Document aJ9V8o34Z9zw9DvbwEzyq6EYB

[G/1!' 't*K J'f St.Aiifil -1, .SI 6-522, May I97l| 'Ij^\,f,% f/<\n 4 \-'t **w r; -i'n--w( :I >rO;i!cii-.J;-nW t\>nJ'LT \^jy} ChaOHiiC1 ^rHrk }& o>. A #1 UT-J*t*m*?,'-T. V s'.r'<r> ft 0 c I < P. L. Viola, A. Bigotti, and A. Caput to iVt rtS Institute /or Cancer Research. Rome. Italy '! SUMMARY to vinyl chloride follows a singular pattern for the different tissues and origins of the rat. Rats (Ar/IRE Wisiir strain) exposed for 12 months to vapors of vinyl chloride developed tumors of the skin, lungs, and bones. The cutaneous tumors, which always appeared in the area in which submaxillary and parotid glands are located, have been histologically recognized as epidermoid carcinomas, papillomas, and mucoepidermoid carcinomas. The morphological characteristics of lung tumors, which occurred in a lower percentage, were mainly of the adenocarcinoma MATERIALS AND METHODS r The experiments were performed with vinyl chloride (CU;=C!!C!, the monoh.-dcgenjte derivative of ethylene) of a commercial grade (39T> purity) assumed to contain insignificant amounts of various noncarcinogeuic type, with the exception of a single epidermoid tumor contaminants. originating from the epithelial covering1 cells. In a minor, Three-month-old WRtar (Ar/TRE) male allrino rats (about number of tats, a large proliferation of cartilaginous tissue 150 g body weight) were exposed to vinyl chloride vapors for diagnosed as osteochondroma developed in the metacarpal and 4 hr a day, 5 days a week, for 12 months. The animals were metatarsal regions of the four limbs. kept in metal or plastic, air-right caves in which a constant flow of air, containing y/o v/v (u-nua! to 30.000 ppm) of vinyl INTRODUCTION chloride, was introduced. Twenty-five rats of the same strain were the control group. At the cud of the treatment, the oncogenic properties of some chemical organic compounds used for the preparation of "plastics" have been widely investigated, and their limits and effectiveness have been well estaidislicd. Detailed information on this subject may be found m the literature (5, 6, S); however, all information and references are exclusively related to highly polymerized compounds of roughly the same size as used in various industries. Oncogenic polymers produce sarcomatous tumors, with the exception of polymethnris which, as resorted by Ihieper (6), also indues adenocarcinomas. Recently, it lias been demonstrated that sarcomatous tumois fl-4, 7) are transplantable, and it has been suggested .bat they may originate from the. tissues cf the capsule that gradually covers tile pijsrie fdm. Thu?,, or;,mi cc (2--it nave observed premahgnaut areas made of poorly differentiated fibroblasts whtah were firmly attached to the pLitic film up to the moment of malignant transformation. Tins investigation demons:rates that even the monomer vinyl chloride possesses oncogenic pic-porties when used with an appropriate model different from the mode!; previously reported by several authors (P-i 2). The carcinogenic response sti wiving animals were kvted at 20-cay intervals, end the most important lhsttes and organs were examined histologically by standard methods. During !ue period of exposure, the animals were slightly soporific; however, the fire: few month; of treatment were well tolerated and no changes in growth or behavior were noticed. After 10 months of treatment, some animats began to show a hard mass in the paraauricular tegmu vrhich became progressively larger until it leached the size of a walnut or slightly larger. In most cases, the swelling was unilateral; it was bilateral in only a few animals. A.fter 1 or 2 months, the growing masses become ulcerated and discharged necrotic debris, while a certain amount of tumorous tissue began to form on their .'.m faces. In addition, we observed that the masses were an integral part of the paraauricular region and could not be distinguished from the local tissues. Caseous necrotic zones were iotmJ. Pleura and pericaiuium often showed diffuse inflammation of a fibrous nature and, in many cases, the lungs were covered with a number of white formations as large as giants of rice or even larger and harder than the lungs themselves. In 2 cases, the lungs were hemorrhagic uith milky, thick fluid in the pleural cavities.The liver was some time; increased in size and very fragile. The animal; were subjected to X-ray analyses at different intervals from the beginning of treatment in order to control the state 1 A preliminary repurt of the results reported here wjs -tvcti at the Tenth hutniauotul Cancel Coi.iul-v-. Ilv-.ismri, Te.va', May 22--2-i, 197t eil July jl, 1970: accepted January [7, 5 971. of rite skeletal bones. A!! the av.tir.als that inhaled vinyl chloride showed a series of parenchyma! lesions. Among; these, most prominent ware the disappearance of jynr.ulnr and Purkinjo ceil-:, degeneration ~C 516 CANCER RESEARCH VOL 31 * t;v cerebellum, severe chronic hepatitic iicjfri'.i.il Wart)' suhuuiiV.nl >r growth emred in some rats. The -.uni moderate swelling of the kidney ; -ndiyim, histological picture showed p ' ..ir epithelial proliferation, i msummg the pattern or lubutoncphrosis. with progressive increase in the thickness of the epidermis (Fig. 1). T.TS The papillary warts of exophytic type had a fibrous vascular stroma and various degrees of inflammatory' lymphocytic survival and the main findings arc stimtimi/.ed infiltration, marked hyperkeratosis, parakeratosis, acanthosis-, Almost all lire animals developed tumors of the and areas of individual dyskeratosis or pearl-like horny j;;d lungs. Very few animals developed bone tumors; in formations. cases, the tumors were localized in the metacarpal and The epithelial cells of the penetrating columns (Fig. 2) were tarsal bones of all 4 extremities. Shin tumors were by far irregularly arranged and were frequently accompanied by an -os! frequent, amounting to 65 or 107a. inflammatory infiltration of the dermis. The typical features ... Tumors. The tumor that developed most frequently in of the Malpighian layer and of the stratum corncurn of the arcauricular region was the epidermoid carcinoma, but we prickle cells and of germinal layers were easily recognized (Fig. observed papillomas and rarely mucoepidermoid 3.). The horny layer was composed largely of cell nests, which .omas. In 2ll cases, tire ncnj.M;,rns were of epithelial appeared at certain points within the epithelial masses and e. The 3 patterns noticed cannot be compared to vntions assumed the well-known appearance of "horny pearls" (Fig. 3, types but rather to a transition of one type into the other arrows); they were made of-flattened and compressed prickle ad which is more likely, to different stages of the same cells without nuclei and were located around a central core of crative type. keratin. Table 1 , Oncogenic effects of inhaled vinyl chloride as a function of time The animals were exposed to vinyl chloride vapors for 4 hr a day. 5 days a week, for a total of 12 months, in a constant fldw of air containing 33> v/v vinyl chloride. Rat 1 2,3 4 5 6 7 8 14 16, 17 2] 22 23 24 25 26 Survival rate 300 280-300 310 333 337 347 347 354 359 350 3SQ 330 380 ' 380 380 Tumors Skin Lungs Rones MucC'Cpi'krmoUl carcinoma Epidermoid carcinoma, kcrat'uiiing type Epidermoid carcinoma, kera tinizing type Papilloma, heraldic type Epidermoid carcinoma Epidermoid carcinoma Mucoepidermoid carcinoma Epidermoid carcinoma Epidermoid carcinoma Epidc smotd carcinoma Epidermoid carcinoma - Epidermoid carcinoma Epidermoid carcinoma Epidermoid carcinoma Epidermoid carcinoma Adenoacanthom;' No tumor Adenocarcinoma No tumor No tumor No tumor No tumor No tumor Adenocarcinoma No tumor Adenocarcinoma No tumor Mucus-producing adenocarcinoma (alveolar cell carcinoma?) No tumor Squamous cell carcinoma Osteochondroma No tumor No tumor Osteochondroma Osteochondroma No tumor Osteochondroma No tumor No tumor No tumor Osteochondroma No tumor No tumor No tumor No tumor 971 I FC 33<r>5 517 P. L. Viuhi, A. Mxviti, and A. Oputc' .i ' ( ReralimV.ation was irregular end oitar p.u.-.keratosis was cartilaginous zonespossessing regressive features, such ai I observed in the jreas of the turner in which the cells were fibrosis and hyaiinosis. The perichondrium appeared often as a . loosely aggregated and undergoing an individual rather than a compressed and structurally altered fibrous fisuic. ; lice live type of kcratini/ation 41. !n dyskeratotic areas, In some cases, the tumor growth was related to the stage of ! cw epithelial cells tended to form pearls. The tumor seldom the endochondral ossification occurring below the "epiphysial ; showed an undifferentiated growth with cellularplate." Ossification was irregular, so that osseous trabecula: . pleomorphism and several mitotic I inures (h ist. 5). A fewvaried greatly in thickness and contours. In other cases, foci of tumors showed little nests of isolated pale cells (Figs. 6 and 7) active cellular proliferation, cartilaginous areas, chondroid I of 3 types: mucin-producing cells foririnaiimt from the duct developmental nests, and calcified bones occurred in the : epithelium of sweat glands or salivary glands); squamous cells', deeper portions of thetrabeculae (Fig. IS). i and intermediate cells with minor tendencies towards The new formation appeared to be an osteochondroma and ! differentiation. consisted essentially of a bony protuberance capped by ; Respiratory Tract. These tumors, although occurring rarely, cartilage and a fibrous layer, which represented the were mainly ndcnocarcinornatous. Only in I rar did we observe perichondrium. y an epidermoid tumor originating from the epithelium-covering The fibrous layer was continuous with the periosteum of \ cells. Sometimes, the tumors were seen in their early the adjacent cortical bone and extended inward to form septa ; development and consisted predominantly of cubic or separating and enclosing lobules of cartilage. t columnar cells arranged as regular or irregular tubular ond Control Animals. The control rats were kept under the same * papillary dements (fig. S) and supported by poorly developed conditions as the experimental rats and at the appropriate time ; fibrous stroma (Fig. 9). were subjected to a constant llow of air without vinyl ' In other eases, glandular structures were often imperfectly chloride. None of these animals developed tumors or the types 4 formed and appeared as sheet-like proliferations of of parenchymal lesions developed by the rats that inhaled undifferentiated or pleomorphic character. The cells showed a vinyl chloride. In a very few of the control rats, there was 2 : tendency to extend into the pulmonary' parenchyma, thus swelling of the liver and kidneys. simulating the microscopic features of the so-called alveolar cell carcinoma (Fig. 10). Sometimes, this was the prevailing pattern. The pulmonary air sacs were limited by 1 or more DISCUSSION layers of cubic, columnar, or polyhedral cells with abundant cytoplasm that was faintly eosinophilic (Fig. I f); frectuently, As in many carcinogenesis studies in which multiple tumors ' ^^enopnpillary excrescences spreading into the alveolar spaces arise in different tissues and organs, the data must be evaluated ^Btc present. in terms of a more prompt positive response to be obtained In some areas, foci of cellular polymorphism with with the ideal concentration of the carcinogenic compound, i hypcrchromatic nuclei were noticed; mucin was produced in The cutaneous system is the most susceptible to the oncogenic ' varying amounts and secreted into the lumen of the tubules effects of vinyl chloride. j and acini. There were small pools of mucin in which signet ring cells occurred, cither alone or in small clusters (Fig. 12). The alveolar walls were often quite thick and, at times, showed an inflammatory' infiltration. Our experimental data do not explain why the cutaneous . tumors developed in the same site, is., the region including : the area in which the submaxillary' and parotid glands are located. It is possible that the salivary glands may' by involved As mentioned before, a single tumor showed squamous in the concentration or excretion of vinyl chloride or some of structures and appeared to have been formed mainly by its active decomposition products. This hypothesis is strong!)' spindle and oval undifferentiated cells tFig. 12). supported by morphological findings showing the specific . Hones, hi the metacarpal and metatarsal regions of the A tendency of the developed tumor to appear as 2 limbs, a large proliferation of cartilaginous tissues arose mucoepidermoid carcinoma, which indicates the active outward from the periosteum and, from the appearance of its contribution of the mucus glandular ceils to the tumorous cells, seemed to derive directly from the cortical bone (Fig. growth Such kinds of histoivpcs are often related ;o some 14). The periosteum also grew and in some areas spread as giandular aggregates, and. therefore, the histogenesis of human finger-like prolongations into the newly formed cartilage (Fig. mucoepidermoid carcinoma has bee:', restricted to tire cells of 15). In these places, a gradual transition between fibrous intercalated ducts. This hypothetical interp.retion must be cartilage, periosteum, and bone could be noticed. confirmed by future experiments in which the action of the - The newly formed cartilage appeared irregular with atypical vinyl chloride should he restricted to the salivary' system. At ; areas; the ceils, winch had nuclei larger than the normal the concentrations used, sattuation and wetting of the fu: chondrocytes, lay in wcil-iormcd, eapsnlared lacunae. The cells might well be expected. Under these circumstances, the occurred singly, in pairs, or in tetrads and, although of natural cleansing habit of the rat might add a significant . different size and shape, they usually contained a single, ingestion problem witli subsequent concentration of vinyl . cl a* kly stained nucleus. The cartilaginous growth was not chloride in die salivary glands. The local extreme homogeneous, as shown by the extension of the firmer-like concentration amid 1 . the result of the difficulty of 2 ^Ariongatiuns into ilie boundary of newly formed tissue, complete cleansing hy the rat. ^^^ides the choudiohlastrc, ckon.lmcy tic, anil angiomatous The neoplastic response of the lower respiratory' tract, areas which indicated a rapid growth, there were also although of lesser magnitude, is of relevant interest, since some j 1 51E "n66 CANCER RESEARCH VOL. 31