Abstract
K-ras mutations have been identified in up to 95% of pancreatic cancers, implying their critical role in the molecular pathogenesis. Expression of K-ras oncogene in an immortalized human pancreatic ductal epithelial cell line, originally derived from normal pancreas (H6c7), induced the formation of carcinoma in mice. We hypothesized that K-ras oncogene correlates with increased non-mitochondrial-generated superoxide (O2.-), which could be involved in regulating cell growth contributing to tumor progression. In the H6c7 cell line and its derivatives, H6c7er-Kras+ (H6c7 cells expressing K-ras oncogene), and H6c7eR-KrasT (tumorigenic H6c7 cells expressing K-ras oncogene), there was an increase in hydroethidine fluorescence in cell lines that express K-ras. Western blots and activity assays for the antioxidant enzymes that detoxify O2.- were similar in these cell lines suggesting that the increase in hydroethidine fluorescence was not due to decreased antioxidant capacity. To determine a possible non-mitochondrial source of the increased levels of O2.-, Western analysis demonstrated the absence of NADPH oxidase-2 (NOX2) in H6c7 cells but present in the H6c7 cell lines expressing K-ras and other pancreatic cancer cell lines. Inhibition of NOX2 decreased hydroethidine fluorescence and clonogenic survival. Furthermore, in the cell lines with the K-ras oncogene, overexpression of superoxide dismutases that detoxify non-mitochondrial sources of O2.-, and treatment with the small molecule O2.- scavenger Tempol, also decreased hydroethidine fluorescence, inhibited clonogenic survival and inhibited growth of tumor xenografts. Thus, O2.- produced by NOX2 in pancreatic cancer cells with K-ras, may regulate pancreatic cancer cell growth.
Original language | English (US) |
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Pages (from-to) | 555-567 |
Number of pages | 13 |
Journal | Molecular Carcinogenesis |
Volume | 52 |
Issue number | 7 |
DOIs | |
State | Published - Jul 2013 |
Externally published | Yes |
Keywords
- Oncogene
- Pancreatic cancer
- Superoxide
ASJC Scopus subject areas
- Molecular Biology
- Cancer Research