Gas chromatography/mass spectrometry (GC/MS) was used to determine the amounts of eight oxidative base modifications in DNA extracted from 11 specimens of bones and soft tissues, ranging in age from 40 to >50 000 years. Among the compounds assayed hydantoin derivatives of pyrimidines were quantitatively dominant. From five of the specimens endogenous ancient DNA sequences could be amplified by PCR. The DNA from these specimens contained substantially lower amounts of hydantoins than the six specimens from which no DNA could be amplified. Other types of damage, e.g. oxidation products of purines, did not correlate with the inability to retrieve DNA sequences. Furthermore, all samples with low amounts of damage and from which DNA could be amplified stemmed from regions where low temperatures have prevailed throughout the burial period of the specimens.

Free rudi&induscd damegc to DNA in vivo is implicated to play II role in cwcinogcncris. Ewidcncc exists thal DNA dnmnpc by cndoynous free radiuls occurs in vivo, und thcrc is a rtcadpstatc lwcl of free radic&moditIcd hascs in ccllullrr DNA. WC hove invaligPtcd cndogcnous lcvcls of typical free rztdic&induscd DNA bits modifications in chromriz of various human cancerous tissues and their canswfrec rurrounding~issucr.Five different lypcr of sur@cally rcmovcd tirsucr were UK& nttmcly eolon, stomach. ovary, brain and lung tissues. In chromntin samples ivolatcd fram thcsc tissues. iivc pyrimidinedcrivcd and six purinc-dcrivcd modillcd DNA busts wcrc idcntincd and quantitatcd by ~schromatographyltnass spsctromctry with rslcctcd.ion monitoring, Thcsc wcrc 5.hydrox~S~mcthylhydantoin, 5.hydroxyhydantoin, 5~(hydroxymcthyl)urcil, S.hydroxycy. torinc, 5,6.dihydroxycyt6dac. 4.6~diamino.S-formnmidopyrimidinc.t.hydr.rxyudcninc, xnnthinc, I.hydronyodcninc, 2,6diaminc&hydron~5. furmnmidopyrimidinc, and 8*hydroxy8uaninc. That compounds arc known to bc formed typically by hydroxyl rsdisal attach on DNA bw. In all ems, clcvatcd umounts over control lcvcls of modifIcd DNA bares WCFC found in cancerous tirrucr. The umounta of modified beset dcpndcd nn the tiwc type, Lung tissues rcmovcd from mokcrs hlrd the highest incrcnrlr of modified bases ubovc the conrrol Icvcls, and the hifisst overall umounts, Colon cunscr tissue samples hurl the lowcrt lncrcuscs of mdiClcd bttscs over the control Icwls. The results clearly indicate hi&r rtcady&!tc lcvclr of moditlcd DNA basss in cancerous tirsucr thaw in their cunccr.frcc surrounding tirruss~ Some of thcsc l-ions arc known lo tx promutagenic. although others have not been invcrriylltcd for their mutpycnicity, Identified DNA lctions mny play B cwsativc role in atrcinoycncr!r.

The formation of monomeric products in DNA upon exposure to UV radiation was investigated. Three novel products were identified in DNA in aqueous solution upon exposure to UV radiation at 254 nm in a dose range from 100 to 10,000 J/m2. These were 4,6-diamino-5-formamidopyrimidine, 2,6-diamino-4-hydroxy-5-formamidopyrimidine, and 5-hydroxy-5,6-dihydrothymine. These three products are known to be substrates for base excision repair enzymes involved in the reversal of oxidative DNA damage. The dependence of the yields of formamidopyrimidines on UV radiation dose was nonlinear, whereas the yield of 5-hydroxy-5,6-dihydrothymine was increased linearly in the entire dose range. Of these products, 4,6-diamino-5-formamidopyrimidine was the only compound produced in appreciable amounts at 310 nm. At the highest dose used, the formation of other pyrimidine- and purine-derived products was also observed. Their amounts, however, were increased above control levels up to 2-fold only. The hydroxyl radical scavenger dimethyl sulfoxide had no effect on product yields excluding the involvement of hydroxyl radical in product formation. 4,6-Diamino-5-formamidopyrimidine and 2,6-diamino-4-hydroxy-5-formamidopyrimidine may be produced by hydration of adenine and guanine, respectively, across the N(7)-C(8) double bond by mechanisms similar to those proposed previously for well-known formation of pyrimidine hydrates with the hydroxyl group located at C(6). Formation of 5-hydroxy-5,6-dihydrothymine indicates that hydration of thymine with the hydroxyl group located at C(5) of the pyrimidine ring also occurs.(ABSTRACT TRUNCATED AT 250 WORDS)

.4bstractWe have investigated levels of antioxidant enzymes and free radical-induced DNA base modifications in human cancerous lung tissues and in their cancer-free surrounding tissues. Various DNA base lesions in chromatin of lung tissues were measured by gas chromatography-mass spectrometry. .4ctivities of superoxide dismutase, catalase and glutathione peroxidase were also measured in lung tissues. Higher levels of DNA lesions were observed m cancerous tissues than in cancer-free surrounding tissues. Antioxidant enzyme levels were lower in cancerous tissues. The results indicate an association between decreased activities of antioxidant enzymes and increased levels of DNA lesions in cancerous tissues. Higher levels of DNA lesions suggest that free radical reactions may be increased in malignant tumor cells.