Carcinogenic Effect of a Dimethyl Sulphoxide Extract of Betel Nut on the Mucosa of the Hamster Buccal Pouch

Abstract

THE high incidence of oral cancer in the Far East is generally attributed to the habitual use of betel nut “quids” which may contain, as well as betel nut, cured tobacco and various other organic and inorganic materials^1–4. Attempts to extract from betel nut a material carcinogenic for oral tissues have not been successful^5,6, possibly because extracts were prepared with solvents in which the carcinogenic materials were not soluble. We have therefore extracted betel nut, alone or in combination with cured tobacco, with dimethyl sulphoxide (DMSO) and applied the extracts in this vehicle. Our choice of DMSO was based on the evidence that it is an excellent solvent with a low toxicity⁷, that it has great powers of penetration⁸ and that it enhances the absorption of various drugs through skin and mucous membranes without apparently affecting their pharmacological properties^9–12. Furthermore, the use of DMSO as a vehicle decreases the latency period for the production of oral tumours in hamsters with dimethylbenzanthracene^13–14. We have found that repeated, topical applications of DMSO extracts of betel nut to the mucosa of the buccal pouch of hamsters result in the development of leukoplakia and tumours. The incidence of tumours increases when the extract is made from a mixture of betel nut and cured tobacco, although extracts of tobacco alone cause leukoplakia but not tumours.