Guanxiang Qian

Putative tumor suppressor miR-145 inhibits colon cancer cell growth by targeting oncogene friend leukemia virus integration 1 gene

Tumor suppressor microRNA miR‐145 is commonly down‐regulated in colon carcinoma tissues, but its specific role in tumors remains unknown.

Long noncoding RNA-mediated intrachromosomal interactions promote imprinting at the Kcnq1 locus

A long noncoding RNA directly builds an intrachromosomal interaction complex to establish allele-specific transcriptional gene silencing over a large chromosomal domain.

The regulation of toll-like receptor 2 by miR-143 suppresses the invasion and migration of a subset of human colorectal carcinoma cells

BackgroundThe Toll-like receptor 2 (TLR2)-driven tissue response may promote neoangiogenesis and tumour growth by mechanisms that are poorly understood.MethodsWe investigated the expression levels of TLR2 and associated-miRNAs in colorectal carcinoma (CRC) tissues and cell lines using real-time PCR, northern blotting and western blotting. Survival curver was generated by Log-Rank test and the role of TLR2 signalling in tumour invasion and migration was determined by transwell analysis kits.ResultsWe observed that the tissues from CRC patients express relatively high levels of TLR2. Targeting TLR2 markedly reduces the invasion and migration of CRC cells. We also found that miR-143, a putative tumour suppressor that is down-regulated in CRC tissues, reduces the invasion and migration of CRC cells primarily via TLR2. Utilising a xenograft mouse model, we demonstrated that re-expression of miR-143 inhibits CRC cell colonisation in vivo.ConclusionmiR-143 blocks the TLR2 signalling pathway in human CRC cells. This knowledge may pave the way for new clinical applications utilising miR-143 mimics in the treatment of patients with CRC.

MiR-145, a new regulator of the DNA Fragmentation Factor-45 (DFF45)-mediated apoptotic network

BackgroundMicroRNA-145 (miR-145) is considered to play key roles in many cellular processes, such as proliferation, differentiation and apoptosis, by inhibiting target gene expression. DNA Fragmentation Factor-45 (DFF45) has been found to be the substrate of Caspase-3, and the cleavage of DFF45 by caspase-3 during apoptosis releases DFF40 that degrades chromosomal DNA into nucleosomal fragments. There are currently no in-depth studies on the relationship between miR-145 and the DFF45 gene.ResultsIn this study, we identified DFF45 as a novel target of miR-145. We demonstrated that miR-145 targets a putative binding site in the coding sequence (CDS) of DFF45, and its abundance is inversely associated with DFF45 expression in colon cancer cells. Using a luciferase reporter system, we found that miR-145 suppresses the expression of the luciferase reporter gene fused to the putative binding site of DFF45. The level of DFF45 protein, but not DFF45 mRNA, was decreased by miR-145, suggesting a mechanism of translational regulation. Furthermore, we demonstrate that this specific silencing of DFF45 by miR-145 accounts, at least in part, for the staurosporine-induced tumor cell apoptosis in vitro.ConclusionsOur study reveals a previously unrecognized function of miR-145 in DFF45 processing, which may underlie crucial aspects of cancer biology.

Interruption of intrachromosomal looping by CCCTC binding factor decoy proteins abrogates genomic imprinting of human insulin-like growth factor II

CCCTC binding factor (CTCF) mutants that cannot bind components of the polycomb repressive complex-2 (PRC2) do not form the chromatin loops that regulate monoallelic gene expression.

Long non-coding RNA ROR decoys gene- specific histone methylation to promote tumorigenesis

Long non-coding RNAs (lncRNAs) are not translated into proteins and were initially considered to be part of the ‘dark matter’ of the genome. Recently, it has been shown that lncRNAs play a role in the recruitment of chromatin modifying complexes and can influence gene expression. However, it is unknown if lncRNAs function in a similar way in cancer. Here, we show that the lncRNA ROR occupies and activates the TESC promoter by repelling the histone G9A methyltransferase and promoting the release of histone H3K9 methylation. Suppression of ROR in tumors results in silencing of TESC expression, and G9A-mediated histone H3K9 methylation in the TESC promoter is restored, which significantly reduces tumor growth and metastasis. Without ROR silencing, TESC knockdown presents consistent and significant reductions in tumor progression. Our results reveal a novel mechanism by which ROR may serve as a decoy oncoRNA that blocks binding surfaces, preventing the recruitment of histone modifying enzymes, thereby specifying a new pattern of histone modifications that promote tumorigenesis.BackgroundLong non-coding RNAs (lncRNAs) are not translated into proteins and were initially considered to be part of the ‘dark matter’ of the genome. Recently, it has been shown that lncRNAs play a role in the recruitment of chromatin modifying complexes and can influence gene expression. However, it is unknown if lncRNAs function in a similar way in cancer.ResultsHere, we show that the lncRNA ROR occupies and activates the TESC promoter by repelling the histone G9A methyltransferase and promoting the release of histone H3K9 methylation. Suppression of ROR in tumors results in silencing of TESC expression, and G9A-mediated histone H3K9 methylation in the TESC promoter is restored, which significantly reduces tumor growth and metastasis. Without ROR silencing, TESC knockdown presents consistent and significant reductions in tumor progression.ConclusionsOur results reveal a novel mechanism by which ROR may serve as a decoy oncoRNA that blocks binding surfaces, preventing the recruitment of histone modifying enzymes, thereby specifying a new pattern of histone modifications that promote tumorigenesis.

Microarray-based analysis: identification of hypoxia-regulated microRNAs in retinoblastoma cells.

Hypoxia is an essential feature of retinoblastoma and contributes to poor prognosis and resistance to conventional therapy. MicroRNAs (miRNAs) are small non-coding RNAs involved in a wide variety of biological processes, including cell differentiation, proliferation, death and metabolism. However, the relationship between hypoxia and the expression of miRNAs in retinoblastoma is not well understood. In this study, we aimed to analyze the pattern of miRNA expression in a retinoblastoma cell line under hypoxic conditions and to identify the miRNAs regulated by hypoxia, as well as their possible functions. miRNA expression profiling in retinoblastoma cells (HXO-RB44) under normal and hypoxic conditions was assessed by microarray techniques. The differentially expressed miRNAs were subjected to bioinformatic analyses to predict and categorise the key miRNAs and their target genes. A quantitative real-time RT-PCR approach was used to validate their expression. A Cell Counting kit was used to evaluate the functional significance of miR-181b in RB cell proliferation. There were 46 miRNAs that changed expression more than 2-fold in response to hypoxia (34 up-regulated and 12 down-regulated). We identified a cluster of miRNAs that includes miR-181b, miR-125a-3p, miR-30c-2, miR-497 and miR-491-3p as hypoxia-regulated miRNAs (HRMs) in retinoblastoma cells, of which miR-181b was the most typically differentially expressed miRNA under hypoxic conditions. Functionally, these HRMs are involved in apoptosis, cell adhesion, cell proliferation and mRNA processing, all processes that associate closely with the hypoxia response of cancer cells. Additionally, we found that administration of miR-181b inhibitor can suppress proliferation of retinoblastoma cells. These findings provide the first evidence that miRNAs play an important role in the hypoxia response of retinoblastoma cells. MiR-181b, the most typically up-regulated miRNA may aid in future clinical intervention of retinoblastoma.

Knockdown of TIGAR by RNA interference induces apoptosis and autophagy in HepG2 hepatocellular carcinoma cells.

Apoptosis and autophagy are crucial mechanisms regulating cell death, and the relationship between apoptosis and autophagy in the liver has yet to be thoroughly explored. TIGAR (TP53-induced glycolysis and apoptosis regulator), which is a p53-inducible gene, functions in the suppression of ROS (reactive oxygen species) and protects U2OS cells from undergoing cell death. In this study, silencing TIGAR by RNAi (RNA interference) in HepG2 cells down-regulated both TIGAR mRNA (∼75%) and protein levels (∼80%) and led to the inhibition of cell growth (P<0.01) by apoptosis (P<0.001) and autophagy. We demonstrated that TIGAR can increase ROS levels in HepG2 cells. The down-regulation of TIGAR led to the induction of LC-3 II (specific autophagic marker), the formation of the autophagosome, and increased Beclin-1 expression. 3-MA (3-Methyladenine), an inhibitor of autophagic sequestration blocker, inhibited TIGAR siRNA-enhanced autophagy, as indicated by the decrease in LC-3 II levels. Consequently, these data provide the first evidence that targeted silencing of TIGAR induces apoptotic and autophagic cell death in HepG2 cells, and our data raise hope for the future successful application of TIGAR siRNA in patients with hepatocellular carcinoma (HCC).

WWOX-mediated apoptosis in A549 cells mainly involves the mitochondrial pathway

The human WWOX gene, known as WW domain-containing oxidoreductase, is located on 16q23.3-24.1, a chromosome region that spans the common fragile site, FRA16D. Abnormal transcripts or even loss of expression are frequently found in a number of cancer cell types, including breast, ovarian, prostate and lung cancer cells. It has therefore been proposed that the WWOX gene encodes a candidate tumor suppressor, possibly a pro-apoptotic protein. However, the mechanism behind this is not entirely clear. In the present study, we examined the pro-apoptotic action of WWOX using transient expression in A549 cells. We observed that the ectopic expression of WWOX caused apoptosis in A549 cells. We further observed procaspase-3 and procaspase-9 activation and the release of cytochrome C from the mitochondria in A549 cells transfected with pcDNA3.0-WWOX. These data indicate that WWOX induces apoptosis in A549 cells via the mitochondrial pathway.

Hypoxia inducible factor-1α-mediated activation of survivin in cervical cancer cells

Aim:  Hypoxia, a characteristic of almost all types of solid tumors, has been associated with poor outcome in a number of human malignancies. The aim of this study was to investigate the molecular mechanisms involved in hypoxia‐induced activation of the human survivin gene promoter in cervical HeLa cells.