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ABSTRACT: The murine double minutes 2 (MDM2) oncoprotein inhibits p53-mediated tumor suppression. MDM2 has been shown to be overexpressed
in sarcomas and more recently was implicated in the pathogenesis of carcinomas. The purpose of this study was to determine
the expression pattern of MDM2 in adenomas and colorectal adenocarcinomas and decide whether there is a correlation between
MDM2 and p53 protein status. Paraffin-embedded tissues from 52 colorectal cancer (CRC) specimens and their adjacent normal
tissue (N-CRC) were studied. In addition, 56 sporadic adenomas were investigated for the immunohistochemical expression of
MDM2 and p53 proteins. Immunoreactivity of p53 indicating p53 gene mutation (p53 +) was significantly higher in CRC (44%)
compared to adenomas (23.2%) (P <0.01). None of the N-CRC specimens expressed the immunoreactive p53 protein. MDM2 overexpression (MDM2+) was similar in
adenomas (30.3%) and CRC (25%), but only 2 (3.8%) of 52 N-CRC specimens showed overexpression of MDM2. In most cases MDM2
expression was associated with negative p53 expression (wild-type p53) in both adenomas (r = 0.59, P <0.001) and CRC (r = 0.69, P <0.0001). No correlation was found between MDM2, p53 expression, and either the histologic grade, nodal stage or morphology
of the tumors. There is greater p53 mutation in CRC compared to adenomas and N-CRC. The data indicate that MDM2 is overexpressed
in CRC and is significantly associated with wild-type p53 compared to N-CRC specimens from the same patient. The MDM2 expression
pattern is similar in adenomas and CRC, which may suggest that MDM2 overexpression is an early event in the progression of
CRC.
Journal of Gastrointestinal Surgery 04/2012; 4(1):109-114. · 2.83 Impact Factor
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ABSTRACT: This study is to investigate the mechanism underlying the anti-apoptotic effects of freeze-dried grape powder (FDGP) and identify the polyphenolic compounds involved. We examined apoptotic signaling pathways affected by FDGP and by its active components, including epicatechin, cyanidin, quercetin, and resveratrol, in human Huh7 hepatoma cells by assaying cell viability assays, the activities of caspase 3 and caspase 7, and the expression of endoplasmic reticulum stress-associated proteins. FDGP dramatically decreased taurodeoxycholic acid (TDCA)-induced production of reactive oxygen species (ROS). Assessment of individual active components revealed that at concentrations corresponding to 300 μg/mL FDGP, only quercetin demonstrated cytoprotective effects against mitochondrial-mediated apoptosis. In contrast, increased concentrations of other individual polyphenolic compounds were required to produce measurable cytoprotective effect. Only combinations of all four polyphenolic compounds (epicatechin, cyanidin, quercetin, and resveratrol) restored a degree of the anti-apoptotic effects seen with FDGP. The pretreatment of FDGP at 30 μg/mL concentration could reverse the thapsigargin-induced effects on the expression of endoplasmic reticulum stress-associated proteins. In conclusion, FDGP reduced oxidative stress, endoplasmic reticulum stress, and apoptosis. The mechanisms involved in the anti-apoptotic effects of FDGP included reduced generation of ROS, and reduced processing of certain caspases. We demonstrated that quercetin, epicatechin, and cyanidin are active compounds within FDGP that attenuate apoptosis. These findings contribute to our understanding of the molecular mechanisms of anti-apoptotic and anti-oxidant effects of grape and are expected to assist in developing clinical protocols to treat a variety of stress-mediated conditions.
Toxicology and Industrial Health 02/2011; 27(1):19-28. · 1.42 Impact Factor
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ABSTRACT: To investigate the molecular mechanisms involved in anti-apoptotic effects of epicathechin in liver cells.
Human hepatoma cell line (Huh7) was treated with 400 miromol x L(-1) taurodeoxycholic acid (TDCA) for 48 hours to induce apoptosis. Intracellular generation of reactive oxygen species (ROS) was detected with DCFH-DA assay. Caspase-3/7 activity was analyzed with EnzoLyte Homogeneous AMC kit. Cell proliferation was measured by MTT assay. The expression of Bax, Phospho-p38 MAPK and the levels of cytochrome C were assessed by Western-blot analysis.
TDCA-dependent intracellular ROS production was 8-fold higher as compared to untreated cells, consequently resulting in 45% reduction of cell viability. Interestingly, pretreatment of cells with epicatechin resulted in a dose-dependent inhibition of TDCA-induced ROS generation and reduced cell apoptosis by threefold as compared to TDCA treatment alone. In addition epicatechin reduced Bax expression with consequential inhibition of cytochrome C release from mitochondria, inhibition of caspase 3/7 activation and p38 MAPK phosphorylation.
Epicatechin protects Huh7 cells from oxidative stress and mitochondria-induced apoptosis. The molecular mechanisms of anti-apoptotic effects of epicatechin were associated with inhibition of p38 MAPK phosphorylation and Bax expression, and reduction of ROS production. These findings implicate epicathechin might have potential as protective agent against a variety of oxidative stress-mediated liver conditions.
Zhongguo Zhong yao za zhi = Zhongguo zhongyao zazhi = China journal of Chinese materia medica 06/2009; 34(10):1272-5.
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ABSTRACT: The Env glycoproteins of retroviruses play an important role in the initial steps of infection involving the binding to cell surface receptors and entry by membrane fusion. The Env glycoprotein also plays an important role in viral assembly at a late step of infection. Although the Env glycoprotein interacts with viral matrix proteins and cellular proteins associated with lipid rafts, its possible role during the early replication events remains unclear. Truncation of the cytoplasmic tail (CT) of the Env glycoprotein is acquired by SIV in the course of adaptation to human cells, and is known to be a determinant of SIV pathogenicity.
We compared SIV viruses with full length or truncated (T) Env glycoproteins to analyze possible differences in entry and post-entry events, and assembly of virions. We observed that early steps in replication of SIV with full length or T Env were similar in dividing and non-dividing cells. However, the proviral DNA of the pathogenic virus clone SIVmac239 with full length Env was imported to the nucleus about 20-fold more efficiently than proviral DNA of SIVmac239T with T Env, and 100-fold more efficiently than an SIVmac18T variant with a single mutation A239T in the SU subunit and with a truncated cytoplasmic tail (CT). In contrast, proviral DNA of SIVmac18 with a full length CT and with a single mutation A239T in the SU subunit was imported to the nucleus about 50-fold more efficiently than SIVmac18T. SIV particles with full length Env were released from rhesus monkey PBMC, whereas a restriction of release of virus particles was observed from human 293T, CEMx174, HUT78 or macrophages. In contrast, SIV with T Envs were able to overcome the inhibition of release in human HUT78, CEMx174, 293T or growth-arrested CEMx174 cells and macrophages resulting in production of infectious particles. We found that the long CT of the Env glycoprotein was required for association of Env with lipid rafts. An Env mutant C787S which eliminated palmitoylation did not abolish Env incorporation into lipid rafts, but prevented virus assembly.
The results indicate that the long cytoplasmic tail of the SIV Env glycoprotein may govern post-entry replication events and plays a role in the assembly process.
Retrovirology 02/2007; 4:94. · 6.47 Impact Factor
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ABSTRACT: Abstract
Background
The Env glycoproteins of retroviruses play an important role in the initial steps of infection involving the binding to cell surface receptors and entry by membrane fusion. The Env glycoprotein also plays an important role in viral assembly at a late step of infection. Although the Env glycoprotein interacts with viral matrix proteins and cellular proteins associated with lipid rafts, its possible role during the early replication events remains unclear. Truncation of the cytoplasmic tail (CT) of the Env glycoprotein is acquired by SIV in the course of adaptation to human cells, and is known to be a determinant of SIV pathogenicity.
Results
We compared SIV viruses with full length or truncated (T) Env glycoproteins to analyze possible differences in entry and post-entry events, and assembly of virions. We observed that early steps in replication of SIV with full length or T Env were similar in dividing and non-dividing cells. However, the proviral DNA of the pathogenic virus clone SIVmac239 with full length Env was imported to the nucleus about 20-fold more efficiently than proviral DNA of SIVmac239T with T Env, and 100-fold more efficiently than an SIVmac18T variant with a single mutation A239T in the SU subunit and with a truncated cytoplasmic tail (CT). In contrast, proviral DNA of SIVmac18 with a full length CT and with a single mutation A239T in the SU subunit was imported to the nucleus about 50-fold more efficiently than SIVmac18T. SIV particles with full length Env were released from rhesus monkey PBMC, whereas a restriction of release of virus particles was observed from human 293T, CEMx174, HUT78 or macrophages. In contrast, SIV with T Envs were able to overcome the inhibition of release in human HUT78, CEMx174, 293T or growth-arrested CEMx174 cells and macrophages resulting in production of infectious particles. We found that the long CT of the Env glycoprotein was required for association of Env with lipid rafts. An Env mutant C787S which eliminated palmitoylation did not abolish Env incorporation into lipid rafts, but prevented virus assembly.
Conclusion
The results indicate that the long cytoplasmic tail of the SIV Env glycoprotein may govern post-entry replication events and plays a role in the assembly process.
Retrovirology. 01/2007;
