Biomedical subjects

Zhongmin Liu

Publications and source records attributed to Zhongmin Liu.

10 recordsLinked to original sources

PubMed2005

5-Aza-2'-deoxycytidine induces retinoic acid receptor-beta(2) demethylation and growth inhibition in esophageal squamous carcinoma cells.

Esophageal squamous cell carcinoma (ESCC) is one of the most common tumors in human. Previous studies showed that multiple genetic and epigenetic alterations involved in carcinogenesis of esophagus, whereas the molecular mechanisms are poorly understood. So far, more and more ESCC-related genes have been found and retinoic acid receptor beta(2) (RARbeta(2)) is such a gene which was recognized as a putative tumor suppressor gene since reduced RARbeta(2) mRNA expression has been observed in several solid tumors, including ESCC. A growing evidence indicated that RARbeta(2) was required for the growth inhibitory effect of retinoic acid (RA). However, the molecular mechanism of its inactivation remained obscure in ESCC. The RARbeta2 methylation status was assessed by methylation-specific PCR (MSP) in 12 ESCC cell lines and compared with their mRNA and protein expression level. Bisulfite sequencing of RARbeta(2) promoter region was performed to confirm the MSP results. After 5-aza-2'-deoxycytidine (5-aza-dc) treatment the expression of RARbeta(2) was reversed in two RARbeta(2)-downregulated cell lines. Therefore, hypermethylation of the promoter regions of RARbeta2 gene is a major mechanism of transcriptional inactivation and might be involved in tumor development of esophagus in some ESCC cell lines suggesting that multiple mechanisms contribute to the loss of RARbeta(2) expression in ESCC cell lines. Furthermore, the methylation status of RARbeta(2) promoter region and its expression was analyzed in 51 ESCC tissue samples with their adjacent normal epithelia and two normal esophageal epithelia. The results showed that there was a statistically significant correlation between methylation status of RARbeta(2) and tumor grade; Moreover, a relationship between methylation status and decreased RARbeta(2) expression was found only in G(2) stage tumors. After 5-aza-dc treatment, RARbeta(2) restoration was accompanied by growth inhibition and this might be one of the mechanisms but not the only mechanism for the tumor cell growth inhibition by 5-aza-dc. This study may have clinical applications for ESCC therapy and prevention.

Adult↗

PubMed2005

Overexpression of stefin A in human esophageal squamous cell carcinoma cells inhibits tumor cell growth, angiogenesis, invasion, and metastasis.

PURPOSE: Evidence is accumulating that an inverse correlation exists between stefin A level and malignant progression. The aim of this study is to investigate the role of stefin A in human esophageal squamous cell carcinoma cells and to evaluate the possibility of stefin A for cancer therapy. EXPERIMENTAL DESIGN: We stably transfected stefin A cDNA into human EC9706 or KYSE150 esophageal squamous cell carcinoma cells. Subsequently, we evaluated the effect of stefin A overexpression on cell growth, cathepsin B activity, cell motility and invasion, tumor growth, and metastasis. Immunoanalysis was done to assess the expression of factor VIII and to support the localization of stefin A and cathepsin B. We also evaluated the effect of CA074Me, a selective membrane-permeant cathepsin B inhibitor. RESULTS: Both transfection of stefin A and treatment with 10 micromol/L CA074Me significantly reduced cathepsin B activity and inhibited the Matrigel invasion. Combination of both further reduced cathepsin B activity and inhibited the Matrigel invasion. Overexpression of stefin A delayed the in vitro and in vivo growth of cells and significantly inhibited lung metastasis compared with 50% of lung metastasis in xenograft mice from EC9706 or empty vector cells. Transfection with stefin A showed a dramatic reduction of factor VIII staining in the tumors of xenograft mice. CONCLUSIONS: Our data strongly indicate that stefin A plays an important role in the growth, angiogenesis, invasion, and metastasis of human esophageal squamous cell carcinoma cells and suggest that stefin A may be useful in cancer therapy.

Animals↗

PubMed2005

Allelic imbalance of chromosome 1q in esophageal squamous cell carcinomas from China: a novel region of allelic loss and significant association with differentiation.

Our previous work has shown that a number of genes locating on 1q21 were down-regulated in esophageal squamous cell carcinomas (ESCC) and they may involve in carcinogenesis. To determine whether chromosome 1q LOH occurs in ESCC, we analyzed LOH in 61 ESCCs using 18 microsatellite markers on chromosome 1q. Forty-six of 61 (75.4%) tumors presented LOH at one or more loci. A significant association was found between chromosome 1q LOH and histopathological grade. LOH on D1S3466 had a negative correlation with family history, whereas LOH on D1S2777 positively correlated with smoking. These results suggest this region harbor putative tumor suppressor gene(s) contributing to tumorigenesis and differentiation in ESCC.

Aged↗

PubMed2005

Specific tolerance induction of allo-K(b)-skin grafts by FK506 in the CD8-depleted H-2(k) recipients required low amounts of K(b)-antigen.

MHC class I allo-grafts can be directly rejected by recipient CD8 T cells and be indirectly rejected by recipient CD4 T cells. Although the experimental results using the bm mutant and C57BL/6 mice indicated that CD4-mediated rejection of class I-disparate grafts is a relatively weak process and is expected to be more sensitive to additional exogenous immunosuppression, it is unclear that whether this mechanism can be used for inducing a specific tolerance of class I disparate grafts. In this study, we hypothesize that a short course of FK506 may induce a specific tolerance of class I-disparate skin grafts in the CD8-depleted recipients. K(b)-transgenic C3H mice, Tg.H-2 K(b)-1 and Tg.H-2 K(b)-2 mice that express high copies and low copies of K(b)-antigen respectively were used as donors. Wild type C3H mice (H-2(k)) in which either CD4 or CD8 T cells were depleted by administration of anti-CD4 or CD8 monoclonal antibody (mAb) were used as recipients. Results showed that FK506 promoted longer survival of allo-K(b) skin grafts in CD8-depleted C3H mice than in CD4-depleted C3H mice. Graft survival from Tg.H-2 K(b)-2 mice was significantly longer than Tg.H-2 K(b)-1 mice. A short course of FK506 induced long-term survival of skin grafts from Tg.H-2K(b)-2 mice, but not from Tg.H-2K(b)-1 mice in CD8-depleted C3H recipients, even after FK506 was stopped. These mice also accepted grafts of Tg.H-2K(b)-1 mice when challenged with skin grafts from Tg.H-2K(b)-1 mice, but promptly rejected third party skin grafts from BALB/c (H-2(d)) mice. T cells from K(b)-tolerant C3H mice did not respond to allo-K(b)-antigen in in vitro assays of mixed lymphocyte culture and cell-mediated cytotoxicity. In conclusion we found that a short course of FK506 treatment and low amounts of K(b)-antigen induced a K(b)-specific tolerance in the CD8-depleted recipients, and this tolerance maintained even after withdrawing the anti-CD8 mAb treatment.

Animals↗

PubMed2005

Subspace-based prototyping and classification of chromosome images.

Chromosomes are essential genomic information carriers. Chromosome classification constitutes an important part of routine clinical and cancer cytogenetics analysis. Cytogeneticists perform visual interpretation of banded chromosome images according to the diagrammatic models of various chromosome types known as the ideograms, which mimic artists' depiction of the chromosomes. In this paper, we present a subspace-based approach for automated prototyping and classification of chromosome images. We show that 1) prototype chromosome images can be quantitatively synthesized from a subspace to objectively represent the chromosome images of a given type or population, and 2) the transformation coefficients (or projected coordinate values of sample chromosomes) in the subspace can be utilized as the extracted feature measurements for classification purposes. We examine in particular the formation of three well-known subspaces, namely the ones derived from principal component analysis (PCA), Fisher's linear discriminant analysis, and the discrete cosine transform (DCT). These subspaces are implemented and evaluated for prototyping two-dimensional (2-D) images and for classification of both 2-D images and one-dimensional profiles of chromosomes. Experimental results show that previously unseen prototype chromosome images of high visual quality can be synthesized using the proposed subspace-based method, and that PCA and the DCT significantly outperform the well-known benchmark technique of weighted density distribution functions in classifying 2-D chromosome images.

Algorithms↗

PubMed2004

Effect of pharmacologic preconditioning with tetrandrine on subsequent ischemia/reperfusion injury in rat liver.

The effect of tetrandrine (TET) pretreatment of Wistar rats subjected to warm hepatic ischemia/reperfusion (I/R) was investigated. After 50 minutes of ischemia in the left and median lobes of the liver and 24 hours of reperfusion (I/R group), the rats were killed. The TET+I/R group rats were pretreated with TET (50 mg/kg body weight IP) 30 minutes prior to the onset of ischemia. Blood samples were taken for measurement of alanine aminotransferase (ALT), aspartate aminotransferase (AST), and lactate dehydrogenase (LDH). Tissue was taken from the ischemic lobes for measurement of superoxide dismutase (SOD), malonyldialdehyde (MDA), and myeloperoxidase (MPO); determination of the wet/dry weight (W/D) ratio; and histologic studies. The results showed that ALT, AST, and LDH levels in serum were increased in the I/R group; tissue MDA generation, MPO activity, and the W/D ratio were also increased, accompanied by decreased SOD activity. The serum ALT, AST, and LDH levels, as well as the tissue MPO level and W/D ratio, were lower in the TET+ I/R group than in the I/R group; and the SOD level was higher in the TET+IR group than in the I/R group. Moreover, the serum ALT and AST, tissue MDA, and W/D ratio in the TET+I/R group were higher, and the SOD was lower than in the sham group. The histologic examination showed protection against liver damage in the TET+I/R group. The results demonstrated that pretreatment with TET could somewhat protect the liver against I/R injury but does not prevent it. The simultaneous decrease of both lipid peroxide generation and polymorphonuclear neutrophil infiltration in the ischemic liver may explain the acquisition of tolerance following administration of TET.

Alanine Transaminase↗

PubMed2002

Cascaded differential and wavelet compression of chromosome images.

This paper proposes a new method for chromosome image compression based on an important characteristic of these images: the regions of interest (ROIs) to cytogeneticists for evaluation and diagnosis are well determined and segmented. Such information is utilized to advantage in our compression algorithm, which combines lossless compression of chromosome ROIs with lossy-to-lossless coding of the remaining image parts. This is accomplished by first performing a differential operation on chromosome ROIs for decorrelation, followed by critically sampled integer wavelet transforms on these regions and the remaining image parts. The well-known set partitioning in hierarchical trees (SPIHT) (Said and Perlman, 1996) algorithm is modified to generate separate embedded bit streams for both chromosome ROIs and the rest of the image that allow continuous lossy-to-lossless compression of both (although lossless compression of the former is commonly used in practice). Experiments on two sets of sample chromosome spread and karyotype images indicate that the proposed approach significantly outperforms current compression techniques used in commercial karyotyping systems and JPEG-2000 compression, which does not provide the desirable support for lossless compression of arbitrary ROIs.

Algorithms↗

PubMed2002

Detection of occult metastases in lymph nodes from patients with colorectal carcinoma by reverse transcriptase-polymerase chain reaction.

OBJECTIVE: To detect occult metastases in lymph nodes from patients with colorectal carcinoma and its clinical significance. METHODS: The metastases in 260 lymph nodes from 39 histologically verified colorectal cancer patients were studied by both hematoxylin-eosin (HE) staining and cytokeratin-20 (CK20) specific RT-PCR. Ten normal lymph nodes were served as negative controls, and HT29 colon cancer cell line and 5 colorectal cancer specimens as positive controls. RESULTS: Ten normal lymph nodes were CK20-negative, HT29 cells and 5 tumor specimens were all CK20-positive. All 29 lymph nodes from 16 patients which confirmed metastases by HE staining exhibited CK20 positive expression; an additional 28 lymph nodes from 5 patients with no histologically detectable metastases expressed CK20 mRNA, i.e. presence of metastases. The difference of the positivity was significant (11.1% vs 21.9%, P < 0.01). According to the HE staining, the cases of Dukes' A, B, C and D were 3, 20, 12 and 4, respectively. In the 20 patients of Dukes' B stage, 5 of them had CK20-positive lymph nodes. CONCLUSION: CK20-specific RT-PCR is a highly sensitive, specific and simple method for detecting occult metastases in lymph nodes. The detection of CK20 mRNA expression in lymph nodes is recommended to precisely determine tumor stage and postoperative adjuvant therapy for patients with colorectal cancer, and further studies should be done in future to confirm the findings.

Adult↗

PubMed2002

[Significance of cytokeratin gene (CK-20 mRNA) expression in metastatic lymph nodes in colon carcinoma patients].

OBJECTIVE: To elucidate the significance of detecting cytokeratin gene (CK-20 mRNA) expression in metastatic lymph nodes of colon carcinoma patients. METHODS: The expression of CK-20 mRNA was detected in 342 lymph nodes by reverse transcription-polymerase chain reaction (RT-PCR) in 49 colon carcinoma patients. Its incidence was compared with that by routine pathologic examination. RESULTS: The positive rates of detecting metastasis in the lymph nodes were 21.9% by RT-PCR and 11.1% by routine pathologic examination. CONCLUSION: The detection of cancer metastasis in the lymph nodes in colon carcinoma is almost doubled (21.9% vs 11.1%) by CK-20 mRNA, which may provide a guiding significance in staging, treatment planning and prognosis in the prognostic estimation of colon carcinoma patients.

Adult↗

PubMedDate not supplied

Quantified MS analysis applied to combinatorial heterogeneous catalyst libraries.

A high-throughput screening system for secondary catalyst libraries has been developed by incorporation of an 80-pass reactor and a quantified multistream mass spectrometer screening (MSMSS) technique. With a low-melting alloy as the heating medium, a uniform reaction temperature could be obtained in the multistream reactor (maximum temperature differences are less than 1 K at 673 K). Quantification of the results was realized by combination of a gas chromatogram with the MSMSS, which could provide the product selectivities of each catalyst in a heterogeneous catalyst library. Because the catalyst loading of each reaction tube is comparable to that of the conventional microreaction system and because the parallel reactions could be operated under identical conditions (homogeneous temperature, same pressure and WHSV), the reaction results of a promising catalyst selected from the library could be reasonably applied to the further scale-up of the system. The aldol condensation of acetone, with obvious differences in the product distribution over different kind of catalysts, was selected as a model reaction to validate the screening system.

Catalysis↗