Document 3eMRbjn8vyQgmbemQEq5kL1yx

|- AP000I8433 mmUrn **. flteili iJOi yt'uA* yf-*5*Sd m the rel of DM rtytir pcocww la HrolaogtMdi md grande moeenpUbllity to omomr. HtnaBCtf 1. VftlctiMlbara, N X.. Worn, J., M Uttla, 3. a. (19K). Utur 266* m, I. ViichMlbM, K. IU, M**i J. and UtUrn, J. a. 1X978) < Submitted. a.<*. Uttl*. J. Bataln, a.. md wLlllama, j- a. (L9TSU In "Molecular **~-*vrrlran far the kfir of CM" (9. C. tMMMlt ud X. a. Satlow* eds.) t 792-7*9. Menu* mi( Maw fork. re*''** .IWOJ vsr a(r, % *0 IsJlrtJLC a^ DVBA raapMT MM9HMM ENVIRONMENTAL CHEMICALS CAUSING CARCE* AM) GENETIC BIRTH DEFECTS Bruce N. Ames Department of Biochemistry, University of California, Berkeley, California 94720 Oarage to ONA appears to be the cause of most cancer and genetic birth defects and may contribute to aging and heart disease as well. A major part of this DNA damage Is caused by environmental chemicals, both natural and man made. Many ore chemicals will be added to the current list of human carcinogens and mutagens. Since the late 1950s we have been exposed to a flood of chemicals--'from flame retardants In our children's pajamas to pesticides accumulating In our body fat--that were not tested for carcinogenicity or mutagenicity before their use. In the past this problem has been largely Ignored; even high-production chemicals, with extensive human exposure, have been produced for decades iHthout adequate carcinogenicity or mutagenicity tests. A few of these chemi cals am now being tested in animals, hut for most of them the human population Is serving as the test animal. Because the 20- to 30-year lag time for chemical carcinogenesis In humans is almost over, the Incidence of cancer may increase steeply if too many of the thousands of hew chemicals to which hunans have been exposed turn out to be powerful mutagens and carcinogens (figures 1 and 2). Me must identify the agents that have caused the cancer and genetic birth defects of today (nany of these are natural compounds present in our diet as complex mixtures) and test the many man-made chemicals that have been introduced Into the environment in the last fat decades. Existing animal tests and human epidemiology atom* are Inadequate procedures for this task for a number of rea sons including time, expense, and the difficulty of dealing with complex mixtures. Over the last 14 years we have developed a slaple method for Identifying chemical mutagens, and we have shown that almost all chemical carcinogens are mutagens (1). This test conhines on a petrt plate special strains of SrlnraeZZe bac teria (as indicators of reverse mutation) and maomwlitn liver homogenates (rodent or hunan autopsy--to provide mammalian metabolism) (Figures 3 and 4) (4-6), Me have validated the test for detection of carcinogens as mutagens by testing over 300 chemicals and have reported that almost all chemical t> iw*r **-- tat At %W> V irpim kn tann wwii IW1 UQMI < > f.. K i V \ m HI. MUCBN.AMES DMA ftEPAin MECHANISMS i i ! S f i i i i FIGURE 1. Cigarette smoking and lung cancer are unmis takably related* but the nature of the relation remained ebsevre because of the long latent period between the Increase In cigarette consumption and the Increase In the Incidence of lung cancer. The data are for England and Hales. In men ! (solid line) smoking began to Increase at the beginning of the FIGURE 2. Production of two mutagens-caretnogem with Ii 20th centary, but the corresponding trend In deaths from lung cancer did not begin intll after 1920. In women (dotted line) widespread huaan exposure: ethylene dlchloride and vinyl chloride (production data from "Top-50 Chemicals" Issues of seeking began later, and lung cancers are only now appearing. Chemical and fingincaring Ktwo). Approximately 100 billion 1b (Fro* J. Cairns, "The Cancer Problem." Copyright 1975 by of ethylene dlchloride and over 50 billion lb of vinyl chlo Scientific American. Ine. All rights reserved.) ride have been produced since I960. Ethylene dlchloride is a Even if we could Identify new hazardous chaelcals by htfnen epidemiology, people will already have been exposed for - decades, and the discovery may be too late. Thfs happened volatile liquid that is the precursor of vinyl chloride and Is also used extensively as a finfgant, solvent, gasoline addi tive (200 million Ib/yr), and metal degreaser. Ethylene dl- with vinyl chloride; It was in millions of spray cans end In chloride ms first shown to be a mutagen in Drocapkila In i i foods packaged In PVC (polyvinyl chloride) containers. The 20- to 30-year lag tine needed for cancer to develop from the 1960, and later In barley and Salmonella* but this fact IMS been ignored. The first adequate cancer test In animals has exposure to the tremendous Increase In chemicals that started during the late 1950s and early 1960s (Figure 2) is almost ever. Thus, we may expect e steep Increase In human cancer If any of these thousands of new chemicals are Indeed powerful mutegem and carcinogens with widespread hisnan exposure. just been completed by the H.C.I. (Kovember 1977) and Is posi tive la both sexes of both rats and mice. Vinyl chloride gas Is used to make polyvinyl chloride (PVC; vinyl) plastic. It was shown to be a carcinogen in rats and In people in the mid1970s, and a mutagen in Salmonella and other systems shortly afterwards. (From B. h. Ames, 'Environmental Chemicals Causing Cancer and Genetic Birth Defects," Institute of Govern mental Studies, University of California, Berkeley, 1978.) AP00018434 AP00018435 ii i rifn'ifWWi & Oh BKUCC N. AMES DMA REPAIR HECMANISMS m the market. Since AF-2 had already been tested for carcino genicity in two animal systems and found negative, it is unlikely that further tests would have been conducted If it had not been shown to be mutagenic. the ciUl of plate* C and D, i rat liver nicrosmrel activation system (S-9 Mix). Mutagens were applied to 6hh filter-paper discs* which were then pieced In the center of each plate: (a) spontaneous reveruntsi (0) the Japanese food additive furylfurMide fAF-2> (I ug|; (c) the sold carcinogen afla- tokin B) (1 pg); (P| 2-aminofluerene (10 ug). Mutagen" Induced revertaRts appear as a ring of colonies around each disc. (Reprinted fro* Ref. 1.) The food additive furytfuraartde was used extensively In Japan from 1965 until recently at, aa antibacterial additive In a wide variety of comm food products such as soybean curd and fish sausage. It showed to carcinogenic activity in tests oa nts in 1962 and on nice in 1971. t 1973, Japanese scien tists found It to be highly mutagenic In a strain of Beaheri*hia ooli bacteria (It was also found to be extraordinarily potent In reverting our Salmonella tester strain TA100). They subsequently examined It In higher (eukaryotic) organises and found It to be autagenie In yeast and teurospora, and to cause chromosome breaks in human white blood cells. Animal tests for carcinogenicity, more extensive than the previous ones, sure Initiated, and these tests have recently shown that AF-2 H, In fact, a carcinogen. As a consequence of this finding, the Japanese government prohibited the use of Af-2 as a food additive, and all products containing AF-2 were removed from tmw r r t- i, \' FIGURE 4. The flame retardant tr*m(2,3-d1bromopropyl) phosphate and the pesticide dfbroaiochleropropane were In the presence of rat liver homogenate. All compounds were tested an Salmonella strain TA100. The amount of the Industrial chemical ethylene dibromide added was ten times that indi cated on the scale. (Reprinted from Ref. 2.) Since this and the Prival at at. (3) studies, trio has been shown to be a carcinogen In rats and mice. Fifty million children have been exposed. Dlbromochloropropane (D6CP) has now been shown to have sterilized a large lumber of factory workers. . t- k 5 i !{ N i * i ' < r i i * I m ut. axucs N. AMES carcinogen* tested in wbywk In this test (157/175) and nit "nun-carcinogens" (95/108) art negative. A number of the "false positives" generated by this study appear to be explainable as consequences of statistical limitations of uiIhI carcinogenicity tests (4.7). . The test Is particularly useful for the detection of utagens/carclnogens In coaqriex Mixtures (such as cigarette smoke. water, air pollution, food, and urine) (8-10). Me have recently developed a single method for examining human urine in our test system and have shown that cigarette smokers have awtagens In their urine and non-smokers do not (10). The test Is also useful in the development of drugs and Industrial chemicals where large maters of chemicals must be screened. Host of the major drug and chemical companies In the world are now using the test system. Me are exposed to a very large number of chemicals that are mutagens and carcinogens, many of tb* quite useful for society, and it is clearly Impractical to ban them all, yet foolish to Ignore their potential danger. Me must have some way of setting priorities for regulation of these cheelcals, and this requires an assessment of human risk. Me (with C. Sawyer, N. K. Hooper, A. Friedman, and ft. Peto, following the lead of Metelson and Russell [11]) have shown by the quantita tive analysis of animal cancer tests that there Is over a million-fold range In the strength of carcinogens,'and this knowledge, combined with knowledge on human exposure, nay enable an assessment of human risk to be done la a more rational manner. Because few chemicals (or mixtures) In the environment have been tested In animal cancer tests, we need additional ways of obtaining Information as to the mutagenic and carcinogenic danger of chemicals. we believe that short-term tests such as Satmonolla will play an essential role In priority setting: a key Issue, how ever, Is what they can tell us about potency. Me have prelim inary studies on the relation between nutagenic and carcino genic potency. There arm a mater of reasons why one should not expect a very dose quantitative correlation between muta genicity In bacteria and carcinogenicity in animals. Never theless, there Is over a million-fold range 1m Mutagenic potency In the SaUvnolla test and a similar range In carcino genic potency and even a rough quantitative correlation would be very useful in human risk assessment. There Is an indica tion. from Ifcselson and Russell's work (11) and our own that there Is a quantitative correlation, not only for carcinogens In the same chemical class, but also across a broad range of classes. Further work will show how general this correlation It. There appears to be a correlation between mutagenic potency in SeUonolla (and at least one short-term test using human cells [12]). Thus It appears likely that potency In a IMA REPAIR MECHANISMS *7 battery of short-term tests (ny good ones have now been developed) may be able to be used as an aid In human risk assessment. Me believe that a major area of public health can best be attacked by prevention: identifying environmental mutagens/ carcinogens, making a rough estimate of human risk based on potency and amount of human exposure, and minimising human exposure to the more dangerous of these agents. It seems likely that we will soon know how dearly we will have to pay In increased cancer and birth defects for the modem world of Industrial chemicals, pesticides, food additives, and plas tics. It appears likely, however, that the new methods end discoveries from basic biology that have been developed over the last decade and that are being developed at present will help In making future decisions more rational. REFERENCES I have kept the reference list fairly brief. A good general reference Is Origin* of Himmt Cancer, H. H. Hiatt, J. 0. Matson, and J. A. Kinston, eds. (Cold Spring Harbor, New Tort: Cold Spring Harbor Laboratory, 1977). 1. Ames, B. H., HcCann, J., and Yamasaki, E. (1975). ftthodt for detecting carcinogens and mutagens with the teZmonetZo/mammallan-nicrosome wUgenictty test. Mrt. tec. 31, 347-364. 2. Blun,-^., and Ames, 8. H. (1977). Flame-retardant addi tives as possible cancer hazards. Seionoo 195, 17-73. 3. Frlval, H. J., McCoy, E. C., Gutter, B., awTKosencrant, M. S. (1977). Tr!s(2,3-dlbromopropy!)pha$phate: Muta genicity of a widely used flame retardant. Saionoo 195, 4. McCann, J., and Ames. 8. N. (1977). The 3al*en*llaf microtome mutagenicity test: Predictive value for animal carcinogenicity, (ft Origin* of Human ameer, M. H. Hiatt, J. 9. Watson, and J, A. Winsten, eds, (Cold Spring harbor. New fork: Cold Spring Harbor laboratory, 1977), pp. 14311450. 5. McCann, J., Choi, E,, Yamasaki, E., and Ames, 8. It. (1975). Detection of carcinogens as mutagens In the SatrnonolUi/micmam test: Assay of 300 chemicals. Free. Hatl. head. Soi. USA 72, S135-S139. 6. McCann, J., and Amest~1T. N. (1976). Detection of carcino gens as mutagens In the teteoneZla/mfcrosome test: Assay of 300 chemicals. Discussion. Pm. Hatl. Arad. fH, USA' 73, 950-954. AP00018436 APOOO18437 AtiiiBii'iitiiin iininitiiiH.il^i., n rmf iftianaidu 1-4^. tm ni.BMfCEN.AMn pwa had. MmAmUwn *' 7. tbnahue, I. V., HcCam, 4., gnrf AttS. 8. II. (1978). Detection sf mutagenic lapwrltles In carcinogens and non- carcinogens by high-pressure liquid chros*tography and the StlmonaZZa/afcrotOme test. Ctmoor Acaeareh 38. 431-438. * . icier, L. P., YHnsakI, E., and Ams. B. R. (1974). Detection of nutagenlc activity In cigarette smoke con densates. Proa. Matl. Acad. Soi. USA 71. 4159-41(3. 9* Durston, V. E.. and Ames. B. N. (1974). A simple method For the detection of mutagens In urine: Studies with the carcinogen 2-aeetylamlnofIuorene. Proa. Kid. Aaad. Soi. USA 71. 737-741. 10. Vamtsakl* E., and Anes. B. R. (1977). The concentration f mutagens from urine by XAD-2 adsorption: Cigarette smokers have mutagenic urine. Proa. Uatt. Aood. SH. USA 74. 55-3559. 11. MeseTson, and Russell. K. (1977)7 Comparisons of carcinogenic and mutagenic potency. In Origin* of pmtm Cmoor. H. H. Hiatt. 3. o. Hitson, and J. A. Minster, eds. (Cold Spring Harbor. New York: Cold Spring Harbor Laboratory. 1977), pp. 1473-1482. 12. Painter, R. 8., and Howard, R. (1978). Mit. At*.*, In press. BOBKSOD* SIMUMTt Chemical Dams#* emd IIiUiwmU tm UmmILw SfltMt C. T. Arlatt, WC Cell Mutation unit, University of anin, filwr, Br letton BN1 OQO. ftiglsed Fran th divers* coatrlbut lano of ths lit opaokoro at this VarKUmp threa Mjor time* oaa bn roaolvodi. Tho first non corns tho possibility of tho oxtstosce of diff*ront repair nodot for different olassoa of DM dowse* in ntnlln colts. Beth Straus* and noborts produced biochemical evidence that suggests that colls nay hue* available a nunber of alternative repair pathways to aodlfy a apeclfle typo of danaee. thus It ia possible to prodwc* evidence that tho decision rcjmlr procoasea which handlo tho aryalkyl retidu** nay b* discriainatod Iron thorn which Modify thynlae dinars produced by UV Irradiation (Dlpple and Roberta, 1977). Although ehenleal adducts can bo eacieed they nay also bo bypaaaed by tho repli cation nachinory, the nochanisn of bypass probably Involve* branch migration (Higgins, Xato and Strausw, 1970). Tho con sequences to tho cell of the continued existence of adducts ia not known but they nay bo diluted out of the ayatee If repllesticn can continue, in addition they are still available as substrates for ewclolfla repair. Support, at the biological level, for the existence of dif * (' ,' f ferential repair modes was provided by Usher and Arlett. Maher showed that defects in excision repair, particularly le xeroderma ptgmcntosua (Ip) cells are vary serious for the lethal response whom cel la ere treated with UV or chemicals which produce 'UV-llke* VUttrtlM tn the OKA. Indeed, the mors move.c the defects In excision the more severe are the effects on call killing or mutation. Other chemicals which do aot produce 'UV-llke* damage shew no differential killing effect* in JCP cells. These data Indicate a specificity of recognition of the lesion by part tcuiar repair process. These observations wore complemented by those of Arlett sho showed that by exposlay an array of human mutants with speci h. i fic eeaeitlottlos to IMA dawsglng scoots tittle cross sensi tivity waa observed. Further, the human OKA dsnsge-seosltiva ayndromaa can bo used to identify the mode of action of other agsots (Arlett, 1977). A second aa.|or theso ana concerned with the complexities ef the technology Involved la perforata* autatleti studies with : ! cultsrod *mmUui cells. Fox Illustrated the difficulties \ which are encountered In the a* experiments by shoving that the ehnpe of the sutation dose response curves, which are vital for thw proper evaluation of the data, are erittealty dependmt upon experimental dMlpi. The linear doae-rsapomaa curves produced by the so-called repeating technique (Fox end mM i\ k r w a <w r "IV .i T t . >t!i \ 4 I I