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As a naturally occurring class of gene regulators, microRNAs (miRNAs) have attracted much attention as promising targets for therapeutic development. However, RNAs including miRNAs have long been considered undruggable, and most efforts have been devoted to using synthetic oligonucleotides to regulate miRNAs. Encouragingly, recent findings have revealed that miRNAs can also be drugged with small molecules that directly target miRNAs. In this review paper, we give a summary of recently emerged small-molecule inhibitors (SMIs) and small-molecule degraders (SMDs) for miRNAs. SMIs are small molecules that directly bind to miRNAs to inhibit their biogenesis, and SMDs are bifunctional small molecules that upon binding to miRNAs induce miRNA degradation. Strategies for discovering SMIs and developing SMDs were summarized. Applications of SMIs and SMDs in miRNA inhibition and cancer therapy were also introduced. Overall, SMIs and SMDs introduced here have high potency and specificity in miRNA inhibition. We envision that these small molecules will pave the way for developing novel therapeutics toward miRNAs that were previously considered undruggable.

Proteolysis-targeting chimeras (PROTACs) are heterobifunctional chemicals that degrade proteins at the post-translational level, which represent an emerging therapeutic modality to fight cancer and other diseases. Although several PROTACs have now entered clinical trials, potential off-tissue side effects have resulted from nonspecific accumulation at non-cancerous sites after systemic administration, and this remains a major challenge. To this end, in the past 3 years, activatable PROTACs whose activity can only be launched on demand have gained tremendous momentum. In this review, we provide an overview of these new smart activatable PROTACs, which exert protein degradation action only in response to internal or external stimuli. We categorize these activatable PROTACs according to their activation mechanism contributed by different stimuli, including reduction-activatable, hypoxia-activatable, and enzyme-activatable PROTACs and photo-caged or photo-switchable PROTACs. The use of stimuli-responsive chemical blocks in these activatable PROTACs allows local activation of the antitumor effects while reducing the incidence of off-site side effects for precision cancer therapy. The design principle and category of smart PROTACs are introduced along with an overview of their therapeutic prospects and challenges.

Introduction and Objectives Hepatocellular carcinoma (HCC) is one of the most common and fatal cancers in the world. This study aims to investigate the mechanism by which miR-221-3p regulates HCC cell proliferation, migration and invasion, so as to provide a new idea for targeted therapy towards HCC. Materials and Methods Expression quantification data including mature miRNA and mRNA were accessed from TCGA-LIHC dataset, and matched clinical information was obtained as well, which helped identify the miRNA of interest. Thereafter, effect of the miRNA on HCC cell biological functions was assessed with a series of in vitro experiments, such as qRT-PCR, MTT, wound healing assay and Transwell. To gain more insight into the mechanism of the miRNA in HCC, bioinformatics method was conducted to predict downstream target gene. The potential targeting relationship between the miRNA and the predicted mRNA was validated by dual-luciferase reporter assay. Western blot was performed to test protein expression. Results MiR-221-3p identified by differential expression analysis was found to be significantly elevated in HCC tissue. Overexpressing miR-221-3p noticeably enhanced HCC cell proliferative, migratory and invasive abilities. Leukemia inhibitory factor receptor (LIFR), confirmed as a downstream target of miR-221-3p in HCC by dual-luciferase reporter assay, was poorly expressed in HCC tissue and cells. Additionally, the expression of LIFR was decreased following the targeted binding between miR-221-3p and LIFR 3’-UTR, while increasing the expression of LIFR attenuated the promoting effect of miR-221-3p on HCC cells. Conclusion MiR-221-3p is an oncogene in HCC cells, and it exerts its role in HCC cell viability and motility via targeting LIFR.

MicroRNAs (miRNAs) are small non-coding RNAs that have been identified as key endogenous biomolecules that are able to regulate gene expression at the post-transcriptional level. The abnormal expression or function of miRNAs has been demonstrated to be closely related to the occurrence or development of various human diseases, including cancers. Regulation of these abnormal miRNAs thus holds great promise for therapeutic treatments. In this review, we summarize exogenous molecules that are able to regulate endogenous miRNAs, including small molecule regulators of miRNAs and synthetic oligonucleotides. Strategies for screening small molecule regulators of miRNAs and recently reported small molecules are introduced and summarized. Synthetic oligonucleotides including antisense miRNA oligonucleotides and miRNA mimics, as well as delivery systems for these synthetic oligonucleotides to enter cells, that regulate endogenous miRNAs are also summarized. In addition, we discuss recent applications of these small molecules and synthetic oligonucleotides in therapeutic treatments. Overall, this review aims to provide a brief synopsis of recent achievements of using both small molecule regulators and synthetic oligonucleotides to regulate endogenous miRNAs and achieve therapeutic outcomes. We envision that these regulators of endogenous miRNAs will ultimately contribute to the development of new therapies in the future.

As demonstrated in previous studies, the phosphorylated form of 4E‑binding protein 1 (p‑4E‑BP1) may be a suitable tumor biomarker. The aim of the current study was to examine the expression status of p‑4E‑BP1 in colorectal cancer (CRC), in order to determine its clinical significance. The present study enrolled 89 patients with CRC that had undergone radical resection. Paired tumor and adjacent normal tissues were evaluated using immunohistochemistry to detect the protein expression of p‑4E‑BP1 and phosphatase and tensin homolog (PTEN). The study identified 53 cases (59.6%) that exhibited moderate or high expression of p‑4E‑BP1 in tumor tissues, compared with little or no expression in the adjacent normal tissues. Conversely, PTEN protein expression was markedly lower in CRC compared with adjacent normal tissues. p‑4E‑BP1 protein upregulation tissues samples was consistent with PTEN downregulation in CRC samples. p‑4E‑BP1 overexpression was predominant in patients with metastasis to the regional lymph nodes. Moderate/high expression of p‑4E‑BP1 protein was significantly associated with adverse overall survival (OS) in patients. Statistical analysis using the Cox proportional hazards model, indicated that p‑4E‑BP1 expression was an independent factor suitable for predicting OS in CRC patients, which was independent of lymph node metastasis. In conclusion, p‑4E‑BP1 protein expression appears to be upregulated in CRC, suggesting that it may be a suitable biomarker for predicting CRC prognosis.

MicroRNAs (miRNAs) are small, non-coding RNAs that post-transcriptionally regulate gene expression. Aberrant miRNA expression or function have close links with various human diseases. Therefore, therapeutic treatments with disease-associated miRNAs as targets are emerging. However, the intracellular miRNA networks are extremely complicated and poorly understood, which thus hinder the development of miRNA-targeted therapeutics. Small molecules that are able to regulate endogenous miRNAs hold great potential in both elucidation of miRNA networks and treatment of miRNA-related diseases. Herein, we summarize current strategies for discovery of small molecule modifiers of miRNAs, and we highlight aspects of miRNA cellular biology elucidated by using these small molecules and miRNA-targeted therapeutics realized by these small molecules. We envision that this area will expand dramatically in the near future and will ultimately contribute to a better understanding of miRNA-involved cellular processes and development of therapeutic agents for miRNA-associated diseases.

The zinc finger protein Snail1 is an important factor in the regulation of the epithelial‑mesenchymal transition (EMT) of hepatocellular carcinoma (HCC) cells. The present study demonstrated that the expression of Snail1 in HCC tissues was significantly higher compared with its expression in tissues adjacent to primary sites, as determined via western blotting. Furthermore, the results of a dual luciferase assay revealed that hsa‑microRNA(miR)199a‑5p negatively regulated the protein expression of Snail1 by binding to its 3' untranslated region. However, in a comparative analysis of primary HCC and its metastatic tissues using reverse transcription‑quantitative polymerase chain reaction and western blotting, it was demonstrated that the expression of hsa‑miR199a‑5p and Snail1 in HCC metastatic tissues were significantly higher compared with primary lesions and an association between them identified that hsa‑miR199a‑5p lost its ability to negatively regulate Snail1. This result is contradictive to the fact that hsa‑miR199a‑5p inhibits the expression of the Snail1 protein. The present study hypothesized that the aberrant expression of long non‑coding RNA was the cause of hsa‑miR199a‑5p inactivation based on loss of function rather than a reduction in content. The data collected in the present study confirmed the hypothesis that AB209371 binds to hsa‑miR199a‑5p and weakened the inhibitory effect of hsa‑miR199a‑5p on Snail1 expression. In addition, an in vitro EMT model was established in the present study by inducing HCC cells with TGF‑β1. The results revealed that AB209371 silencing effectively reversed the hsa‑miR199a‑5p mediated inhibition of EMT by negatively regulating Snail1 protein expression. Therefore, AB209371 silencing in combination with hsa‑miR199a‑5p expression may serve as an effective means to inhibit EMT in HCC cells. The present study also revealed that hsa‑miR199a‑5p/Snail1 exhibits a dominant regulatory effect in the EMT of HCC cells via a Snail1 recovery experiment. In conclusion, to the best of our knowledge, the present study confirmed for the first time that the high expression of AB209371 is favorable for the EMT in HCC cells and may be a direct cause of hsa‑miR199a‑5p inactivation (an HCC metastasis suppressor). Additionally, AB209371 silencing combined with hsa‑miR199a‑5p overexpression may be an effective means to inhibit the metastasis of HCC and the EMT of HCC cells.

Nucleic acids, including DNA, microRNA (miRNA), small interfering RNA (siRNA), and antisense oligonucleotide (ASO), are powerful gene regulators, which have been demonstrated as promising drug candidates for therapeutic treatments. Nevertheless, poor cellular membrane permeability and serum stability have greatly hindered the applications of nucleic acids in biomedicine. To address these issues, associate carriers that can encapsulate and protect nucleic acids are urgently required. Mesoporous silica nanoparticles (MSNs or MSNPs), which are nanomaterials with excellent biocompatibility, large surface area for functionalization, and tunable pore size for encapsulating different cargos, are emerging as novel and ideal biomaterials for different biomedical applications. In this review paper, we focus on the applications of MSNs in nucleic acid delivery and nucleic acid-guided therapeutic treatments. General strategies for the preparation of nucleic acid-MSN complexes will be firstly introduced, followed by a summary of recent applications of MSNs in nucleic acid delivery and nucleic acid-guided therapeutics.

In this study, we aimed to study the role of growth factor receptor-bound protein 2 (Grb2) in palmitic acid-induced steatosis and other "fatty liver" symptoms in vitro. HepG2 cells, with or without stably suppressed Grb2 expression, were incubated with palmitic acid for 24 h to induce typical clinical "fatty liver" features, including steatosis, impaired glucose metabolism, oxidative stress, and apoptosis. MTT and Oil Red O assays were applied to test cell viability and fat deposition, respectively. Glucose uptake assay was used to evaluate the glucose utilization of cells. Quantitative polymerase chain reaction and Western blot were used to measure expressional changes of key markers of insulin signaling, lipid/glucose metabolism, oxidative stress, and apoptosis. After 24-h palmitic acid induction, increased fat accumulation, reduced glucose uptake, impaired insulin signaling, enhanced oxidative stress, and increased apoptosis were observed in HepG2 cells. Suppression of Grb2 in HepG2 significantly reduced fat accumulation, improved glucose metabolism, ameliorated oxidative stress, and restored the activity of insulin receptor substrate-1/Akt and MEK/ERK pathways. In addition, Grb2 deficiency attenuated hepatic apoptosis shown by reduced activation of caspase-3 and fluorescent staining. Modulation of Bcl-2 and Bak1 also contributed to reduced apoptosis. In conclusion, suppression of Grb2 expression in HepG2 cells improved hepatic steatosis, glucose metabolism, oxidative stress, and apoptosis induced by palmitic acid incubation partly though modulating the insulin signaling pathway.

Hepatocellular carcinoma is one of the most common and lethal cancers worldwide, especially in developing countries. In the present study, we found that the expression of a microRNA, miR-590-5P, was down-regulated and S100A10 was up-regulated in six hepatocellular carcinoma cell lines. The reporter gene assay showed that overexpression of miR-590-5P effectively reduced the activity of luciferase expressed by a vector bearing the 3' untranslated region of S100A10 mRNA. Ectopic miR-590-5P overexpression mediated by lentiviral infection decreased expression of S100A10. Infection of Lv-miR-590-5P inhibited cell growth and induced cell cycle G1 arrest in HepG2 cells. In addition, miR-590-5P expression suppressed the expression of Wnt5a, cMyc and cyclin D1, and increased the phosphorylation of β-catenin and expression of Caspase 3, which may contribute to the inhibitory effect of miR-590-5P on cell growth. Taken together, our data suggest that down-regulation of miR-590-5P is involved in hepatocellular carcinoma and the restoration of miR-590-5P can impair the growth of cancer cells, suggesting that miR-590-5P may be a potential target molecule for the therapy of hepatocellular carcinoma.

Long non-coding RNAs (lncRNAs) have been proven to serve a critical role in cancer development and progression. The aim of this study was to elucidate clinical significance of lncRNA MALAT1 expression in breast cancer (BC). A total of 78 BC patients treated with radical resection were enrolled in this study. Quantitative reverse transcription-polymerase chain reaction was used to detect MALAT1 expression in tissues and serum samples. The receiver operating characteristics (ROC) curve was constructed to describe diagnostic specificity and sensitivity. Lentivirus-mediated RNA interference was used to knockdown MALAT1 in the MDA-MB-231 cell line, and then cell proliferation and invasion were explored. Results showed that MALAT1 expression was significantly up-regulated in 85.9% (67/78) of cancerous tissues compared with normal counterparts (P0.01). Further, an elevated MALAT1 expression in BC tissue was significantly associated with lymph metastasis (P=0.037) and adverse 5-year disease-free survival (mean 48.5 months vs 62.7 months, P=0.012). Suppression of lncRNA MALAT1 significantly inhibited BC cells proliferation, migration and invasion, induced apoptosis and cell cycle G1 arrest. In addition, serum MALAT1 levels in BC patients were much higher than levels in patients with benign breast disease (P0.001), its diagnostic efficacy was satisfactory, area under the curve (AUC) was 0.833. In conclusion, MALAT1 upregulation plays an important rolein BC development, and serum MALAT1 level may be a potential tumor marker for BC diagnosis.

The aim of the present study was to evaluate the effects of S100A10 silencing on the inflammatory response in human chondrocytes (HCs).The inflammation induced by lipopolysaccharide (LPS) was investigated in HCs in which the S100A10 was blocked with a lentiviral shRNA vector. A lentiviral shRNA vector targeting S100A10 was constructed and packaged to effectively block S100A10 expression in HCs. HCs were infected with the lentivirus. S100A10 expression levels in HCs were detected by western blot analysis. Enzyme-linked immunosorbent assay (ELISA) was employed to evaluate the change of cytokine secretion levels. The effects of S100A10 silencing on the activation of mitogen-activated protein kinases (MAPKs) and NF-κB signaling pathway were also determined by western blot analysis. In addition, fluo-3-AM was used to demonstrate the change in calcium mobilization. Lentivirus effectively infected the HCs and inhibited the expression of S100A10. HCs with downregulated S100A10 showed significantly decreased production of inflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-10. S100A10 silencing markedly suppressed the activation of MAPKs induced by LPS. Furthermore, the calcium concentration increase in HCs stimulated by LPS was also inhibited by S100A10 knockdown. Our investigation demonstrated that S100A10 might be considered as a potential target for anti-inflammatory treatment.

Bax-interacting factor-1 (Bif-1) interacts with Beclin1 [the mammalian ortholog of yeast autophagy-related gene 6 (Atg6)] and affects the formation of autophagosomes during autophagy. The aim of this study was to explore Bif-1 expression and its prognostic significance in comparison with various clinicopathological predictors of survival. Bif-1 protein expression was determined by immunohistochemistry in 206 hepatocellular carcinomas. Cytoplasmic immunoreactivity was scored semi-quantitatively. The results were analyzed in correlation with various clinicopathological characteristics, including patient survival. The Chi-square test and Kaplan-Meier survival analysis were applied. The expression of Bif-1 was significantly higher in the hepatocellular cancers than in the adjacent matched non-tumor tissues (51.5 vs. 33.0%, P