RESUMEN
Objective@#To investigate the role of hypoxia-inducible factor-1α (HIF-1α) in arsenite-induced epithelial-mesenchymal transition (EMT) and malignant transformation of human liver epithelial cells (L-02 cells).@*Methods@#After the L-02 cells were chronic treated with 2.0 μmol/L NaAsO2 for 0 (reference), 10, 20, or 30 passages, con siRNA or HIF-1α siRNA was transfected into arsenite-transformed L-02 (T-L-02) cells by lipofectamineTM2000 and were set as T-L-02+con siRNA group and T-L-02+HIF-1α siRNA group as well as L-02 group and T-L-02 group, EMT index and levels of HIF-1α were detected by western blots. The reporter assays were performed to determine if HIF-1α directly regulate Snail transcriptional activity, and soft agar colony formation and Transwell assay were used to detect the malignancy, invasion, and migration ability of cells.@*Results@#When L-02 cells were treated for 10 generations with 2 μmol/L NaAsO2, relative expressions of E-cadherin were gradually increased compared to control cells, while the levels of N-cadherin, Snail, and HIF-1α were gradually increased in the L-02 cells compared to control cells, showing the longer the treatment time was, the more obvious the change was (P<0.05) . Down regulating the level of HIF-1α by siNRA caused E-cadherin levels to rise compared to T-L-02 group, while the levels of N-cadherin and Snail fall back compared to T-L-02 group (P<0.05) . Double luciferase reporter gene assays showed that HIF-1α directly targeted Snail to regulate its expression. Soft agar colony formation and Transwell assays showed that the numbers of formed colonies, invasion cells, and metastasis cells of cells in T-L-02 group were all lower than those in L-02 group (P<0.05) .@*Conclusion@#HIF-1α is involved in arsenite-induced EMT and malignant transformation of human liver epithelial cells via regulating Snail.
RESUMEN
Objective@#To investigate DNA damage in the transformed human bronchial epithelial cells (16HBE) induced by hexavalent chromium (Cr6+) and further elucidate the potential carcinogenesis mechanism of Cr6+.@*Methods@#16HBE were treated with different concentration of Cr6+ (0, 0.625, 1.25, 2.5 μmol/L) for 15 weeks. The malignant degrees of transformed cells were identified by the assays for anchorage-independent growth and tumorigenicity. According to the single cell gel electrophoresis (SCGE) assay, the DNA damage rate was calculated. The expression level of 53BP1 was determined by Western blot.@*Results@#Chromium-treated cells could form colonies in soft agar and tumors in nude mice. Compared with the control group, colony formation efficiency of 1.25μmol/L and 2.5 μmol/L Cr6+-treated cells in soft agar showed significant increases (p<0.05) . The 2.5 μmol/L Cr6+-treated cells also formed tumors subcutaneously in nude mice. Cr6+ could cause different degree of DNA damage to 16HBE cells in a dose-dependent manner. In addition, Western blot analyses showed that 53BP1 was aberrantly down-regulated at 2.5 μmol/L dose and has no significant changes at 0.625 μmol/L and 1.25 μmol/L dose under the treatment of Cr6+.@*Conclusion@#The declined expression of 53BP1 may mediate Cr6+-induced DNA damage and further involved in the cell malignant transformation.