Attempts to Induce Stomach Tumors

Thirty years ago Fibiger (4) described experimentally induced papilloma of the forestomachs of rats and mice, and also one transplantable squamous carcinoma in the forestomach of a mouse; these occurred in animals maintained on a diet of white bread and water, and infested with a round worm, Gongylonema neoplasticurn, of which the intermediate host was the cockroach. Fibiger's experiments involved many uncontrolled factors, notably deficiency of vitamin A in the diet, the significance of which could not be appreciated in 1915. Since then many workers have tried by various means to induce malignant tumors in the stomachs of rodents, but for the most part without success. Recent reviews of the literature have been published by Klein and Palmer (6), Sugiura (16), and Kirby (5) . The advent of pure hydrocarbons as carcinogens led to renewed attempts to induce tumors of the alimentary canal in animals. In 1936 Oberling and his associates (10), and Waterman (19) independently, obtained malignant tumors of the forestomach in mice receiving 3,4-benzpyrene orally. Few positive results were reported, however, and no stomach tumors were obtained in mice fed with 1,2,5,6-dibenzanthracene for 6 months (8,18), while only squamous papillomas were obtained in mice fed 20-methylcholanthrene for the same length of time (8). More recent successes in the induction of gastric tumors following the injection of carcinogens into the stomach wall by Stewart and Lorenz (14) offer additional evidence of the susceptibility of the gastric mucosa of mice to the action of recognized carcinogens but, as they involve a different procedure, will not be considered here. The experiments now reported form part of an investigation of alimentary cancer begun in 1939 in this laboratory. The induction of benign gastropapillomatosis in rats maintained on an adequate diet to which were added fats previously heated to the maximum temperatures used in domestic cooking, has already been reported (2). It was shown that this result was