Beta-carotene and vitamin E in oral cancer prevention

Marked Inhibition of Cellular Proliferation in the Normal Human Esophageal Epithelial Cells and Human Esophageal Squamous Cancer Cells in Culture by Carotenoids: Role for Prevention and Early Treatment of Esophageal Cancer

Background:

Globally Esophageal cancer is a common cancer arising from human esophageal mucosal tissue. Epidemiological studies suggest inverse correlation between carotenoid intake and incident risk of this devastating malignancy.

Methods:

In an effort to examine the modulatory role of carotenoids in human esophageal carcinogenesis at a cellular level, we examined the effects of α-carotene and β-carotenes, on cell proliferation and DNA synthesis in human esophageal epithelial (HEE) cells and human esophageal squamous cancer (HESC) cells in in-vitro cultures. HEE and HESC cells were incubated with different concentrations of α- and β-carotenes both individually and in combination.

Results:

Both Carotenes significantly inhibited (p<0.05) cellular proliferation and decreased DNA synthesis in HEE and HESC cells. The effect of α- and β-carotene together on DNA synthesis in HEE and HESC cells was significantly greater than either carotenoid alone, suggesting a synergistic effect. Greater magnitude of cellular inhibition of DNA synthesis was observed on HEE cells than HESC cells.

Conclusion:

Our results suggest that a combination of α-and β-carotene may provide a novel strategy for prevention and treatment of esophageal and upper aero digestive tract cancer in humans.

[Dietary guidelines for the Brazilian population: implications for the Brazilian National Policy on Oral Health]

Dietary guidelines are intended to orient dietary habits and policies for health promotion and disease prevention. This article discusses Brazil's national dietary guidelines, aiming to identify issues that can support the strategies proposed by the National Policy on Oral Health. The two currently available official guidelines produced by the Ministry of Health were reviewed: the Dietary Guidelines for Children under Two and the Population Dietary Guidelines. The guidelines recommend reduction in sugar intake, essential for caries prevention, and other measures to prevent tooth decay and oral cancer. These guidelines are thus a key part of an oral and overall health promotion strategy and should be integrated into the National Policy on Oral Health.

Dietary exposures and oral precancerous lesions in Srikakulam District, Andhra Pradesh, India

OBJECTIVE

To test the effect of dietary nutrients on oral precancerous lesions in a reverse-smoking (i.e. smoking with the glowing end inside the mouth) population in South India.

DESIGN

Case-control. Cases with precancerous lesions were matched to an equal number of lesion-free controls matched on age (+/- 5 years), sex and village. All subjects used tobacco in some form. Dietary data were obtained using an interviewer-administered food-frequency questionnaire, designed for use in this population. All interviews were conducted blinded to the disease status of the subject. Data were analysed using logistic regression.

SETTING

Nineteen rural villages in Srikakulam District, Andhra Pradesh.

SUBJECTS

From a survey of 6007 tobacco users, 485 (79% women) were found to have precancerous, mostly palatal, lesions (cases), and 487 lesion-free subjects were selected as controls.

RESULTS

All eligible subjects consented to participate and nearly all (> 99%) had complete data for analyses. Reverse smoking was the most common form of tobacco use among cases (81.9%) and controls (73.5%), and reverse smokers were 5.19 times more likely than chewers to have these lesions (95% confidence interval = 1.35, 19.9). After controlling for relevant covariates, including the type of tobacco use, protective linear effects were observed for zinc (70% reduction across the interquartile range, P < 0.002), calcium (34% reduction, P < 0.002), fibre (30% reduction, P < 0.009), riboflavin (22% reduction, P < 0.03) and iron (17% reduction, P < 0.05).

CONCLUSIONS

Several dietary nutrients appear to protect against oral precancerous lesions that are strongly associated with reverse smoking. The results of this study indicate scope for targeting dietary factors in preventing oral cancer, which should be coupled with aggressive anti-tobacco use efforts.

Experimental basis for cancer prevention by vitamin E

Recent clinical trials have demonstrated the significant cancer preventive potential of vitamin E in many different cancer sites, ranging from oral and pharyngeal cancer to prostate cancer. There is an extensive experimental basis for this clinical cancer inhibition. The experimental background includes animal studies (experimental pathology, immunology and molecular biology, synergism, selectivity and safety), in vitro biochemical studies, and human studies (epidemiology and biomarkers, prevention of many pathologic entities other than cancer).

Long-term supplementation with alpha-tocopherol and beta-carotene and prevalence of oral mucosal lesions in smokers

OBJECTIVE

To assess the effect of alpha-tocopherol and beta-carotene supplementation on the prevalence of oral mucosal lesions in smokers.

DESIGN

An end-point examination of a random sample of participants in a controlled trial for 5-7 years (Alpha-Tocopherol Beta-Carotene Cancer Prevention Study) in Helsinki, Finland.

SUBJECTS

A total of 409 white male cigarette smokers, aged 55-74 years who received either alpha-tocopherol (50 mg per day) or beta-carotene (20 mg per day) supplementation, both of these or placebo capsules.

METHODS

Clinical examination of oral mucosae, histological examination of lesions showing leukoplakia and cytological examination of buccal epithelium. Statistical analysis using Fisher's exact test.

RESULTS

No statistically significant differences were found between the study groups either in the prevalence of oral mucosal lesions or in the cells of unkeratinized epithelium. Leukoplakia was present in 24 (5.9%) of the subjects. Seven lesions showed dysplasia.

CONCLUSION

The present study on oral health does not support the hypothesis that alpha-tocopherol or beta-carotene supplementation plays an essential role in preventing oral mucosal changes in smokers.

Mechanisms of cancer inhibition by anti-oxidant nutrients

The cancer inhibitory properties of anti-oxidant micronutrients have been well established in experimental animal models and cell culture studies. Human studies have also tended to indicate an inhibition of various forms of cancer and the regression of some precancerous lesions. The biological mechanisms for cancer inhibition and regression are now gradually becoming understood, and the anti-oxidant nutrients appear to act through a number of pathways common to most of the agents studied. These various micronutrients appear to act through a complex group of "common pathways" of anticancer activity based upon three major mechanisms: (1) tumour inhibition by immune cytokines; (2) stimulation of cancer suppressor genes, such as "wild type" p53, and diminished expression or dysregulation of oncogenes such as mutant p53 and H-ras; (3) inhibition of tumour angiogenesis through the inhibition of angiogenesis-stimulating factors such as TGF alpha. Retinoid action differs, in some respects, from other micronutrient anticancer mechanisms and appears to relate to its stimulation of cellular differentiation and resultant apoptosis of neoplastic cells. Combinations of anti-oxidant nutrients have been shown to be synergistic in their anticancer activity, probably due to their optimal anticancer activity at different oxygen potentials. Selectivity in the action on cancer cells, as opposed to normal cells, is a major feature of the anti-oxidant micronutrients.