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Tumor Induction in the Trachea of Hamsters with N-Nitroso-N-methylurea¹

The University of Tennessee-Oak Ridge Graduate School of Biomedical Sciences [T. Y.], and Biology Division, Oak Ridge National Laboratory [P. N., M. L. W.], Oak Ridge, Tennessee 37830

Experiments were conducted to study the tumor response of hamster tracheas to N-nitroso-N-methylurea. Tracheas were exposed repeatedly with the use of a tracheal catheter. Ten to 30 exposures were given over a period of 5 to 20 weeks. The carcinoma incidence (including carcinoma in situ) was 0, 42, 67, 88, and 94% for 10, 15, 20, 25, and 30 twice-weekly exposures, respectively. With 10 exposures 2 of 12 hamsters developed benign tracheal tumors. Mean tumor induction time decreased when frequency of exposure was increased from 50 weeks with 10 to 15 exposures to 28 weeks with 25 to 30 exposures. The major histological types of invasive carcinomas observed were epidermoid carcinomas (54%), anaplastic large-cell and small-cell carcinomas (26%), adenocarcinomas (13%), and combined epidermoid-adenocarcinomas (7%). Sacrifice studies revealed that with 10 to 20 twice-weekly exposures only metaplastic lesions with varying degrees of cellular atypia are present at the time of the last exposure. Neoplastic lesions develop during the subsequent exposure-free interval. The data suggest that this tracheal tumor induction system may be well suited for studying problems related to development and progression of neoplastic disease.

¹ Research jointly supported by the National Cancer Institute and the Department of Energy under contract with the Union Carbide Corporation.

² Postdoctoral investigator supported by Subcontract 3322 from the Biology Division of Oak Ridge National Laboratory to The University of Tennessee. To whom requests for reprints should be addressed.

Received 9/23/77. Accepted 3/14/78.