Guangmei Yan

Targeting oncogenic miR-335 inhibits growth and invasion of malignant astrocytoma cells

BackgroundAstrocytomas are the most common and aggressive brain tumors characterized by their highly invasive growth. Gain of chromosome 7 with a hot spot at 7q32 appears to be the most prominent aberration in astrocytoma. Previously reports have shown that microRNA-335 (miR-335) resided on chromosome 7q32 is deregulated in many cancers; however, the biological function of miR-335 in astrocytoma has yet to be elucidated.ResultsWe report that miR-335 acts as a tumor promoter in conferring tumorigenic features such as growth and invasion on malignant astrocytoma. The miR-335 level is highly elevated in C6 astrocytoma cells and human malignant astrocytomas. Ectopic expression of miR-335 in C6 cells dramatically enhances cell viability, colony-forming ability and invasiveness. Conversely, delivery of antagonist specific for miR-335 (antagomir-335) to C6 cells results in growth arrest, cell apoptosis, invasion repression and marked regression of astrocytoma xenografts. Further investigation reveals that miR-335 targets disheveled-associated activator of morphogenesis 1(Daam1) at posttranscriptional level. Moreover, silencing of endogenous Daam1 (siDaam1) could mimic the oncogenic effects of miR-335 and reverse the growth arrest, proapoptotic and invasion repression effects induced by antagomir-335. Notably, the oncogenic effects of miR-335 and siDAAM1 together with anti-tumor effects of antagomir-335 are also confirmed in human astrocytoma U87-MG cells.ConclusionThese findings suggest an oncogenic role of miR-335 and shed new lights on the therapy of malignant astrocytomas by targeting miR-335.

Transcriptome analysis of Deinagkistrodon acutus venomous gland focusing on cellular structure and functional aspects using expressed sequence tags

BackgroundThe snake venom gland is a specialized organ, which synthesizes and secretes the complex and abundant toxin proteins. Though gene expression in the snake venom gland has been extensively studied, the focus has been on the components of the venom. As far as the molecular mechanism of toxin secretion and metabolism is concerned, we still knew a little. Therefore, a fundamental question being arisen is what genes are expressed in the snake venom glands besides many toxin components?ResultsTo examine extensively the transcripts expressed in the venom gland of Deinagkistrodon acutus and unveil the potential of its products on cellular structure and functional aspects, we generated 8696 expressed sequence tags (ESTs) from a non-normalized cDNA library. All ESTs were clustered into 3416 clusters, of which 40.16% of total ESTs belong to recognized toxin-coding sequences; 39.85% are similar to cellular transcripts; and 20.00% have no significant similarity to any known sequences. By analyzing cellular functional transcripts, we found high expression of some venom related genes and gland-specific genes, such as calglandulin EF-hand protein gene and protein disulfide isomerase gene. The transcripts of creatine kinase and NADH dehydrogenase were also identified at high level. Moreover, abundant cellular structural proteins similar to mammalian muscle tissues were also identified. The phylogenetic analysis of two snake venom toxin families of group III metalloproteinase and serine protease in suborder Colubroidea showed an early single recruitment event in the viperids evolutionary process.ConclusionGene cataloguing and profiling of the venom gland of Deinagkistrodon acutus is an essential requisite to provide molecular reagents for functional genomic studies needed for elucidating mechanisms of action of toxins and surveying physiological events taking place in the very specialized secretory tissue. So this study provides a first global view of the genetic programs for the venom gland of Deinagkistrodon acutus described so far and an insight into molecular mechanism of toxin secreting.All sequences data reported in this paper have been submitted into the public database [GenBank: DV556511-DV565206].

A Small-Molecule Triptolide Suppresses Angiogenesis and Invasion of Human Anaplastic Thyroid Carcinoma Cells via Down-Regulation of the Nuclear Factor-κB Pathway

Anaplastic thyroid carcinoma (ATC) is among the most aggressive malignancies known and is characterized with rapid growth, early invasion, and complete refractoriness to current therapies. Here we report that triptolide, a small molecule from a Chinese herb, could potently inhibit proliferation in vitro, angiogenesis in vivo, and invasion in a Matrigel model in human ATC cell line TA-K cells at nanomolar concentrations. We further elucidate that triptolide inhibits the nuclear factor-κB (NF-κB) transcriptional activity via blocking the association of p65 subunit with CREB-binding protein (CBP)/p300 in the early stage and via decreasing the protein level of p65 in the late stage. Expression of the NF-κB targeting genes cyclin D1, vascular endothelial growth factor, and urokinase-type plasminogen activator is significantly reduced by triptolide in both TA-K and 8505C human ATC cell lines, which are well known to be critical for proliferation, angiogenesis, and invasion in solid tumors. Our findings suggest that triptolide may function as a small molecule inhibitor of tumor angiogenesis and invasion and may provide novel mechanistic insights into the potential therapy for human ATC.

Cholera toxin induces malignant glioma cell differentiation via the PKA/CREB pathway

Malignant gliomas are one of the leading causes of cancer deaths worldwide, but chemoprevention strategies for them are few and poorly investigated. Here, we show that cholera toxin, the traditional biotoxin and well known inducer of accumulation of cellular cAMP, is capable of inducing differentiation on malignant gliomas in vitro with rat C6 and primary cultured human glioma cells. Cholera toxin-induced differentiation was characterized by typical morphological changes, increased expression of glial fibrillary acid protein, decreased expression of Ki-67, inhibition of cellular proliferation, and accumulation of cells in the G1 phase of the cell cycle. Cholera toxin also triggered a significant reduction in the G1 cell-cycle regulatory proteins cyclin D1 and Cdk2 along with an overexpression of cell-cycle inhibitory proteins p21Cip1 and p27Kip1. Abrogation of cAMP-dependent protein kinase A activity by protein kinase A inhibitor or silencing of cAMP-responsive element binding proteins by RNA interference resulted in suppressed differentiation. These findings imply the attractiveness of cholera toxin as a drug candidate for further development of differentiation therapy. Furthermore, activation of the protein kinase A/cAMP-responsive element binding protein pathway may be a key and requisite factor in glioma differentiation.

Isoflurane Produces Delayed Preconditioning against Spinal Cord Ischemic Injury via Release of Free Radicals in Rabbits

Background:Whether isoflurane preconditioning produces delayed neuroprotection in the spinal cord is unclear. The authors tested the hypothesis that isoflurane produces delayed preconditioning against spinal cord ischemic injury and, further, that the beneficial effect is dependent on free radicals. Methods:In experiment 1, 63 rabbits were randomly assigned to seven groups (n = 9 each): Animals in the control group only underwent spinal cord ischemia without pretreatment; animals in the Iso24h, Iso48h, and Iso72h groups received 40 min of 1.0 minimum alveolar concentration isoflurane in 100% oxygen each day for 5 consecutive days, with the last pretreatment at 24, 48, and 72 h, respectively, before spinal cord ischemia; animals in the O224h, O248h, and O272h groups received 40 min of 100% oxygen each day for 5 consecutive days, with the last pretreatment at 24, 48, and 72 h, respectively, before spinal cord ischemia. In experiment 2, 48 rabbits were randomly assigned into four groups (n = 12 each): Animals in the O2 and Iso groups received 3 ml/kg saline intraperitoneally 1 h before each session of oxygen pretreatment and isoflurane pretreatment, respectively. In the DMTU+Iso and DMTU+O2 groups, 10% dimethylthiourea (DMTU, a potent free radical scavenger) dissolved in saline (3 ml/kg) was administered at the same time point. Twenty-four hours after the last pretreatment, animals were subjected to spinal cord ischemia. Spinal cord ischemia was induced by an infrarenal aorta clamping for 20 min. Forty-eight hours after reperfusion, neurologic function and histopathology of the spinal cord were examined. Results:In experiment 1, the neurologic and histopathologic outcomes in the Iso24h and Iso48h groups were better than those in the control group (P < 0.005 for each comparison); the neurologic and histopathologic outcomes in the control group showed no significant differences in comparison with the O224h, O248h, O272h, and Iso72h groups (P > 0.05 for each comparison). In experiment 2, the neurologic and histopathologic outcomes in the Iso group were better than those in the DMTU+Iso, O2, and DMTU+O2 groups (P < 0.01 for each comparison); there were no significant differences in the neurologic and histopathologic outcomes among the DMTU+Iso, O2, and DMTU+O2 groups (P > 0.05 for each comparison). Conclusions:Isoflurane produces delayed preconditioning against spinal cord ischemic injury, and the beneficial effect may be dependent on the release of free radicals.

MicroRNA 335 is required for differentiation of malignant glioma cells induced by activation of cAMP/protein kinase A pathway.

Glioma is the most common malignant cancer affecting the central nerve system, with dismal prognosis. Differentiation-inducing therapy is a novel strategy that has been preliminarily proved effective against malignant glioma. We have reported previously that activation of cAMP/protein kinase A (PKA) pathway is capable of inducing glioma cell differentiation, characterized by astrocyte-like shape and dramatic induction of astrocyte biomarker glial fibrillary acidic protein (GFAP). However, little progress has been made on molecular mechanisms related. Here we demonstrate that microRNA 335 (miR-335) is responsible for the glioma cell differentiation stimulated by activation of cAMP/PKA pathway. In the cAMP elevator cholera toxin-induced differentiation model of rat C6 glioma cells, miR-335 was significantly up-regulated, which was mimicked by other typical cAMP/PKA pathway activators (e.g., forskolin, dibutyryl-cAMP) and abolished by PKA-specific inhibitor (9R,10S,12S)-2,3,9,10,11,12-hexahydro-10-hydroxy-9-methyl-1-oxo-9,12-epoxy-1H-diindolo[1,2,3-fg:3′,2′,1′-kl]pyrrolo[3,4-i] [1,6]benzodiazocine-10-carboxylic acid, hexyl ester (KT5720). In an assay measuring gain and loss of miR-335 function, exogenetic miR-335 resulted in induction of GFAP, whereas miR-335 specific inhibitor antagomir-335 violently blocked cholera toxin-induced GFAP up-regulation. It is noteworthy that in human U87-MG glioma cells and human primary culture glioma cells, miR-335 also mediated cholera toxin-induced differentiation. Taken together, our findings suggest that miR-335 is potently required for differentiation of malignant glioma cells induced by cAMP/PKA pathway activation, and a single microRNA may act as an important fate determinant to control the differentiation status of malignant gliomas, which has provided a new insight into differentiation-inducing therapy against malignant gliomas.

Identification and characterization of alphavirus M1 as a selective oncolytic virus targeting ZAP-defective human cancers

Significance Although oncolytic virotherapy is showing great promise in clinical trials, not all patients are benefiting. Identifying predictors of therapeutic effectiveness for each oncolytic virus would provide a good chance to increase response rate. Here, we describe an alphavirus (M1) that possesses selective and potent antitumor activity through intravenous infusion, whereas its replication is controlled by the zinc-finger antiviral protein (ZAP) gene. A survey of cancer tissue banks reveals that ZAP is commonly deficient in human cancers, suggesting extensive application prospects of M1. Our work provides an example of a potentially personalized cancer therapy using a targeted oncolytic virus that can be selectively administered to patients with ZAP-deficient tumors. We predict that such agents will form the armamentarium of cancer therapy in the future. Oncolytic virotherapy is a growing treatment modality that uses replicating viruses as selective antineoplastic agents. Safety and efficacy considerations dictate that an ideal oncolytic agent would discriminate between normal and cancer cells on the basis of common genetic abnormalities in human cancers. Here, we identify a naturally occurring alphavirus (M1) as a novel selective killer targeting zinc-finger antiviral protein (ZAP)-deficient cancer cells. In vitro, in vivo, and ex vivo studies showed potent oncolytic efficacy and high tumor tropism of M1. We showed that the selectivity depends on ZAP deficiency by systematic identification. A large-scale multicenter pathology study using tissue microarrays reveals that ZAP is commonly deficient in human cancers, suggesting extensive application prospects for M1. Additionally, M1 killed cancer cells by inducing endoplasmic reticulum stress-mediated apoptosis. Our report provides novel insights into potentially personalized cancer therapy using oncolytic viruses.

Inactivation of lysyl oxidase by β-aminopropionitrile inhibits hypoxia-induced invasion and migration of cervical cancer cells

Tumor invasion and migration are major causes of mortality in patients with cervical carcinoma. Tumors under hypoxic conditions are more invasive and have a higher metastasic activity. Lysyl oxidase (LOX) is a hypoxia-responsive gene. LOX has been shown to be essential for hypoxia-induced metastasis in breast cancer. However, the direct impact of LOX on cervical cancer cell motility remains poorly understood. Our study revealed that LOX expression at protein and catalytic levels is upregulated in cervical cancer cells upon exposure to hypoxia. Hypoxia induced mesenchymal-like morphological changes in HeLa and SiHa cells which were accompanied by upregulation of α-SMA and vimentin, two mesenchymal markers, and downregulation of E-cadherin, an epithelial marker, indicating the epithelial-mesenchymal transition (EMT) of cervical cancer cells occurred under hypoxic conditions. Treatment of tumor cells with β-aminopropionitrile (BAPN), an active site inhibitor of LOX, blocked the hypoxia-induced EMT morphological and marker protein changes, and inhibited invasion and migration capacities of cervical carcinoma cells in vitro. Collectively, these findings suggest LOX enhances hypoxia-induced invasion and migration in cervical cancer cells mediated by the EMT which can be inhibited by BAPN.

Triptolide-induced cell cycle arrest and apoptosis in human renal cell carcinoma cells

Renal cell carcinoma (RCC) is the most frequent type of renal-originated malignancy. Although nephrectomy is successfully used to save the lives of patients with localized RCC, treatment of advanced and other refractory RCCs is poor and still inadequate. Here, we show that triptolide, a small molecule and a well-known anti-inflammatory and anti-immunity agent used in the clinic, is capable of inducing cell apoptosis via the mitochondrial pathway in the 786-0 RCC cell line. This induction occurred in concert with reduced expression of genes related to the stabilization of mitochondria such as Bcl-2 and Bcl-XL. Cell cycle analysis showed that exposure to triptolide decreased the proportion of cells in the G0/G1 and G2/M phases, and increased the proportion of cells in the S phase. Cell accumulation in the S phase can be attributed to reduced expression of cell cycle checkpoint regulators such as cyclin A, cyclin B, CDK1, CDK2 and retinoblastoma proteins (Rb). These results raise the possibility that triptolide-induced apoptosis is mediated by cell cycle arrest. Similarly, in another human RCC cell line, OS-RC-2, triptolide-induced apoptosis and cell accumulation in S phase were also observed. Therefore, triptolide emerges as a stimulator of apoptosis by influencing coordinate regulation of proliferation and apoptosis, and may be applicable to the treatment of human renal cell carcinoma.

Activation of a pro-survival pathway IL-6/JAK2/STAT3 contributes to glial fibrillary acidic protein induction during the cholera toxin-induced differentiation of C6 malignant glioma cells

Differentiation‐inducing therapy has been proposed to be a novel potential approach to treat malignant gliomas. Glial fibrillary acidic protein (GFAP) is a well‐known specific astrocyte biomarker and acts as a tumor suppressor gene (TSG) in glioma pathogenesis. Previously we reported that a traditional biotoxin cholera toxin could induce malignant glioma cell differentiation characterized by morphologic changes and dramatic GFAP expression. However, the molecular mechanisms underlying GFAP induction are still largely unknown. Here we demonstrate that an oncogenic pathway interleukin‐6/janus kinase‐2/signal transducer and activator of transcription 3 (IL‐6/JAK2/STAT3) cascade mediates the cholera toxin‐induced GFAP expression. Cholera toxin dramatically stimulated GFAP expression at the transcriptional level in C6 glioma cells. Meanwhile, phosphorylation of STAT3 and JAK2 was highly induced in a time‐dependent manner after cholera toxin incubation, whereas no changes of STAT3 and JAK2 were observed. Furthermore, the IL‐6 gene was quickly induced by cholera toxin and subsequent IL‐6 protein secretion was stimulated. Importantly, exogenous recombinant rat IL‐6 can also induce phosphorylation of STAT3 concomitant with GFAP expression while JAK2 specific inhibitor AG490 could effectively block both cholera toxin‐ and IL‐6‐induced GFAP expression. Given that the methylation of the STAT3 binding element can suppress GFAP expression, we detected the methylation status of the critical recognition sequence of STAT3 in the promoter of GFAP gene (−1518 ∼ −1510) and found that it was unmethylated in C6 glioma cells. In addition, neither DNA methyltransferase1 (DNMT1) inhibitor 5‐Aza‐2′‐deoxycytidine (5‐AZa‐CdR) nor silencing DNMT1 can stimulate GFAP expression, indicating that the loss of GFAP expression in C6 cells is not caused by its promoter hypermethylation. Taken together, our findings suggest that activation of a pro‐survival IL‐6/JAK2/STAT3 cascade contributes to cholera toxin‐induced GFAP expression, which implies that a survival‐promoting signal may also play a differentiation‐supporting role in malignant gliomas.