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Wang M.,Soochow University of China | Wang M.,Johns Hopkins University | Shim J.S.,Johns Hopkins University | Shim J.S.,University of Macau | And 7 more authors.
British Journal of Pharmacology

Background and Purpose Finding new indications for existing drugs, also known as drug repositioning or repurposing, is a powerful approach to accelerate drug discovery and development. The unfolded protein response pathways have been proposed to be a viable target for developing new anticancer drugs. Experimental Approach We screened the Johns Hopkins Drug Library for inhibitors of prostate cancer cell proliferation to identify new antiprostate cancer treatments among known drugs. We systematically investigated the mechanism underlying the anticancer activity of a hit and assessed its efficacy in blocking prostate tumour growth in a mouse model. Key Results The antibacterial drug clofoctol was identified as a novel inhibitor of prostate cancer cell proliferation. Morphologically, cells treated with clofoctol were found to undergo massive vacuolization, reminiscent of endoplasmic reticulum stress. Indeed, all three unfolded protein response pathways including inositol requiring enzyme 1, double-stranded RNA-activated PK-like ER kinase and activating transcription factor 6 were found to be activated by clofoctol. Activation of unfolded protein response pathways by clofoctol led to the inhibition of protein translation in cells and the induction of G1 cell cycle arrest in prostate cancer cells. Clofoctol also inhibited prostate cancer xenograft growth in vivo without apparent toxicity. Conclusion and Implications Our findings revealed clofoctol as a novel activator of the unfolded protein response pathways and a promising inhibitor of prostate cancer. As clofoctol has been used in the clinic for years, it is ready for clinical evaluation as a novel antiprostate cancer drug candidate. © 2014 The British Pharmacological Society. Source

Li X.,Fudan University | Li Z.,Fudan University | Li Z.,Key Laboratory of Molecular Medicine | Li N.,Fudan University | And 13 more authors.
International Journal of Molecular Medicine

Adaptor proteins are involved in the assembly of various intracellular complexes and the regulation of cellular functions. Membrane-associated guanylate kinase inverted 2 (MAGI2), also known as synaptic scaffolding molecule (S-SCAM), plays a critical role in signal transduction by assembling and anchoring its ligands. However, the role of MAGI2 in mediating apoptosis remains largely unknown. In the present study, BEL-7404 human hepatocellular carcinoma cells were transfected with a plasmid containing myc-MAGI2 or an empty plasmid and cell viability was then determined using the Cell Counting kit-8. Apoptosis was also detected using an Annexin V apoptosis assay. The cells were then treated with various doses of staurosporine (STS) for different periods of time. The overexpression of myc-MAGI2 was found to sensitize the BEL-7404 cells to apoptosis in response to STS in a time- and dose-dependent manner. Our results demonstrated that MAGI2 enhanced STS-induced apoptosis by increasing the protein expression of cytoplasmic phosphatase and tensin homologue deleted on chromosome 10 (PTEN) and decreasing its protein degradation. The apoptotic sensitivity of the cells caused by the overexpression of myc-MAGI2 was reversed by the silencing of PTEN expression by PTEN siRNA, thus revealing a momentous role of PTEN in the enhancement of the sensitivity of cancer cells to STS-induced apoptosis by MAGI2. Finally, we observed that the MAGI-PTEN complex triggered by MAGI2 overexpression reduced the phosphorylation levels of AKT. These results suggest that MAGI2 overexpression enhances the sensitivity of cancer cells harboring ectopic PTEN to STS-induced apoptosis. Source

Lu R.,Key Laboratory of Molecular Medicine | Lu R.,Fudan University | Wu C.,Key Laboratory of Molecular Medicine | Guo L.,Fudan University | And 6 more authors.
BMC Cancer

Background: Malignant glioma is a common primary tumor of the central nervous system. Brevican, an abundant extracellular matrix component in the adult brain, plays a critical role in the process of glioma. The mechanisms for the highly invasive behavior of gliomas are still poorly understood. The aim of this study was to examine whether brevican is a predictor of glioma and its roles in glioma cell motility.Methods: In this study, immunohistochemistry staining for brevican expression was performed in malignant gliomas and benign controls. We also explored the effects of brevican on cell adhesion and migration in brevican-overexpressed cells. Knockdown of brevican expression was achieved by stable transfection of U251 cells transduced with a construct encoding a short hairpin DNA directed against the brevican gene, which correspondingly, down-regulated the proliferation, invasion and spread of brevican-expressing cells. Moreover, the role of brevican in the growth and progression of glioma was demonstrated by in vivo studies.Results: Our results provide evidence for the molecular and cellular mechanisms that may underlie the motility-promoting role of brevican in the progression of glioma. The role of brevican as a target for immunotherapy might be taken into consideration in future studies.Conclusions: This study suggests that expression of brevican is associated with glioma cell adhesion, motility and tumor growth, and also is related to glioma cell differentiation, therefore it may be a marker for malignance degree of glioma. © 2012 Lu et al.; licensee BioMed Central Ltd. Source

Qi J.,Fudan University | Qi J.,Shanghai JiaoTong University | Li N.,Fudan University | Fan K.,Fudan University | And 12 more authors.

Receptor-like protein tyrosine phosphatases (RPTPs) are type I transmembrane glycoproteins with N-glycans whose catalytic activities are regulated by dimerization. However, the intrinsic mechanism involved in dimerizing processes remains obscure. In this study, receptor protein tyrosine phosphatase rho (PTPRT) is identified as a novel substrate of N-Acetylglucosaminyltransferase V (GnT-V). We show that addition of β1,6 GlcNAc branches on PTPRT prolongs PTPRT's cell-surface retention time. GnT-V overexpression enhances galectin-3's cell-surface retention and promotes PTPRT's dimerization mediated by galectin-3. Increased dimerization subsequently reduces PTPRT's catalytic activity on the dephosphorylation of signal transducer and activator of transcription 3 (STAT3) at tyrosine residue 705 (pY705 STAT3), then the accumulated pY705 STAT3 translocates into the nucleus. Collectively, these findings provide an insight into the molecular mechanism by which GnT-V promotes cell migration, suggesting that accumulation of β1,6 GlcNAc branched N-glycans promotes PTPRT's dimerization and decreases its catalytic activity, resulting in enhanced cell migratory capacity. © 2014 Qi et al. Source

Liu Y.,Fudan University | Mei C.,Fudan University | Sun L.,Fudan University | Li X.,Fudan University | And 15 more authors.
Cellular Signalling

The calpains are a family of cysteine proteases involved in some biological processes whose activities are highly dependent on Ca2+. Calpain 6 (CAPN6), one member of the family, is unique in that it lacks the active-site cysteine residues for protease activity. According to the data that CAPN6 was up-regulated in the Akt transformed mouse embryonic fibroblast cells by cDNA chip, the mechanisms underlying elevated CAPN6 expression by PI3K-Akt signaling pathway and its biological functions were studied. The results showed that CAPN6 was down-regulated on transcriptional and post-transcriptional levels by the PI3K inhibitor or Akt deletion. CAPN6 protein was stabilized by PI3K-GSK-3β pathway. Deleted CAPN6 promoters activity were assessed by dual-luciferase reporter system, and the founding indicated that -93/+200 DNA fragment was the core promoter of it. Transcription factor binding sites in the CAPN6 promoter were mutated and the results showed that AP1, Oct-1, and FoxD3 were the critical transcription factors in regulation of CAPN6 expression. In addition, CAPN6 promoted cancer cell proliferation and inhibited its apoptosis. The finding demonstrates that CAPN6 is regulated by the PI3K-Akt signaling pathway and provides evidence that it may be a therapeutic target of cancer. © 2011. Source

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