Restoring microRNA-34a overcomes acquired drug resistance and disease progression in human breast cancer cell lines via suppressing the ABCC1 gene

PURPOSE

Breast cancer is one of the leading types of cancer diagnosed in women. Despite the improvements in chemotherapeutic cure strategies, drug resistance is still an obstacle leading to disease aggressiveness. The small non-coding RNA molecules, miRNAs, have been implicated recently to be involved as regulators of gene expression through the silencing of mRNA targets that contributed to several cellular processes related to cancer metastasis. Hence, the present study aimed to investigate the beneficial role and mechanism of miRNA-34a-based gene therapy as a novel approach for conquering drug resistance mediated by ATP-binding cassette (ABC) transporters in breast cancer cells, besides exploring the associated invasive behaviors.

MATERIAL AND METHODS

Bioinformatics tools were used to predict miRNA ABC transporter targets by tracking the ABC transporter pathway. After the establishment of drug-resistant breast cancer MCF-7 and MDA-MB-231 sublines, cells were transfected with the mimic or inhibitor of miRNA-34a-5p. The quantitative expression of genes involved in drug resistance was performed by QRT-PCR, and the exact ABC transporter target specification interaction was confirmed by dual-luciferase reporter assay. Furthermore, flow cytometric analysis was utilized to determine the ability of miRNA-34a-treated cells against doxorubicin uptake and accumulation in cell cycle phases. The spreading capability was examined by colony formation, migration, and wound healing assays. The apoptotic activity was estimated as well.

RESULTS

Our findings firstly discovered the mechanism of miRNA-34a-5p restoration as an anti-drug-resistant molecule that highly significantly attenuates the expression of ABCC1 via the direct targeting of its 3'- untranslated regions in resistant breast cancer cell lines, with a significant increase of doxorubicin influx by MDA-MB-231/Dox-resistant cells. Additionally, the current data validated a significant reduction of metastatic potentials upon miRNA-34a-5p upregulation in both types of breast cancer-resistant cells.

CONCLUSION

The ectopic expression of miRNA-34a ameliorates the acquired drug resistance and the migration properties that may eventually lead to improved clinical strategies and outcomes for breast cancer patients. Additionally, miRNA-34a could be monitored as a diagnostic/prognostic biomarker for resistant conditions.

Significance of MiRNA-34a and MiRNA-192 as a risk factor for nonalcoholic fatty liver disease

BACKGROUND AND AIMS

NAFLD is one of the fast-growing health problems that affects up to 25% of people worldwide. Numerous miRNAs have been clarified as important regulators of liver pathophysiology, including NAFLD. Thus, we investigated the expression of the MiRNA-34a and MiRNA-192 as diagnostic markers for NAFLD.

PATIENTS AND METHODS

Blood samples were collected from NAFLD cases and healthy controls. The expression profile of both studied miRNAs was detected via real-time PCR analysis.

RESULTS

The present study showed that both studied miRNAs were upregulated in NAFLD patients compared to controls. Interestingly, miRNA-34a and MiRNA-192 are upregulated in NAFLD patients with early fibrosis compared to controls [with a fold change of 4.02 ± 11.49 (P = 0.05) and 18.43 ± 47.8 (P = 0.017), respectively]. However, miRNA-34a is downregulated in NAFLD patients with advanced fibrosis compared to controls, with fold expression of 0.65 ± 1.17 (P = 0.831). The area under the receiver operating characteristics (AUROC) for miRNA-34a and miRNA-192 were 0.790 and 0.643, respectively; furthermore, the sensitivities and specificities were 76.7%, 100% for miRNA-34a and 63.3%, and 93.3% for miRNA-192 (P < 0.05). Additionally, MiRNA34a was positively correlated with hypertension and fasting blood sugar, and it also was negatively correlated with hemoglobin level and total leucocyte count (P < 0.05).

CONCLUSION

The results obtained indicated that both studied miRNAs could potentially be used as diagnostic biomarkers for the early stage of liver fibrosis in NAFLD cases. Also, miRNA-34a was positively correlated with metabolic disorders associated with NAFLD such as hypertension and diabetes. However, their expression showed no association with advanced fibrosis. Thus, larger cohorts are necessitated to certify the utility of serum MiRNA-34a and MiRNA-192 in monitoring the deterioration of NAFLD.

A combined experimental and computational study on peptide nucleic acid (PNA) analogues of tumor suppressive miRNA-34a

MicroRNAs are a ubiquitous class of non-coding RNAs able to regulate gene expression in diverse biological processes. Widespread miRNAs deregulation was reported in numerous diseases including cancer, with several miRNAs playing oncogenic and/or tumor suppressive role by targeting multiple mRNAs simultaneously. Based on these findings, miRNAs have emerged as promising therapeutic tools for cancer treatment. Herein, for the first time, peptide nucleic acids (PNAs) were studied to develop a new class of molecules able to target 3'UTR on MYCN mRNA without a fully complementary base pairing sequence (as miRNAs). For our proof of concept study we have selected as a model the miRNA-34a, which acts as a tumor suppressor in a number of cancers including neuroblastoma. In particular, miRNA-34a is a direct regulator of MYCN oncogene, whose overexpression is a prominent biomarker for the highly aggressive neuroblastoma phenotype. The design and synthesis of three PNA-based oligomers of different length was described, and their interaction with two binding sites on the target MYCN mRNA was investigated by molecular dynamics simulation, and spectroscopic techniques (CD, UV). Intake assay and confocal microscopy of PNA sequences were also carried out in vitro on neuroblastoma Kelly cells. Despite the presence of multiple mismatches, the PNA/RNA hetero duplexes retain very interesting features in terms of stability, affinity as well as of cellular uptake.

miRNA-34a reduces neointima formation through inhibiting smooth muscle cell proliferation and migration

AIMS

We have recently reported that microRNA-34a (miR-34a) regulates vascular smooth muscle cell (VSMC) differentiation from stem cells in vitro and in vivo. However, little is known about the functional involvements of miR-34a in VSMC functions and vessel injury-induced neointima formation. In the current study, we aimed to establish the causal role of miR-34a and its target genes in VSMC proliferation, migration and neointima lesion formation.

METHODS AND RESULTS

Various pathological stimuli regulate miR-34a expression in VSMCs through a transcriptional mechanism, and the P53 binding site is required for miR-34a gene regulation by these stimuli. miR-34a over-expression in serum-starved VSMCs significantly inhibited VSMC proliferation and migration, while knockdown of miR-34a dramatically promoted VSMC proliferation and migration, respectively. Notch homolog 1 (Notch1), a well-reported regulator in VSMC functions and arterial remodeling, was predicted as one of the top targets of miR-34a by using several computational miRNA target prediction tools, and was negatively regulated by miR-34a in VSMCs. Luciferase assay showed miR-34a substantially repressed wild type Notch1-3'-UTR-luciferase activity in VSMCs, but not mutant Notch1-3'-UTR-luciferease reporter, confirming the Notch1 is the functional target of miR-34a in VSMCs. Data from co-transfection experiments also revealed that miR-34a inhibited VSMC proliferation and migration through modulating Notch gene expression levels. Importantly, the expression level of miR-34a was significantly down-regulated in injured arteries, and miR-34a perivascular over-expression significantly reduced Notch1 expression levels, decreased VSMC proliferation, and inhibited neointima formation in wire-injured femoral arteries.

CONCLUSION

Our data have demonstrated that miR-34a is an important regulator in VSMC functions and neointima hyperplasia, suggesting its potential therapeutic application for vascular diseases.