are still unclear, we aimed to analyze the potential involvement of miRNAs within this study. miRNA microarray and qPCR data of more than 400 AML patient specimens revealed correlation between decreased expression of RKIP and increased expression of miR-23a, a member of the miR-23a/27a/24-2 cluster. In functional experiments, overexpression of miR-23a decreased RKIP mRNA and protein expression, whereas miR-23a inhibition caused the opposite effect. By using an RKIP 3 0 -untranslated region luciferase reporter construct with and without mutation or deletion of the putative miR-23a-binding site, we could show that RKIP modulation by miR-23a is mediated via direct binding to this region. Importantly, miR-23a overexpression induced a significant increase of proliferation in hematopoietic cells. Simultaneous transfection of an RKIP expression construct lacking the miR23a-binding sites reversed this phenotype, indicating that this effect is truly mediated via downregulation of RKIP. Finally, by analyzing more than 4,300 primary patient specimens via database retrieval from The Cancer Genome Atlas, we could highlight the importance of the miR-23a/RKIP axis in a broad range of human cancer entities. In conclusion, we have identified miR-23a as a negative regulator of RKIP expression in AML and have provided data that suggest the importance of our observation beyond this tumor entity.

EZH2 dysregulation: Potential biomarkers predicting prognosis and guiding treatment choice in acute myeloid leukaemia

“…Kaplan-Meier survival curves of OS and LFS in low and high EZH2 expression group. Moreover, for microRNAs, we observed that EZH2 expression was negatively correlated with several mi-croRNAs such as miR-21, miR-23a, miR-500, let-7a-3, miR-362, let-7eand miR-10a, which were found to be associated with AML pathogenesis and/or prognosis by previous investigations [28][29][30][31][32][33][34][35]. However, previous study demonstrated that low EZH2 protein levels correlated with poor prognosis in AML patients, which was different from our results 18.…”

Therapeutic Resistance in Acute Myeloid Leukemia: The Role of Non-Coding RNAs

“…Whereas miR-203 shows downregulation in approximately 10% of AML patient samples as well [92], this does not apply for miR-23a. In previous work of our own and other groups, including both in vitro and in vivo approaches, miR-23a was demonstrated to act rather as oncogene within this disease [21,102]. From a mechanistic point of view, increased expression of miR-23a caused a downregulation of the tumor- and metastasis suppressor RKIP thereby increasing the proliferation of leukemic cells.…”

“…On the other hand, expression of ncRNAs is frequently under the control of other players within these networks as well, thereby forming complex circuits which finally orchestrate malignant transformation. Among others, these networks include prominent players in leukemogenesis, such as fms-like tyrosine kinase 3 ( FLT3 ), nucleophosmin ( NPM1 ), CCAAT/Enhancer Binding Protein Alpha ( CEBPA ), tumor protein P53 ( TP53 ) or the RAS-mitogen-activated protein kinase/extracellular signal-regulated kinase (RAS-MAPK/ERK) signaling cascade [19,20,21,22,23]. Lately, the role of ncRNA in mediating sensitivity and resistance to cytotoxic agents, respectively, has been discovered, which makes them attractive targets of novel anti-cancer therapies.…”

The implication of lncRNA expression pattern and potential function of lncRNA RP4‐576H24.2 in acute myeloid leukemia

“…Profiting from the development of RNA sequencing and bioinformatics analysis, investigation of the heterogenetic pathology of AML has become more profound, among which the role of ncRNAs in development and progression of AML has been increasingly revealed in recent decades, including forming regulatory networks that could mediate multiple pathways related to AML . Nonetheless, previous studies investigating the roles of lncRNAs in AML only begin recently, and are quite limited, even though lncRNAs have been found to be crucial genetic factors in other malignancies …”

“…Profiting from the development of RNA sequencing and bioinformatics analysis, investigation of the heterogenetic pathology of AML has become more profound, among which the role of ncRNAs in development and progression of AML has been increasingly revealed in recent decades, including forming regulatory networks that could mediate multiple pathways related to AML. [15][16][17] Nonetheless, previous studies investigating the roles of lncRNAs in AML only begin recently, and are quite limited, even though lncRNAs have been found to be crucial genetic factors in other malignancies. 18,19 In terms of the studies including RNA sequencing in AML, in a study using miRNA sequencing and transcription factor (TF) activity array, 308 dysregulated miRNAs and 84 dysregulated TFs are detected, then 1462 miRNA-target gene pairs, 982 TF-target gene pairs, and 196 TF-miRNA pairs are identified subsequently; after emerging as a regulatory network of these dysregulated miRNAs and TF, the KEGG pathway analysis finds that the network is markedly enriched in 33 pathways with the AML-related pathways the most significant.…”