A History of Cancer Research: Carcinogens and Mutagens

A History of Cancer Research: Carcinogensand Mutagens

Joseph Lipsick

Department of Pathology, Genetics, and Biology, Stanford University, Stanford, California 94305-5324, USA

Correspondence: [email protected]

Observations of the incidence of tumors among chimney sweeps in the eighteenth centuryand later experiments with coal tars provided early evidence that carcinogens in the envi-ronment can promote cancer. Subsequent studies of individuals exposed to radiation, workon fly genetics, and the discovery that DNAwas the genetic material led to the idea that thesecarcinogens act by inducing mutations in DNA that change the behavior of cells and ulti-mately cause cancer. In this excerpt fromhis forthcoming book, Joe Lipsick looks back at howthe concepts of mutagenesis and carcinogenesis emerged, how these converged with devel-opment of the Ames test, and how biochemistry and crystallography ultimately revealed theunderlying molecular basis.

AN UNCLEAN SWEEP

Despite all the chim chim-in-ey, chim chim-in-ey, chim chim cheeriness of Dick Van

Dyke in the film Mary Poppins, it turns outthat chimney sweeps were not as lucky as luckycan be. The poet William Blake was far closer tothe mark than Disney’s songwriters (Fig. 1). In-deed, it was only by a twist of plot that OliverTwist, another boy who almost became a chim-ney sweep, escaped such a far more dismal fatethan that eventually chronicled by CharlesDickens.

The hero of our own tale is Percival Pott, anEnglish surgeon. In 1775, he reported that can-cer of the scrotum occurred in chimney sweepsin London, but rarely if ever in anyone else (Fig.2). This strong correlation between a rare diseaseand a relatively rare occupation suggested acausal relationship. Based on the anatomic loca-tion and course of the disease, Pott proposedthat the causative agent was chimney soot that

remained lodged in the furrowed folds of scrotalskin:

The fate of these people seems singularly hard; intheir early infancy, they are most frequently treat-ed with great brutality, and almost starved withcold and hunger; they are thrust up narrow, andsometime hot chimneys, where they are bruised,burned, and almost suffocated; and when they getto puberty, become peculiarly liable to a noisome,painful and fatal disease… the cancer of the scro-tum and testicles. The disease, in these people,seems to derive its origin from a lodgment ofsoot in the rugae of the scrotum.—Percival Pott,1775

Pott’s observation was the first (but hardly thelast) example of an occupational cancer, onecaused by specific agents in the workplace. Be-cause scrotal cancer was thought to develop inchildhood, a law was enacted in 1788 prohibit-ing boys under the age of 8 from working aschimney sweeps. However, attempts to replacesmall boys at risk in chimneys with mechanical

From the forthcoming volume Stalking the Enemy Within: A History of Cancer Research, by Joseph LipsickAdditional Perspectives on A History of Cancer Research available at www.perspectivesinmedicine.org

Copyright © 2021 Joseph Lipsick; published by Cold Spring Harbor Laboratory Press; all rights reservedCite this article as Cold Spring Harb Perspect Med 2021;11:a035857

1

ww

w.p

ersp

ecti

vesi

nm

edic

ine.

org

on May 29, 2022 - Published by Cold Spring Harbor Laboratory Press http://perspectivesinmedicine.cshlp.org/Downloaded from

mailto:[email protected]

mailto:[email protected]

http://www.perspectivesinmedicine.org



http://www.perspectivesinmedicine.org/site/misc/terms.xhtml



http://perspectivesinmedicine.cshlp.org/

devices were defeated by the efforts of the Mas-ter Sweeps and insurance industry, the latterfearing a repeat of the Great Fire of London.Indeed, it was this catastrophic blaze that hadresulted in the practice of constructing the longand tortuous chimneys, which in turn led to theuse of climbing boys as chimney sweeps. In1844, a law was finally passed prohibiting any-one under the age of 21 from sweeping chim-neys. Nevertheless, this law was reportedly notenforced until 1875, exactly 100 years after Pott’sinitial report.

It was widely believed that the incidence ofthe “chimney sweeps’ cancer” declined rapidlyafter 1875, because the disease was thought torequire extensive exposure to soot prior to pu-berty. However, a careful survey of actual hospi-tal case records byHenry Butlin in 1892 stronglycontradicted this prevalent view.

There has seldom been seen a more curious illus-tration of the steady growth and progress of afalse impression than this in relation to the declineof chimney-sweeps’ cancer. One is irresistibly re-minded by it of the growth of a slander or of thatentertaining winter evening game in which theplayers sit in a long row and the first tells in awhisper to the second some short tale or anecdote.The second repeats it to the third, still in awhisper,and third to the fourth, and so on through the row,until the last player tells it aloud to the infiniteamusement of the whole, who can scarcely recog-nise in the garbled version the story as it left themeach in turn.—Butlin, 1892

Butlin’s observations provide an early exampleof the importance of quantitative studies of can-cer incidence and cancer deaths, as opposed toanecdotal evidence.

A puzzle arose regarding the chimneysweeps’ cancer—why England? Although chim-ney sweeps plied their trade all across Europe

When my mother died I was very young,And my father sold me while yet my tongue,Could scarcely cry weep weep weep weep.So your chimneys I sweep & in soot I sleep.

There’s little Tom Dacre, who cried when his headThat curl’d like a lambs back, was shav’d, so I said,Hush Tom never mind it, for when your head’s bare,You know that the soot cannot spoil your white hair.

And so he was quiet, & that very night,As Tom was a sleeping he had such a sight,That thousands of sweepers Dick, Joe, Ned & JackWere all of them lock’d up in coffins of black.

Figure 1. On the plight of eighteenth-century English chimney sweeps. From William Blake’s “The ChimneySweeper,” in Songs of Experience, 1794.

Figure 2.Cancer of the scrotum, illustrated by HoraceBenge Dobell in 1848. (Reproduced from https://wellcomecollection.org/works/njqbesup.)

J. Lipsick

2 Cite this article as Cold Spring Harb Perspect Med 2021;11:a035857

ww

w.p

ersp

ecti

vesi

nm

edic

ine.

org


https://wellcomecollection.org/works/njqbesup






and in the United States, cancer of the scrotumwas very rare outside of England. Various hy-potheses were proposed to account for this dif-ference: unusually narrow and tortuous Englishchimneys, local differences in the compositionof coal, or the lack of protective clothing. How-ever, the most likely explanation was the differ-ing practice of personal hygiene in England.Richard Doll has noted that the medical recordsof a 25-year-old sweep treated for scrotal cancerin 1848 included the following statement: “Hesays he has worked in soot since boyhood andthat when young he was never washed for 5 or 6years at a time.”Doll further noted that althoughthe average age of death from scrotal cancer hadrisen to 60 years by the 1920s, the annual mor-tality from this disease in chimney sweeps wasstill remarkably high—350 times higher inchimney sweeps than in agricultural workers.Pott’s son-in-law James Earle later noted an un-usually aggressive skin cancer on the hand of anEnglish gardener. Because chimney soot ap-peared to cause scrotal cancer and becausechimney soot was sometimes spread by garden-ers to kill snails, Earle reasoned that the sameagent might cause both types of these occupa-tional cancers. However, at least one twentieth-century scholar has argued that exposure toultraviolet light may have been responsible forthis “soot cancer” of the hand.

COAL TAR—FROM OBSERVATION TOEXPERIMENT

Although chimney sweeps’ cancer was not oftenseen outside of England, cancers of the scrotumand other skin cancers did occur amongworkersin the coal distillation industry in Germany. Inthe late 1800s, Richard von Volkmann and oth-ers reported a correlation between exposure tocoal tars and mineral oils and the developmentof these cancers. These reports stimulated at-tempts by experimental pathologists to inducecancer in animals with coal tars andmineral oils.

In the late nineteenth century there wereseveral popular theories about the origin of can-cer. Rudolph Virchow and his followers heldthat irritation or injury of a particular tissuewas a direct cause of cancer. Julius Connheim

proposed that cancers arose from remnants ofembryonic tissue that are left behind during de-velopment and retain the capacity to proliferate.The tremendous success of Louis Pasteur, Rob-ert Koch, and others in showing that infectiousagents cause many diseases, including pneumo-nia, anthrax, and rabies, led to proposals thatcancer might be an infectious disease.

The finding of parasitic worms in some hu-man tumors led to the hypothesis that suchworms might be the direct cause of some can-cers. In 1913, Johannes Fibiger reported that hecould cause cancers of the stomach and esoph-agus in rats by introducing a nematode worm,called Spiroptera carcinoma, found in cock-roaches contaminating the animals’ food. Fibi-ger had studied with Robert Koch and wasProfessor and Director of the Institute of Ana-tomic Pathology at the University of Copenha-gen. His work provided the first widely acceptedevidence of an experimentally induced cancer.Fibiger was awarded the Nobel Prize for his dis-covery in 1926. However, others were unable torepeat his work. It eventually became clear thatthe worms were neither necessary nor sufficientto cause cancer. Rather, the changes Figiber hadobserved in the stomach and esophagus werenot in fact cancers but metaplasia (the replace-ment of one type of epithelium with another,often in response to chronic inflammation).

Meanwhile in Japan, Katsusabura Yama-giwa and Koichi Ichikawa were busy applyingcoal tar extracts to the ears of rabbits in anattempt to induce cancer. Yamagiwa hadtrained with Virchow in Germany and washimself a firm believer in Virchow’s hypothesisthat irritation was the major cause of cancer.Given that coal tar was the likely cause of can-cer in chimney sweeps in England and in coaldistillation workers in Germany, it seemed like-ly that coal tar might be just such a carcino-genic irritant. Many others had tried and failedto induce cancer in various animal species overthe previous 50 years. However, Yamagiwa andIchikawa were incredibly persistent in paintingthe inner ears of rabbits with coal tar everysingle day over the course of four long years.They eventually produced 16 carcinomas in 10of these rabbits. Their findings were published

Carcinogens and Mutagens

Cite this article as Cold Spring Harb Perspect Med 2021;11:a035857 3

ww

w.p

ersp

ecti

vesi

nm

edic

ine.

org



in Japan in 1915, and then in the United Statesin 1918 (Fig. 3).

Yamagiwa and Ichikawa had shown thatcoal tar could directly cause cancer at the siteof repeated application. However, once a cancerformed, the application of coal tar was notrequired for further growth of the tumor. Im-portantly, Yamagiwa and Ichikawa were able todescribe for the first time the progression ofcancer—from benign proliferation, to carcino-ma in situ, to invasive cancer, to metastasis. Be-ing a poet as well as a scientist, Yamagiwa com-posed a haiku to celebrate his success.

Unfortunately, because Fibiger had errone-ously beaten him to the punch in describing thefirst experimentally induced cancer, Yamagiwawas never awarded a Nobel Prize for his owndiscovery. Folke Hensche, a Swedish scientistwho had argued in favor of awarding the NobelPrize toFibiger, would later cite a quotation fromthe Belgian pathologist Albert Dustin whenlauding the groundbreaking work of Yamagiwa:

Theman who solves the enigma of cancer does notneed a Nobel Prize.

COOKING WITH GAS

Yamagiwa’s experiments demonstrated un-equivocally that coal tar could directly cause

cancer. However, it remained unclear whethercoal tar was just one of many irritants capable ofcausing cancer, or whether it contained a spe-cific substance required for carcinogenesis. But-lin held that, “The very nature of soot renders ithighly improbable that it contains within itself acancerous element, even in suspension.” How-ever, many investigators had tried and failed toinduce cancer in animals with a variety of veryirritating substances. Their experimental ani-mals often displayed local inflammation, hy-perplasia, and/or metaplasia, but not invasivecancer. These results indicated that there wasindeed something special about coal tar, al-though the substance itself was chemically com-plex and variable.

Bruno Block, a Swiss dermatologist, report-ed in 1921 that the carcinogenic component ofcoal tar had specific chemical properties. It had ahigh boiling point, could be extracted neither byacid nor by alkali, and contained neither nitro-gen nor sulfur. Ernest Kennaway and his col-leagues in London subsequently performed aseries of careful experiments that allowed themto synthesize the first chemically pure carcino-gen. They found that carcinogenic productscould be obtained simply by heating simple hy-drocarbons (e.g., isoprene or acetylene) to veryhigh temperatures in a hydrogen atmosphere.

Figure 3. (Left) A rabbit’s ear with cancers induced by coal tar. (Right) Yamagiwa’s haiku: “Cancer was produced!Proudly I walk a few steps.” (Left, Image from Fujiki H 2014. Cancer Science 105: 143–149; originally fromYamagiwa K, Ichikawa K. 1915. Mitteilungen of Medical Faculty of Imperial University of Tokyo 15: 295–344;right, from Shimkin MB 1977. “Contrary to Nature,” HHS Publication No. (NIH) 76-720, U.S. Department ofHealth, Education and Welfare, Washington, DC.)

J. Lipsick


ww

w.p

ersp

ecti

vesi

nm

edic

ine.

org



This could also occur at much lower tempera-tures by starting with double-ringed naphtha-lene compounds and aluminum catalysts. Theproducts of both types of reaction were highlyfluorescent, and this property co-purified withtheir carcinogenic properties. The spectra ofKennaway’s synthetic carcinogens were remark-ably similar to those previously described for thefour-ringed benzanthracene. Trials of differentderivatives of benzanthracene demonstratedthat several of these chemicals could indeedcause cancer in mice. In particular, a very highlypurified sample of a related synthetic chemical,1,2:5,6-dibenzanthracene, proved to be a partic-ularly potent carcinogen (Fig. 4).

The isolationof the carcinogenic agent in coaltar required a cooperative effort between scienceand industry. Two tons of coal tar pitch were dis-tilled at the Becton works of the Gas Light andCoke Company for this purpose in 1930. Usingfluorescence as an assay, seven grams of a highlypotent carcinogenwerepurified, a nearlyonemil-lion-fold enrichment from the starting material.The active component was eventually identifiedby JamesCookasbenzo[a]pyrene (Fig. 4). Chem-ical synthesis of this compound confirmed bothits identity and carcinogenicity. As a result ofthis work, chemically defined polycyclic aromatichydrocarbons became the agents of choice forstudies of carcinogenesis.

THE X FILES—RADIATION CAUSES CANCER

In 1895 Wilhem Roentgen, a German physicist,discovered X-rays while investigating the prop-erties of vacuum tubes. He soon discovered that

these rays could penetrate human soft tissues,but not bones (Fig. 5). Soon, physicians wereusing X-rays to examine broken bones and tosearch for metal bullets in soft tissues. X-raysbecame a widely used tool, from industrial anal-ysis to dental diagnosis.

Like many technological advances, X-raysproved to be a double-edged sword. As early as1902, physicians began to notice an increase indermatitis and skin cancer among roentgenolo-gists (radiologists). This occurred because theytested for X-ray production by seeing if the skinof their hand reddened when place in the path ofthe beam. These case reports prompted PierreEdouard Jean Clunet to test whether X-raysalone could cause cancer in an experimentalanimal. In 1908 he irradiated four rats, repeatingthe treatment as soon as the radiation-inducedulcerations had healed. After four such cyclesover a period of 14 months, an invasive cancerdeveloped within the irradiated field in the twosurviving animals. Although this experimentalinduction of cancer preceded those reported byFibiger (erroneously) and by Yamagiwa, Clunetviewed his own accomplishment as a verificationof a previous clinical observation rather than as amajor scientific breakthrough. Despite Clunet’sobservations, the use of X-rays remained quitepopular in a variety of settings of dubious merit,including the treatment of acne and the pedo-scope, a fluoroscopic device designed to help inthe fitting of shoes (Fig. 6). These devices were astandard attraction in many shoe stores in theUnited States from the 1920s until the 1960s.More recently questions have arisen about therisk versus benefit of various new high-energy

Figure 4.Two polycyclic aromatic hydrocarbon carcinogens: 1,2:5,6-dibenzanthracene (left) and benzo[a]pyrene(right).



ww

w.p

ersp

ecti

vesi

nm

edic

ine.

org



computed tomography (CT) scans, particularlygiven the financial incentives involved.

Because X-rays cause ulceration of the skin,one can imagine that proponents of the irrita-tion theory of cancer would have viewed Clu-net’s observations as a confirmation of theirhypothesis. However, a groundbreaking seriesof experiments in the 1920s suggested other-wise. The most successful experimental geneti-cists in the early twentieth century focused

intensively on two model organisms—maize(Zea mays) and the fruit fly (Drosophila mela-nogaster). In both systems, the identification ofnewmutants resulted from random genetic var-iation coupled with keen observation. This wasessentially the same method used by GregorMendel in his landmark studies of inheritancein the garden pea.

HermannMuller had trained as a student inThomas Morgan’s fly group at Columbia Uni-

Figure 5. (Left) Early X-ray of the hand of Wilhelm Roentgen’s wife, Anna Berthe. (Right) Drawing of X-ray-induced damage to the hand. (Reproduced from Leonard Mark, 1908, from Saint Bartholomew’s HospitalMuseum and Archives; http://www.calmhosting01.com/BartsHealth/CalmView/Record.aspx?src=CalmView.Catalog&id=%2f35%2f22.)

Figure 6. (Left) The pedoscope, a fixture in American shoe stores from the 1920s to the1960s. (Right) If the shoefits, wear it. (Reprinted, with permission, from Oak Ridge Associated Universities [http://www.orau.org/ptp/collection/shoefittingfluor/shoe.htm], © ORAU.)

J. Lipsick


ww

w.p

ersp

ecti

vesi

nm

edic

ine.

org


https://www.calmhosting01.com/BartsHealth/CalmView/Record.aspx?src=CalmView.Catalog&id=&percnt;2f35&percnt;2f22








versity, but eventually became their fierce scien-tific competitor. At the University of Texas,Muller began to study the effects of radiation(using radium and X-rays) on mutation rates.High doses of X-rays caused sterility, but Mullerfound that lower doses permitted fertility whilecausing recessive lethal mutations. Eventuallyhe was able to generate a remarkable array ofX-ray-induced mutant phenotypes, many ofthem similar to those previously discovered viathe laborious isolation of spontaneous mutants.Careful genetic analysis coupled with the cyto-logic staining of giant salivary gland polytenechromosomes, a method developed by Theo-philus Painter, revealed that many of theseX-ray-induced mutants contained gross chro-mosomal rearrangements (inversions, deletions,duplications, translocations, rings) (Fig. 7).

In the course of characterizing his new mu-tants, Muller discovered a number of importantbiological phenomena—gene dosage effects,dosage compensation for hemizygous geneson the male X chromosome, the presence ofspecialized telomeres at the ends of linearchromosomes, and epigenetic control of geneexpression by position-effect variegation. Mostimportantly, X-rays provided a new tool for in-

ducing mutations at will, rather than having todepend on rare spontaneous mutations.

Muller was a believer in eugenics and advo-cated artificial insemination, using sperm only25 years after a donor’s death to avoid passing ongenetic defects that might become apparent latein life or in one’s offspring. In the 1930s, hebecame disillusioned with racism and what heconsidered to be capitalist exploitation in theUnited States. He moved to Germany and thento Russia. However, the harsh reality of Stalin-ism and the destruction of Russian genetics byLysenko caused him to flee in 1937. Because ofhis political views and perhaps because of hispersonality, Muller had great difficulty findingan academic position upon his return to theUnited States. After a stint as a lecturer at Am-herst College, he was finally hired as a facultymember at Indiana University in 1945 at theage of 53. The following year he was awardedtheNobel Prize “for the discovery of the produc-tion ofmutations bymeans of X-ray irradiation”that he had first published in 1927.

Oswald Avery and colleagues in 1944showed that DNA was the genetic material, be-cause it could transform the genotype of onebacterial strain into another. Additional support

scsc

ww

fa

cvcv

g g

12

10fw

fa w

cv

m

wscy

scllz

fwm

fa

cv

11

f f

bb bb

falzlz

fwfw

Figure 7. (Left) Bloated wings caused by the X-ray-induced delta-49 inversion. (Right) Schematic and cameralucida drawings of paired X chromosomes from the larval salivary gland of aDrosophila that was heterozygous forthe X chromosomewith the delta-49 inversion. (Left, Reprinted fromMuller HJ. 1930. J Genet 20: 299–334; right,reprinted from Painter TS. 1934. Genetics 19: 448–469.)



ww

w.p

ersp

ecti

vesi

nm

edic

ine.

org



for this conclusion came from the “Waring blen-der” experiment performed by Alfred Hersheyand Martha Chase in 1952, in which theyshowed that DNA rather than protein was thecritical genetic component transferred duringinfection of bacteria by bacteriophage. The en-suing race to discover the structure of DNAwaswon by James Watson and Francis Crick, whopostulated a double-helical structure. These re-sults led to the conclusion that the X-ray-in-duced chromosomal rearrangements first seenby Muller were the results of double-strandedbreaks in DNA.

Following the devastation caused by atomicbombs at Hiroshima and Nagasaki, Muller be-came a strong advocate for the control of nuclearweapons and for an end to open-air testing ofatomic bombs. An increased incidence of cancerwas seen in survivors of atomic bomb blasts inJapan, in American observers of atomic bombtests, and eventually in American workers whohad purified uranium for bomb production. Notsurprisingly, the cancer cells of those irradiatedindividuals often showed chromosomal rear-rangements.

In 1951, Muller proposed that cancer arosevia multiple mutations in a single somatic cell,thus accounting for the long latency often seenbetween the initial exposure to a carcinogen andthe appearance of cancer. In 1968, James Cleaverdiscovered that patients with an inherited pre-disposition to skin cancer (xeroderma pigmen-tosum) were unable to effectively repair DNAdamaged by ultraviolet radiation, which wasconsistent with Muller’s hypothesis.

PHYSICAL AND CHEMICAL: MOSTCARCINOGENS ARE MUTAGENS

Studies of radiation in the early twentieth cen-tury led to the following line of reasoning: X-rayswere carcinogens (Clunet); X-rays were muta-gens (Muller); therefore, carcinogens were mu-tagens. It would, therefore, not have been a largeleap of faith to think that chemical carcinogensmight also act as mutagens. However, an influ-ential review by Burdette in 1955 claimed theopposite. One of the major arguments was thefailure of some very potent chemical carcino-gens, such as benzo[a]pyrene, to act as muta-gens in test systems, particularly in well-studiedmicroorganisms. James and Elizabeth Miller in1960 provided the key to this puzzle. They foundthat chemically active derivatives of benzo-pyrene were formed within the tissues of car-cinogen-treated rats, and that inhibition of themetabolic activation of these carcinogens pre-vented formation of cancer (Fig. 8). Work by anumber of laboratories then identified intracel-lular cytochrome P450 proteins of animals asthe culprits. Normally these enzymes inactivat-ed and detoxified various chemicals, but thesame enzymes could cause the deleterious acti-vation of other chemicals, including some car-cinogens.

The circle was closed by Bruce Ames andcoworkers, who showed in 1973 that many car-cinogens were indeed mutagens. They used asimple bacterial assay in which Salmonellastrains with different mutations in the histidinebiosynthesis pathway were scored for genetic

Benzo[a]pyrene (BP) (+)–(7R,8S,9S,10R)-BP DE trans 10S BP-dG Adduct

CYP450

HO HO

HO

N

N

N

NH

NH

O

sugar

OH OH

O

Figure 8.Metabolically activated benzo[a]pyrene (BP) covalently bonds to DNA bases. (Modified, with permis-sion, from Bauer J, et al. 2007. Proc Natl Acad Sci 104: 14905–14910, © National Academy of Sciences, USA.)

J. Lipsick


ww

w.p

ersp

ecti

vesi

nm

edic

ine.

org



reversion via survival on histidine-free medium.One class of carcinogens (direct) scored posi-tively in the assay with no further treatment. Asecond class of carcinogens (indirect) scoredpositively in this assay only after preincubationwith a homogenate of rat liver containing en-zymes capable of metabolic activation. This“Ames test” was rapidly adopted as a test forscreening new and old chemical compoundsfor their mutagenic, and hence their likely car-cinogenic, properties. However, some caveatsemerged. First, not all known carcinogeniccompounds appeared to act as mutagens (e.g.,asbestos, estrogens, androgens). Second, despiteinitial reports of a strong correlation betweenmutagenesis in theAmes test and carcinogenesisin animal tests, additional work showed that thiswas not the case (Fig. 9). Finally, more than one-half of all compounds tested at high doses inrodents could cause cancer. Eventually bothAmes and Lois Gold, who had spearheadedthe development of a large database of potentialcarcinogens, questioned the wisdom of usingeither of these tests for governmental regulation

of chemicals present at low concentrations in theenvironment.

FLIPPING OUT—HOW BENZO[a]PYRENECAUSES MUTATIONS

How did a polycyclic aromatic hydrocarbon likebenzo[a]pyrene (BP) produce the mutationsthat ultimately cause cancer? Work in the1950s and 1960s showed that BP could bind toproteins, RNA, and DNA. A comparison of thebiochemical and biological activities of a seriesof related compounds indicated that binding toDNA correlated best with carcinogenesis. Care-ful chemical detective work in a number of lab-oratories in the 1970s resulted in a model inwhich BP was converted to a highly reactiveepoxide that then became covalently bound topurine bases within DNA (Fig. 8).

Analysis of the mutations caused by meta-bolically activated BP revealed predominantlyframeshifts (–1) and substitutions at guaninenucleotides. Peculiarly, the base 50 to the BP-dG adduct determined the base incorporated

Mutagenic Potency (log slope)

Car

cino

geni

c P

oten

cy (

log

1/T

D50

)

–2–5

–4

–3

–2

–1

0

1

2

3

4

HAA AFB

SAC

0 2 4

mg/

kg/d

ay g

ivin

g 50

% tu

mor

indu

ctio

n in

24

mon

ths

g required to induce 100 Salmonella revertants10–3

10–3

10–2

10–1

10

102

1

10–2 10–1

(Fungal toxins)

Sterigmatocystin

Benzo(a)pyrene

Benzidine

Moca

2-Naphthylamine

4-Aminobiphenyl

AflatoxinB1

MMS

Propane sulfone

Dibenz (a, h)anthracene

10 1021

Figure 9.Mutagenicity versus carcinogenicity. (Left) An oft-cited early report showing a strong correlation (R=∼0.9). (Right) Amore thorough study showing amuch weaker correlation (R=∼0.3). (AFB) aflatoxin B1, (HAA)N-hydroxy-2-acetylaminofluorene, (SAC) saccharin. (Left, Reprinted from Meselson M, Russell K. 1977. InOrigins of Human Cancer (ed. Hiatt H, et al.), pp. 1473–1481, © Cold Spring Harbor Laboratory Press; right,reprinted, with permission, from McCann, et al. 1988. Mutat Res 205: 183–195, © Elsevier.)



ww

w.p

ersp

ecti

vesi

nm

edic

ine.

org



opposite the lesion. For example, mutation of a50-TGC sequences results in a G=>T transver-sion to 50-TTC >95% of the time.

The covalent adducts formed by BP and nu-cleic acid bases block the enzymatic synthesis ofDNA. The high-fidelity DNA polymerases usedto replicate genomic DNA generally cannot by-pass bulky adducts like those formed by BP ep-oxides. However, themore error-prone Y-familyDNA polymerases can bypass such lesions.

X-ray crystallography in the early twenty-first century revealed the structure of a BP-DNA adduct together with an active DNApolymerase and dATP. Three different struc-tures were seen, presumably representing inter-mediates in trans-lesion DNA synthesis. In thefirst (Fig. 10A,D), the BP ring is stacked betweentwo adjacent bases within the DNA doublehelix, thereby blocking DNA synthesis. In the

second (Fig. 10B,E), the BP-dG adduct hasflipped out of the DNA helix into a hydrophobicpocket within the polymerase. This permits thepolymerase to add the next nucleotide to theprimer strand using the base (T) adjacent tothe BP-dG on the template strand to determinethe next nucleotide added to the primer strand.The result is insertion of an A instead of aC. When the new strand itself is eventually rep-licated, this will result in the G=>T transversiontypical of BP-induced mutagenesis. The abilityof the Y-family polymerase to accommodate aflipped-out hydrophobic adduct appears to per-mit DNA synthesis to proceed beyond the BP-dG adduct. The third structure explains the –1frameshift mutations also caused in vivo by BP(Fig. 10C,F ). These crystallographic studies fi-nally revealed in precise molecular detail howthe chimney sweeps’ cancers described by Per-

A

D

BPG-1A BPG-1B BPG-23 3 3

55 5

55

55 5 5 5 53 3 3 3

33

5 5

PPI

PPI55A dATP dATP

A (13th) A (13th) A (13th)TT

AT A

TG* G* G*

E F

B C

Figure 10. The hydrophobic BP-DNA adduct prefers to intercalate between the hydrophobic bases of the DNAdouble helix (A,D). However, a hydrophobic pocket peculiar to the Y-familyDNApolymerases flips the BP-DNAadduct out of the double helix (B,C,E,F ), thereby permitting bypass synthesis. (Reprinted, with permission, fromBauer J, et al. 2007. Proc Natl Acad Sci 104: 14905–14910, © National Academy of Sciences, USA.)

J. Lipsick


ww

w.p

ersp

ecti

vesi

nm

edic

ine.

org



cival Pott in 1775 were caused by the soot inwhich they toiled.

SUGGESTED READING

Chimney Sweeps’ CancerBrown JR, Thornton JL. 1957. Percival Pott (1714–1788) and

chimney sweepers’ cancer of the scrotum. Br J IndustrialMed 14: 68–71.

Butlin HT. 1892. Three lectures on cancer of the scrotum inchimney-sweeps and others: delivered at the Royal Col-lege of Surgeons of England. J Brit Med Assoc 1: 1341–1346; July 2: 1–6; July 9: 66–71. doi:10.1136/bmj.1.1643.1341

Doll R. 1975. Part III: 7th Walter Hubert lecture. Pott andthe prospects for prevention. Br J Cancer 32: 263–272.doi:10.1038/bjc.1975.212

Coal Tar–Induced CancerFujiki H. 2014. Gist of Dr. Katsusaburo Yamagiwa’s papers

entitled “Experimental study on the pathogenesis of epi-thelial tumors” (I to VI reports).Cancer Sci 105: 143–149.doi:10.1111/cas.12333

Henschen F. 1968. Yamagiwa’s tar cancer and its historicalsignificance—from Percival Pott to Katsusaburo Yama-giwa. Gann 59: 447–451.

Stolt CM, Klein G, Jansson AT. 2004. An analysis of a wrongNobel Prize—Johannes Figiber, 1926: a study in the No-bel archives. Adv Cancer Res 92: 1–12. doi:10.1016/S0065-230X(04)92001-5

Yamagiwa K, Ichikawa K. 1918. Experimental study of thepathogenesis of carcinoma. J. Cancer Res 3: 1–29. [Re-printed in CA Cancer J Clin 27: 174–181 (1977).]

Radiation-Induced CancerCleaver JE. 1968. Defective repair replication of DNA in

xeroderma pigmentosum. Nature 218: 652–656. doi:10.1038/218652a0

Muller HJ. 1927. Artificial transmutation of the gene. Science66: 84–87. doi:10.1126/science.66.1699.84

Mustacchi P, Shimkin MB. 1956. Radiation cancer andJean Clunet. Cancer 9: 1073–1074. doi:10.1002/1097-0142(195611/12)9:6<1073::AID-CNCR2820090602>3.0.CO;2-9

Chemical CarcinogensAmes BN, Gold LS. 2000. Paracelsus to parascience:

the environmental cancer distraction. Mutation Res447: 3–13. doi:10.1016/S0027-5107(99)00194-3

Ames BN, Durston WE, Yamasaki E, Lee FD. 1973. Carcin-ogens are mutagens: a simple test system combining liverhomogenates for activation and bacteria for detection.Proc Natl Acad Sci 70: 2281–2285. doi:10.1073/pnas.70.8.2281

Bauer J, Xing G, Yagi H, Sayer JM, Jerina DM, Ling H. 2007.A structural gap in Dpo4 supports mutagenic bypass of amajor benzo[a]pyrene dG adduct in DNA through tem-plate misalignment. Proc Natl Acad Sci 104: 14905–14910. doi:10.1073/pnas.0700717104

Kennaway E. 1955. The identification of a carcinogenic com-pound in coal-tar. Br Med J 2: 749–752. doi:10.1136/bmj.2.4942.749

Malling HV. 2004. Incorporation of mammalian metabo-lism into mutagenicity testing. Mutation Res 566: 183–189. doi:10.1016/j.mrrev.2003.11.003

Shear MJ. 1969. Yamagiwa’s tar cancer and its historicalsignificance—from Yamagiwa to Kennaway. Gann 60:121–127.



ww

w.p

ersp

ecti

vesi

nm

edic

ine.

org



2021; doi: 10.1101/cshperspect.a035857Cold Spring Harb Perspect Med Joseph Lipsick A History of Cancer Research: Carcinogens and Mutagens

Subject Collection A History of Cancer Research

OncogenesA History of Cancer Research: Retroviral

Joseph LipsickMutagensA History of Cancer Research: Carcinogens and

Joseph Lipsick

http://perspectivesinmedicine.cshlp.org/cgi/collection/ For additional articles in this collection, see

Copyright © 2021 Joseph Lipsick; published by Cold Spring Harbor Laboratory Press; all rights reserved


http://perspectivesinmedicine.cshlp.org/cgi/collection/

http://perspectivesinmedicine.cshlp.org/cgi/collection/


A History of Cancer Research: Carcinogens and Mutagens

Documents

Transcript of A History of Cancer Research: Carcinogens and Mutagens