Malignancy of 4Nqo-Induced Oral Squamous Cell Carcinomas in the Rat

Abstract

Oral carcinomas in the rat were induced hy painting the hard palate threc times a week for 22 weeks with the carcinogen 4-nitrochinoline N-oxide (4NQO). The induction resulted almost consistently in highly differentiated squamous cell carcinomas, often shcwing excessive keratinization. No metastases were recorded from any of the primary tumours. Transplantation experiments. per-formed on 23 out of a total of 26 induced carcinomas. generally yielded a negative result. only one tumour being transplantable. The biological significance of these features of 4NQO-induced oral rat cxcinonlah are discussed.