MicroRNA-9 enhances sensitivity to cetuximab in epithelial phenotype hepatocellular carcinoma cells through regulation of the eukaryotic translation initiation factor 5A-2

Relationship of micro-RNA, mRNA and eIF Expression in Tamoxifen-Adapted MCF-7 Breast Cancer Cells: Impact of miR-1972 on Gene Expression, Proliferation and Migration

Background: Tamoxifen-adapted MCF-7-Tam cells represent an in-vitro model for acquired tamoxifen resistance, which is still a problem in clinics. We here investigated the correlation of microRNA-, mRNA- and eukaryotic initiation factors (eIFs) expression in this model. Methods: MicroRNA- and gene expression were analyzed by nCounter and qRT-PCR technology; eIFs by Western blotting. Protein translation mode was determined using a reporter gene assay. Cells were transfected with a miR-1972-mimic. Results: miR-181b-5p,-3p and miR-455-5p were up-, miR-375, and miR-1972 down-regulated and are significant in survival analysis. About 5% of the predicted target genes were significantly altered. Pathway enrichment analysis suggested a contribution of the FoxO1 pathway. The ratio of polio-IRES driven to cap-dependent protein translation shifted towards cap-dependent initiation. Protein expression of eIF2A, -4G, -4H and -6 decreased, whereas eIF3H was higher in MCF-7-Tam. Significant correlations between tamoxifen-regulated miRNAs and eIFs were found in representative breast cancer cell lines. Transfection with a miR-1972-mimic reverses tamoxifen-induced expression for a subset of genes and increased proliferation in MCF-7, but reduced proliferation in MCF-7-Tam, especially in the presence of 4OH-tamoxifen. Migration was inhibited in MCF-7-Tam cells. Translation mode remained unaffected. Conclusions: miR-1972 contributes to the orchestration of gene-expression and physiological consequences of tamoxifen adaption.

Circ_0003998 enhances doxorubicin resistance in hepatocellular carcinoma by regulating miR-218-5p/EIF5A2 pathway

BACKGROUND

The involvement of circular RNAs (circRNAs) in chemoresistance of tumors has been identified. Herein, this study aims to investigate the role and the underlying mechanism of circ_0003998 in doxorubicin (DOX) resistance in hepatocellular carcinoma (HCC).

METHODS

The expression of circ_0003998 and microRNA (miR)-218-5p and eukaryotic translation initiation factor 5A-2 (EIF5A2) mRNA was detected using quantitative real-time polymerase chain reaction. Cell viability, migration and invasion were analyzed using cell counting kit-8, colony formation and transwell assay, respectively. The levels of matrix metallopeptidase 9 (MMP-9), E-cadherin, Vimentin, N-cadherin and EIF5A2 protein were detected using western blot. The interaction between miR-218-5p and circ_0003998 or EIF5A2 was confirmed by dual-luciferase reporter assay. In vivo experiments were performed using murine xenograft models.

RESULTS

Circ_0003998 was elevated in HCC tissues, DOX-resistant tissues and cells, and circ_0003998 knockdown promoted DOX-sensitivity in HCC by inhibiting resistant cell viability, migration, invasion and EMT in vitro and enhanced DOX cytotoxicity in vivo. Bioinformatics analysis revealed circ_0003998 inhibited miR-218-5p expression, which was clarified to be a target of circ_0003998, and circ_0003998 knockdown sensitized HCC cell to DOX by sponging miR-218-5p. EIF5A2 was a target of miR-218-5p, and miR-218-5p mitigated DOX resistance in HCC cells through modulating EIF5A2 expression. Additionally, circ_0003998 served as a competing endogenous RNA for miR-218-5p to regulate EIF5A2 expression.

CONCLUSION

Circ_0003998 knockdown sensitized HCC cell to DOX by regulating miR-218-5p/EIF5A2 axis, indicating new markers of poor response to DOX and potential therapeutic strategies for the chemotherapy of HCC.

Eukaryotic translation initiation factor 5A in the pathogenesis of cancers

Cancer is the leading cause of death worldwide. The absence of obvious symptoms and insufficiently sensitive biomarkers in early stages of carcinoma limits early diagnosis. Cancer therapy agents and targeted therapy have been used extensively against tissues or organs of specific cancers. However, the intrinsic and/or acquired resistance to the agents or targeted drugs as well as the serious toxic side effects of the drugs would limit their use. Therefore, identifying biomarkers involved in tumorigenesis and progression represents a challenge for cancer diagnosis and therapeutic strategy development. The eukaryotic translation factor 5A (eIF5A), originally identified as an initiation factor, was later shown to promote translation elongation of iterated proline sequences. There are two eIF5A isoforms (eIF5A1 and eIF5A2). eIF5A2 protein consists of 153 residues, and shares 84% amino acid identity with eIF5A1. However, the biological functions of these two isoforms may be significantly different. Recently, it was demonstrated that eIF5Ais widely involved in the pathogenesis of a number of diseases, including cancers. In particular, eIF5A plays an important role in regulating tumor growth, invasion, metastasis and tumor microenvironment. It was also shown to serve as a potential biomarker and target for the diagnosis and treatment of cancers. The present review briefly discusses the latest findings of eIF5A in the pathogenesis of certain malignant cancers and evolving clinical applications.

Overexpression of microRNA-9 enhances cisplatin sensitivity in hepatocellular carcinoma by regulating EIF5A2-mediated epithelial-mesenchymal transition

We investigated the role of microRNA (miR)-9 in modulating chemoresistance in hepatocellular carcinoma (HCC) cells. MiR-9 was overexpressed or knocked down in HCC cell lines. Cell viability, cell proliferation, the expression of EIF5A2 and the epithelial-mesenchymal transition (EMT)-related proteins were examined. HCC cells overexpressing miR-9 were more sensitive to cisplatin; miR-9 knockdown yielded the opposite result. The in vivo nude mouse HCC xenograft tumors yielded the same results. EIF5A2 was identified as a potential target of miR-9, where miR-9 regulated EIF5A2 expression at mRNA and protein level. EIF5A2 knockdown reversed miR-9 inhibition-mediated cisplatin resistance. Altering miR-9 and EIF5A2 expression changed E-cadherin and vimentin expression. Furthermore, EIF5A2 mediated miR-9 EMT pathway regulation, indicating that miR-9 can enhance cisplatin sensitivity by targeting EIF5A2 and inhibiting the EMT pathway. Targeting miR-9 may be useful for overcoming drug resistance in HCC.

MicroRNA-383 inhibits doxorubicin resistance in hepatocellular carcinoma by targeting eukaryotic translation initiation factor 5A2

Drug resistance occurs commonly in cancers, especially in hepatocellular carcinoma (HCC). Accumulating evidence has demonstrated that microRNAs (miRNAs) play a vital role in tumour chemoresistance. However, little is known about the role of miR-383 in HCC chemoresistance. In the present study, RT-PCR and western blotting were used to identify the expression profile of miR-383 and eukaryotic translation initiation factor 5A2 (EIF5A2). The bioinformatics website Targetscan was used to predict the target genes of miR-383. In vitro and in vivo loss- and gain-of-function studies were performed to reveal the effects and potential mechanism of the miR-383/EIF5A2 axis in chemoresistance of HCC cells. The expression level of miR-383 correlated negatively with doxorubicin (Dox) sensitivity. Overexpression of miR-383 promoted HCC cells to undergo Dox-induced cytotoxicity and apoptosis, whereas miR-383 knockdown had the opposite effects. EIF5A2 was predicted as a target gene of miR-383. EIF5A2 knockdown sensitized HCC cells to Dox. Moreover, miR-383 inhibition-mediated HCC Dox resistance could be reversed by silencing EIF5A2. Finally, we demonstrated that miR-383 inhibition could enhance Dox sensitivity by targeting EIF5A2 in vivo. The results indicated that miR-383 inhibited Dox resistance in HCC cells by targeting EIF5A2. Targeting the miR-383/EIF5A2 axis might help to alleviate the chemoresistance of HCC cells.

The emerging role of microRNAs and long noncoding RNAs in drug resistance of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common malignancy worldwide and the second most lethal human cancer. A portion of patients with advanced HCC can significantly benefit from treatments with sorafenib, adriamycin, 5-fluorouracil and platinum drugs. However, most HCC patients eventually develop drug resistance, resulting in a poor prognosis. The mechanisms involved in HCC drug resistance are complex and inconclusive. Human transcripts without protein-coding potential are known as noncoding RNAs (ncRNAs), including microRNAs (miRNAs), small nucleolar RNAs (snoRNAs), long noncoding RNAs (lncRNAs) and circular RNA (circRNA). Accumulated evidences demonstrate that several deregulated miRNAs and lncRNAs are important regulators in the development of HCC drug resistance which elucidates their potential clinical implications. In this review, we summarized the detailed mechanisms by which miRNAs and lncRNAs affect HCC drug resistance. Multiple tumor-specific miRNAs and lncRNAs may serve as novel therapeutic targets and prognostic biomarkers for HCC.

MicroRNA-9 inhibits gastric cancer cell proliferation and migration by targeting neuropilin-1

Gastric cancer (GC) is a global health problem with poor clinical outcomes. The mechanism of its development and progression remains largely unclear. The present study investigated the role of microRNA-9 (miR-9-5p) in the development and progression of GC. Overexpression of miR-9-5p led to reduced expression of neuropilin-1 (NRP-1) in GC cells. Dual-luciferase reporter assay results indicated that miR-9-5p directly targeted NRP-1. Furthermore, overexpression of miR-9-5p in GC cells increased the expression of mesenchymal markers, N-cadherin and vimentin, and decreased the expression of epithelial markers, E-cadherin and β-catenin. Overexpression of miR-9-5p inhibited GC cell proliferation, migration and invasion, and increased the sensitivity of GC cells to the anti-cancer drug cisplatin. By contrast, the opposite effects were observed in GC cells following downregulation of miR-9-5p. Taken together, the present findings suggested that miR-9-5p suppressed NRP-1 expression and inhibited GC cell proliferation and invasion. In addition, miR-9-5p overexpression attenuated GC cell resistance to anti-cancer drugs, which highlighted the potential of miR-9-5p as a target for the treatment of GC.

Eukaryotic initiation factor 5A2 and human digestive system neoplasms

Eukaryotic initiation factor 5A2 (eIF5A2), as one of the two isoforms in the family, is reported to be a novel oncogenic protein that is involved in multiple aspects of many types of human cancer. Overexpression or gene amplification of EIF5A2 has been demonstrated in many cancers. Accumulated evidence shows that eIF5A2 initiates tumor formation, enhances cancer cell growth, increases cancer cell metastasis, and promotes treatment resistance through multiple means, including inducing epithelial–mesenchymal transition, cytoskeletal rearrangement, angiogenesis, and metabolic reprogramming. Expression of eIF5A2 in cancer correlates with poor survival, advanced disease stage, as well as metastasis, suggesting that eIF5A2 function is crucial for tumor development and maintenance but not for normal tissue homeostasis. All these studies suggest that eIF5A2 is a useful biomarker in the prediction of cancer prognosis and serves as an anticancer molecular target. This review focuses on the expression, subcellular localization, post-translational modifications, and regulatory networks of eIF5A2, as well as its biochemical functions and evolving clinical applications in cancer, especially in human digestive system neoplasms.

miR-9 Enhances the Chemosensitivity of AML Cells to Daunorubicin by Targeting the EIF5A2/MCL-1 Axis

Daunorubicin (Dnr) is at the forefront of acute myeloid leukemia (AML) therapy, but drug resistance poses a major threat to treatment success. MicroRNA (miR)-9 has been shown to have a pivotal role in AML development. However, little is known about the role of miR-9 in Dnr resistance in AML. We explored the potential role of miR-9 in Dnr resistance in AML cells and its mechanism of action. AML cell lines with high half-maximal inhibitory concentration to Dnr in vivo had significantly low miR-9 expression. miR-9 overexpresssion sensitized AML cells to Dnr, inhibited cell proliferation, and enhanced the ability of Dnr to induce apoptosis; miR-9 knockdown had the opposite effects. Mechanistic studies demonstrated that eukaryotic translation initiation factor 5A-2 (EIF5A2) was a putative target of miR-9, which was inversely correlated with the expression and role of miR-9 in AML cells. miR-9 improved the anti-tumor effects of Dnr by inhibiting myeloid cell leukemia-1 (MCL-1) expression, which was dependent on downregulation of EIF5A2 expression. These results suggest that miR-9 has an essential role in Dnr resistance in AML cells through inhibition of the EIF5A2/MCL-1 axis in AML cells. Our data highlight the potential application of miR-9 in chemotherapy for AML patients.

Potential Regulatory Roles of MicroRNAs and Long Noncoding RNAs in Anticancer Therapies

MicroRNAs and long noncoding RNAs have long been investigated due to their roles as diagnostic and prognostic biomarkers of cancers and regulators of tumorigenesis, and the potential regulatory roles of these molecules in anticancer therapies are attracting increasing interest as more in-depth studies are performed. The major clinical therapies for cancer include chemotherapy, immunotherapy, and targeted molecular therapy. MicroRNAs and long noncoding RNAs function through various mechanisms in these approaches, and the mechanisms involve direct targeting of immune checkpoints, cooperation with exosomes in the tumor microenvironment, and alteration of drug resistance through regulation of different signaling pathways. Herein we review the regulatory functions and significance of microRNAs and long noncoding RNAs in three anticancer therapies, especially in targeted molecular therapy, and their mechanisms.