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Lifeguard (LFG) is an anti-apoptotic protein that inhibits Fas-mediated death in tumour cells. However, the molecular function of human LFG in the carcinogenesis of human breast cells is uncertain. We studied the expression and function of endogenous LFG in four breast cancer cell lines (MCF-7, MDA-MB-231, T-47D and HS 578T), a human breast epithelial cell line (HS 578Bst), and in healthy and cancerous breast tissues. Molecular (Western blot and RT-PCR) and immunohistochemical techniques were used to investigate the LFG expression. To investigate the breast cancer cell proliferation in the presence of Fas, we performed fluorescent cell viability assays. The possible association of Fas with LFG was analyzed by immunofluorescence microscopy. In this paper, we provide convincing evidence that LFG is overexpressed in several human breast cancer cell lines. More importantly, we found that the LFG expression correlates with high tumour grades in primary breast tumours. Finally, we demonstrated that Fas sensitivity is reduced in breast cancer cell lines expressing LFG. Our results indicated that LFG is strongly expressed in breast cancer epithelial cells. Moreover, the overexpression of LFG correlated with tumour grade and reduced Fas sensitivity. Our findings support the idea that LFG may have a role in the downregulation of apoptosis in breast cancer cells.
One of the most promising strategies in colon cancer therapy is the sensitization of cancer cells to natural proapoptotic cytokines, such as death ligands and interferons, which are able to eliminate abnormal cells. The investigation of mechanisms determining the immune escape of cancer cells revealed the presence of antiapoptotic proteins, such as cFLIP, which inhibit cell death signal transduction. Numerous studies showed that the use of different metabolic inhibitors, such as cycloheximide (CHX), reduces the cFLIP protein level, thus restoring the susceptibility to TNF-a-induced apoptosis. However, high non-specific toxicity of CHX excludes the clinical use of this substance. The current efforts are focused on identification of bioactive compounds which could safely support immunotherapy. The review presents in vitro and in vivo evidence that butyrate (Bt), fatty acid produced in colon during fermentation process and parthenolide (PN), sesquiterpene lactone isolated from Tanacetum parthenium specifically affect different cancer cells. Among described various molecular mechanisms of Bt and PN action, one reduces the level of antiapoptotic proteins. This paper clearly demonstrates that bioactive compounds, especially combined with immune cytokines could be seriously considered as an alternative for routine colon anti-cancer therapy.
We previously demonstrated that the anti-apoptosis protein, survivin, plays a protective role against alcohol-induced gastric injury. Since the endothelium is a primary target of alcohol-induced gastric damage, we investigated whether survivin expression is a key factor in the greater susceptibility of gastric endothelial vs. epithelial cells to alcohol-induced injury. Here, we demonstrate that rat gastric epithelial cells (RGM1 cells, an epithelial cell line derived from normal rat gastric mucosa) expressed 7.5-fold greater survivin protein levels vs. rat gastric endothelial cells. Survivin expression correlated with resistance of gastric epithelial vs. endothelial cells to both alcohol-induced cell damage and alcohol-induced apoptosis. Suppression of survivin protein expression levels using siRNA rendered the gastric epithelial cells as susceptible to both alcohol-induced cell damage and apoptosis as the gastric endothelial cells. Conversely, forced overexpression of survivin by transient transfection rendered gastric endothelial cells as resistant to both alcohol-induced cell damage and apoptosis as mock-transfected gastric epithelial cells. Moreover, overexpression of a threonine-34 to glutamate phosphorylation mimic mutant survivin construct rendered gastric endothelial cells significantly more resistant to alcohol-induced damage and apoptosis vs. mock-transfected gastric epithelial cells. These findings indicate that disparate survivin expression levels can explain the discrepancy between gastric epithelial and endothelial cell susceptibility to alcohol-induced injury; and, that a negative charge at amino acid residue 34 on survivin, such as that which naturally occurs by phosphorylation of threonine-34, enhances its property in conferring gastric mucosal protection.
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