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1 Department of Environment and Primary Prevention, Istituto Superiore di Sanita, Rome, Italy; 2 Istituto Nazionale per la Ricerca sul Cancro, Genova, Italy; 3 Cancer Research UK, London Research Institute, Clare Hall Laboratories, Herts, United Kingdom; and 4 Department of Microbiology, Immunology and Molecular Genetics and the Molecular Biology Institute, University of California, Los Angeles, California
| ABSTRACT |
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| Introduction |
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TA transversion) in mutM mutY double mutants (3)
. The increase is synergistic, and inactivation of each gene alone confers only a modest mutator phenotype. A third component of the protective process, the MutT-encoded hydrolase, prevents incorporation of 8-oxoG into DNA by removing 8-oxo-dGTP from the deoxynucleoside triphosphate pool (4)
. In contrast to MutM and MutY, inactivation of MutT alone is sufficient to produce a severe mutator phenotype (>100-fold increase), particularly in AT
CG transversions. Each of these protective factors has a counterpart in mammalian cells. Independent disruption of the murine MutM, MutY, or MutT homologues (OGG1, MYH, and MTH) confers, at most, only a minor increase in spontaneous mutation rate. In Ogg1/ mice (5
, 6)
and in Myh/ ES cells (7)
, this increase is
2-fold. In Mth/ mice, although there is a change in the mutational spectrum, in particular an increase in A:T to C:G transversions and frameshifts, there is no significant increase in overall rate (8)
, apparently due to the presence of a related back-up hydrolase (9)
. Age-dependent accumulation of DNA 8-oxodG occurs in hepatocytes but not in splenocytes, spermatocytes, or renal cells of Ogg1/ mice (10) . No information is available on the levels of this oxidized base in the DNA of tissues of Myh-defective mice. We therefore compared the levels of DNA 8-oxodG in several organs of Myh/ mice to those of doubly defective Myh//Ogg1/ animals. Our data demonstrate that, as with OGG1, inactivation of MYH does not cause significant age-dependent accumulation of DNA 8-oxodG in mouse tissues, with the notable exception of liver. When both MYH and OGG1 are inactivated, 8-oxodG gradually accumulated in the DNA of lung and small intestine. Because there is an increased incidence of lung or small intestine cancer in double Myh/Ogg1 knockout mice (11) , our results are consistent with a model in which the accumulation of unrepaired oxidized bases in DNA contributes to neoplastic transformation.
| Materials and Methods |
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Preparation of Liver, Spleen, Kidney, Brain, Small Intestine, and Lung DNA.
Similar numbers of males and females have been used to prepare DNA for 8-oxodG measurements. Mice were killed by cervical dislocation, and excised organs were washed with ice-cold PBS. Liver was diced and washed with hypotonic KCl. Washed tissues were snap-frozen in liquid nitrogen. Before DNA extraction, thawed tissues were finely minced in lysis buffer [10 mM Tris HCl (pH 8.0), 10 mM EDTA, 10 mM NaCl, and 0.5% SDS]. DNA was extracted by a high-salt protein precipitation method. Briefly, following lysis tissues were digested with RNase at 37°C for 1 h and protease (Qiagen) at 37°C overnight. Proteins were precipitated by adding NaCl to 1.5 M, and DNA in the supernatant was collected by addition of 2 vol of ethanol.
Measurements of 8-OxodG.
DNA 8-oxodG was measured by high-performance liquid chromatography with electrochemical detection as described previously (12)
. Briefly, DNA was resuspended in Tris-EDTA, incubated with RNases A and T1 at 37°C for 1 h, and precipitated again with ethanol. Enzymatic digestion was then performed at 37°C using nuclease P1 (Boehringer Mannheim) for 2 h and alkaline phosphatase (Boehringer Mannheim) for 1 h. Enzymes were precipitated by addition of CHCl3, and the upper liquid layer stored at 80°C under N2 for subsequent analysis 8-oxodG. The DNA hydrolysate was analyzed by high-performance liquid chromatography with electrochemical detection (Coulochem I; ESA, Inc., Chelmsford, MA) using a C18 250 x 46 mm 5-µm Uptishere column (Interchim) equipped with a C18 guard column. The eluent was 50 mM ammonium acetate (pH 5.5), containing 9% methanol, at a flow rate of 0.7 ml/min. The potentials applied were 150 and 400 mV for E1 and E2, respectively. The retention time of 8-oxodG was
23 min. Deoxyguanosine was measured in the same run of corresponding 8-oxodG with a UV detector (model SPD-2A; Shimadzu, Kyoto, Japan) at 256 nm; the retention time was
17 min.
| Results |
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4-fold increase in liver DNA 8-oxodG (0.2 versus 0.78 8-oxodG x 10-6 dG) over a 10-month period (Fig. 2B)
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6-fold (R2 = 0.695; P = 0.000; Fig. 2C
3-fold (R2 = 0.569; P = 0.005) by 16 months. Over the same period, there was a similar increase in the level of 8-oxodG in DNA of the small intestine of Myh//Ogg1/ mice. Although the increase was of a similar magnitude, the final levels of DNA 8-oxodG were higher because the level of background DNA oxidation was
2-fold higher in this tissue independent of the genotype of the mouse (Fig. 3BF)| Discussion |
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The complexity of the mammalian organism is, however, reflected in the age dependency and tissue specificity of DNA 8-oxodG accumulation. Age-dependent accumulation of DNA 8-oxodG was not observed in all organs of the double knockout animals. There was no significant change in the steady-state level of the oxidized purine in brain, kidney, or spleen. The reason for the selective accumulation in lung and small intestine DNA is unclear. It is striking, however, that it is these organs in which there is an increased cancer incidence in the doubly defective Myh//Ogg1/ mice (11) . These findings suggest that oxidized DNA purines can play a causative role in the development of cancer. Liver is the only organ in which inactivation of a single gene, either Ogg1 (10) or Myh (present article), is associated with an age-dependent accumulation of DNA 8-oxoG. This may reflect a high level of oxidative metabolism or the role of this organ in detoxification. However, this accumulation of the lesion in liver DNA is not associated with carcinogenesis in Ogg1/ or Myh/ mice (5 , 6 , 11) .
The absence of significant age-associated accumulation of oxidized DNA purines in the majority of tissues of Myh//Ogg1/ mice suggests that there may be other DNA repair systems to deal with this type of DNA damage. Candidates include the recently characterized homologue of the bacterial Fpg/Nei DNA glycosylase, Neil 1, which shares with OGG1 the ability to remove 8-oxoG from 8-oxoG:C bp (14) . In addition, DNA mismatch repair is known to play a role in reducing the burden of DNA 8-oxoG and associated mutations (15 , 16) . In view of the tissue selectivity of DNA 8-oxodG accumulation, it may be that these alternative repair systems are limiting in certain organs. In this connection, it is noteworthy that inactivation of mismatch repair or MTH1 in mice is associated with small intestinal tumors (17) and lung tumors, respectively (18) .
In humans, inherited MYH variants are associated with colorectal carcinomas (19 , 20) , and deficiencies in 8-oxoG repair might be a risk factor for lung cancer (21) . Possibly, additional deficiencies in mismatch repair or other base excision repair genes might enhance tumorigenesis in these tissues.
| ACKNOWLEDGMENTS |
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| FOOTNOTES |
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The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Note: M. Russo and G. De Luca contributed equally to this work.
Requests for reprints: Margherita Bignami. E-mail: bignami{at}iss.it
Received 2/ 3/04. Revised 3/26/04. Accepted 5/ 7/04.
| REFERENCES |
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T:A mutations in colorectal tumors. Nat Genet, 30: 227-232, 2002.[CrossRef][Medline]
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