[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.