Combination treatment with doxorubicin and microRNA-21 inhibitor synergistically augments anticancer activity through upregulation of tumor suppressing genes

Engineered smart materials for RNA based molecular therapy to treat Glioblastoma

Glioblastoma (GBM) is an aggressive malignancy of the central nervous system (CNS) that remains incurable despite the multitude of improvements in cancer therapeutics. The conventional chemo and radiotherapy post-surgery have only been able to improve the prognosis slightly; however, the development of resistance and/or tumor recurrence is almost inevitable. There is a pressing need for adjuvant molecular therapies that can successfully and efficiently block tumor progression. During the last few decades, non-coding RNAs (ncRNAs) have emerged as key players in regulating various hallmarks of cancer including that of GBM. The levels of many ncRNAs are dysregulated in cancer, and ectopic modulation of their levels by delivering antagonists or overexpression constructs could serve as an attractive option for cancer therapy. The therapeutic potential of several types of ncRNAs, including miRNAs, lncRNAs, and circRNAs, has been validated in both in vitro and in vivo models of GBM. However, the delivery of these RNA-based therapeutics is highly challenging, especially to the tumors of the brain as the blood-brain barrier (BBB) poses as a major obstacle, among others. Also, since RNA is extremely fragile in nature, careful considerations must be met while designing a delivery agent. In this review we have shed light on how ncRNA therapy can overcome the limitations of its predecessor conventional therapy with an emphasis on smart nanomaterials that can aide in the safe and targeted delivery of nucleic acids to treat GBM. Additionally, critical gaps that currently exist for successful transition from viral to non-viral vector delivery systems have been identified. Finally, we have provided a perspective on the future directions, potential pathways, and target areas for achieving rapid clinical translation of, RNA-based macromolecular therapy to advance the effective treatment of GBM and other related diseases.

miR-21-5p prevents doxorubicin-induced cardiomyopathy by downregulating BTG2

Cardiomyocyte apoptosis has been characterized as one of the major mechanisms underlying doxorubicin (DOX)-induced cardiomyopathy. MicroRNA-21-5p (miR-21-5p) was reported to mitigate ischemia-induced cardiomyocyte apoptosis and cardiac injury. However, to our knowledge, the functional role of miR-21-5p in DOX-induced cardiomyopathy is unclear. In this study, we explored the role of miR-21-5p in DOX-induced cardiac injury. The expression level of miR-21-5p was detected by quantitative real-time polymerase chain reaction (qRT-PCR). Dual luciferase reporter assay was used to verify the potential target gene of miR-21-5p. The apoptosis rate of NRCMs was detected by TUNEL staining assay. Western blot analysis was used to detect the protein expression levels of Bax, Bcl-2, Caspase3, cleaved-Caspase3 and BTG2. For animal studies, mice were injected with AAV9-miR-21-5p or AAV9-Empty viruses, and treated with DOX at a dose of 5 mg/kg per week through intraperitoneally administration. After 4 weeks of DOX treatment, mice were subjected to echocardiography to measure the left ventricular ejection fraction (EF) and fractional shortening (FS). Results showed that miR-21-5p was upregulated in both DOX-treated primary cardiomyocytes and mouse heart tissues. Interestingly, enhanced miR-21-5p expression inhibited DOX-induced cardiomyocyte apoptosis and oxidative stress, while decreased miR-21-5p expression promoted cardiomyocyte apoptosis and oxidative stress. Furthermore, cardiac overexpression of miR-21-5p protected against DOX-induced cardiac injury. The mechanistic study indicated that BTG2 was a target gene of miR-21-5p. The anti-apoptotic effect of miR-21-5p could be inhibited by BTG2 overexpression. Conversely, inhibition of BTG2 rescued the pro-apoptotic effect of miR-21-5p inhibitor. Taken together, our study showed that miR-21-5p could prevent DOX-induced cardiomyopathy by downregulating BTG2.

Perphenazine and prochlorperazine decrease glioblastoma U‑87 MG cell migration and invasion: Analysis of the ABCB1 and ABCG2 transporters, E‑cadherin, α‑tubulin and integrins (α3, α5, and β1) levels

Glioblastoma multiforme is the most frequent type of malignant brain tumor, and is one of the most lethal and untreatable human tumors with a very poor survival rate. Therefore, novel and effective strategies of treatment are required. Integrins play a crucial role in the regulation of cellular adhesion and invasion. Integrins and α-tubulin are very important in cell migration, whereas E-cadherin plays a main role in tumor metastasis. Notably, drugs serve a crucial role in glioblastoma treatment; however, they have to penetrate the blood-brain barrier (BBB) to be effective. ABC transporters, including ATP binding cassette subfamily B member 1 (ABCB1) and ATP binding cassette subfamily G member 2 (ABCG2), are localized in the brain endothelial capillaries of the BBB, have a crucial role in the development of multidrug resistance and are modulated by phenothiazine derivatives. The impact of perphenazine and prochlorperazine on the motility of human Uppsala 87 malignant glioma (U87-MG) cells was evaluated using a wound-healing assay, cellular migration and invasion were assessed by Transwell assay, and the protein expression levels of ABCB1, ABCG2, E-cadherin, α-tubulin and integrins were determined by western blotting. The present study explored the effects of perphenazine and prochlorperazine on the levels of ABCB1, ABCG2, E-cadherin, α-tubulin and integrins (α3, α5, and β1), as well as on the migratory and invasive ability of U87-MG cells. The results suggested that perphenazine and prochlorperazine may modulate the expression levels of multidrug resistance proteins (they decreased ABCB1 and increased ABCG2 expression), E-cadherin, α-tubulin and integrins, and could impair the migration and invasion of U-87 MG cells. In conclusion, the decrease in migratory and invasive ability following treatment with phenothiazine derivatives due to the increase in ABCG2 and E-cadherin expression, and decrease in α-tubulin and integrins expression, may suggest that research on perphenazine and prochlorperazine in the treatment of glioblastoma is worth continuing.

Spatial Dissection of Invasive Front from Tumor Mass Enables Discovery of Novel microRNA Drivers of Glioblastoma Invasion

Diffuse invasion is the primary cause of treatment failure of glioblastoma (GBM). Previous studies on GBM invasion have long been forced to use the resected tumor mass cells. Here, a strategy to reliably isolate matching pairs of invasive (GBMINV ) and tumor core (GBMTC ) cells from the brains of 6 highly invasive patient-derived orthotopic models is described. Direct comparison of these GBMINV and GBMTC cells reveals a significantly elevated invasion capacity in GBMINV cells, detects 23/768 miRNAs over-expressed in the GBMINV cells (miRNAINV ) and 22/768 in the GBMTC cells (miRNATC ), respectively. Silencing the top 3 miRNAsINV (miR-126, miR-369-5p, miR-487b) successfully blocks invasion of GBMINV cells in vitro and in mouse brains. Integrated analysis with mRNA expression identifies miRNAINV target genes and discovers KCNA1 as the sole common computational target gene of which 3 inhibitors significantly suppress invasion in vitro. Furthermore, in vivo treatment with 4-aminopyridine (4-AP) effectively eliminates GBM invasion and significantly prolongs animal survival times (P = 0.035). The results highlight the power of spatial dissection of functionally accurate GBMINV and GBMTC cells in identifying novel drivers of GBM invasion and provide strong rationale to support the use of biologically accurate starting materials in understanding cancer invasion and metastasis.

Anticancer roles of let-7f-1-3p in non-small cell lung cancer via direct targeting of integrin β1

Lung cancer is one of the most common types of cancer, with the highest mortality rate worldwide. MicroRNAs play notable roles in the chemotherapeutic effects of anticancer drugs. The present study used reverse transcription-quantitative PCR, western blotting and cell migration and invasion assays to reveal the role of let-7f-1-3p in non-small cell lung cancer (NSCLC) and explore the effect of let-7f-1-3p on doxorubicin (DOX) treatment. It was demonstrated that the levels of let-7f-1-3p in carcinoma tissues were lower compared with those in paracarcinoma tissues. Thus, let-7f-1-3p may act as a suppressor gene. The present study also explored the role of let-7f-1-3p in A549 and NCI-H1975 cells. Results revealed that let-7f-1-3p could inhibit the viability, migration and invasion of NSCLC cells and induce their apoptosis. Integrin β1 acted as a target gene regulated by let-7f-1-3p. This suggested that let-7f-1-3p could enhance DOX-inhibited cell viability, migration and invasion in vitro. Overall, the present study demonstrated that let-7f-1-3p may act as a target for drug design and lung cancer therapy.

Role of microRNAs in glioblastoma

Glioblastoma is the most common and aggressive primary human brain cancer. MicroRNAs (miRNAs) are a set of small endogenous non-coding RNA molecules which play critical roles in different biological processes including cancer. The realization of miRNA regulatory functions in GBM has demonstrated that these molecules play a critical role in its initiation, progression and response to therapy. In this review we discuss the studies related to miRNA discovery and function in glioblastoma. We first summarize the typical miRNAs and their roles in GBM. Then we debate the potential for miRNA-based therapy for glioblastoma, including various delivery strategies. We surmise that future directions identified by these studies will point towards the necessity for therapeutic development and optimization to improve the outcomes for patients with glioblastoma.

Exosomal noncoding RNAs: key players in glioblastoma drug resistance

Glioma, as one of the most severe human malignancies, is defined as the Central Nervous System's (CNS) tumors. Glioblastoma (GBM) in this regard, is the most malignant type of gliomas. There are multiple therapeutic strategies to cure GBM, for which chemotherapy is often the first-line treatment. Still, various cellular processes, such as uncontrolled proliferation, invasion and metastasis, may disturb the treatment efficacy. Drug resistance is another process in this way, which can also cause undesirable effects. Thereupon, identifying the mechanisms, involved in developing drug resistance and the relevant mechanisms can be very helpful in GBM management. The discovery of exosomal non-coding RNAs (ncRNAs), RNA molecules that can be transferred between the cells and different tissues using the exosomes, was a milestone in this regard. It has been revealed that the key exosomal ncRNAs, including circular RNAs, microRNAs, and long ncRNAs, are able to modulate GBM drug resistance through different signaling pathways or by affecting regulatory proteins and their corresponding genes. Nowadays, researchers are trying to overcome the limitations of chemotherapy by targeting these RNA molecules. Accordingly, this review aims to clarify the substantial roles of exosomal ncRNAs in GBM drug resistance and involved mechanisms.

Mechanisms of temozolomide resistance in glioblastoma - a comprehensive review

Glioblastoma (GBM) is the most common primary malignant brain tumor in adults and has an exceedingly low median overall survival of only 15 months. Current standard-of-care for GBM consists of gross total surgical resection followed by radiation with concurrent and adjuvant chemotherapy. Temozolomide (TMZ) is the first-choice chemotherapeutic agent in GBM; however, the development of resistance to TMZ often becomes the limiting factor in effective treatment. While O6-methylguanine-DNA methyltransferase repair activity and uniquely resistant populations of glioma stem cells are the most well-known contributors to TMZ resistance, many other molecular mechanisms have come to light in recent years. Key emerging mechanisms include the involvement of other DNA repair systems, aberrant signaling pathways, autophagy, epigenetic modifications, microRNAs, and extracellular vesicle production. This review aims to provide a comprehensive overview of the clinically relevant molecular mechanisms and their extensive interconnections to better inform efforts to combat TMZ resistance.

Possible Susceptibility Genes for Intervention against Chemotherapy-Induced Cardiotoxicity

Recent therapeutic advances have significantly improved the short- and long-term survival rates in patients with heart disease and cancer. Survival in cancer patients may, however, be accompanied by disadvantages, namely, increased rates of cardiovascular events. Chemotherapy-related cardiac dysfunction is an important side effect of anticancer therapy. While advances in cancer treatment have increased patient survival, treatments are associated with cardiovascular complications, including heart failure (HF), arrhythmias, cardiac ischemia, valve disease, pericarditis, and fibrosis of the pericardium and myocardium. The molecular mechanisms of cardiotoxicity caused by cancer treatment have not yet been elucidated, and they may be both varied and complex. By identifying the functional genetic variations responsible for this toxicity, we may be able to improve our understanding of the potential mechanisms and pathways of treatment, paving the way for the development of new therapies to target these toxicities. Data from studies on genetic defects and pharmacological interventions have suggested that many molecules, primarily those regulating oxidative stress, inflammation, autophagy, apoptosis, and metabolism, contribute to the pathogenesis of cardiotoxicity induced by cancer treatment. Here, we review the progress of genetic research in illuminating the molecular mechanisms of cancer treatment-mediated cardiotoxicity and provide insights for the research and development of new therapies to treat or even prevent cardiotoxicity in patients undergoing cancer treatment. The current evidence is not clear about the role of pharmacogenomic screening of susceptible genes. Further studies need to done in chemotherapy-induced cardiotoxicity.

The Roles of miRNA in Glioblastoma Tumor Cell Communication: Diplomatic and Aggressive Negotiations

Glioblastoma (GBM) consists of a heterogeneous collection of competing cellular clones which communicate with each other and with the tumor microenvironment (TME). MicroRNAs (miRNAs) present various exchange mechanisms: free miRNA, extracellular vesicles (EVs), or gap junctions (GJs). GBM cells transfer miR-4519 and miR-5096 to astrocytes through GJs. Oligodendrocytes located in the invasion front present high levels of miR-219-5p, miR-219-2-3p, and miR-338-3p, all related to their differentiation. There is a reciprocal exchange between GBM cells and endothelial cells (ECs) as miR-5096 promotes angiogenesis after being transferred into ECs, whereas miR-145-5p acts as a tumor suppressor. In glioma stem cells (GSCs), miR-1587 and miR-3620-5p increase the proliferation and miR-1587 inhibits the hormone receptor co-repressor-1 (NCOR1) after EVs transfers. GBM-derived EVs carry miR-21 and miR-451 that are up-taken by microglia and monocytes/macrophages, promoting their proliferation. Macrophages release EVs enriched in miR-21 that are transferred to glioma cells. This bidirectional miR-21 exchange increases STAT3 activity in GBM cells and macrophages, promoting invasion, proliferation, angiogenesis, and resistance to treatment. miR-1238 is upregulated in resistant GBM clones and their EVs, conferring resistance to adjacent cells via the CAV1/EGFR signaling pathway. Decrypting these mechanisms could lead to a better patient stratification and the development of novel target therapies.

Micro RNA Molecules as Modulators of Treatment Resistance, Immune Checkpoints Controllers and Sensitive Biomarkers in Glioblastoma Multiforme

Based on genome sequencing, it is estimated that over 90% of genes stored in human genetic material are transcribed, but only 3% of them contain the information needed for the production of body proteins. This group also includes micro RNAs representing about 1%–3% of the human genome. Recent studies confirmed the hypothesis that targeting molecules called Immune Checkpoint (IC) open new opportunities to take control over glioblastoma multiforme (GBM). Detection of markers that indicate the presence of the cancer occupies a very important place in modern oncology. This function can be performed by both the cancer cells themselves as well as their components and other substances detected in the patients’ bodies. Efforts have been made for many years to find a suitable marker useful in the diagnosis and monitoring of gliomas, including glioblastoma.

Sustained Delivery of Doxorubicin via Acetalated Dextran Scaffold Prevents Glioblastoma Recurrence after Surgical Resection

The primary cause of mortality for glioblastoma (GBM) is local tumor recurrence following standard-of-care therapies, including surgical resection. With most tumors recurring near the site of surgical resection, local delivery of chemotherapy at the time of surgery is a promising strategy. Herein drug-loaded polymer scaffolds with two distinct degradation profiles were fabricated to investigate the effect of local drug delivery rate on GBM recurrence following surgical resection. The novel biopolymer, acetalated dextran (Ace-DEX), was compared with commercially available polyester, poly(l-lactide) (PLA). Steady-state doxorubicin (DXR) release from Ace-DEX scaffolds was found to be faster when compared with scaffolds composed of PLA, in vitro. This increased drug release rate translated to improved therapeutic outcomes in a novel surgical model of orthotopic glioblastoma resection and recurrence. Mice treated with DXR-loaded Ace-DEX scaffolds (Ace-DEX/10DXR) resulted in 57% long-term survival out to study completion at 120 days compared with 20% survival following treatment with DXR-loaded PLA scaffolds (PLA/10DXR). Additionally, all mice treated with PLA/10DXR scaffolds exhibited disease progression by day 38, as defined by a 5-fold growth in tumor bioluminescent signal. In contrast, 57% of mice treated with Ace-DEX/10DXR scaffolds displayed a reduction in tumor burden, with 43% exhibiting complete remission. These results underscore the importance of polymer choice and drug release rate when evaluating local drug delivery strategies to improve prognosis for GBM patients undergoing tumor resection.

MicroRNAs in glioblastoma pathogenesis and therapy: A comprehensive review

Glioblastoma (GBM), also known as grade IV astrocytoma, is the most aggressive primary intracranial tumor of the adult brain. MicroRNAs (miRNAs), a class of small non-coding RNA species, have critical functions across various biological processes. A great deal of progress has been made recently in dissecting miRNA pathways associated with the pathogenesis of GBM. miRNA expression signatures called gene signatures also characterize and contribute to the phenotypic diversity of GBM subclasses through their ability to regulate developmental growth and differentiation. miRNA molecules have been identified as diagnostic and prognostic biomarkers for patient stratification and may also serve as therapeutic targets and agents. This review summarizes: (i) the current understanding of the roles of miRNAs in the pathogenesis of GBM, (ii) the potential use of miRNAs in GBM diagnosis and glioma grading, (iii) further prospects of developing miRNAs as novel biomarkers and therapeutic targets for GBM, and (iv) important practical considerations when considering miRNA therapy for GBM patients.

microRNAs: Emerging players in oral cancers and inflammatory disorders

Association of oral diseases and disorders with altered microRNA profiles is firmly recognized. These evidences support the potential use of microRNAs as therapeutic tools for diagnosis, prognosis, and treatment of various diseases. In this review, we highlight the association of altered microRNA signatures in oral cancers and oral inflammatory diseases. Advances in our ability to detect microRNAs in human sera and saliva further highlight their clinical value as potential biomarkers. We have discussed key mechanisms underlying microRNA dysregulation in pathological conditions. The use of microRNAs in diagnostics and their potential therapeutic value in the treatment of oral diseases are reviewed.

The ascidian natural product eusynstyelamide B is a novel topoisomerase II poison that induces DNA damage and growth arrest in prostate and breast cancer cells

As part of an anti-cancer natural product drug discovery program, we recently identified eusynstyelamide B (EB), which displayed cytotoxicity against MDA-MB-231 breast cancer cells (IC₅₀ = 5 μM) and induced apoptosis. Here, we investigated the mechanism of action of EB in cancer cell lines of the prostate (LNCaP) and breast (MDA-MB-231). EB inhibited cell growth (IC₅₀ = 5 μM) and induced a G2 cell cycle arrest, as shown by a significant increase in the G2/M cell population in the absence of elevated levels of the mitotic marker phospho-histone H3. In contrast to MDA-MB-231 cells, EB did not induce cell death in LNCaP cells when treated for up to 10 days. Transcript profiling and Ingenuity Pathway Analysis suggested that EB activated DNA damage pathways in LNCaP cells. Consistent with this, CHK2 phosphorylation was increased, p21^CIP1/WAF1 was up-regulated and CDC2 expression strongly reduced by EB. Importantly, EB caused DNA double-strand breaks, yet did not directly interact with DNA. Analysis of topoisomerase II-mediated decatenation discovered that EB is a novel topoisomerase II poison.

MicroRNAs in glioblastoma multiforme pathogenesis and therapeutics

Glioblastoma multiforme (GBM) is the most common and lethal cancer of the adult brain, remaining incurable with a median survival time of only 15 months. In an effort to identify new targets for GBM diagnostics and therapeutics, recent studies have focused on molecular phenotyping of GBM subtypes. This has resulted in mounting interest in microRNAs (miRNAs) due to their regulatory capacities in both normal development and in pathological conditions such as cancer. miRNAs have a wide range of targets, allowing them to modulate many pathways critical to cancer progression, including proliferation, cell death, metastasis, angiogenesis, and drug resistance. This review explores our current understanding of miRNAs that are differentially modulated and pathologically involved in GBM as well as the current state of miRNA-based therapeutics. As the role of miRNAs in GBM becomes more well understood and novel delivery methods are developed and optimized, miRNA-based therapies could provide a critical step forward in cancer treatment.

Current state of phenolic and terpenoidal dietary factors and natural products as non-coding RNA/microRNA modulators for improved cancer therapy and prevention

The epigenetic regulation of cancer cells by small non-coding RNA molecules, the microRNAs (miRNAs), has raised particular interest in the field of oncology. These miRNAs play crucial roles concerning pathogenic properties of cancer cells and the sensitivity of cancer cells towards anticancer drugs. Certain miRNAs are responsible for an enhanced activity of drugs, while others lead to the formation of tumor resistance. In addition, miRNAs regulate survival and proliferation of cancer cells, in particular of cancer stem-like cells (CSCs), that are especially drug-resistant and, thus, cause tumor relapse in many cases. Various small molecule compounds were discovered that target miRNAs that are known to modulate tumor aggressiveness and drug resistance. This review comprises the effects of naturally occurring small molecules (phenolic compounds and terpenoids) on miRNAs involved in cancer diseases.

Direct Comparison of Metastasis-Related miRNAs Expression Levels in Circulating Tumor Cells, Corresponding Plasma, and Primary Tumors of Breast Cancer Patients

BACKGROUND

Circulating tumor cells (CTCs) and microRNAs (miRNAs) are important in liquid biopsies in which peripheral blood is used to characterize the evolution of solid tumors. We evaluated the expression levels of miR-21, miR-146a, miR-200c, and miR-210 in CTCs of breast cancer patients with verified metastasis and compared their expression levels in corresponding plasma and primary tumors.

METHODS

Expression levels of the miRNAs were quantified by quantitative reverse transcription PCR (RT-qPCR) in (a) 89 primary breast tumors and 30 noncancerous breast tissues and (b) CTCs and corresponding plasma of 55 patients with metastatic breast cancer and 20 healthy donors. For 30 of these patients, CTCs, corresponding plasma, and primary tumor tissues were available.

RESULTS

In formalin-fixed, paraffin-embedded tissues, these miRNAs were differentially expressed between primary breast tumors and noncancerous breast tissues. miR-21 (P < 0.001) and miR-146a (P = 0.001) were overexpressed, whereas miR-200c (P = 0.004) and miR-210 (P = 0.002) were underexpressed. In multivariate analysis, miR-146a overexpression was significantly [hazard ratio 2.969 (1.231–7.157), P = 0.015] associated with progression-free survival. In peripheral blood, all miRNAs studied were overexpressed in both CTC and corresponding plasma. There was a significant association between miR-21 expression levels in CTCs and plasma for 36 of 55 samples (P = 0.008). In plasma, ROC curve analysis revealed that miR-21, miR-146a, and miR-210 could discriminate patients from healthy individuals.

CONCLUSIONS

Metastasis-related miRNAs are overexpressed in CTCs and corresponding plasma; miR-21 expression levels highly correlate in CTCs and plasma; and miR-21, miR-146a, and miR-210 are valuable plasma biomarkers for discriminating patients from healthy individuals.

Failure of a patient-derived xenograft for brain tumor model prepared by implantation of tissue fragments

Background

With the continuing development of new anti-cancer drugs comes a need for preclinical experimental models capable of predicting the clinical activity of these novel agents in cancer patients. However existing models have a limited ability to recapitulate the clinical characteristics and associated drug sensitivity of tumors. Among the more promising approaches for improving preclinical models is direct implantation of patient-derived tumor tissue into immunocompromised mice, such as athymic nude or non-obese diabetic/severe combined immunodeficient (NOD/SCID) mice. In the current study, we attempted to develop patient-derived xenograft (PDX) models using tissue fragments from surgical samples of brain tumors.

Methods

In this approach, tiny tissue fragments of tumors were biopsied from eight brain tumor patients—seven glioblastoma patients and one primitive neuroectodermal tumor patient. Two administration methods—a cut-down syringe and a pipette—were used to implant tissue fragments from each patient into the brains of athymic nude mice.

Results

In contrast to previous reports, and contrary to our expectations, we found that none of these fragments from brain tumor biopsies resulted in the successful establishment of xenograft tumors.

Conclusions

These results suggest that fragments of surgical specimens from brain tumor patients are unsuitable for implementation of brain tumor PDX models, and instead recommend other in vivo testing platforms for brain tumors, such as cell-based brain tumor models.

Electronic supplementary material

The online version of this article (doi:10.1186/s12935-016-0319-0) contains supplementary material, which is available to authorized users.

Targeting oncomiRNAs and mimicking tumor suppressor miRNAs: Νew trends in the development of miRNA therapeutic strategies in oncology (Review)

MicroRNA (miRNA or miR) therapeutics in cancer are based on targeting or mimicking miRNAs involved in cancer onset, progression, angiogenesis, epithelial-mesenchymal transition and metastasis. Several studies conclusively have demonstrated that miRNAs are deeply involved in tumor onset and progression, either behaving as tumor-promoting miRNAs (oncomiRNAs and metastamiRNAs) or as tumor suppressor miRNAs. This review focuses on the most promising examples potentially leading to the development of anticancer, miRNA-based therapeutic protocols. The inhibition of miRNA activity can be readily achieved by the use of miRNA inhibitors and oligomers, including RNA, DNA and DNA analogues (miRNA antisense therapy), small molecule inhibitors, miRNA sponges or through miRNA masking. On the contrary, the enhancement of miRNA function (miRNA replacement therapy) can be achieved by the use of modified miRNA mimetics, such as plasmid or lentiviral vectors carrying miRNA sequences. Combination strategies have been recently developed based on the observation that i) the combined administration of different antagomiR molecules induces greater antitumor effects and ii) some anti-miR molecules can sensitize drug-resistant tumor cell lines to therapeutic drugs. In this review, we discuss two additional issues: i) the combination of miRNA replacement therapy with drug administration and ii) the combination of antagomiR and miRNA replacement therapy. One of the solid results emerging from different independent studies is that miRNA replacement therapy can enhance the antitumor effects of the antitumor drugs. The second important conclusion of the reviewed studies is that the combination of anti-miRNA and miRNA replacement strategies may lead to excellent results, in terms of antitumor effects.

A Targeted DNAzyme-Nanocomposite Probe Equipped with Built-in Zn(2+) Arsenal for Combined Treatment of Gene Regulation and Drug Delivery

As catalytic nucleic acids, DNAzymes have been extensively used in the design of sensing platforms. However, their potentials as intelligent drug carriers for responsive drug release in gene therapy and chemotherapy were rarely explored. Herein, we report a dual-functional probe composed of gold nanoparticles (GNPs), catalytic Zn(2+)-dependent DNAzyme, anticancer drug doxorubicin (Dox), targeted AS1411 aptamer and acid-decomposable ZnO quantum dots (ZnO QDs) to achieve intracellular gene regulation and drug delivery in a controlled manner. By means of aptamer-guided targeting and receptor-mediated endocytosis, the probes were specifically internalized into the HeLa cells and trapped in the acidic endo-/lysosomes, where the ZnO QDs as the built-in Zn(2+) arsenal were promptly dissolved to offer Zn(2+), leading to the activation of DNAzyme to cleave the substrate strands, and subsequent drug release. Meanwhile, as designed, one part of the cleaved substrate, hybridized with the overexpressed miR-21 in the target cells, thereby declining its intracellular level. Taken together, the down-regulation of miR-21 has a synergistic effect with Dox to efficiently eradicate the cancer cells. Thus, the favorable biocompatibility, cancer cell specificity and combined treatment make the probe promising for therapy of multidrug-resistant cancer and in vivo application.

MiR-21 Protected Cardiomyocytes against Doxorubicin-Induced Apoptosis by Targeting BTG2

Doxorubicin (DOX) is an anthracycline drug with a wide spectrum of antineoplastic activities. However, it causes cardiac cytotoxicity, and this limits its clinical applications. MicroRNA-21 (miR-21) plays a vital role in regulating cell proliferation and apoptosis. While miR-21 is preferentially expressed in adult cardiomyocytes and involved in cardiac development and heart disease, little is known regarding its biological functions in responding to DOX-induced cardiac cytotoxicity. In this study, the effects of DOX on mouse cardiac function and the expression of miR-21 were examined in both mouse heart tissues and rat H9C2 cardiomyocytes. The results showed that the cardiac functions were more aggravated in chronic DOX injury mice compared with acute DOX-injury mice; DOX treatment significantly increased miR-21 expression in both mouse heart tissue and H9C2 cells. Over-expression of miR-21 attenuated DOX-induced apoptosis in cardiamyocytes whereas knocking down its expression increased DOX-induced apoptosis. These gain- and loss- of function experiments showed that B cell translocation gene 2 (BTG2) was a target of miR-21. The expression of BTG2 was significantly decreased both in myocardium and H9C2 cells treated with DOX. The present study has revealed that miR-21 protects mouse myocardium and H9C2 cells against DOX-induced cardiotoxicity probably by targeting BTG2.