G-quadruplex Structures in Promoters of MET Proto-oncogene / 中国医科大学学报

Objective To identify G?quadruplex structures in the promoter region of MET. Methods CD spectroscopy,UV spectroscopy,non?denatured electrophoresis and PCR stop assay were applied to indicate the G?quadruplex structure and its function. Results The Pu23WT se?quence in the promoter of MET adopted an intramolecular parallel G?quadruplex structure under physiological conditions in vitro,which can stop the extension of Pmet. Conclusion G?quadruplex structure in the promoter might inhibit MET gene expression in vivo.

Glucosamine induces cell death via proteasome inhibition in human ALVA41 prostate cancer cell

Glucosamine, a naturally occurring amino monosaccharide, has been reported to play a role in the regulation of apoptosis more than half century. However the effect of glucosamine on tumor cells and the involved molecular mechanisms have not been thoroughly investigated. Glucosamine enters the hexosamine biosynthetic pathway (HBP) downstream of the rate-limiting step catalyzed by the GFAT (glutamine:fluctose-6-phosphate amidotransferase), providing UDP-GlcNAc substrates for O-linked beta-N-acetylglucosamine (O-GlcNAc) protein modification. Considering that O-GlcNAc modification of proteasome subunits inhibits its activity, we examined whether glucosamine induces growth inhibition via affecting proteasomal activity. In the present study, we found glucosamine inhibited proteasomal activity and the proliferation of ALVA41 prostate cancer cells. The inhibition of proteasomal activity results in the accumulation of ubiquitinated proteins, followed by induction of apoptosis. In addition, we demonstrated that glucosamine downregulated proteasome activator PA28gamma and overexpression of PA28gamma rescued the proteasomal activity and growth inhibition mediated by glucosamine. We further demonstrated that inhibition of O-GlcNAc abrogated PA28gamma suppression induced by glucosamine. These findings suggest that glucosamine may inhibit growth of ALVA41 cancer cells through downregulation of PA28gamma and inhibition of proteasomal activity via O-GlcNAc modification.

The Construction and Expression Confirmation of JC Virus T Antigen Expression Plasmid in Gastric Mucosa / 中国医科大学学报

Objective To construct and confirm the JC virus(JCV) T antigen expression plasmid using mouse keratin 19 (K19) promoter specific for the gastric epithelial cells.Methods The Ndel site was mutated by FCR with Bell insertion at both sides.The DNA fragment digested by Bcl Ⅰ was ligated with the plasmid containing K19 promoter via Bam Ⅰ site.The DNA sequence was confirmed by restriction enzyme digestion and direct DNA sequencing.Cytokeratin 19 protein was examined to screen gastric carcinoma cell for transfection of K19-JCV T antigen expression plasmid by immunohistochemistry.The Western blot was employed to detect the JCV T antigen expression in the gastric carcinoma transfectant.Results K19-JCV T antigen expressing plasmid was successfully constructed.The ACS strongly expressed cytokeratin 19 protein and was selected for the transfection of K19-JCV T antigen expressing plasmid.JCV T antigen was positively expressed in the AGS transfectant.Conclusion The synonymous mutation and compatible ligation are useful in the plasmid construction.The methy lation of restriction enzyme should be considered.It is meaning for the transgenic animal model of gastric carcinoma to successfully construct the JC virus T antigen expression plasmid in gastric mucosa.

Tunicamycin enhances TRAIL-induced apoptosis by inhibition of cyclin D1 and the subsequent downregulation of survivin

TNF-related apoptosis-inducing ligand (TRAIL) has been proposed as a promising cancer therapy that preferentially induces apoptosis in cancer cells, but not most normal tissues. However, many cancers are resistant to TRAIL by mechanisms that are poorly understood. In this study, we showed that tunicamycin, a naturally occurring antibiotic, was a potent enhancer of TRAIL-induced apoptosis through downregulation of survivin. The tunicamycin-mediated sensitization to TRAIL was efficiently reduced by forced expression of survivin, suggesting that the sensitization was mediated at least in part through inhibition of survivin expression. Tunicamycin also repressed expression of cyclin D1, a cell cycle regulator commonly overexpressed in thyroid carcinoma. Furthermore, silencing cyclin D1 by RNA interference reduced survivin expression and sensitized thyroid cancer cells to TRAIL; in contrast, forced expression of cyclin D1 attenuated tunicamycin-potentiated TRAIL-induced apoptosis via over-riding downregulation of survivin. Collectively, our results demonstrated that tunicamycin promoted TRAIL-induced apoptosis, at least in part, by inhibiting the expression of cyclin D1 and subsequent survivin. Of note, tunicamycin did not sensitize the differentiated thyroid epithelial cells to TRAIL-induced apoptosis. Thus, combined treatment with tunicamycin and TRAIL may offer an attractive strategy for safely treating resistant thyroid cancers.

Tunicamycin enhances TRAIL-induced apoptosis by inhibition of cyclin D1 and the subsequent downregulation of survivin

TNF-related apoptosis-inducing ligand (TRAIL) has been proposed as a promising cancer therapy that preferentially induces apoptosis in cancer cells, but not most normal tissues. However, many cancers are resistant to TRAIL by mechanisms that are poorly understood. In this study, we showed that tunicamycin, a naturally occurring antibiotic, was a potent enhancer of TRAIL-induced apoptosis through downregulation of survivin. The tunicamycin-mediated sensitization to TRAIL was efficiently reduced by forced expression of survivin, suggesting that the sensitization was mediated at least in part through inhibition of survivin expression. Tunicamycin also repressed expression of cyclin D1, a cell cycle regulator commonly overexpressed in thyroid carcinoma. Furthermore, silencing cyclin D1 by RNA interference reduced survivin expression and sensitized thyroid cancer cells to TRAIL; in contrast, forced expression of cyclin D1 attenuated tunicamycin-potentiated TRAIL-induced apoptosis via over-riding downregulation of survivin. Collectively, our results demonstrated that tunicamycin promoted TRAIL-induced apoptosis, at least in part, by inhibiting the expression of cyclin D1 and subsequent survivin. Of note, tunicamycin did not sensitize the differentiated thyroid epithelial cells to TRAIL-induced apoptosis. Thus, combined treatment with tunicamycin and TRAIL may offer an attractive strategy for safely treating resistant thyroid cancers.