Lack of promoting ability of snuff in rats initiated with 4-nitroquinoline-N-oxide

In an experiment to evaluate the carcinogenicity and promoting capacity of snuff, a reservoir was created in the lower lip of male Sprague-Dawley rats. Groups of 30 rats were treated with snuff only (twice a day on five days a week), propylene glycol (solvent) three times weekly for four weeks, painting of the hard palate with 4-nitroquinoline-N-oxide (4-NQO) three times weekly for four weeks followed by snuff, 4-NQO only for four weeks, or cotton pellets only (twice a day on five days a week). The experiment was continued up to 108 weeks. High levels of tobacco-specific nitrosamines were found in the snuff (a commercial US brand). Rats treated with snuff only, 4-NQO followed by snuff and 4-NQO only had a significantly higher number of squamous-cell tumours and hyperplastic squamous lesions of the lip, oral and nasal cavity and forestomach than solvent or untreated controls. The total number of neoplasms was significantly higher in rats treated with snuff only and with 4-NQO followed by snuff in comparison to the other groups. Thus, snuff and 4-NQO by themselves can induce benign and malignant tumours. Snuff appears to have a general tumorigenic effect but lacked promoting ability after initiation with 4-NQO.