Changes in vitamin A conditioned hamster cheek pouch epithelium on exposure to commercial shell lime (calcium hydroxide) and tobacco. I-Optical histopathology

Role of vitamins C and E as chemopreventive agents in the hamster cheek pouch treated with the oral carcinogen-DMBA

OBJECTIVE

To evaluate the role of vitamins C and E as chemopreventive agents in oral carcinogenesis by optical and ultrastructural studies.

MATERIALS AND METHODS

The cheek pouch of male hamsters was treated with the oral carcinogen, dimethylbenz(a)anthracene (DMBA), to induce multiple tumour formation. Vitamins C and E were applied either singly or in combination as a chemopreventive agent. Paraffin and resin-embedded sections of the hamster cheek pouch were studied optically and ultrastructurally.

RESULTS

The epithelium of control hamsters showed hyperorthokeratosis and parakeratosis, but did not develop well differentiated squamous cell carcinoma (WDSCC). Ninety percent of the animals treated with DMBA alone showed WDSCC while 10% of the animals developed papillomas. There was also a marked increase in the number of cells undergoing mitosis in this group. A reduction in the yield (1.1 tumour/animal) and rate 60-80% of squamous cell carcinomas but not of papillomas (2.0 papillomas/animal) was observed in groups VI-VIII treated with DMBA and vitamins C and E singly or in combination as compared to those of DMBA only. In animals treated with DMBA plus vitamins C and E, statistical significant decrease in the number of animals with tumours and mitotic basal cells was observed when compared with the DMBA treated group. Control animals showed normal ultrastructural morphology while tumour-bearing animals showed basal lamina in a discontinuous, fragmented, broken and diffused basement membrane, with diminished lamina densa, fewer hemidesmosomes and invagination of the basal cell cytoplasmic processes in the subepithelium.

CONCLUSION

These results indicate that vitamin E singly or in combination with vitamin C plays a role in the inhibition of tumour cell growth.

The effect of vitamin C on the hamster cheek pouch treated with the water soluble carcinogen 4-nitroquinoline-1-oxide (4NQO)

Vitamin C is an essential nutrient whose protective influence is carcinogenesis has been reported frequently, suggesting that vitamin C inhibits the formation of some carcinogens and decreases the incidence and delays of the neoplastic lesions. However, the mechanisms by which this occurs are unknown. In this study, the water soluble carcinogen 4-nitroquinoline-1-oxide (4NQO) has been used to induce a high yield of tumours in the oral cavity either singly or in combination with tobacco. Since the mucosa of rats is less susceptible to carcinogens than the hamster cheek pouch, the hamster cheek pouch has been used to study the influence of vitamin C on 4NQO-induced oral malignancy. The aim of this study was to determine whether topically applied vitamin C had an effect on the oral carcinogenesis induced by application of 4NQO. Similarly, an attempt was made to study the modulating effect of vitamin C on the histopathological and ultrastructural changes during the neoplastic process in the hamster. Vitamin C appeared to delay tumour induction and had other protective effects against neoplasia.

Snuff dipping and oral cancer in Sudan: a retrospective study

A retrospective study involving 78 cases of oral carcinoma was conducted to investigate their association with the habit of taking snuff orally known as 'snuff-dipping' and locally termed 'saffa'. It was found that 50 (81%) of the 62 questioned patients used snuff in the form of saffa. It was also found that carcinomatous changes usually developed in the area of the mouth where the snuff was habitually placed. It was concluded that the association between saffa and development of oral carcinoma is likely to be causal.

Combined effect of herpes simplex virus and tobacco on the histopathologic changes in lips of mice

In the present study we have examined the combined effect of HSV-1 inoculation and tobacco application (snuff water extract or smoking tar condensate) on the histopathologic changes of mouse labial mucosa. Two months' exposure to tobacco or HSV-1 inoculation alone did not induce dysplasia in the epithelium of labial mucosa, while HSV-1 inoculation combined with snuff water extract or smoking tar condensate produced epithelial dysplasia and other histomorphologic changes (that is, hyperkeratosis, increased granular cell layer thickness, acanthosis, and increased inflammatory cell infiltration in a significant number of animals). This result indicates that HSV-1 and tobacco could possibly act synergistically in the development of precancerous oral lesions and oral cancer.

Carcinogenicity examination of betel quid. II. Effect of vitamin A deficiency on rats fed semipurified diet containing betel nut and calcium hydroxide

The effect of vitamin A deficiency on the carcinogenicity of betel quid was studied, using long-term feeding of vitamin-A-deficient and -sufficient diets with and without betel nut and calcium hydroxide in ACI rats. A high incidence of focal epithelial hyperplasia was observed in the upper digestive tract (tongue, buccal oral mucosa, esophagus, and forestomach) of rats in the group given the vitamin-A-deficient diet mixed with betel nut and calcium hydroxide. The vitamin-A-deficient group also showed a high incidence of squamous papilloma in the tongue, buccal mucosa, and forestomach. The incidence of hyperplastic lesions of the tongue and buccal oral mucosa was significantly higher in this group than in the group receiving the vitamin-A-sufficient diet with betel nut and calcium hydroxide. These results suggest that the vitamin-A-deficient condition enhanced the growth of epithelial hyperplasia that was due to the administration of the betel quid ingredients. However, vitamin A did not protect against the development of altered liver cell foci, which were frequently seen with a small number of hepatocellular neoplasms in all groups given the diets containing betel nut and calcium hydroxide (both vitamin-A-deficient and -sufficient groups).

Snuff-induced lesions of the oral mucosa - an experimental model in the rat

An experimental model in the white rat has been developed in order to study the influence of snuff on oral mucosa. A test canal in the lower lip, with one orifice buccally to the incisors and one on the lip side, was created by surgical means. The connection between the canal and the oral cavity was made to ensure the presence of saliva in the canal so that physiological conditions resembling those of the oral cavity were obtained. The canal was filled with snuff morning and night 5 days a week. The mean value for the maximal retention time of the snuff was 6 h. The animals tolerated the dose and time of exposure without signs of severe toxic symptoms. Histological examination of the canals after 9 months of exposure to snuff showed a mildly to moderately hyperplastic epithelium with hyperorthokeratosis. Locally deep proliferations of epithelium with acanthotic rete pegs could be seen. In the stratum basale hyperplasia with disturbed polarity and hyperchromatic nuclei and single mitosis were noted.

The histopathologic features which follow repeated applications of tobacco tar to rat lip mucosa

The response of rat lip mucosa to two tobacco tar preparations combined with heat was examined histopathologically. It was shown that the magnitude of irritational hyperplasia produced was related to the level of irritation. This was greatest in those rats subjected to the longest period of application of the tobacco extract with the greatest concentration of tar combined with heating the site of application. Neoplastic changes were not produced.

The induction of hyperkeratotic white lesions in hamster cheek pouches with mouthwash

Listerine mouthwash applied to the left cheek pouch mucosa of thirty-seven hamsters 45 minutes daily for 41 days caused diffuse, corrugated white lesions showing hyperkeratosis in 100 percent of the animals. The right (control) side showed essentially no changes in response to saline solution applied similarly. The significance of these findings is discussed.