Genetic marker patterns of inbred strains of mice at the Cancer Research Institute, Bombay

Long-term carcinogenicity of pan masala in Swiss mice

Carcinogenicity of pan masala, a dry powdered chewing mixture of areca nut, catechu, lime, spices and flavoring agents was evaluated by means of the long-term animal bio-assay 6- to 7-week old male and female S/RVCri mice were divided randomly into intermediate and lifetime exposure groups and fed normal diet without pan masala-(zero dose) or diet containing 2.5% and 5% pan masala. Animals in the intermediate-exposure group (n = 10/gender/dose group) were killed after 6, 12 or 18 months of treatment, while those in the lifetime-exposure group (n = 54/gender/dose group) were killed when moribund or at the termination of the experiment at 24 months. Several tissues were processed for histopathological examination. The body weight and survival rate of mice fed pan masala were lower than that of the controls. Histopathological observations of tissues from control animals did not reveal any neoplastic alterations. However, lifetime feeding of pan masala induced adenoma of the liver, stomach, prostate and sebaceous glands, also forestomach papilloma, liver hamartoma, hepatoma and hemangioma, carcinoma of the forestomach, adenocarcinoma of the lung and liver, and testicular lymphoma. Neoplastic lesions appeared mainly in the liver (n = 13), stomach (n = 3) and lung (n = 8). Lung adenocarcinoma, the most frequent malignant tumor type, was observed in 2/120 mice in the intermediate-exposure group and in 8/216 animals in the lifetime-exposure group. Statistical analysis of tumor-induction data revealed a significant dose-related increase in lung adenocarcinomas but not in liver and stomach neoplasms indicating that lung is the major target tissue for the carcinogenic action of pan masala.

Weak carcinogenic effect of masheri, a pyrolysed tobacco product, in mouse skin tumor models

Two commonly used varieties of masheri, pyrolysed tobacco products, were tested for their skin carcinogenicity in Swiss mice and the more sensitive strain of Swiss bare mice. In Swiss mice, painting of brown and black varieties of masheri extract did not show any tumorgenic effect; however, a marginal synergistic effect of 7,12-dimethylbenz[a]anthracene (DMBA) and black masheri extract was observed when DMBA was used as an initiator. In Swiss bare mice, black masheri extract induced tumors in 20%-35% animals at both the doses tested. In an initiation/promotion protocol with DMBA as an initiator, induction of tumors in 50%-52% Swiss bare mice and a slight synergistic effect of black masheri extract were observed with a low dose of DMBA, suggesting a synergistic effect.

Differential effects of phorbol ester tumor promoters on 3-methylcholanthrene-induced epithelial and mesenchymal skin tumorigenesis

The effects of TPA, PDD, PDB, PDA, or MEZ on epithelial and mesenchymal skin tumors induced by a s.c. injection of MCA were studied histologically. Group-I mice received only MCA. At 6 weeks after MCA injection, mice in groups II to VII received acetone, 1.8 nmol TPA, PDD, PDB, PDA, or 6.1 nmol MEZ respectively in 0.1 ml acetone twice weekly until tumor development. Alterations in skin tumor induction patterns were also studied in animals that had been exposed to TPA or acetone for 10 weeks prior to s.c. injection of MCA. Exposure of mouse skin to TPA before or after carcinogen administration increased 2- to 3.5-fold, the incidence of carcinoma and mixed tumors of epithelial and mesenchymal histogenesis. The average time of tumor induction decreased in mice treated with MCA + TPA and 100% of the test animals in the TPA + MCA group developed tumors. In contrast, TPA-related phorbol esters inhibited skin tumor development, particularly trichoepithelioma and fibrosarcoma and increased the average time of tumor induction.

Acute toxicity of folic acid in mice

The toxicity of folic acid (PGA) was studied in different inbred strains of mice. LD50 values of PGA by the i.p. route showed a unique toxicity pattern. In some strains, convulsions, ataxia and weakness were observed. Histopathological study in strains S/RVCri, BDF1, DBA/2 and DBA/2fNCri showed acute renal tubular necrosis.