Upregulation of microRNA-492 induced by epigenetic drug treatment inhibits the malignant phenotype of clear cell renal cell carcinoma in vitro

Current status and future perspectives in dysregulated miR-492

MicroRNAs (miRNAs) are a class of single-stranded small non-coding RNAs with a length of 21-23 nucleotides. One such miRNA, miR-492, is located in the KRT19 pseudogene 2 (KRT19P2) of chromosome 12q22 and can also be generated from the processing of the KRT19 transcript at chromosome 17q21. Aberrant expression of miR-492 has been observed in cancers of various physiological systems. miR-492 has been shown to target at least 11 protein-coding genes, which are involved in the regulation of cellular behaviors such as growth, cell cycle, proliferation, epithelial- mesenchymal transition (EMT), invasion and migration. The expression of miR-492 can be regulated by both endogenous and exogenous factors. Furthermore, miR-492 is involved in the regulation of several signaling pathways including the PI3K/AKT signaling pathway, WNT/β-catenin signaling pathway, and MAPK signaling pathway. High expression of miR-492 has been closely associated with shorter overall survival in patients with gastric cancer, ovarian cancer, oropharyngeal carcinoma, colorectal cancer, and hepatocellular carcinoma. This study systematically summarizes the related research findings on miR-492, providing potential insights for future investigations.

The paradigm of drug resistance in cancer: an epigenetic perspective

Innate and acquired resistance towards the conventional therapeutic regimen imposes a significant challenge for the successful management of cancer for decades. In patients with advanced carcinomas, acquisition of drug resistance often leads to tumor recurrence and poor prognosis after the first therapeutic cycle. In this context, cancer stem cells (CSCs) are considered as the prime drivers of therapy resistance in cancer due to their 'non-targetable' nature. Drug resistance in cancer is immensely influenced by different properties of CSCs such as epithelial-to-mesenchymal transition (EMT), a profound expression of drug efflux pump genes, detoxification genes, quiescence, and evasion of apoptosis, has been highlighted in this review article. The crucial epigenetic alterations that are intricately associated with regulating different mechanisms of drug resistance, have been discussed thoroughly. Additionally, special attention is drawn towards the epigenetic mechanisms behind the interaction between the cancer cells and their microenvironment which assists in tumor progression and therapy resistance. Finally, we have provided a cumulative overview of the alternative treatment strategies and epigenome-modifying therapies that show the potential of sensitizing the resistant cells towards the conventional treatment strategies. Thus, this review summarizes the epigenetic and molecular background behind therapy resistance, the prime hindrance of present day anti-cancer therapies, and provides an account of the novel complementary epi-drug-based therapeutic strategies to combat drug resistance.

MicroRNA Signature in Renal Cell Carcinoma

Renal cell carcinoma (RCC) includes 2.2% of all diagnosed cancers and 1.8% of cancer-related mortalities. The available biomarkers or screening methods for RCC suffer from lack of sensitivity or high cost, necessitating identification of novel biomarkers that facilitate early diagnosis of this cancer especially in the susceptible individuals. MicroRNAs (miRNAs) have several advantageous properties that potentiate them as biomarkers for cancer detection. Expression profile of miRNAs has been assessed in biological samples from RCC patients. Circulatory or urinary levels of certain miRNAs have been proposed as markers for RCC diagnosis or follow-up. Moreover, expression profile of some miRNAs has been correlated with response to chemotherapy, immunotherapy or targeted therapeutic options such as sunitinib. In the current study, we summarize the results of studies that assessed the application of miRNAs as biomarkers, therapeutic targets or modulators of response to treatment modalities in RCC patients.

Understanding the Mechanisms by Which Epigenetic Modifiers Avert Therapy Resistance in Cancer

The development of resistance to anti-cancer therapeutics remains one of the core issues preventing the improvement of survival rates in cancer. Therapy resistance can arise in a multitude of ways, including the accumulation of epigenetic alterations in cancer cells. By remodeling DNA methylation patterns or modifying histone proteins during oncogenesis, cancer cells reorient their epigenomic landscapes in order to aggressively resist anti-cancer therapy. To combat these chemoresistant effects, epigenetic modifiers such as DNA hypomethylating agents, histone deacetylase inhibitors, histone demethylase inhibitors, along with others have been used. While these modifiers have achieved moderate success when used either alone or in combination with one another, the most positive outcomes were achieved when they were used in conjunction with conventional anti-cancer therapies. Epigenome modifying drugs have succeeded in sensitizing cancer cells to anti-cancer therapy via a variety of mechanisms: disrupting pro-survival/anti-apoptotic signaling, restoring cell cycle control and preventing DNA damage repair, suppressing immune system evasion, regulating altered metabolism, disengaging pro-survival microenvironmental interactions and increasing protein expression for targeted therapies. In this review, we explore different mechanisms by which epigenetic modifiers induce sensitivity to anti-cancer therapies and encourage the further identification of the specific genes involved with sensitization to facilitate development of clinical trials.

Circular RNA circ_0001368 inhibited growth and invasion in renal cell carcinoma by sponging miR-492 and targeting LATS2

Circular RNAs (circRNAs) act as essential regulators in the tumorigenesis of renal cell carcinoma. Our study aims to investigate the underlying function and the molecular mechanisms of circ_0001368 in renal cell carcinoma. The qRT-PCR results indicate that the circ_0001368 expression level was downregulated in the carcinoma cells and tissues of the renal cell. circ_0001368 weakened cell proliferation and invasion in the ACHN and 786-O cells. The luciferase reporter assay showed that circ_0001368 functioned as an endogenous sponge for miR-492. The transwell and CCK8 assays showed that circ_0001368 suppressed cell proliferation and invasion in the ACHN and 786-O cells. Large tumor suppressor kinase 2 (LATS2) was confirmed by Targetscan as a target gene of miR-492. The overexpression of LATS2 repressed the growth and invasion of ACHN and 786-O cells. circ_0001368 upregulated the LATS2 expression and suppressed ACHN and 786-O cell growth and invasion by sponging miR-492. circ_0001368 suppressed the proliferation ability of 786-O in vivo. In conclusion, circ_0001368 was identified in this study as a novel anti-tumor RNA in renal cell carcinoma and can function as a potential therapeutic target for renal cell carcinoma treatment.

Molecular Mechanisms in Clear Cell Renal Cell Carcinoma: Role of miRNAs and Hypermethylated miRNA Genes in Crucial Oncogenic Pathways and Processes

Clear cell renal cell carcinoma (ccRCC) is the third most common urological cancer, and it has the highest mortality rate. The increasing drug resistance of metastatic ccRCC has resulted in the search for new biomarkers. Epigenetic regulatory mechanisms, such as genome-wide DNA methylation and inhibition of protein translation by interaction of microRNA (miRNA) with its target messenger RNA (mRNA), are deeply involved in the pathogenesis of human cancers, including ccRCC, and may be used in its diagnosis and prognosis. Here, we review oncogenic and oncosuppressive miRNAs, their putative target genes, and the crucial pathways they are involved in. The contradictory behavior of a number of miRNAs, such as suppressive and anti-metastatic miRNAs with oncogenic potential (for example, miR-99a, miR-106a, miR-125b, miR-144, miR-203, miR-378), is examined. miRNAs that contribute mostly to important pathways and processes in ccRCC, for instance, PI3K/AKT/mTOR, Wnt-β, histone modification, and chromatin remodeling, are discussed in detail. We also separately consider their participation in crucial oncogenic processes, such as hypoxia and angiogenesis, metastasis, and epithelial-mesenchymal transition (EMT). The review also considers the interactions of long non-coding RNAs (lncRNAs) and miRNAs of significance in ccRCC. Recent advances in the understanding of the role of hypermethylated miRNA genes in ccRCC and their usefulness as biomarkers are reviewed based on our own data and those available in the literature. Finally, new data and perspectives concerning the clinical applications of miRNAs in the diagnosis, prognosis, and treatment of ccRCC are discussed.

Inhibition of microRNA‑492 attenuates cell proliferation and invasion in retinoblastoma via directly targeting LATS2

Numerous studies have demonstrated that microRNAs (miRNAs) are upregulated or downregulated in retinoblastoma (RB), and that this phenomenon is associated with the modulation of various malignant behaviours during RB occurrence and development. Therefore, the mechanisms that associate deregulated miRNAs with RB initiation and progression must be understood to identify effective therapeutic techniques for patients with RB. In the present study, miR‑492 expression was upregulated in RB tissues and cell lines. The effects of miR‑492 inhibition on the proliferation and invasion of RB cells were examined using Cell Counting kit‑8 and invasion assays. The results revealed that miR‑492 downregulation significantly decreased the proliferation and invasion of RB cells. Bioinformatics analysis predicted that large tumour‑suppressor kinase 2 (LATS2) was a putative target of miR‑492. Luciferase reporter assay, reverse transcription‑quantitative polymerase chain reaction and western blot analysis demonstrated that LATS2 was a direct target gene of miR‑492 in RB cells. In addition, LATS2 expression was downregulated in RB tissues, and its downregulation was inversely correlated with miR‑492 level. Furthermore, LATS2‑knockdown abrogated the effects of miR‑492 downregulation in RB cells. In conclusion, miR‑492 inhibition may impede the malignant behaviour of RB by directly targeting LATS2. Therefore, targeting this miRNA may be an effective therapeutic method for treating patients with RB.

Combined Treatment with Valproic Acid and 5-Aza-2'-Deoxycytidine Synergistically Inhibits Human Clear Cell Renal Cell Carcinoma Growth and Migration

Background

Histone acetylation and DNA methylation are important mammalian epigenetic modifications that participate in the regulation of gene expression. Because dysregulation of histone deacetylase and DNA methyltransferases are hallmarks of malignancy, they have become promising therapeutic targets. In this study, we explored the anti-tumor activity of valproic acid (VPA), a histone deacetylase inhibitor (HDACi) and 5-Aza-2′-deoxycytidine (5-Aza), an inhibitor of DNA methyltransferases, on renal cell carcinoma (RCC) cell lines 786-O and 769-P.

Material/Methods

The cell proliferation was detected by xCELLigence RTCA DP Instrument, viability by CCK8 assay, cell apoptosis and cell cycle by flow cytometry, and cell migration by wound healing assay, Transwell assay and xCELLigence RTCA DP Instrument.

Results

We discovered that VPA and 5-Aza could individually induce decreased viability and have an inhibitory effect on the proliferation of 786-O and 769-P cells. This anti-growth effect was more pronounced when the cells were treated with both VPA and 5-Aza. The combination of VPA and 5-Aza also elicited more apoptosis and produced more cell cycle arrest in the G1 phase for both cell lines. On the other hand, treatment of RCC cells with VPA, 5-Aza, or a combination of both resulted in slow wound healing and impaired migration.

Conclusions

These findings clearly demonstrated that VPA combined with 5-Aza could significantly increase anti-RCC effects by inhibiting cellular proliferation, inducing apoptosis, promoting cell cycle arrest and prohibiting the migration of human RCC cells.

The biological roles and clinical implications of microRNAs in clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) accounts for about 3% of tumors in adults as well as 85% of all primary renal carcinoma. And it is the third most predominant urological carcinoma, but it has the maximum mortality rate. Early diagnosis and proper follow-up of ccRCC patients may improve the prognosis of the illness. Thus, it is imperative to understand the new biomarkers of ccRCC and study new method for the modern therapy of this deadly disease. Furthermore, a large number of microRNAs (miRNAs), small non-coding RNAs, have been relevant to tumor type, stage, or survival and miRNAs might be progressed as the markers of diagnosis or prognosis in ccRCC. A growing body of data also advised the rationality of regarding miRNAs as therapeutic targets for ccRCC treatment. In this review, we tried to summarize biogenesis of miRNAs and their expression profiles, biological roles, and clinical implications in ccRCC.