miRNA expression profile in human osteosarcoma: role of miR-1 and miR-133b in proliferation and cell cycle control

Increased expression of microRNA-148a in osteosarcoma promotes cancer cell growth by targeting PTEN

Osteosarcoma is the most common type of primary malignant bone tumor, and deregulated microRNAs (miRNAs or miRs) in osteosarcoma have attracted great attention. In the present study, through miRNA microarray analysis, it was identified that miR-148a expression was significantly increased in osteosarcoma tissues. Increased miR-148a expression was significantly correlated with tumor progression and prognosis. Furthermore, increased miR-148a expression could promote osteosarcoma growth in vitro and in vivo, and the tumor-promoting effect was due to enhanced activation of the phosphoinositide 3-kinase signaling pathway caused by miR-148a-mediated inhibition of phosphatase and tensin homolog expression. Together, the present results suggest a role for miR-148a in osteosarcoma development and its potential use in prognosis prediction and cancer therapy.

Constitutive activation of MET signaling impairs myogenic differentiation of rhabdomyosarcoma and promotes its development and progression

Rhabdomyosarcoma (RMS) is a soft tissue sarcoma, which may originate from impaired differentiation of mesenchymal stem cells (MSC). Expression of MET receptor is elevated in alveolar RMS subtype (ARMS) which is associated with worse prognosis, compared to embryonal RMS (ERMS). Forced differentiation of ARMS cells diminishes MET level and, as shown previously, MET silencing induces differentiation of ARMS. In ERMS cells introduction of TPR-MET oncogene leads to an uncontrolled overstimulation of the MET receptor downstream signaling pathways. In vivo, tumors formed by those cells in NOD-SCID mice display inhibited differentiation, enhanced proliferation, diminished apoptosis and increased infiltration of neutrophils. Consequently, tumors grow significantly faster and they display enhanced ability to metastasize to lungs and to vascularize due to elevated VEGF, MMP9 and miR-378 expression. In vitro, TPR-MET ERMS cells display enhanced migration, chemotaxis and invasion toward HGF and SDF-1. Introduction of TPR-MET into MSC increases survival and may induce expression of early myogenic factors depending on the genetic background, and it blocks terminal differentiation of skeletal myoblasts. To conclude, our results suggest that activation of MET signaling may cause defects in myogenic differentiation leading to rhabdomyosarcoma development and progression.

miRNAs Related to Skeletal Diseases

miRNAs as non-coding, short, double-stranded RNA segments are important for cellular biological functions, such as proliferation, differentiation, and apoptosis. miRNAs mainly contribute to the inhibition of important protein translations through their cleavage or direct repression of target messenger RNAs expressions. In the last decade, miRNAs got in the focus of interest with new publications on miRNAs in the context of different diseases. For many types of cancer or myocardial damage, typical signatures of local or systemically circulating miRNAs have already been described. However, little is known about miRNA expressions and their molecular effect in skeletal diseases. An overview of published studies reporting miRNAs detection linked with skeletal diseases was conducted. All regulated miRNAs were summarized and their molecular interactions were illustrated. This review summarizes the involvement and interaction of miRNAs in different skeletal diseases. Thereby, 59 miRNAs were described to be deregulated in tissue, cells, or in the circulation of osteoarthritis (OA), 23 miRNAs deregulated in osteoporosis, and 107 miRNAs deregulated in osteosarcoma (OS). The molecular influences of miRNAs regarding OA, osteoporosis, and OS were illustrated. Specific miRNA signatures for skeletal diseases are described in the literature. Some overlapped, but also unique ones for each disease exist. These miRNAs may present useful targets for the development of new therapeutic approaches and are candidates for diagnostic evaluations.

MiR-125b Functions as a Tumor Suppressor and Enhances Chemosensitivity to Cisplatin in Osteosarcoma

MicroRNAs are highly conserved noncoding RNA that negatively modulate protein expression at a posttranscriptional and/or translational level and are deeply involved in the pathogenesis of several types of cancers. To date, the potential microRNAs regulating the growth and progression of osteosarcoma are not fully identified yet. Previous reports have shown differentially expressed miR-125b in osteosarcoma. However, the role of miR-125b in human osteosarcoma has not been totally illuminated. In this study, we have shown that miR-125b was downregulated in human osteosarcoma tissues compared to the adjacent tissues and effects as a tumor suppressor in vitro. We found that stable overexpression of miR-125b in osteosarcoma cell lines U2OS and MG-63 inhibited cell proliferation, migration, and invasion. Our data also verified that Bcl-2 is the target of miR-125b. Meanwhile, we showed that Bcl-2 was inversely correlated with miR-125b in osteosarcoma tissues. More importantly, we proved that miR-125b increased the chemosensitivity of osteosarcoma cell lines to cisplatin by targeting Bcl-2. In conclusion, our data demonstrate that miR-125b is a tumor suppressor and support its potential application for the treatment of osteosarcoma in the future.

Involvement and Clinical Aspects of MicroRNA in Osteosarcoma

Osteosarcoma (OS) is the most common primary bone cancer in children and adolescents, but its pathogenesis has been difficult to establish because of its well-known heterogeneous nature. OS has been associated with genetic and cytogenetic abnormalities, which include function-impairing mutations in tumor suppressors and the activation of oncogenes. OS tumorigenesis has been linked to alterations of several genes characterized by a high level of genetic instability and recurrent DNA amplifications and deletions. MicroRNAs (miRNAs), 18–25-nucleotide noncoding RNAs, are critical for various biological processes like differentiation, cell growth and cell death. Dysregulation of miRNA expression leads to phenotypic and genotypic changes in cells, which leads to cancer. Studies on miRNAs have initiated a significant effect in both diagnosis and treatment of cancer. This review focuses on the current knowledge of clinical applications of miRNAs for the better diagnosis and management of OS.

miR-1 suppresses the growth of esophageal squamous cell carcinoma in vivo and in vitro through the downregulation of MET, cyclin D1 and CDK4 expression

Several aberrant microRNAs (miRNAs or miRs) have been implicated in esophageal cancer (EC), which is widely prevalent in China. However, their role in EC tumorigenesis has not yet been fully elucidated. In the present study, we determined that miR-1 was downregulated in esophageal squamous cell carcinoma (ESCC) tissues compared with adjacent non-neoplastic tissues using RT-qPCR, and confirmed this using an ESCC cell line. Using a nude mouse xenograft model, we confirmed that the re-expression of miR-1 significantly inhibited ESCC tumor growth. A tetrazolium assay and a trypan blue exclusion assay revealed that miR-1 suppressed ESCC cell proliferation and increased apoptosis, whereas the silencing of miR-1 promoted cell proliferation and decreased apoptosis, suggesting that miR-1 is a novel tumor suppressor. To elucidate the molecular mechanisms of action of miR-1 in ESCC, we investigated putative targets using bioinformatics tools. MET, cyclin D1 and cyclin-dependent kinase 4 (CDK4), which are involved in the hepatocyte growth factor (HGF)/MET signaling pathway, were found to be targets of miR-1. miR-1 expression inversely correlated with MET, cyclin D1 and CDK4 expression in ESCC cells. miR-1 directly targeted MET, cyclin D1 and CDK4, suppressing ESCC cell growth. The newly identified miR-1/MET/cyclin D1/CDK4 axis provides new insight into the molecular mechanisms of ESCC pathogenesis and indicates a novel strategy for the diagnosis and treatment of ESCC.

MicroRNA-1 properties in cancer regulatory networks and tumor biology

Short non-coding microRNAs have been identified to orchestrate crucial mechanisms in cancer progression and treatment resistance. MicroRNAs are involved in posttranscriptional modulation of gene expression and therefore represent promising targets for anticancer therapy. As mircoRNA-1 (miR-1) exerted to be predominantly downregulated in the majority of examined tumors, miR-1 is classified to be a tumor suppressor with high potential to diminish tumor development and therapy resistance. Here we review the complex functionality of miR-1 in tumor biology.

Green tea polyphenol EGCG suppresses osteosarcoma cell growth through upregulating miR-1

(-)-Epigallocatechin-3-gallate (EGCG), the most abundant and active polyphenol in green tea, has been demonstrated to have anticancer effects in a wide variety of human cancer. MicroRNAs (miRNAs) are a class of short noncoding RNAs and play important role in gene regulation and are critically involved in the pathogenesis and progression of human cancer. This study aims to investigate the effects of EGCG on osteosarcoma (OS) cells and elucidate the underlying mechanism. Cellular function assays revealed that EGCG inhibited cell proliferation, induced cell cycle arrest and promoted apoptosis of OS cells in vitro, and also inhibited the growth of transplanted tumors in vivo. By miRNA microarray and RT-qPCR analysis, miR-1 was found to be significantly upregulated in MG-63 and U-2OS treated by EGCG in dose- and time-dependent manners, and miR-1 downregulation by inhibitor mimics attenuated EGCG-induced inhibition on cell growth of OS cells. We also confirmed that miR-1 was also frequently decreased in clinical OS tumor tissues. Moreover, both EGCG and miR-1 mimic inhibited c-MET expression, and combination treatment with EGCG and c-MET inhibitor (crizotinib) had enhanced inhibitory effects on the growth of MG-63 and U-2OS cells. Taken together, these results suggest that EGCG has an anticancer effect on OS cells, at least partially, through regulating miR-1/c-MET interaction.

Roles of the canonical myomiRs miR-1, -133 and -206 in cell development and disease

MicroRNAs are small non-coding RNAs that participate in different biological processes, providing subtle combinational regulation of cellular pathways, often by regulating components of signalling pathways. Aberrant expression of miRNAs is an important factor in the development and progression of disease. The canonical myomiRs (miR-1, -133 and -206) are central to the development and health of mammalian skeletal and cardiac muscles, but new findings show they have regulatory roles in the development of other mammalian non-muscle tissues, including nerve, brain structures, adipose and some specialised immunological cells. Moreover, the deregulation of myomiR expression is associated with a variety of different cancers, where typically they have tumor suppressor functions, although examples of an oncogenic role illustrate their diverse function in different cell environments. This review examines the involvement of the related myomiRs at the crossroads between cell development/tissue regeneration/tissue inflammation responses, and cancer development.

Biological roles of microRNA-140 in tumor growth, migration, and metastasis of osteosarcoma in vivo and in vitro

The objective of this study was to explore the biological roles of microRNA-140 (miR-140) in tumor growth, migration, and metastasis of osteosarcoma (OS) in vivo and in vitro. Between 2007 and 2014, 47 cases of OS samples and normal bone tissue samples adjacent to OS were selected from our hospital. Tissue biopsies from OS patients were used to measure miR-140 levels to obtain a correlation between clinicopathological features and miR-140 expression. In vitro, MG63 human osteosarcoma cells were divided into four groups: blank group, miR-140 mimic group, miR-140 inhibitor group, and negative control (NC; empty plasmid) group. qRT-PCR was used to detect miR-140 expression, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to detect cell proliferation, flow cytometry was used to detect cell cycle distribution, and scratch migration assay was used to detect cell migration. In vivo, the relative expression of miR-140 level in OS tissue was lower than that in the adjacent normal bone tissue. miR-140 expression is inversely correlated with tumor size, Enneking stage, and tumor metastasis. In vitro, compared with blank group and NC group, relative miR-140 expression was increased, cell proliferation was inhibited, cell population in G0/G1 phase was increased, cell population in G2/M phase and S phases and proliferation index (PI), and cell migration distance were decreased in the miR-140 mimic group, but the relative expression and all the cell indexes were found opposite trend in the miR-140 inhibitor group. In conclusion, in vivo and vitro findings provided evidence that miR-140 could inhibit the growth, migration, and metastasis of OS cells.

What Do We Know about the Role of miRNAs in Pediatric Sarcoma?

Non-coding RNAs have received a lot of attention in recent years, with especial focus on microRNAs (miRNAs), so much so that in the just over two decades since the first miRNA, Lin4, was described, almost 40,000 publications about miRNAs have been generated. Less than 500 of these focus on sarcoma, and only a fraction of those on sarcomas of childhood specifically, with some of these representing observational studies and others containing functionally validated data. This is a group of cancers for which prognosis is often poor and therapeutic options limited, and it is especially in these areas that strides in understanding the role of non-coding RNAs and miRNAs in particular are to be welcomed. This review deals with the main forms of pediatric sarcoma, exploring what is known about the diagnostic and prognostic profiles of miRNAs in these tumours and where novel therapeutic options might present themselves for further exploration.

Combinational treatment with microRNA‑133b and cetuximab has increased inhibitory effects on the growth and invasion of colorectal cancer cells by regulating EGFR

Colorectal cancer (CRC) is the third most common cancer with a very poor prognosis predominantly due to its high rate of tumor invasion and migration, and its resistance to anti‑epidermal growth factor receptor (EGFR) therapy. Although CRC has been widely studied, the underlying molecular mechanism remains to be elucidated. MicroRNA (miR)‑133b has been demonstrated to act as a tumor suppressor in several human cancer types by regulating EGFR. However, the detailed involvement of miR‑133b and EGFR in CRC cells remain to be elucidated. The present study used reverse transcription quantitative polymerase chain reaction and characterized the downregulation of the expression levels of miR‑133b in CRC tissues and cell lines. Cell functional assays demonstrated that restored expression of miR‑133b inhibited the growth and invasion of CRC cells. In addition, a luciferase reporter assay revealed that miR‑133b directly targeted EGFR and repressed its expression levels in CRC cells. Additionally, combination treatment with miR‑133b mimics and the monoclonal anti‑EGFR antibody, cetuximab, which is approved and frequently used for treating patients with CRC, exhibited improved inhibitory effects on the growth and invasion of CRC cells compared with treatment with either alone. Taken together, the present study characterized the role of the miR‑133b/EGFR interaction in CRC cells and this suggested the combinational therapy with cetuximab and miR‑133b was positive and may be a potential novel treatment for patients with CRC in the future.

Enhanced regulation of cell cycle and suppression of osteoblast differentiation molecular signatures by prostate cancer stem-like holoclones

AIMS

Targeting the stem cell properties of tumor-initiating cells is an avenue through which cancer treatment may be improved. Before this can be achieved, so-called 'cancer stem cell' (CSC) models must be developed and characterized in specific malignancies.

METHODS

In this study, holoclone formation assays were used to characterise stem-like molecular signatures in prostate cancer (PCa) cells.

RESULTS

LNCaP and PC3 parent cells were capable of responding to stem cell differentiation morphogen retinoic acid (RA), suggesting the presence of inherent stem-like properties. LNCaP cells, which represent early, androgen-responsive disease, formed holoclones after twenty six days. PC3 cells, which represent advanced, metastatic, castration-resistant disease, formed holoclones after only six days. Holoclones displayed decreased expression of RA-genes, suggesting a more immature, less differentiated phenotype. Gene and microRNA arrays demonstrated that holoclones downregulated a number of stem cell differentiation regulators while displaying enhanced regulation of G2 to M transition and the mitotic spindle checkpoint components of the cell cycle. PC3 holoclones displayed pronounced downregulation of known regulators of osteoblast differentiation from mesenchymal stem cells and Epithelial Mesenchymal Transition.

CONCLUSIONS

Our results suggest that some PCa cells retain the ability to transition to a more immature state in which differentiation and metastatic mechanisms are suppressed. The highlighting of osteoblast differentiation regulators in this mechanism is particularly notable, considering the propensity of PCa to metastasise to bone.

Up-Regulation of MiR-300 Promotes Proliferation and Invasion of Osteosarcoma by Targeting BRD7

Increasing reports suggest that deregulated microRNAs (miRNAs) might provide novel therapeutic targets for cancers. However, the expression and function of miR-300 in osteosarcoma is still unknown. In our study, we found that the expression of miR-300 was up-regulated in osteosarcoma tissues and cells compared with paired adjacent non-tumor bone tissues and osteoblastic cells using RT-qPCR. The enforced expression of miR-300 could promote cell proliferation, invasion and epithelial-mesenchymal transition (EMT). Moreover, we identified that bromodomain-containing protein 7 (BRD7), a new tumor suppressor gene, was a direct target of miR-300. Ectopic expression of BRD7 could significantly inhibit miR-300-promoted proliferation, invasion and EMT. Therefore, our results identify an important role for miR-300 in osteosarcoma through regulating BRD7 expression.

Identification of MicroRNA for Intermuscular Bone Development in Blunt Snout Bream (Megalobrama amblycephala)

Intermuscular bone (IB), which occurs only in the myosepta of the lower teleosts, is attracting more attention of researchers due to its particular development and lack of genetic information. MicroRNAs (miRNAs) are emerging as important regulators for biological processes. In the present study, miRNAs from IBs and connective tissue (CT; encircled IBs) from six-month-old Megalobrama amblycephala were characterized and compared. The results revealed the sequences and expression levels of 218 known miRNA genes (belonging to 97 families). Of these miRNAs, 44 known microRNA sequences exhibited significant expression differences between the two libraries, with 24 and 20 differentially-expressed miRNAs exhibiting higher expression in the CT and IBs libraries, respectively. The expressions of 11 miRNAs were selected to validate in nine tissues. Among the high-ranked predicted gene targets, differentiation, cell cycle, metabolism, signal transduction and transcriptional regulation were implicated. The pathway analysis of differentially-expressed miRNAs indicated that they were abundantly involved in regulating the development and differentiation of IBs and CT. This study characterized the miRNA for IBs of teleosts for the first time, which provides an opportunity for further understanding of miRNA function in the regulation of IB development.

Downregulation of miR-22 acts as an unfavorable prognostic biomarker in osteosarcoma

miRNA-22 (miR-22) has been showed to involve in a variety of cancers; however, the association between miR-22 expression level and the prognosis of osteosarcoma is also poorly unknown. Fifty-two patients with surgically resected paired osteosarcoma and non-neoplastic disease between 2008 and 2014 were involved in this study. Real-time PCR was performed to examine the expression level of miR-22 in osteosarcoma tissues and noncancerous bone tissues. Then the association between miR-22 expression and clinical-pathological parameters were further evaluated. Kaplan-Meier analysis and Cox proportional hazards regression models were explored to reveal the correlations of miR-22 expression with survival of patients. The results indicated that miR-22 was downregulated in osteosarcoma tissues in comparison with noncancerous bone tissues. In addition, there is statistically significance between miR-22 expression level and recurrence, metastasis, and chemotherapy response. The patients with lower miR-22 expression level had both poorer overall survival and disease-free survival. The multivariant analysis revealed that the miR-22 expression level and metastasis status are independent prognosis factors for osteosarcoma. In conclusion, miR-22 was downregulated in osteosarcoma and its expression level was correlated with a variety of important clinical-pathological parameters. Moreover, miR-22 may serve as a promising biomarker for predicting the prognosis of osteosarcoma.

The microRNA-217 functions as a tumor suppressor and is frequently downregulated in human osteosarcoma

OBJECTIVE

Dysregulation of miRNA is always associated with cancer development and progression. Aberrant expression of miR-217 has been found in some types of cancer. However, its expression and function in osteosarcoma remain unclear. The aim of this study was to explore the effects of miR-217 in osteosarcoma tumorigenesis and development.

METHODS

The expression level of miR-217 was quantified by real-time RT-PCR in human osteosarcoma cell lines and tissues. MTT, flow cytometric, transwell invasion and migration assays, and tumorigenicity in vivo were adopted to observe the effects of miR-217 on MG-63 cell phenotypes.

RESULTS

MiR-217 was significantly downregulated in osteosarcoma cell lines and clinical specimens. Decreased miR-217 expression was significantly associated with large tumor size, positive distant metastasis, and advanced clinical stage. Low miR-217 expression in osteosarcoma was an independent predictor of poor survival. Overexpression of miR-217 can inhibit the proliferation, invasion, migration and promoted apoptosis of MG-63 cells in vitro and in vivo.

CONCLUSIONS

These findings indicate that miR-217 may act as a tumor suppressor in osteosarcoma and would serve as a novel therapeutic agent for miRNA-based therapy.

MicroRNAs in osteosarcoma

Osteosarcoma (OS) is a primary malignant bone tumor with high morbidity that principally emerges in children and adolescents. Presently, the prognosis of OS patients remains poor due to resistance to chemotherapy, highlighting the need for new therapeutic approaches. MicroRNAs (miRNAs), a class of small noncoding RNA molecules, can negatively modulate protein expression at the post-transcriptional level. miRNAs regulate a variety of normal physiologic processes and are involved in tumorigenesis and development of multiple malignancies, including OS. Some miRNAs are differentially expressed in OS tissues, cell lines and serum, and have been shown to correlate with the malignant phenotype and prognosis. These altered miRNAs function as oncogenes or tumor suppressor genes in this process. Moreover, restoration of miRNA expression has shown promise for the treatment of OS. Here, we describe miRNA biochemistry with a focus on expression profile, role and therapeutic potential in OS. A better understanding will facilitate the identification and characterization of novel biomarkers and development of miRNA-targeted therapies.

MicroRNA-1 participates in nitric oxide-induced apoptotic insults to MC3T3-E1 cells by targeting heat-shock protein-70

Our previous studies showed that nitric oxide (NO) could induce osteoblast apoptosis. MicroRNA-1 (miR-1), a skeletal- and cardiac muscle-specific small non-coding RNA, contributes to the regulation of multiple cell activities. In this study, we evaluated the roles of miR-1 in NO-induced insults to osteoblasts and the possible mechanisms. Exposure of mouse MC3T3-E1 cells to sodium nitroprusside (SNP) increased amounts of cellular NO and intracellular reactive oxygen species. Sequentially, SNP decreased cell survival but induced caspase-3 activation, DNA fragmentation, and cell apoptosis. In parallel, treatment with SNP induced miR-1 expression in a time-dependent manner. Application of miR-1 antisense inhibitors to osteoblasts caused significant inhibition of SNP-induced miR-1 expression. Knocking down miR-1 concurrently attenuated SNP-induced alterations in cell morphology and survival. Consecutively, SNP time-dependently inhibited heat-shock protein (HSP)-70 messenger (m)RNA and protein expressions. A bioinformatic search predicted the existence of miR-1-specific binding elements in the 3'-untranslational region of HSP-70 mRNA. Downregulation of miR-1 expression simultaneously lessened SNP-induced inhibition of HSP-70 mRNA and protein expressions. Consequently, SNP-induced modifications in the mitochondrial membrane potential, caspase-3 activation, DNA fragmentation, and apoptotic insults were significantly alleviated by miR-1 antisense inhibitors. Therefore, this study showed that miR-1 participates in NO-induced apoptotic insults through targeting HSP-70 gene expression.

microRNA-377 suppresses the proliferation of human osteosarcoma MG-63 cells by targeting CDK6

MicroRNAs (miRNAs) are essential to the progression of osteosarcoma. Previous research using osteosarcoma samples confirmed that miR-377 expression is less than that observed in normal human osteoblast expression. These data suggest a role for miR-377 in osteosarcoma that warrants investigation. To address this concept, we measured miR-377 expression in two cell models, and we also observed that miR-377 was less expressed in osteosarcoma MG-63 cells compared to the hFOB1.19 human fetal osteoblastic cell line. Moreover, miR-377 overexpression reduced cell proliferation and suppressed invasion of MG-63 cells but had no effect on MG-63 cell apoptosis. Because cyclin-dependent kinase 6 (CDK6) may be a potential target of miR-377 in osteosarcoma cells, we overexpressed CDK6 and observed that overexpression attenuated tumor suppressive effects of miR-377 on cell proliferation. Our data suggest that miR-377 can suppress proliferation in MG-63 cells in part by targeting CDK6.

MiR-133b acts as a tumor suppressor and negatively regulates TBPL1 in colorectal cancer cells

INTRODUCTION

MicroRNAs have emerged as post-transcriptional regulators that are critically involved in tumorigenesis. This study was designed to explore the effect of miRNA 133b on the proliferation and expression of TBPL1 in colon cancer cells.

METHODS

Human colon cancer SW-620 cells and human colon adenocarcinoma HT-29 cells were cultured. MiRNA 133b mimcs, miRNA 133b inhibitors, siRNA for TBPL1 and scrambled control were synthesized and transfected into cells. MiR-133b levels in cells and CRC tumor tissue was measured by real-time PCR. TBPL1 mRNA was detected by RT-PCR. Cell proliferation was studied with MTT assay. Western blotting was applied to detect TBPL1 protein levels. Luciferase assays were conducted using a pGL3-promoter vector cloned with full length of 3'UTR of human TBPL1 or 3'UTR with mutant sequence of miR-133b target site in order to confirm if the putative binding site is responsible for the negative regulation of TBPL1 by miR- 133b.

RESULTS

Real time PCR results showed that miRNA 133b was lower in CRC tissue than that in adjacent tissue. After miR-133b transfection, its level was elevated till 48h, accompanied by lower proliferation in both SW-620 and HT-29 cells. According to that listed in http://www.targetscan.org, the 3'-UTR of TBPL1 mRNA (NM_004865) contains one putative binding site of miR-133b. This site was confirmed to be responsible for the negative regulation by miR-133b with luciferase assay. Further, Western blotting and immunohistochemistry both indicated a higher TBPL1 protein expression level in CRC tissue. Finally, a siRNA for TBPL1 transfection obviously slowed down the cell proliferation in both SW-620 and HT-29 cells.

CONCLUSION

MiR-133b might act as a tumor suppressor and negatively regulate TBPL1 in CRC.

c-Met and miRs in Cancer

c-Met, a member of the receptor tyrosine kinase family, is involved in a wide range of cellular processes, including tumor survival, cell growth, angiogenesis and metastasis, and resulting in overexpression in many human cancers, leading to a constitutive activation of the downstream pathways. Recently identified MicroRNAs are a family of small noncoding RNA molecules, extensively studied in cancer, that exert their action by inhibiting gene expression at the posttranscriptional level in several biological processes. Aberrant regulation of microRNAs expression has been implicated in the pathogenesis of different human neoplasia. Several publications point out the connections between c-Met and its ligand hepatocyte growth factor (HGF) and microRNAs. This review summarizes the current knowledge about the interplay between c-Met/HGF and microRNAs and provides evidence that microRNAs are a novel and additional system to regulate c-Met expression in tumors. In the future, microRNAs connected to c-Met may provide an additional option to inhibiting this oncogene from orchestrating an invasive growth program.

The expression and function of miRNA-451 in osteosarcoma

MicroRNA-451 has been proven down-regulated in many human malignancies and correlated with tumor progression. However, its expression and clinical significance in osteosarcoma is still unclear. Thus, the aim of this study was to explore the effects of miR-451 in osteosarcoma tumorigenesis and development. The expression level of miR-451 was quantified by quantitative real-time reverse-transcriptase-polymerase chain reaction in primary osteosarcoma tissues and osteosarcoma cell lines. MTT, flow cytometric, and scratch migration assay were used to test the proliferation, apoptosis, and migration of miR-451 transfection osteosarcoma cells, and a mouse model was used to investigate tumorigenesis. The expression levels of miR-451 in osteosarcoma tissues were significantly lower than those in corresponding noncancerous bone tissues (P < 0.001). In addition, miR-451 down-regulation more frequently occurred in osteosarcoma specimens with advanced clinical stage (P < 0.001), positive distant metastasis (P = 0.015), and poor response to neoadjuvant chemotherapy (P < 0.001). Univariate and multivariate analysis identified low miR-451 expression as an unfavorable prognostic factor for both overall and disease-free survival. After miR-451 transfection, cell proliferation, migration, and tumorigenesis in the osteosarcoma cells were significantly inhibited and cell apoptosis was increased. These findings indicate that miR-451 may act not only as a novel diagnostic and prognostic marker, but also as a potential target for molecular therapy of osteosarcoma.

Deep Sequencing the microRNA profile in rhabdomyosarcoma reveals down-regulation of miR-378 family members

BACKGROUND

Rhabdomyosarcoma (RMS) is a highly malignant tumour accounting for nearly half of soft tissue sarcomas in children. MicroRNAs (miRNAs) represent a class of short, non-coding, regulatory RNAs which play a critical role in different cellular processes. Altered miRNA levels have been reported in human cancers, including RMS.

METHODS

Using deep sequencing technology, a total of 685 miRNAs were investigated in a group of alveolar RMSs (ARMSs), embryonal RMSs (ERMSs) as well as in normal skeletal muscle (NSM). Q-PCR, MTT, cytofluorimetry, migration assay, western blot and immunofluorescence experiments were carried out to determine the role of miR-378a-3p in cancer cell growth, apoptosis, migration and differentiation. Bioinformatics pipelines were used for miRNA target prediction and clustering analysis.

RESULTS

Ninety-seven miRNAs were significantly deregulated in ARMS and ERMS when compared to NSM. MiR-378 family members were dramatically decreased in RMS tumour tissue and cell lines. Interestingly, members of the miR-378 family presented as a possible target the insulin-like growth factor receptor 1 (IGF1R), a key signalling molecule in RMS. MiR-378a-3p over-expression in an RMS-derived cell line suppressed IGF1R expression and affected phosphorylated-Akt protein levels. Ectopic expression of miR-378a-3p caused significant changes in apoptosis, cell migration, cytoskeleton organization as well as a modulation of the muscular markers MyoD1, MyoR, desmin and MyHC. In addition, DNA demethylation by 5-aza-2'-deoxycytidine (5-aza-dC) was able to up-regulate miR-378a-3p levels with a concomitant induction of apoptosis, decrease in cell viability and cell cycle arrest in G2-phase. Cells treated with 5-aza-dC clearly changed their morphology and expressed moderate levels of MyHC.

CONCLUSIONS

MiR-378a-3p may function as a tumour suppressor in RMS and the restoration of its expression would be of therapeutic benefit in RMS. Furthermore, the role of epigenetic modifications in RMS deserves further investigations.

MicroRNA-101 inhibits the metastasis of osteosarcoma cells by downregulation of EZH2 expression

MicroRNAs (miRNAs) are a class of small non‑coding RNA molecules, which play regulatory roles at the post-transcriptional level by suppressing the translation of protein‑coding genes or inducing mRNA cleavage. Dysregulated expression of miRNAs is involved in multiple types of cancers and plays important roles in regulating various biological processes including metastasis. miR-101 is downregulated in various types of cancer and functions as a suppressor of cell migration and invasion. Meanwhile, enhancer of zeste homolog 2 (EZH2) is associated with the metastatic potential of several aggressive tumors. In the present study, we reported that ectopic overexpression of miR-101 downregulated the expression level of EZH2 and significantly inhibited migration and invasion of osteosarcoma cells. In addition, knockdown of EZH2 by siRNA showed the same effect of miR-101 on migration and invasion. To conclude, these results indicate that miR-101 may act as a tumor suppressor in osteosarcoma, as it has a suppressive role in cell migration and invasion by targeting EZH2.

MicroRNA-1 functions as a potential tumor suppressor in osteosarcoma by targeting Med1 and Med31

MicroRNA-1 (miR-1) has been shown to function as a critical gene regulator in multiple types of cancers. However, the role of miR-1 in osteosarcoma has not been totally clarified. In the present study, we investigated the effects of miR-1 on osteosarcoma and the underlying mechanism. We found that miR-1 was downregulated in osteosarcoma tissues and osteosarcoma cell lines. Restoration of miR-1 significantly suppressed osteosarcoma cell proliferation by inhibiting cell cycle progression. Mediator complex subunit 1 (Med1) and 31 (Med31) were validated as targets of miR-1 in osteosarcoma by luciferase reporter assay. Downregulation of Med1 and Med31 suppressed the proliferation of osteosarcoma cells, and overexpression of Med1 and Med31 abrogated the effects of miR-1 on cell proliferation. Furthermore, both miR-1 and knockdown of Med1 or Med31 reduced the expression of met proto-oncogene (MET) and blocked the downstream signaling of MET responding to hepatocyte growth factor (HGF). Taken together, the findings of this study suggest that Med1 and Med31 serve as potential gene therapeutic targets in osteosarcoma and miR-1 may prove to be a promising agent.

Prognostic significance of miRNA-1 (miR-1) expression in patients with chordoma

Reliable prognostic biomarkers for chordoma have not yet been established. Recent studies revealed that expression of miRNA-1 (miR-1) is frequently downregulated in several cancer types including chordoma. The goal of this follow-up study is to investigate the expression of miR-1 as a prognostic biomarker and further confirm the functional role of miR-1 in chordoma cell growth and proliferation. We determined the relative expression levels of miR-1 and Met in chordoma tissue samples and correlated those to clinical variables. The results showed that miR-1 was downregulated in 93.7% of chordoma tissues and expression was inversely correlated with Met expression. miR-1 expression levels also correlated with clinical prognosis. To characterize and confirm the functional role of miR-1 in the growth and proliferation of chordoma cells, miR-1 precursors were stably transfected into chordoma cell lines UCH-1 and CH-22. Cell Proliferation Assay and MTT were used to evaluate cell growth and proliferation. Restoring expression of miR-1 precursor decreased cell growth and proliferation in UCH-1 and CH-22 cells. These results indicate that suppressed miR-1 expression in chordoma may in part be a driver for tumor growth, and that miR-1 has potential to serve as prognostic biomarker and therapeutic target for chordoma patients.

Expression of the lysyl oxidase propeptide in hepatocellular carcinoma and its clinical relevance

Lysyl oxidase is an important extracellular matrix remodeling enzyme and plays critical roles in tumor progression and development. Its tumor-suppressor activity has been shown to depend on the propeptide region. Previous studies have reported that the expression levels of lysyl oxidase propeptide (LOX-PP) are associated with cancer of the breast, pancreas, lung, prostate and gastrointestinal system. However, to date, the exact effects and molecular mechanisms of LOX-PP in hepatocellular carcinoma progression are still unclear. The present study aimed to investigate the expression and clinical significance of LOX-PP in human hepatocellular carcinoma. First, 42 cases of hepatocellular carcinoma and corresponding adjacent non-cancerous tissues (ANCTs) were collected, and the expression of LOX-PP in these samples was assessed by immunohistochemistry (IHC). The clinicopathological characteristics of all patients were recorded. Next, in in vitro studies, recombinant adenovirus LOX (ad-LOX-PP) was used to infect hepatocellular carcinoma cell lines to determine the function of LOX-PP. To determine whether ad-LOX-PP affects hepatocellular carcinoma cell survival, cell viability was examined by CCK-8 assay, and cell cycle progression was assessed by flow cytometry. We also investigated the effects of LOX-PP on the expression of cell cycle regulators (cyclin D1 and cyclin E) by western blot analysis. The migration and invasion capacities of hepatocellular carcinoma cells were observed by wound-healing and tranwell invasion assays. To further investigate how LOX-PP affects migration levels of matrix metallopeptidase (MMP)-2 and MMP-9 were assessed by western blot analysis. Additionally, markers of the PI3K and MAPK signaling pathway were detected to further confirm the mechanisms of LOX-PP. As a result, reduced expression of LOX-PP was found in hepatocellular carcinoma tissues, when compared with that in the ANCTs (15 vs. 83%, P<0.01), and its expression was associated with tumor stage and distant metastasis (each P<0.05). Proliferation in hepatocellular carcinoma cells was significantly decreased in the ad-LOX-PP group as indicated by CCK-8 assay. LOX-PP significantly reduced the expression of Ki-67, while prominent increases in the rate of apoptosis and cell cycle arrest were observed. Similarly, cell migration was significantly inhibited in the ad-LOX-PP group as evidenced by transwell invasion and wound-healing assays. The expression levels of MMP-2 and MMP-9 were attenuated in the ad-LOX-PP group, suggesting that LOX-PP inhibits hepatocellular carcinoma cell migration via down-regulation of MMPs expression. When LOX-PP expression was potentiated by an adenovirus containing LOX-PP, the expression of p-ERK was significantly downregulated, indicating that LOX-PP inhibits hepatocellular carcinoma cell proliferation and induces its apoptosis probably through downregulation of the MAPK/ERK pathway.

Upregulated expression of microRNA-214 is linked to tumor progression and adverse prognosis in pediatric osteosarcoma

BACKGROUND

MicroRNA-214 (miR-214) expression has been demonstrated to be dysregulated in human malignancies and to play various roles in tumor progression. While previous study of miRNA expression profiling found that it was one of the most upregulated miRNAs in osteosarcoma signature, the potential role of miR-214 in osteosarcomas has been unclear. Therefore, the aim of this study was to investigate association of miR-214 expression with clinicopathologic features and prognosis in pediatric patients with osteosarcoma.

PROCEDURE

Quantitative real-time reverse transcriptase-polymerase chain reaction analysis was performed to detect expression levels of miR-214 in cancerous and noncancerous bone tissues from 92 children treated for primary osteosarcomas. Then, the clinical significance of miR-214 dysregulation in pediatric osteosarcomas was also determined.

RESULTS

Compared with noncancerous bone tissues, the expression levels of miR-214 were significantly upregulated in osteosarcoma tissues (P < 0.001). High miR-214 expression occurred more frequently in osteosarcoma tissues with large tumor size (P = 0.01), positive metastasis (P = 0.001) and poor response to pre-operative chemotherapy (P = 0.006). Moreover, high miR-214 expression was significantly associated with both shorter overall (P < 0.001) and progression-free survival (PFS; P = 0.001). Multivariate analysis by the Cox proportional hazard model further confirmed that high miR-214 expression was an independent prognostic factor of unfavorable survival in pediatric osteosarcoma (for overall survival: P = 0.008; for PFS: P = 0.01).

CONCLUSION

Our data offer evidence that upregulated expression of miR-214 may be linked to tumor progression and adverse prognosis in pediatric osteosarcoma. Further investigation in prospective studies would appear warranted.

Combined microRNA-340 and ROCK1 mRNA profiling predicts tumor progression and prognosis in pediatric osteosarcoma

To investigate the association of combined microRNA-340 (miR-340) and ROCK1 mRNA profiling with clinicopathologic features and prognosis in pediatric patients with osteosarcoma. Quantitative real-time reverse transcriptase-polymerase chain reaction analysis was performed to detect expression levels of miR-340 and ROCK1 mRNA in cancerous and noncancerous bone tissues from 92 children treated for primary osteosarcomas. Compared with noncancerous bone tissues, the expression levels of miR-340 and ROCK1 mRNA were, respectively, downregulated and upregulated in osteosarcoma tissues (both p < 0.001), which was consistent with the results of in situ hybridization and immunohistochemistry analysis. The downregulation of miR-340 was negatively correlated with the upregulation of ROCK1 mRNA in osteosarcoma tissues (r = −0.78, p = 0.001). In addition, the combined miR-340 downregulation and ROCK1 upregulation (miR-340-low/ROCK1-high) occurred more frequently in osteosarcoma tissues with positive metastasis (p < 0.001) and poor response to pre-operative chemotherapy (p = 0.002). Moreover, miR-340-low/ROCK1-high expression was significantly associated with both shortest overall survival (p < 0.001) and progression-free survival (p < 0.001). Multivariate analysis further confirmed that miR-340-low/ROCK1-high expression was an independent prognostic factor of unfavorable survival in pediatric osteosarcoma (for overall survival: p = 0.006, for progression-free survival: p = 0.008). Our data offer convincing evidence, for the first time, that the combined miR-340 downregulation and ROCK1 upregulation may be linked to tumor progression and adverse prognosis in pediatric osteosarcoma.

Participation of the Fas/FasL signaling pathway and the lung microenvironment in the development of osteosarcoma lung metastases

The lungs are the most common site for the metastatic spread of osteosarcoma. Success in using chemotherapy to improve overall survival has reached a plateau. Understanding the biologic properties that permit osteosarcoma cells to grow in the lungs may allow the identification of novel therapeutic approaches-the goal being to alter the tumor cells' expression of cell surface proteins so that there is no longer compatibility with the metastatic niche. We have demonstrated that the Fas Ligand positive (FasL(+)) lung microenvironment eliminates Fas(+) osteosarcoma cells that metastasize to the lungs. Indeed, osteosarcoma lung metastases from patients are Fas(-), similar to what we found in several different mouse models. The Fas(+) cells are cleared from the lungs through apoptosis induced by the Fas signaling pathway following interaction of Fas on the tumor cell surface with the lung FasL. Blocking the Fas signaling pathway interferes with this process, allowing the Fas(+) cells to grow in the lungs. Our investigations show that Fas expression in osteosarcoma cells is regulated epigenetically by the micro-RNA miR-20a, encoded by the miR-17-92 cluster. Our studies support the feasibility of finding agents that can re-induce Fas expression as a novel therapeutic approach to treat osteosarcoma patients with lung metastases. We have identified two such agents, the histone deacetylase inhibitor entinostat and the chemotherapeutic agent gemcitabine (GCB). Aerosol GCB and oral entinostat induce the upregulation of Fas and the regression of established osteosarcoma lung metastases. Aerosol GCB was not effective in the FasL-deficient gld mouse confirming that the lung microenvironment was central to the success of this therapy. Our studies establish the critical role of the lung microenvironment in the metastatic process of osteosarcoma to the lungs and suggest an alternative focus for therapy, that is, incorporating the lung microenvironment as part of the treatment strategy against established osteosarcoma disease in the lungs.

MiR-133b is down-regulated in human osteosarcoma and inhibits osteosarcoma cells proliferation, migration and invasion, and promotes apoptosis

MicroRNAs (miRNAs) decrease the expression of specific target oncogenes or tumor suppressor genes and thereby play crucial roles in tumorigenesis and tumor growth. To date, the potential miRNAs regulating osteosarcoma growth and progression are not fully identified yet. In this study, the miRNA microarray assay and hierarchical clustering analysis were performed in human osteosarcoma samples. In comparison with normal human skeletal muscle, 43 miRNAs were significantly differentially expressed in human osteosarcomas (fold change ≥2 and p≤0.05). Among these miRNAs, miR-133a and miR-133b expression was decreased by 135 folds and 47 folds respectively and the decreased expression was confirmed in both frozen and paraffin-embedded osteosarcoma samples. The miR-133b precursor expression vector was then transfected into osteosarcoma cell lines U2-OS and MG-63, and the stable transfectants were selected by puromycin. We found that stable over-expression of miR-133b in osteosarcoma cell lines U2-OS and MG-63 inhibited cell proliferation, invasion and migration, and induced apoptosis. Further, over-expression of miR-133b decreased the expression of predicted target genes BCL2L2, MCL-1, IGF1R and MET, as well as the expression of phospho-Akt and FAK. This study provides a new insight into miRNAs dysregulation in osteosarcoma, and indicates that miR-133b may play as a tumor suppressor gene in osteosarcoma.

Changes in circulating microRNAs after radiochemotherapy in head and neck cancer patients

INTRODUCTION

Circulating microRNAs (miRNAs) are easily accessible and have already proven to be useful as prognostic markers in cancer patients. However, their origin and function in the circulation is still under discussion. In the present study we analyzed changes in the miRNAs in blood plasma of head and neck squamous cell carcinoma (HNSCC) patients in response to radiochemotherapy and compared them to the changes in a cell culture model of primary HNSCC cells undergoing simulated anti-cancer therapy.

MATERIALS AND METHODS

MiRNA-profiles were analyzed by qRT-PCR arrays in paired blood plasma samples of HNSCC patients before therapy and after two days of treatment. Candidate miRNAs were validated by single qRT-PCR assays. An in vitro radiochemotherapy model using primary HNSCC cell cultures was established to test the possible tumor origin of the circulating miRNAs. Microarray analysis was performed on primary HNSCC cell cultures followed by validation of deregulated miRNAs via qRT-PCR.

RESULTS

Unsupervised clustering of the expression profiles using the six most regulated miRNAs (miR-425-5p, miR-21-5p, miR-106b-5p, miR-590-5p, miR-574-3p, miR-885-3p) significantly (p = 0.012) separated plasma samples collected prior to treatment from plasma samples collected after two days of radiochemotherapy. MiRNA profiling of primary HNSCC cell cultures treated in vitro with radiochemotherapy revealed differentially expressed miRNAs that were also observed to be therapy-responsive in blood plasma of the patients (miR-425-5p, miR-21-5p, miR-106b-5p, miR-93-5p) and are therefore likely to stem from the tumor. Of these candidate marker miRNAs we were able to validate by qRT-PCR a deregulation of eight plasma miRNAs as well as miR-425-5p and miR-93-5p in primary HNSCC cultures after radiochemotherapy.

CONCLUSION

Changes in the abundance of circulating miRNAs during radiochemotherapy reflect the therapy response of primary HNSCC cells after an in vitro treatment. Therefore, the responsive miRNAs (miR-425-5p, miR-93-5p) may represent novel biomarkers for therapy monitoring. The prognostic value of this exciting observation requires confirmation using an independent patient cohort that includes clinical follow-up data.

MicroRNAs in osteosarcoma: diagnostic and therapeutic aspects

MicroRNAs (miRNAs) are small RNA molecules, which can interfere with the expression of several genes and act as gene regulator. miRNAs have been proved as a successful diagnostic and therapeutic tool in several cancers. In this review, the differential expression of miRNAs in osteosarcoma and their possibility to be used as diagnostic and therapeutic tools have been discussed. Osteosarcoma is the most common primary bone tumor that mainly affects children and adolescents. The current treatment of osteosarcoma remains difficult, and osteosarcoma causes many deaths because of its complex pathogenesis and resistance to conventional treatments. Several studies demonstrated that the differential expression patterns of miRNAs are a promising tool for the diagnosis and treatment of osteosarcoma. Although some aspect of the mechanism of action of miRNAs in controlling osteosarcoma has been identified (e.g., targeting the Notch signaling pathway), it is far beyond to the clear understanding of miRNA targets in osteosarcoma. Identification of the specific target of miRNAs may aid molecular targets for drug development and future relief of osteosarcoma.

Loss of microRNA-132 predicts poor prognosis in patients with primary osteosarcoma

MicroRNA-132 (miR-132), an angiogenic growth factor inducible microRNA in the endothelium, facilitates pathological angiogenesis. Previous study showed that miR-132 was downregulated in human osteosarcoma. However, its functional attributes associated with tumor progression of osteosarcoma have not been fully elucidated. The aim of this study was to investigate the clinical significance of miR-132 expression in human osteosarcoma. miR-132 expression was detected by quantitative reverse transcription polymerase chain reaction using 166 pairs of osteosarcoma and noncancerous bone tissues. Then, the association of miR-132 expression with clinicopathological factors or survival of osteosarcoma patients was also evaluated. miR-132 expression was significantly lower in osteosarcoma tissues than that in corresponding noncancerous bone tissues (P < 0.001). In addition, miR-132 expression was decreased in the osteosarcoma specimens with advanced clinical stage (P = 0.009), positive distant metastasis (P = 0.006), and poor response to chemotherapy (P = 0.009). Moreover, both the univariate and multivariate analyses showed that osteosarcoma patients with low miR-132 expression had poorer overall and disease-free survival (both P < 0.001), and low miR-132 expression was an independent prognostic factor for both overall (P = 0.001) and disease-free survival (P = 0.006). These findings offer the convinced evidence for the first time that miR-132 may participate in tumor progression of osteosarcoma and loss of miR-132 expression may be a predictor for unfavorable outcome of osteosarcoma patients.

miR-150, p53 protein and relevant miRNAs consist of a regulatory network in NSCLC tumorigenesis

microRNAs (miRNAs) are a class of non-coding small RNAs that act as negative regulators of gene expression by binding to the 3'-untranslated region (3'-UTR) of target mRNAs. Tumor protein p53, a transcriptional factor, plays an important role in the progression of tumorigenesis. miR-150 was the only miRNA predicted to target 3'-UTR of p53 by Targetscan. In order to investigate the function of miR-150, p53 and relevant miRNAs in non-small cell lung cancer (NSCLC), we constructed two expression vectors of p53 (pcDNA3.1-p53 and pcDNA3.1-p53-3'-UTR) and two report vectors (pGL3-p53-3'-UTR and pGL3-p53-3'-mUTR). The activity of luciferase transfected with miR-150 mimics was lower by 30% when compared to that of the miRNA-negative control (miRNA-NC). Moreover, the p53 protein was downregulated by at least 50% when miR-150 mimics were cotransfected with pcDNA3.1-p53-3'-UTR when compared to miRNA-NC. We also determined the expression of miR-150 and p53 in NSCLC patient tissue samples. The expression of miR-150 in T2 stage tissue samples was higher than that in T1 stage tissue samples. The corresponding target gene p53 was correlated with miR-150 expression. In the present study, we further analyzed the cell cycle distribution. The cells transfected with pcDNA3.1-p53 were significantly arrested in the G1 phase when compared to the control cells. When miR-150 mimics were cotransfected with pcDNA3.1-p53-3'-UTR, the percentage of cells in the G1 phase was significantly lower by 4% when compared to miRNA-NC. To identify miRNAs that are regulated by the p53 protein, qRT-PCR was performed after pcDNA3.1-p53 transfection. miR-34a, miR-184, miR-181a and miR-148 were upregulated significantly. However, there was no distinct difference in the expression of miR-10a, miR-182 and miR-34c. Our results showed that miR-150 targets the 3'-UTR of p53, and p53 protein promotes the expression of miRNAs which affect cell cycle progression. These findings suggest that miR-150, p53 protein and relevant miRNAs are members of a regulatory network in NSCLC tumorigenesis.

Epigenetic regulation of cardiac fibrosis

Cardiac fibrosis is characterized by excessive extracellular matrix accumulation that ultimately destroys tissue architecture and eventually abolishes normal function. In recent years, despite the underlying mechanisms of cardiac fibrosis are still unknown, numerous studies suggest that epigenetic modifications impact on the development of cardiac fibrosis. Epigenetic modifications control cell proliferation, differentiation, migration, and so on. Epigenetic modifications contain three main processes: DNA methylation, histone modifications, and silencing by microRNAs. We here outline the recent work pertaining to epigenetic changes in cardiac fibrosis. This review focuses on the epigenetic regulation of cardiac fibrosis.