Influence of antilymphocyte serum on DMBA induction of oral carcinomas

Effects of a Single Dose of Rabbit Anti-mouse Lymphocyte Serum on Tumors Induced in Mice by 7,12-Dimethylbenz (a) anthracene Given at Birth

The effects of ALS (anti-lymphocyte serum) and NRS (normal rabbit serum) treatments on the development of malignant lymphoma, lung, subcutaneous and skin tumors induced in mice by 7,12-dimethylbenz (a) anthracene (DMBA) are described. Groups of Charles-River mice, injected at birth with a dose of 100 μg of DMBA, received a single injection of ALS or NRS at the same time as DMBA administration or 10, 20, 30, 40 and 50 days after birth. Incidence, latency, histology and spread of the tumors were studied in all groups. It was found that both ALS and NRS increased tumor incidence and shortened their latency period. Malignant lymphomas were the main tumors whose latency was shortened either by ALS or NRS treatment. In addition ALS treatment apparently increased dissemination of DMBA induced lymphoma in bone marrow.

Effects of Repeated Injections of Rabbit Anti-mouse Lymphocyte Serum on Tumors Induced in Mice by 7,12-dimethylbenz (a) anthracene Given at Birth

The present paper describes the effects of repeated administration of rabbit anti-mouse lymphocyte serum (ALS) or normal rabbit serum (NRS) on tumors induced in Charles–River mice by 7,12-dimethylbenz (a) anthracene (DMBA) given at birth. ALS or NRS were given at the same time of DMBA administration and subsequently at weekly intervals for the first 10 weeks of life or at daily intervals for 7 days during the first, second, third or fourth week of life. Incidence, latency, diffusion and histology of the tumors were studied. It was found that either chronic administration of ALS or treatment of very young mice with the serum, greatly reduced the mean survival time of mice, markedly increased the number of tumor bearing mice and the incidence of all histological types of tumors, and decreased their latency period. Administration of ALS in the other experimental groups gave results essentially similar to those observed in DMBA control and NRS treated mice.

Experimental basis for cancer prevention by vitamin E

Recent clinical trials have demonstrated the significant cancer preventive potential of vitamin E in many different cancer sites, ranging from oral and pharyngeal cancer to prostate cancer. There is an extensive experimental basis for this clinical cancer inhibition. The experimental background includes animal studies (experimental pathology, immunology and molecular biology, synergism, selectivity and safety), in vitro biochemical studies, and human studies (epidemiology and biomarkers, prevention of many pathologic entities other than cancer).

Oral cancer inhibition by micronutrients. The experimental basis for clinical trials

Extensive research has been carried out in experimental animals to demonstrate the anticancer activity of retinoids, carotenoids and tocopherol on oral cancer and oral precancerous leukoplakia. The anticancer properties of these micronutrients have been studied in experiments dealing with inhibition of carcinogenesis, prevention of oral cancer development and regression of established oral carcinoma. Synergism has been demonstrated in the anticancer activity of beta carotene and alpha tocopherol. Synergism has also been demonstrated between beta carotene and anticancer alkylating agents such as melphalan and cyclophosphamide. Micronutrients such as beta carotene have been found to inhibit both major phases of carcinogenesis--initiation and promotion. Animal studies of oral cancer inhibition, prevention and regression have been substantiated by tissue culture studies, using animal and human derived oral cancer cell lines and normal epithelial cells. Mechanisms of the anticancer activity of the micronutrients on experimental oral cancer have been explored. They include stimulation of elements of the immune system to kill cancer cells, and enhanced expression of heat-shock proteins and repressor genes such as P 53.

International Commission for Protection Against Environmental Mutagens and Carcinogens. ICPEMC Working Paper No. 2. Diet, mutation and cancer

Experimental research designed to determine the effects of variations in diet on the carcinogenic and mutagenic processes is difficult to conduct and even more difficult to interpret in terms of the likely response that such variations will have on the expression of human cancer and mutation. Although some of these difficulties may be due to a failure to persuade adequate numbers of highly trained nutritionists to enter into this type of research, a more germaine reason may be that the high level of complexity of both diet and the disease processes is such as to confound present efforts at interpretation. It is suggested that a stepwise analysis of the effects of dietary factors on each critical stage in carcinogenesis or mutagenesis may ultimately lead to results that are more easily interpreted in terms of human response. To this end it is proposed that studies of DNA-carcinogen or DNA-mutagen adduct formation, or other DNA damage, DNA replication and relevant DNA repair at the target site may be a useful guide to the effect of nutritional changes on mutation and/or cancer initiation. DNA replication at various stages of carcinogenesis, modification of hormonal levels, modification of immune response, or other factors as influenced by diet may provide markers for cancer development. The integration of this data to give an overall perception of the effects of nutrition is briefly discussed.

RA can alter the distribution of ATPase-positive Langerhans cells in the hamster cheek pouch in association with DMBA application

Thirty-six young adult male and female Syrian hamsters were divided into four groups. Group 1 (N = 6) was treated with mineral oil, Group 2 (N = 12) was treated with 7,12-dimethylbenz[a]anthracene (DMBA), Group 3 (N = 12) was treated with DMBA and 13-cis-retinoic acid (RA), and Group 4 (N = 6) was treated with RA only. The hamsters were treated three times a week for six weeks. When the DMBA-treated animals were also treated with RA, tumor formation was inhibited. In the DMBA-treated animals that did not have RA, there was a significant reduction in the number of Langerhans cells (LCs) located interfocally and in foci compared with controls (p less than or equal to 0.001). The systemic administration of 10 mg of RA significantly increased the number of ATPase-positive LCs in the focal aggregates (p less than or equal to 0.001). Interfocally, the number of ATPase-positive LCs was statistically elevated in pouches from RA- and DMBA-treated animals (Group 2 vs. Group 3, p less than or equal to 0.01). Following the administration of RA (Group 4), there was a statistically significant increase of LCs interfocally compared with Groups 2 or 3 (p less than or equal to 0.001). RA administered alone resulted in a small increase in foci compared with Group 3 but in a significant decrease compared with the control group (p less than or equal to 0.001). Systemic RA appears to not only affect the number of ATPase-positive LCs but also to alter the distribution of these cells in DMBA-treated pouches.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute effect of DMBA application on Langerhans cells of the hamster buccal pouch mucosa

One, two, and three applications of DMBA in mineral oil to hamster buccal pouch mucosa did not result in obvious histologic alterations in experimental periods ranging from 4 1/2 hours to 2 weeks after the last DMBA application. However, there were significant increases in the number of Langerhans cells, as disclosed histochemically with ATPase staining. There was also an increase in the length and size of the dendritic processes of the Langerhans cells. Applications of DMBA in oil resulted in a consistently significant increase in Langerhans cells when compared to the buccal pouch mucosa of untreated animals. However, mineral oil applications also resulted in a slight increase in Langerhans cells when compared to the mucosa of untreated controls. The major effects of the DMBA on Langerhans cells occurred after 2 weeks and with increasing numbers of applications. The increase in Langerhans cells is interpreted as an enhanced response by immunologically competent cells which may represent an early immune response to the very early changes in carcinogenesis.

Animal models of intra-oral chemical carcinogenesis: a review

Early attempts to induce malignant oral tumours were largely unsuccessful, as the oral mucosa is considerably more resistant to the actions of chemical carcinogens than skin. The first consistent success came when strong carcinogens were applied to the hamster cheek pouch. This model remains the most popular for studies of intra-oral carcinogenesis and is discussed at length. The advantages and disadvantages are critically reviewed. The models of intra-oral carcinogenesis in extra-pouch sites in the hamster, mouse, rat and nonhuman primates are considered. The possible reasons for the relative resistance of oral mucosa to chemical carcinogens are discussed, particularly in relation to portals of entry and saliva. Finally, the relative merits of the more popular models of intra-oral carcinogenesis are briefly discussed.

Inhibition of hamster buccal pouch carcinogenesis by 13-cis-retinoic acid

Sixty-four male and female Syrian hamsters, 3 months of age and weighing 90 to 120 grams, were divided into four equal experimental groups. In animals of Groups 1 and 2 the left buccal pouch was painted three times weekly with a 0.5% solution of DMBA in heavy mineral oil. Group 2 animals also received 10 mg. of 13-cis-retinoic acid in peanut oil administered orally twice a week by pipette. Carcinogen retinoid were administered on alternate days. Group 3 animals served as controls, receiving only 13-cis-retinoic acid. Group 4 animals served as untreated controls. Four animals in each group (two males and two females) were killed at 10, 12, 14, and 16 weeks. The Group 2 animals, which received 13-cis-retinoic acid, exhibited a significant delay in DMBA carcinogenesis of buccal pouch mucosa, as studied both grossly and histologically. Both groups eventually demonstrated well-differentiated epidermoid carcinomas, but the tumors were smaller in the DMBA-retinoid animals.

Experimental intra-oral carcinoma

Fundamental studies of tumour host relationships in oral cancer cases would be assisted if a suitable animal model could be found. Current concepts in the use of animal models for the study of intra-oral carcinoma are reviewed and the development of a unique transplantable tumour system which had been induced and maintained only in syngeneic animals, is recorded.

Transplantation of hamster buccal pouch carcinoma to neonatal hamsters

Epidermoid carcinomas of oral mucosa were induced with DMBA in the buccal pouches of hamsters. The well-differentiated primary tumors were allografted into the peritoneal cavities of neonatal hamsters that had been treated with antilymphocyte serum. Solid tumors grew rapidly in the peritoneum and were harvested 6 to 31 days postimplantation. Gross and histopathologic specimens revealed infiltrative masses of tumor that had become more anaplastic than the original tumor. This in vivo model has considerable potential as a means of studying the immunology of oral cancers during tumor progression.

Alcohol and hamster buccal pouch carcinogenesis

Alcohol was shown to enhance the carcinogenic effect of DMBA applied to hamster buccal pouch. DMBA animals given alcohol developed dysplastic leukoplakic lesions and epidermoid carcinomas 2 weeks ahead of water-drinking control animals. The tumors also grew to larger size, were more invasive, and were more anaplastic histologically. Forty young adult Syrian hamsters were divided into four groups (alcohol-DMBA, DMBA control, untreated control, and alcohol control) and were killed after 10, 12, and 14 weeks of DMBA applications three times weekly. Alcohol was given as a 10 percent solution instead of drinking water.

Spontaneous regression of induced parotid gland tumors in rats

Pellets of powdered DMBA were implanted in the parotid glands of inbred male Fischer rats, and all experimental animals in which the carcinogen was implanted for 8, 10, 12, and 14 weeks developed well-differentiated squamous-cell carcinomas. When the carcinogen was implanted for longer periods of time, tumors developed in a smaller percentage of the experimental animals. Also, the weight of the parotid glands continued to increase with time following implantation of DMBA, reaching its highest level after 10 weeks, and then gradually decreasing with time. Different possible explanations for the regression of the induced parotid tumors are offered.

Lingual carcinogenesis in an inbred strain of hamsters

Epidermoid carcinoma of the lateral border of the tongue can be induced in a standard strain of hamsters, applying DMBA in acetone after traumatizing the area with a root canal broach. Employing the same technique in an inbred strain of hamsters resulted in the more rapid development of carcinomas. The inbred strain should be a useful model for experimental carcinogenesis of tongue.

Levamisole and hamster pouch carcinogenesis

Seventy-five male and female Syrian hamsters (Cricetus auratus), 10 months of age, were studied for the effects of systemically administered levamisole upon the process of chemical carcinogenesis of buccal pouch mucosa. In twenty-five animals (Group II) the left buccal pouch was painted three times weekly with a 0.5 per cent solution of 9,10-dimethyl-1,2-benzanthracene (DMBA) in heavy mineral oil. After each topical application of carcinogen to the buccal pouch, animals in Group II received approximately 0.7 mg. of levamisole hydrochloride orally by means of a pipette. In another twenty-five animals (Group I) the left buccal pouch was painted three times weekly with DMBA, but they were not given levamisole. The twenty-five animals in Group III served as untreated controls. In those animals which received levamisole chemical carcinogenesis of the buccal pouch was retarded. Fewer tumors developed, and they were of smaller size.

The perturbed cell proliferation kinetics of the EMT6/M/AC tumour in mice treated with anti-mouse lymphocyte serum

The cell proliferation kinetics of the EMT6/M/AC tumour were determined at two volumes, 6-3 mm3 and 180 mm3, in mice treated with anti-mouse lymphocyte serum, AMLS. Comparison of the growth curve with that obtained in non-AMLS treated animals showed a marked increase in the growth rate at all volumes in the treated group. In contrast, the cell cycle time and the intermitotic phase times were not significantly different in the treated and untreated groups at comparable volumes. The increase in the growth rate in AMLS treated mice was obtained in spite of decreases in both the rate constant for cell production and the growth fraction, and was due to a marked decrease in the rate constant for cell loss.

A study of the oncogenicity of adenovirus type 2 transformed rat embryo cells

Rat embryo cells were transformed by adenovirus type 2 at different multiplicities of infection. The oncogenic potential of the resulting transformed lines varied considerably but a relationship was found to exist between transforming virus dose and oncogenicity of the resulting transformed lines. Possible reasons for the considerable variation in oncogenicity of the transformed lines are discussed, giving particular consideration to cellular antigenicity and recent molecular biology studies of adenovirus type 2 transformed cell lines.

Heterologous antilymphocyte serum hastens the growth of 7,12-dimethylbenz(alpha)anthracene induced tumours in mice

The present paper describes the effects of repeated administration of rabbit anti-mouse lymphocyte serum (ALS) or normal rabbit serum (NRS) on tumours induced in Charles-River mice by 7,12-dimethylbenz(α)anthracene (DMBA) given at birth. ALS or NRS were given either at the time of DMBA administration and subsequently at weekly intervals for the first 10 weeks of life, or at daily intervals for 7 days during the first, second, third or fourth week of life. The incidence and histology of the tumours were studied. It was found that treatment of very young mice with ALS greatly reduced the mean survival time of mice and significantly increased the incidence of malignant lymphoma. The incidence of lung tumours was found to be significantly increased in the animals injected with ALS during the second week of life.Treatment with ALS in the other experimental groups gave results essentially similar to those observed in DMBA control and NRS treated mice.