Experimental Production of Carcinoma with Cigarette Tar' ERNEST L. Wynder,† Evarts A. Graham, and Adele B. Croninger {Department of Surgery, W’askington l'airgrvity School of Medicine, &. Lovia, Yo, and the Division of Clinical Investigation of the Sloan-Kettering Institute of the 21 amorial Comtur for Cancer and Allrad Disarm, New York, N.Y.) The increasing frequency of prùnary cancer of the lung in many parts of the world has aroused great interest in this condition and has stimulated a search for an explanation. In 1960, Wynder and Graham (40), on the basis of a clinical and statistical investigation, presented evidence of a real association between lung cancer and smoking, especially of cigarettes. These data have been well substantiated by a large-scale British study by Doll and Hill (9, 10). Both studies showed that the risk of developing cancer of the lung increases in direct proportion to the amount of smoking. Ten other recent studies reached similar conclusions (8, 11, 15, 20, 21, 24, 26, 83, 84, 42). In 1952, The Council of International Organisations of Medical Sciences convened a symposian on the endemioloof lung cancer and agreed that the present evi dence points to a relationship between lung cancer and cigarette smoking (12). Tobacco is also thought to play some role in the production of cancer of the larynx, oral cavity, and esophagus. Although the studies of those relation ships are not so complete as the studies on lung cancer, the collected data are suggestive (33, 41). The increasing incidence of bronchiogenic car cinoma and the available evidence relating amok. ing to it and possibly to cancer of other sites led us to undertake the experimental work reported here. This investigation is directed toward determining in laboratory animals whether there are carcinogenic factors in cigarette smoke. Paviots LarvaIVISATIONS Many attempts have been made with tobacco products to induce cancers in a variety of experimental animal. The first was reported by Broech in 1900 (4). He painted guinea pigs with tobacco "juice" for an unknown period of time and de •This investigation was supported by a research great from the National Cancer Institute of the National Institutes of Health, Public Heath Service. ↑ Present Address: Memorial Center for Cancer and Allied Diseasen, 444 East Sirty-righth Street, New York #1, N.Y. Received for pablication June 8, 1953. scribed epithelial proliferation. Subsequently, many different approaches to the problem were undertaken with various types of tobacco, dife eat methods of tar preparation, and different pe cies of animals. Many of those studies were carried on for too brief a period of time or with too fe animals to be regarded as significant. Hoffman and his associates (17), for instance, painted animals for only 14 days, at which time they noted hair loss. Wacker and Schmincke (57) observed proliferation of epithelium in rabbits' ears 21 days after a subcutaneous injection of pipe tar. The first recorded experiment with mice and with tobacco tars as the suspected carcinogen was the one just cited by Hoffmana and co-workers. The more detailed of the subsequent studies are listed in Table 1. This table attempts to summarise the methods used in the various studies and the sults obtained. In many instances the method ɗ study was not described in sufficient detail to give all the information considered essential. From this survey of the literature it is found that, before our study, all the previous attempts to produce experimental cancer in mice with tobacco products were successful in the production of only seven epidermoid cancers of the skin. Several investigators attempted to induce pa roonary tumors in mice with tobacco smola. Lorens and co-workers (#8) obtained negative resuits in this manner. Campbell (6), and especially Rasenberg (19), however, claim to have found significantly higher percentage of pulmonary adenomas in the experimental than in the contral group. It is doubtful that such a fading is impor tant. At any rate, so far these methods have not induced true bronchiogenic carcinomas. The majority of the investigature working with tobacco tars used rabbits as the experimental assmals (14, 23, 87-92, 36). In view of the fact that the present work deals with mice we shall only briefly list some of the studies with rabbits. Rate reported the production of carcinomas in rabbit ears after painting the ears with a distillate d tobacco (28, 30, 38). Sugiura (36), in attempting WYNDER of el.—Experimental Carcinoma with Cigarette Ter man carcinogen, is present in tobacco, but recent studies by Dan and co-workers (8) based on the arsenic content of various types of European tobacco tends to place less emphasis on this inor ganic element. Rest, cigarette paper, flavoring, and wetting agents have been suggested as etiologic factors in the production of cancer, but it must be noted that clinical evidence has also pointed to cigar smoking, pipe-smoking, and tobacco-chew. ing as possible factors in the production of cancer of the respiratory and alimentary tract. The actual carcinogenic agent or agents to bacco remain to be identified. Studies combining chemical and biologic efforts leading to their iden tification are urgently needed. Should one be able to identify definite carcinogens and succeed in removing them, or at least in reducing their quantity in tobacco, proper preventive methods would be at hand. Such studies may further our understanding of buman and animal carcinogenesis and may lead to the development of practical preventive measures against cancer. SUMMARY AND CONCLUSIONS 1. A cigarette tar condensate was obtained with a smoking machine which simulated buman smok. ing babits. The resulting tar was dissolved in ace tone and applied to the backs of CAF mice in a dosage of 40 mg. of tar/acetone solution 8 times a week. Control mice were painted with acetome 4. Of 81 tarred mice, 59 per cent developed papillomas. The first lesion was noted in the 83d week, and the mean time of appearance was 56 weeks. 3. Of 81 tarred mice, 44 per cent developed histologically proved carcinomas. The first carcinoma was observed in the 49d week, and the average time of appearance was 71 weeka. Of 62 mico alive at 12 months, 58 per cent developed cancer. Seveny-one weeks constitutes approximately one-half of the life span of CAF mice. This corresponds roughly with the fact already noted that in the human about 30-35 years of smoking, or approximately one-half the life span, are required for the production of bronchiogenic carcinoma. 4. One carcinoma was transplanted for 4 gener ations and another one is currently growing in the 15th generation. 6. Control mice painted with acetone alone abowed no skin lesions. At the end of 20 months of painting, 63 per cent were still living, compared to 9.8 per ant in the group painted with tobacco tars. 6. The group of mice painted with croton od in addition to the tar, starting in the 7th month, cannot be properly evaluated because of a greater number of deaths occurring during the 19th and 14th months, although within the period of obser vation no acceleration of cancer formation was noted. 7. The group of mice started with acetone and receiving croton oil beginning in the 7th mouth showed roughening and thickening of the epidermis, but no tumor formation was noted. 8. All CAF, mice painted with 0.3 per cent solution of methylcholanthrene in acetone developed cancer within 44 months. The first papilloma appeared during the 6th week, with average appearance during the 7th seek. The first carci noms was observed during the 12th week, with a mean time of appearance of 16 weeks. 9. The results obtained with CAP, mice estab lish condensed cigarette tar as a carcinogen for mouse epidermis. These studies provide a tool to determine and isolate the possible carcinogenic agent(s) within tobacco tar. At present it is not known which fraction or fructions in tobacco tars are carcinogenic. Combined chemical and biologic studies are now in progress to search for such agents. Such studies, in view of the corollary chinical data relating amoking to various types of cancer, appear urgent. They may result not only in furthering our knowledge of carcinogenesis, but in promoting some practical aspects of cancer pre vention. ACKNOWLEDGMENTS The sethors wish to expram their gratitude to Cala B. Cook, Mary Gay Crow, and Gertrude Camel of Washington L'aiversity School of Medicine, Department of Surgery, St. Louis, Mo., for their technical saasimados. REFERENCES 1. Branam, 1. The Mechanism of Carcinogenesis: 8. Boar, B, and Looam, B. N. Tobacco Tar: An & BARLOW, L. Dos Cigarette Smoking Cause Lung Cancer? 4. Bacaca, A. Theoretische und experimentelle Untermarke & CAEPBELL, J. A. The Efects of Exhaust Gasan i 7. Coore, &; Lara, P. W. M.; Saroana, B.; and Hart, & Dart, IL R; DOLL, E. and Ketaway, & La Cancir of the Lang in Relation to Tobacco. Brit. J. Cancer, 8:1-40, IM!. The following information was given us by the presidents of the leading tobacco companies at the Hotel Plaza this morning. 1. Participants There is no trade association in the cigarette industry. This is because the tobacco companies are prevented by the dissolution decree of 1911 and the criminal convictions under the Anti-Trust Act in 1939 from carrying on many group activities. As a matter of fact, before the current health crisis arose, cigarette manufacturers never met together at any time except at dinners honoring some industry leader. The group was called together by Mr. Paul Hahan, President of the American Tobacco Company. The chief executive officers of all the leading companies R. J. Reynolds, Philip Morris, Benson & Hedges, U. S. Tobacco Company, Brown & Williamson have agreed to go along with a public relations program on the health issue. Liggett & Myers is not participating in the organization because that company feels that the proper procedure is to ignore the whole controversy. In addition to the cigarette companies, the two important groups of tobacco growers involved are enthusiastically supporting the new program. Together these tobacco growers represent some 600,000 farms and 2,700,000 farmers, Obviously, the tobacco growers are the political strength along with the 1,300,000 retail tobacco outlets. The tobacco growers will be represented by officials of the grower organizations. II. Organization Because of the anti-trust background, the companies do not favor the incorporation of a formal association, Instead, they prefer strongly the organization of an informal committee which will be specifically charged with the public relations function and readily identified as such. For example, Mr. Raha reported that one name they had considered was the "Tobacco Industry Committee for Public Information." John Hill suggested that he felt the word "research" should appear along with "information" in the title of the committee, III. The Industry's Position The industry is strongly convinced that there is no sound scientific basis for the charges that have been made. They believe that the more sensational accusations in the recent papers were premature and in some cases represent publicity issued in the hopes of attracting funds and support for further research. They point out that the National Cancer Institute of the U. S. Public Health Administration, which is a government agency and supported by Congressional appropriations, has officially refuted the tie-up betwee cigarette smoking and cancer. Nevertheless, they realize that the industry should not engage merely in a defensive campaign, replying to and answering individual research papers or magazine articles. They feel that they should sponsor a public relations campaign which is positive in nature and is entirely "pro-cigarettes." They are confident they can supply us with comprehensive and authoritative scientific material which completely refutes the health charges. They are also emphatic in saying that the entire activity is a long-term, continuing program, since they feel that the problem is me of promoting cigarettes and protecting them from these and other attacks that may be expected in the future. Each of the company presidents attending emphasized the fact that they consider the program to be a long-term one, IV. Responses to Questions The companies' answers to questions put them by John Hill and the undersigned provide valuable background. They are as follows: Will the cigarette companies organize themselves The companies replied that they had no desire to set up a smoke screen or "front" type of organization. They are perfectly willing to sponsor any statements that may be issued or any institutional advertising that may be recommended and approved. Do they accept the principle that public health Everyone present wholeheartedly agreed to this principle and readily consented to widespread dissemination of a sound statement of principles. Distribution of such a statement it was agreed would probably be the first step in the public relations program that Hill and Knowlton would recommend. Do the companies consider that their own adver- The companies voluntarily admitted this to be the case even before the question was asked. They have informally talked over the problem and will try to do something about it. They do, however, point out that this is the one important public relations activity that might very clearly fall within the purview of the anti-trust act. Accordingly, it is doubtful that we will be able to make any formal recommendation with regard to advertising or selling practices and claims, Will the companies agree to sponsor new research A clear-cut answer to this question vas deferred for the time being. The companies all say that they are carrying on much more research in their own laboratories and are sponsoring more research at hospitals and universities than is generally recognized. They believe that when we are acquainted with all of the scientific and factual material in the hands of the companies, we will agree that the major problem is to dissminate information on hand rather than to conduct new research, However, John Bill did not agree to this and emphatically varned the companies that they should probably expect to sponsor additional research. Do the companies view this problem as being The answer is obvious since the companies have met together for the first time since 1939, since they have promptly proceeded to retain Hill and Knowlton, and are already considering such expensive techniques as the use of institutional advertising. They recognize the possibility that it might be desirable to use institutional advertising to promote the basic statement. |