Résumé
<p><b>OBJECTIVE</b>To investigate the molecular mechanism by which LKB1 regulates epithelial-mesenchymal transition (EMT) in Peutz-Jeghers hamartoma and intestinal epithelial cells.</p><p><b>METHODS</b>Immunohistochemistry was used to detect gene expression of LKB1, E-cadherin, and vimentin in 20 hamartoma tissues and 10 normal intestinal tissues, and collagen fiber deposition was analyzed using Masson trichrome staining. Normal intestinal epithelial NCM460 cells were transfected with LKB1 shRNA plasmid or negative control via lentiviral vectors, and the role of LKB1 in cell polarization and migration were determined using CCK8 and Transwell assays. Western blotting, quantitative real-time PCR (qPCR) and immunofluorescence were used to assess the alterations of EMT markers in the cells with LKB1 knockdown.</p><p><b>RESULTS</b>Compared with normal intestinal tissues, hamartoma polyps showed significantly decreased LKB1 and E-cadherin expressions and increased vimentin expression with increased collagen fiber deposition. The cells with LKB1 knockdown exhibited enhanced cell proliferation and migration activities (P<0.01). Western blot analysis, qPCR and immunofluorescence all detected decreased E-cadherin and increased N-cadherin, vimentin, Snail, and Slug expressions in the cells with LKB1 knockdown.</p><p><b>CONCLUSION</b>s LKB1 deficiency triggers EMT in intestinal epithelial cells and Peutz-Jeghers hamartoma, suggesting that EMT can serve as the therapeutic target for treatment of Peutz-Jeghers syndrome.</p>
Résumé
<p><b>OBJECTIVE</b>To investigate the reactivity of colon cancer cell line SW480 and CD133(+) SW480 subsets to hypoxia in vitro and the changes in the expressions of anti-apoptosis and angiogenesis genes.</p><p><b>METHODS</b>SW480 cells was subjected to CoCl(2) exposure at varying concentrations and for different time lengths to induce hypoxia, and the protein expression of hypoxia induced factor 1α (HIF-1α) was detected by Western blotting. The CD133(+) SW480 cells were sorted by magnetic activated cell sorting (MACS) and their proportion was assayed by flow cytometry (FCM). The CD133(+) SW480 subsets were exposed to CoCl(2) at the optimal concentration with exposure time selected in terms of HIF-1α level, and their tumor stem cell sphere formation ability was evaluated. Real-time PCR was used to compare the mRNA expression levels of the surface markers of colon cancer stem cells (CD133 and PROM1), survivin, and vascular endothelial growth factor (VEGF).</p><p><b>RESULTS</b>Exposure to 200 µmol/L CoCl(2) for 8 h resulted in the highest HIF-1α expression in SW480 cells, but the same exposure failed to induce HIF-1α expression in CD133(+) SW480 subsets. The CD133(+) SW480 subsets, after CoCl(2)-induced hypoxia, showed significantly enhanced ability of cell sphere formation. Hypoxia of SW480 cells caused significant increases in CD133, survivin and VEGF mRNA levels by 1.607∓0.103, 2.745∓0.370 and 3.798∓0.091 folds, respectively (P<0.05).</p><p><b>CONCLUSION</b>CoCl(2) can simulate hypoxia in colon cancer cells in vitro to induce stable HIF-1α expression, which is concentration- and time-dependent. The hypoxia-stimulated tumor stem sells show an enhanced sphere formation and anti-apoptotic and anti-angiogenic abilities.</p>