DNA damage, superoxide, and mutant K-ras in human lung adenocarcinoma cells

• Published in: Free radical biology & medicine Vol. 43; no. 8; pp. 1145 - 1155
• Main Authors: Romanowska, Malgorzata, Maciag, Anna, Smith, Andrew L., Fields, Janet R., Fornwald, Laura W., Kikawa, Keith D., Kasprzak, Kazimierz S., Anderson, Lucy M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 15.10.2007
• Subjects: Adenocarcinoma - genetics; Adenocarcinoma - physiopathology; Cell Line, Tumor; Comet assay; DNA Damage; DNA Glycosylases - metabolism; DNA Repair Enzymes - metabolism; Genes, ras - genetics; Human lung adenocarcinoma; Humans; K-ras; Lung Neoplasms - genetics; Lung Neoplasms - physiopathology; Manganese superoxide dismutase; Neoplasm Invasiveness - genetics; OGG1; Phosphoric Monoester Hydrolases - metabolism; ras Proteins - metabolism; Reactive oxygen species; Single-strand breaks; Superoxide; Superoxide Dismutase - metabolism; Superoxides - metabolism; NBT; PEG-SOD; Reactive oxygen species; DNA damage; OGG1; SOD; Superoxide; Comet assay; Human lung adenocarcinoma; Manganese superoxide dismutase; RBD; K-ras; ROS; DPI; Single-strand breaks
• ISSN: 0891-5849; 1873-4596
• DOI: 10.1016/j.freeradbiomed.2007.07.004

DNA single-strand breaks (quantitative comet assay) were assessed to indicate ongoing genetic instability in a panel of human lung adenocarcinoma cell lines. Of these, 19/20 showed more DNA damage than a nontransformed cell line from human peripheral lung epithelium, HPL1D. DNA damage was significantly greater in those derived from pleural effusates vs those from lymph node metastases. DNA strand breaks correlated positively with superoxide (nitroblue tetrazolium reduction assay), and negatively with amount of OGG1, a repair enzyme for oxidative DNA damage. Levels of CuZn superoxide dismutase varied moderately among the lines and did not correlate with other parameters. A role for mutant K-ras through generation of reactive oxygen species was examined. Cells with mutant K-ras had significantly lower amounts of manganese superoxide dismutase (MnSOD) vs those with wild-type K-ras, but MnSOD protein correlated positively with superoxide levels. In a subset of cell lines with similar levels of MnSOD, comparable to those in HPL1D cells, K-ras activity correlated positively with levels of both superoxide and DNA strand breaks. These results suggest that persistent DNA damage in some lung adenocarcinoma cells may be caused by superoxide resulting from mutant K-ras activity, and that OGG1 is important for prevention of this damage.