title: Regulation of pancreatic cancer growth by superoxide.
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 (O 2.-), 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 O 2.- 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 O 2.-, 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 O 2.-, and treatment with the small molecule O 2.- scavenger Tempol, also decreased hydroethidine fluorescence, inhibited clonogenic survival and inhibited growth of tumor xenografts. Thus, O 2.- produced by NOX2 in pancreatic cancer cells with K-ras, may regulate pancreatic cancer cell growth.
authors.affiliation: Departments of Radiation Oncology, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA.
authors.forename: Juan
authors.initials: J
authors.lastname: Du
authors.forename: Elke S
authors.initials: ES
authors.lastname: Nelson
authors.forename: Andrean L
authors.initials: AL
authors.lastname: Simons
authors.forename: Kristen E
authors.initials: KE
authors.lastname: Olney
authors.forename: Justin C
authors.initials: JC
authors.lastname: Moser
authors.forename: Hannah E
authors.initials: HE
authors.lastname: Schrock
authors.forename: Brett A
authors.initials: BA
authors.lastname: Wagner
authors.forename: Garry R
authors.initials: GR
authors.lastname: Buettner
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Smith
authors.forename: Melissa L T
authors.initials: ML
authors.lastname: Teoh
authors.forename: Ming-Sound
authors.initials: MS
authors.lastname: Tsao
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Cullen
mesh_terms: D000818:Animals; D015153:Blotting, Western; D049109:Cell Proliferation; D003497:Cyclic N-Oxides; D003600:Cytosol / Q000201:enzymology; D005110:Extracellular Space / Q000201:enzymology; D005453:Fluorescence; D006801:Humans; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D008928:Mitochondria / Q000201:enzymology; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000378:metabolism / Q000473:pathology*; D010617:Phenanthridines / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras); D034741:RNA, Small Interfering / Q000235:genetics; D013113:Spin Labels; D013482:Superoxide Dismutase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism*; D014407:Tumor Cells, Cultured; D014410:Tumor Stem Cell Assay; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D003497:Cyclic N-Oxides; C117307:KRAS protein, human; D008562:Membrane Glycoproteins; D010617:Phenanthridines; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D013113:Spin Labels; D013481:Superoxides; C058428:hydroethidine; D013482:Superoxide Dismutase; C056558:CYBB protein, human; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins; C001803:tempol