Homotransplantation of Larynxes of Cigarette Smoke-Exposed Syrian Hamsters 1

In 20% of BIO inbred Syrian hamsters, carcinoma of the laryngeal respiratory epithelium developed after 70-100 wk of daily exposure to smoke generated from IRI Kentucky Reference cigarettes. Even larger numbers of smoke-exposed animals developed less severe epithelial changes in the area of the larynx bordering the vocal cords and including the ventricle of Morgagni (1). Under similar experimental conditions in smaller numbers of BIO 87.20 hamsters, laryngeal carcinoma occurred in 4 % of the animals, epithelial changes lesser than carcinoma in 13%, and metaplasia in 16%. Similar rates for laryngeal epithelial changes and carcinoma had previously been observed by German investigators using German Reference cigarettes and noninbred hamsters (2).

The earliest malignant lesion induced by cigarette smoke in the hamster larynx was observed 73 wk after the start of inhalation, when the aged animal was close to death from degenerative disease attendant upon old age; therefore, little time remained for growth of the neoplastic lesion and metasta-tic spread in this animal (1). Actually, no metastases of laryngeal cancer were found in these experiments, although metastases of a smoke-induced nasopharyngeal sarcoma did occur. It was postulated that transplantation of a cigarette smoke-induced early laryngeal carcinoma might lead to further growth of the tumor in a new host.

BIO 15.16 inbred hamsters, which had proved to be the most receptive hosts for homo- and isotransplantation (3), were chosen for the present study. Because of the microscopic nature of the induced laryngeal cancers, it was impossible to select by previous microscopic study the best possible lesions for transplantation; rather, the largest possible number of smoke-exposed larynxes was taken for transplantation into as many BIO 15.16 cheek pouches as possible. At the end of our smoke inhalation experiments, 15 larynxes of smoke-exposed BIO 15.16 animals and 34 larynxes of BIO 87.20 smoke-exposed animals were available as starting material.