Abstract
Nasopharyngeal carcinoma was induced in an initiation/promotion model in rats by s.c. injection of dinitrosopiperazine in the nasopharyngeal cavity. This was followed by repeated 10-cal administration of an extract of roots of the Chinese medicinal herb WI (botanical family: Thymelaeaceae). Three groups of rats were used: group-1 received DNP followed by repeated WI; group-2 received DNP once; group-3 received WI repeatedly. At 180-205 days after DNP + WI administration 26% of the rats in that group exhibited NPC (two were carcinomas in situ and four were early infiltrating carcinomas). In the other two groups no carcinomas were found. In the group which received DNP followed by WI, other pathological changes, such as hyperplasia of nasopharyngeal epithelium, squamous metaplasia, and papillary hyperplasia, were also more frequent than that in the other two groups.