Abstract
The segmental and subsegmental pieces of human bronchus implanted into the subcutaneous pockets of BALB/c background congenitally athymic nude mice were exposed to 7, 12-dimethylbenzo (α) anthoracene (DMBA). The human bronchi were obtained from surgically resected human lungs of patients, cut into about 20 mm long pieces, and implanted into athymic nude mice. About 4-8 weeks after the implantation, 15 mm long pellets of beeswax containing 3200 μg of DMBA were inserted into the bronchial lumen of the grafts. The histological examination of 4-8 weeks old bronchial grafts showed them to be usually covered by mucociliated epithelium. A total of 13 grafts were exposed to the carcinogen and 4 other grafts were used as unexposed controls. During the longest observation time of 32 weeks, 3 of the experimental animals showed induction of squamous cell carcinoma with various degrees of squamous metaplasia. The development of these carcinoma was recognized in 8, 24, and 32 weeks after insertion of the DMBA pellets. The other 2 grafts showed only squamous cell metaplasia. In addition to these cases, a total of 8 grafts showed the development of sarcoma, including one angiosarcoma and seven spindle cell sarcomas. Chromosome and histological examinations confirmed that most of sarcomas were originated from the host animal tissues. One graft. showed no response to exposure to the carcinogen. The validity of the present results was discussed for the experimental induction of lung cancer.
