[Studies on the DNA damage in the transformed bronchial epithelial cells induced by hexavalent chromium]

Objective: To investigate DNA damage in the transformed human bronchial epithelial cells (16HBE) induced by hexavalent chromium (Cr(6+)) and further elucidate the potential carcinogenesis mechanism of Cr(6+). Methods: 16HBE were treated with different concentration of Cr(6+ ()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 Cr(6+)-treated cells in soft agar showed significant increases (p<0.05) . The 2.5 μmol/L Cr(6+)-treated cells also formed tumors subcutaneously in nude mice. Cr(6+) 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 Cr(6+). Conclusion: The declined expression of 53BP1 may mediate Cr(6+)-induced DNA damage and further involved in the cell malignant transformation.