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Articles by M Yang
Total Records ( 6 ) for M Yang
  F. W Roemer , A Guermazi , Y Zhang , M Yang , D. J Hunter , M. D Crema and K. Bohndorf
 

OBJECTIVE. The purpose of this study was to compare synovitis-like signal changes in Hoffa's fat pad on unenhanced proton density–weighted fat-suppressed sequences with signal alterations in Hoffa's fat pad and peripatellar synovial thickening on T1-weighted fat-suppressed contrast-enhanced sequences in patients with osteoarthritis.

SUBJECTS AND METHODS. Fifty patients with osteoarthritis of the knee participated in the study. MRI was performed with triplanar proton density–weighted fat-suppressed sequences and a sagittal T1-weighted fat-suppressed contrast-enhanced sequence. Signal intensity alterations in Hoffa's fat pad were scored semiquantitatively on unenhanced and contrast-enhanced images by two radiologists in consensus. Peripatellar synovial thickness was measured on the T1-weighted fat-suppressed contrast-enhanced images in six locations. Agreement between scoring of signal changes on unenhanced and contrast-enhanced sequences was assessed with kappa statistics. The sensitivity, specificity, and accuracy of scoring of signal-intensity changes on unenhanced images were calculated with T1-weighted contrast-enhanced MRI as the reference standard. In addition, we also examined the relation between signal changes and summed synovial thickness using Spearman's rank correlation coefficient.

RESULTS. Agreement between unenhanced and contrast-enhanced MRI was fair to moderate (weighted = 0.35 and 0.45). The sensitivity of signal intensity changes in Hoffa's fat pad on proton density–weighted fat-suppressed images was high, but specificity was low. Correlations of signal intensity changes in Hoffa's fat pad with synovial thickness were lower for unenhanced scans but all were statistically significant.

CONCLUSION. Signal intensity alterations in Hoffa's fat pad on unenhanced images do not always represent synovitis but are a nonspecific albeit sensitive finding. Semiquantitative scoring of synovitis of the patellofemoral region in osteoarthritis ideally should be performed with T1-weighted contrast-enhanced sequences and should include scoring of synovial thickness.

  Y Liao , J Tang , M Ma , Z Wu , M Yang , X Wang , T Liu , X Chen , P. C Fletcher and W. Hao
 

Ketamine abuse has been shown to have a deleterious impact on brain function. However, the precise mechanisms of ketamine dependence-induced pathological change remain poorly understood. Although there is evidence for white matter changes in drug abuse, the presence of white matter abnormalities in chronic ketamine users has not been studied. White matter volumes were measured using in vivo diffusion tensor magnetic resonance imaging data in 41 ketamine-dependent subjects and 44 drug-free healthy volunteers. White matter changes associated with chronic ketamine use were found in bilateral frontal and left temporoparietal cortices. There was also evidence that frontal white matter fractional anisotropy correlated with the severity of drug use (as measured by estimated total ketamine consumption). We provide direct evidence for dose-dependent abnormalities of white matter in bilateral frontal and left temporoparietal regions following chronic ketamine use. The findings suggest a microstructural basis for the changes in cognition and experience observed with prolonged ketamine use. Moreover, the similarities of these changes to those observed in chronic schizophrenia have implications for the glutamate model of this illness.

  Y Dai , L Qiao , K. W Chan , M Yang , J Ye , J Ma , B Zou , Q Gu , J Wang , R Pang , H.Y Lan and B. C.Y. Wong
 

Down-regulation of XIAP (X-linked inhibitor of apoptosis protein) sensitizes colon cancer cells to the anticancer effect of peroxisome proliferator-activated receptor- (PPAR) ligands in mice. The aims of this study were to evaluate the effect of embelin (2,5-dihydroxy-3-undecyl-1,4-benzoquinone), an antagonist of XIAP, on colon cancer, with a particular focus on whether PPAR is required for embelin to exert its effect. A dominant-negative PPAR was used to antagonize endogenous PPAR in HCT116 cells. Cells were treated with or without embelin. Cell proliferation, apoptosis, and nuclear factor-B (NF-B) activity were measured. For in vivo studies, 1,2-dimethylhydrazine dihydrochloride (DMH) was s.c. injected to induce colon cancer in PPAR+/+ and PPAR+/– mice. Mice were fed embelin daily for 10 days before DMH injection, and continued for 30 more weeks. Embelin inhibited proliferation and induced apoptosis in HCT116 cells with marked up-regulation of PPAR. In addition, embelin significantly inhibited the expressions of survivin, cyclin D1, and c-Myc. These effects were partially dependent on PPAR. PPAR+/– mice were more susceptible to DMH-induced colon carcinogenesis than PPAR+/+ mice, and embelin significantly reduced the incidence of colon cancer in PPAR+/+ mice but not in PPAR+/– mice. Embelin inhibited NF-B activity in PPAR+/+ mice but marginally so in PPAR+/– mice. Thus, reduced expression of PPAR significantly sensitizes colonic tissues to the carcinogenic effect of DMH. Embelin inhibits chemical carcinogen-induced colon carcinogenesis, but this effect is partially dependent on the presence of functional PPAR, indicating that PPAR is a necessary signaling pathway involved in the antitumor activity of normal organisms. [Cancer Res 2009;69(11):4776–83]

  J Wang , Q Gu , M Li , W Zhang , M Yang , B Zou , S Chan , L Qiao , B Jiang , S Tu , J Ma , I. F Hung , H. Y Lan and B. C.Y. Wong
 

Background and aims: X-linked inhibitor of apoptosis-associated factor 1 (XAF1) was first recognized as an antagonist of X-linked inhibitor of apoptosis in suppressing caspase 3 activity. It has lower expression in cancer cells than normal tissue. Overexpression of XAF1 can inhibit cancer cell growth and sensitize tumor necrosis factor-related apoptosis-inducing ligand- or etoposide-induced apoptosis. The aim of this study is to elucidate the mechanism of XAF1 in regulating cell growth. Methods: Stable transfectants of gastrointestinal (GI) cancer cell lines AGS and SW1116 expressing XAF1 and vector control were generated. Cell growth, apoptosis, mitotic status and cell cycle distribution were assessed. The interaction between XAF1 and G2/M checkpoint proteins was evaluated by immunoblotting, kinase assay and co-immunoprecipitation assay. Mitotic catastrophe was identified by occurrence of aberrant nuclei and centrosomal amplification. Results: Our results showed that overexpression of XAF1 suppressed serum-dependent cancer cell growth, induced mitotic catastrophe and G2/M cell cycle arrest. Interestingly, XAF1 was predominantly expressed in G2/M phase after cell cycle synchronization. XAF1 interacted with and activated checkpoint kinase 1 (Chk1), inactivated Cdc25C and lead to inactivation of Cdc2–cyclin B complex. Suppression of Chk1 abrogated XAF1-induced G2/M arrest. Conclusions: Our findings implicate XAF1 as a novel cell cycle modulator that is recruited in G2/M phase and thus unravel a novel function pathway of XAF1, suggesting the potential role of XAF1 as the target for the management of GI cancers.

  J Cheng , Y Wang , Y Ma , B. T. y Chan , M Yang , A Liang , L Zhang , H Li and J. Du
  Rationale:

Mechanical stress plays an important role in proliferation of venous smooth muscle cells (SMCs) in neointima, a process of formation that contributes to failure of vein grafts. However, it is unknown what intracellular growth signal leads to proliferation of venous SMCs.

Objective:

The objective of this study is to identify mechanisms of mechanical stretch on neointima formation.

Methods and Results:

By a microarray analysis, we found that mechanical cyclic stretch (15% elongation) stimulated the transcription of SGK-1 (serum-, glucocorticoid-regulated kinase-1). Mechanical stretch–induced SGK-1 mRNA expression was blocked by actinomycin D. The mechanism for the SGK-1 expression involved MEK1 but not p38 or JNK signaling pathway. SGK-1 activation in response to stretch is blocked by insulin-like growth factor (IGF)-1 receptor inhibitor and mammalian target of rapamycin complex (mTORC)2 inhibitor (Ku-0063794) but not mTORC1 inhibitor (rapamycin). Mechanical stretch–induced bromodeoxyuridine incorporation was reduced by 83.5% in venous SMCs isolated from SGK-1 knockout mice. In contrast, inhibition of Akt, another downstream signal of PI3K resulted in only partial inhibition of mechanical stretch–induced proliferation of venous SMCs. Mechanical stretch also induced phosphorylation and nuclear exportation of p27kip1, whereas knockout of SGK-1 attenuated this effect of mechanical stretch on p27kip1. In vivo, we found that placement of a vein graft into artery increased SGK-1 expression. Knockout of SGK-1 effectively prevented neointima formation in vein graft. There is significant lower level of p27kip1 located in the nucleus of neointima cells in SGK-1 knockout mice compared with that of wild-type vein graft. In addition, we also found that wire injury of artery or growth factors in vitro increased expression of SGK-1.

Conclusions:

These results suggest that SGK-1 is an injury-responsive kinase that could mediate mechanical stretch–induced proliferation of vascular cells in vein graft, leading to neointima formation.

  J Li , H Huang , L Sun , M Yang , C Pan , W Chen , D Wu , Z Lin , C Zeng , Y Yao , P Zhang and E. Song
 

Purpose: We aim to examine miR-21 expression in tongue squamous cell carcinomas (TSCC) and correlate it with patient clinical status, and to investigate its contribution to TSCC cell growth, apoptosis, and tumorigenesis.

Experimental Design: MicroRNA profiling was done in 10 cases of TSCC with microarray. MiR-21 overexpression was quantitated with quantitative reverse transcription-PCR in 103 patients, and correlated to the pathoclinical status of the patients. Immunohistochemistry was used to examine the expression of TPM1 and PTEN, and terminal deoxynucleotidyl transferase–mediated dUTP labeling to evaluate apoptosis. Moreover, miR-21 antisense oligonucleotide (ASO) was transfected in SCC-15 and CAL27 cell lines, and tumor cell growth was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, adherent colony formation, and soft agar assay, whereas apoptosis was determined by Annexin V assay, cytochrome c release, and caspase 3 assay. Tumorigenesis was evaluated by xenografting SCC-15 cells in nude mice.

Results: MiR-21 is overexpressed in TSCC relative to adjacent normal tissues. The level of miR-21 is reversely correlated with TPM1 and PTEN expression and apoptosis of cancer cells. Multivariate analysis showed that miR-21 expression is an independent prognostic factor indicating poor survival. Inhibiting miR-21 with ASO in TSCC cell lines reduces survival and anchorage-independent growth, and induces apoptosis in TSCC cell lines. Simultaneous silencing of TPM1 with siRNA only partially recapitulates the effect of miR-21 ASO. Furthermore, repeated injection of miR-21 ASO suppresses tumor formation in nude mice by reducing cell proliferation and inducing apoptosis.

Conclusions: miR-21 is an independent prognostic indicator for TSCC, and may play a role in TSCC development by inhibiting cancer cell apoptosis partly via TPM1 silencing.

 
 
 
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