Vitamin E inhibition of lipid peroxidation and ethanol-mediated promotion of esophageal tumorigenesis

The protective mechanism of QGC in feline esophageal epithelial cells by interleukin-1β treatment

In a previous study, Quercetin-3-O-β-D-glucuronopyranoside (QGC) has anti-oxidative and anti-inflammatory effects in vivo. QGC is a flavonoid glucoside extracted from Rumex Aquaticus. We investigated the downstream target proteins involved in IL-1β-stimulated ROS production and the ability of QGC to inhibit ROS production. Cell viability was determined using the MTT reduction assay. Western blot analysis was performed with antibodies to investigate the activation of three MAPKs, NF-κB, and phosphorylated IκB-α (pIB), and the expression of COX-2. 2',7'-dichlorofluorescin diacetate was used to detect the generation of intracellular ROS species. When the cells were exposed to media containing IL-1β for 18 h, cell viability was not affected. QGC did not reduce the COX-2 expression induced by IL-1β. However; QGC attenuated the production of intracellular ROS induced by IL-1β. IL-1β increased the expression of ERK, p38 MAPK, and pIB, and nuclear translocation of NF-κB were recovered by the ROS scavenger N-acetyl-L-cysteine (NAC) and QGC, but not by the NADPH oxidase inhibitor diphenylene iodonium. Pretreatment of cells with the ERK inhibitor PD98059, the p38 MAPK inhibitor SB202190, NAC, and QGC attenuated nuclear translocation of NF-κB and activation of pIB. QGC has a scavenging effect on cytokine-induced ROS production, thereby preventing its downstream effects, nuclear translocation of NF-κB, and activation of pIB is mediated by activation of ERK and p38 MAPK, although QGC does not inhibit IL-1β-stimulated COX-2 expression in feline esophageal epithelial cells. The data suggest that QGC exerts anti-oxidative effects and inhibitory effects against esophageal epithelial cells signals by the action of IL-1β treatment.

Alteration of Lipid Profile in Patients with Head and Neck Malignancy

Lipids are the major cell membrane components, essential for various biological functions including cell growth and division for the maintenance of cell integrity of normal and malignant tissues. The changes in lipid profile have been associated since long with cancer and hypocholesterolemia has been observed in patients with cancers of various organs. The objective of the present study is to evaluate the alterations and clinical significance of plasma lipid profiles in untreated head and neck malignancies. The present case-control study comprises of newly diagnosed and histologically confirmed, 100 head and neck malignancy cases diagnosed between 1st July 2013 and 30th June 2014 in the Department of Otorhinolaryngology and Head and Neck Surgery, Gandhi Medical College, Bhopal. Fasting blood samples were collected and the lipid profile studied. In present study, the authors found that there is a preponderance of head and neck malignancy in the age group of 41-60 years, males having the higher incidence. Malignancy involving oral cavity were the commonest and majority were well differentiated. Statistically, there was a highly significant reduction of mean serum total cholesterol (TC), triglycerides and high density lipoproteins (HDL) in the subjects of head and neck malignancy as compared to the control group. TC and HDL were also found significantly lower among those with habit of tobacco consumption.

Estimation of plasma lipids and its significance on histopathological grades in oral cancer: Prognostic significance an original research

Background Objectives:

Alterations in the lipid profile have long been associated with various cancers because lipids play a key role in maintenance of cell integrity. This study was to estimate the plasma lipid levels in patients with oral cancer and to correlate the values with the histopathological grades.

Materials and Methods:

The study group included 50 patients with oral cancer aged between 20 and 60 years who had visited the Department of Oral Medicine and Radiology during the period of September 2005 to July 2007. After the histotopathological confirmation, their plasma lipid levels were estimated using auto analyzer and the data was statistically analyzed.

Results:

The study revealed a significant decrease in the total plasma lipid levels in patients with oral cancer in comparison with the standard values. Comparing the plasma lipid levels with the histopathological grades, we observed a significant variation in the levels of total cholesterol, very low density lipoprotein, low-density lipoprotein, high-density lipoprotein and triglycerides

Conclusion:

The variation in the levels of plasma cholesterol and other lipid constituents in patients with cancer might be due to their increased utilization by neoplastic cells for new membrane biosynthesis. This study was an attempt to estimate the plasma lipids in oral cancer patients and its significance on histopathological grades. We observed a relationship between lower plasma lipids and oral cancer. The result of our study strongly warrants an in-depth research with larger samples and a longer follow-up to consider the low plasma lipid status in oral cancer patients as a useful indicator to assess the course and prognosis of the disease.

Anti-Oxidative and Anti-Inflammatory Effects of QGC in Cultured Feline Esophageal Epithelial Cells

Quercetin-3-O-β-D-glucuronopyranoside (QGC) is a flavonoid glucoside extracted from Rumex Aquaticus Herba. In the present study, anti-oxidative and anti-inflammatory effects of QGC were tested in vitro. Epithelial cells obtained from cat esophagus were cultured. When the cells were exposed to acid for 2 h, cell viability was decreased to 36%. Pretreatment with 50 µM QGC for 2 h prevented the reduction in cell viability. QGC also inhibited the productions of intracellular ROS by inflammatory inducers such as acid, lipopolysaccharide, indomethacin and ethanol. QGC significantly increased the activities of superoxide dismutase (SOD) and catalase, and also induced the expression of SOD2, while it restored the decrease of catalase expression in cells exposed to acid. QGC inhibited NF-κB translocation, cyclooxygenase-2 expression and PGE₂ secretion in cells exposed to acid, which plays an important role in the pathogenesis of esophagitis. The data suggest that QGC may well be one of the promising substances to attenuate oxidative epithelial cell injury and inflammatory signaling in esophagus inflammation.

The Protective Effect of Quercetin-3-O-β-D-Glucuronopyranoside on Ethanol-induced Damage in Cultured Feline Esophageal Epithelial Cells

Quercetin-3-O-β-D-glucuronopyranoside (QGC) is a flavonoid glucoside extracted from Rumex Aquaticus Herba. We aimed to explore its protective effect against ethanol-induced cell damage and the mechanism involved in the effect in feline esophageal epithelial cells (EEC). Cell viability was tested and 2',7'-dichlorofluorescin diacetate assay was used to detect intracellular H₂O₂ production. Western blotting analysis was performed to investigate MAPK activation and interleukin 6 (IL-6) expression. Exposure of cells to 10% ethanol time-dependently decreased cell viability. Notably, exposure to ethanol for 30 min decreased cell viability to 43.4%. When cells were incubated with 50 µM QGC for 12 h prior to and during ethanol treatment, cell viability was increased to 65%. QGC also inhibited the H₂O₂ production and activation of ERK 1/2 induced by ethanol. Pretreatment of cells with the NADPH oxidase inhibitor, diphenylene iodonium, also inhibited the ethanol-induced ERK 1/2 activation. Treatment of cells with ethanol for 30 or 60 min in the absence or presence of QGC exhibited no changes in the IL-6 expression or release compared to control. Taken together, the data indicate that the cytoprotective effect of QGC against ethanol-induced cell damage may involve inhibition of ROS generation and downstream activation of the ERK 1/2 in feline EEC.

Diet and oral, pharyngeal, and esophageal cancer

Cancers of the upper digestive tract, including those arising in the oral cavity, pharynx, and esophagus, present a significant public health problem worldwide. These cancers are associated with high morbidity and mortality, and identification of protective factors is very important. A number of epidemiological studies have examined the association between vegetables, fruits, carotene, vitamin A, vitamin C, and vitamin E and oral, pharyngeal, and esophageal cancers. The results of 35 epidemiological studies, including one prospective cohort study, one nested case-control study, two randomized controlled trials, nine population-based case-control studies, and 22 hospital-based case-control studies, in addition to in vitro and animal studies, were examined to determine whether the criteria for causal assumption were satisfied for a protective role of these dietary components against development of oral, pharyngeal, and esophageal cancers. There is enough evidence to point to a preventive role of vegetable intake, including green vegetables, cruciferous vegetables, and yellow vegetables, total fruit intake, and citrus fruit intake. Yellow fruits are likely to be protective. Carotene, vitamin C, and vitamin E are protective, most likely in combination with each other and other micronutrients. The role of vitamin A is not clear because of conflicting findings in the studies reviewed.

Final report on the safety assessment of Tocopherol, Tocopheryl Acetate, Tocopheryl Linoleate, Tocopheryl Linoleate/Oleate, Tocopheryl Nicotinate, Tocopheryl Succinate, Dioleyl Tocopheryl Methylsilanol, Potassium Ascorbyl Tocopheryl Phosphate, and Tocophersolan

Tocopherol and its several ester and ether derivatives all function as antioxidants in cosmetic formulations; they also have other functions, such as skin conditioning. Tocopheryl Acetate, Tocopherol, and Tocopheryl Linoleate are used in 2673 formulations, generally at concentrations of up to 36%, 5%, and 2%, respectively, although Tocopheryl Acetate is 100% of vitamin E oil. Tocophersolan, Tocopheryl Linoleate/Oleate, Tocopheryl Nicotinate, Tocopheryl Succinate, Dioleyl Tocopheryl Methylsilanol, and Potassium Ascorbyl Tocopheryl Phosphate, combined, are used in 36 formulations at concentrations lower than those reported for the frequently used ingredients. Tocopherol may be isolated from vegetable oils or synthesized using isophytol and methylhydroquinone. Tocopherol, Tocopheryl Acetate, Tocopheryl Linoleate, and Tocopheryl Succinate all were absorbed in human skin. In rat skin, Tocopheryl Acetate is hydrolyzed to Tocopherol. Tocopherol is a natural component of cell membranes thought to protect against oxidative damage. Tocopherol, Tocopheryl Acetate, and Tocopheryl Succinate each were reported to protect against ultraviolet radiation-induced skin damage. These ingredients are generally not toxic in animal feeding studies, although very high doses (>2 g/kg/day) have hemorrhagic activity. These ingredients are generally not irritating or sensitizing to skin or irritating to eyes, although a Tocopheryl Acetate did produce sensitization in one animal test, and Tocophersolan was a slight eye irritant in an animal test. Reproductive and developmental toxicity tests in animals using Tocopherol, Tocopheryl Acetate, Tocopheryl Succinate, and Tocophersolan were all negative or showed some effect of reducing toxicity. Tocopherol, Tocopheryl Acetate, Tocopheryl Succinate, and Dioleyl Tocopheryl Methylsilanol were almost uniformly negative. These ingredients exhibit antimutagenic activity consistent with their antioxidant properties. Tocopherol was not carcinogenic. The ability of Tocopherol, Tocopheryl Acetate, and Tocopheryl Succinate to modulate the carcinogenic effect of other agents (e.g., tumor promotion) has been extensively studied. One study showing tumor promotion in mice may be discounted as not reproducible and not consistent with the large volume of data suggesting that the antioxidant properties of these agents protect against tumor induction. Specifically, the frequent use of Tocopherol as a negative control in other tumor promotion studies suggests that Tocopherol is not a tumor promoter. Tocopherol has been shown to reduce the photocarcinogenic effect of ultraviolet radiation in mice. Similar studies with Tocopheryl Acetate and Tocopheryl Succinate, however, demonstrated some enhancement of photocarcinogenesis, although the effect was not dose related. In clinical studies, Tocopherol, Tocopheryl Acetate, and Tocopheryl Nicotinate were not irritants or sensitizers. A report of a large number of positive patch-tests to Tocopheryl Linoleate in one cosmetic product were considered to result from a contaminant or metabolite. The Cosmetic Ingredient Review Expert Panel considered that these data provide an adequate basis on which to conclude that Tocopherol, Tocophersolan, Tocopheryl Acetate, Tocopheryl Linoleate, Tocopheryl Linoleate/Oleate, Tocopheryl Nicotinate, Tocopheryl Succinate, Dioleyl Tocopheryl Methylsilanol, and Potassium Ascorbyl Tocopheryl Phosphate are safe as used in cosmetic formulations. Although there were no inhalation toxicity data, these ingredients are used at such low concentrations in hair sprays that no inhalation toxicity risk was considered likely. Because methylhydroquinone is used in the chemical synthesis of Tocopherol, there was concern that hydroquinone may be present as an impurity. In such cases, residual levels of hydroquinone would be expected to be limited to those achieved by good manufacturing practices.

Influence of antioxidative vitamins A, C and E on lipid peroxidation in BOP-induced pancreatic cancer in Syrian hamsters

Persistent oxidative stress is thought to play an important role in carcinogenesis. Vitamins may influence oxygen radical metabolism and thus inhibit tumor growth. In the present trial the effects of Vitamins (Vit.) A, C and E on neoplastic growth and lipid peroxidation in pancreatic tissue were evaluated on chemically-induced pancreatic adenocarcinoma in the Syrian hamster. The incidence of pancreatic cancer was decreased by Vit. A (64.3%) and Vit. C (71.4%) as compared to the control group (100%, P<0.05). All vitamins increased the activity of superoxidedismutase (SOD) in pancreatic carcinomas. Accumulation of vitamins in tumor cells seems to be responsible for high levels of SOD and consecutive intracellular increase of hydrogen peroxide levels. Since this effect is selectively toxic for tumor cells it might be one of the mechanisms decreasing the incidence of pancreatic cancer in our trial.

Micronutrients, vitamins, and cancer risk

There is now considerable evidence that a high intake of fruit and vegetables can decrease the risk of developing cancer. While it is by no means clear how this particular diet alters cancer risk, there is substantial metabolic and experimental evidence to implicate antioxidant micronutrients, The dietary components include some vitamins, such as C and E, the carotenoids, and the flavinoids. In chemical systems, cell culture, and experimental animals, these components have the ability to quench the carcinogenic potential of reactive oxygen species and other carcinogens, such as N-nitrosocompounds. Some of these micronutrients can act synergistically, and high concentrations are often found in tissues, such as the leucocytes and mucosal cells, that are particularly prone to reactive species attack. Experimental systems containing these micronutrients also appear to be able to reduce DNA damage and mutagenesis. However, assessment of individual vitamin intake, as opposed to fruit and vegetable consumption, does not increase the protective association of these components, and the results of intervention studies in man, especially with carotenoids, have been disappointing. We await the results of other clinical trials, but as yet, there is insufficient evidence to recommend supplements of these particular micronutrients for the prevention of cancer. However, it would be prudent to suggest changes in diet that would increase consumption of fruit and vegetables, such as a diet is clearly associated with protection.

Alcohol-stimulated promotion of tumors in the gastrointestinal tract

Alcohol is a major risk factor for cancers of the upper gastrointestinal tract but the association with cancers of the large bowel is not as clearly established. In recent studies, we have provided experimental support for the associations in the esophagus and oral cavity. Our studies also indicate that the tumor promotion ability of ethanol is related to its ability to generate oxygen free radicals as measured by an increase in indices of lipid peroxidation. This increase in lipid peroxidation was evident in the liver as well as the tissues targeted by the site-specific carcinogens and promoted by ethanol. Studies in mice showed that the increased lipid peroxidation as well as tumor incidence was inhibited by the administration of vitamin E, the potent antioxidant. Determination of fatty acid profiles showed significant alterations when ethanol was used as a tumor promoter after treatment with the carcinogen. Ethanol as a promoter caused an increase in esophageal polyunsaturated fatty acids (PUFA). Ethanol promotion was also evident in increased arachidonate and an exaggeration in PUFA that are involved in eicosanoid production. Thus, these results suggest that ethanol-related promotion may be the result of excessive cell proliferation induced by disordered lipid and eicosanoid metabolism that may cause a selective outgrowth of the carcinogen-initiated cells. Supporting evidence for ethanol-induced hyper-regeneration is also reviewed.

Vitamin E and coenzyme Q concentrations in the thyroid tissues of patients with various thyroid disorders

To clarify the different roles of free radical scavenging systems in various thyroid disorders, we measured the levels of alpha-, beta-, and gamma-tocopherols and coenzyme Q in the thyroid tissues of patients with thyroid tumors and Graves' disease using high-performance liquid chromatography. The levels of alpha-tocopherols and gamma-tocopherols in the thyroid tissue of patients with papillary carcinoma and the level of gamma-tocopherol in the thyroid tissue of patients with malignant lymphoma were elevated compared with those in normal thyroid tissues. The level of coenzyme Q was reduced in the thyroid tissue of patients with Graves' disease and follicular and papillary thyroid carcinomas. These findings imply that vitamin E and coenzyme Q as scavengers play some role in thyroid follicular cell hyperfunction or dysfunction.

Postnatal efficacy of antioxidants in the detoxification pathway of suckling neonates and lactating mice

This study evaluates the comparative efficacy of antioxidant vitamins (ascorbic acid and alpha-tocopherol) and non-vitamin antioxidants (glutathione, cysteine and L-2-oxothiazolidine-4-carboxylate (OTZ)) in modulating the detoxification pathway of lactating dams and suckling murine pups. In dams, 100 mg/kg b.w./day treatment of each of the vitamin and non-vitamin antioxidants induced a significant increase in the hepatic level of acid soluble sulfhydryl (-SH) compared to the modulating efficiency of OTZ, glutathione and alpha-tocopherol in the kidney tissue. In the liver and kidney tissues of suckling pups OTZ and alpha-tocopherol were effective in modulating the -SH level. A statistically significant increase in the hepatic glutathione-S-transferase (GST) level was observed by OTZ, glutathione and alpha-tocopherol, while only OTZ was effective in the kidney tissue of dams and pups. In the murine system, the modulation of cellular GST/GSH status, specifically by OTZ, alpha-tocopherol and interacting antioxidant pool, may potentially ameliorate the pathophysiology of oxidative stress.

Esophagitis in Sprague-Dawley rats is mediated by free radicals

Free radical-mediated esophagitis was studied during duodenogastroesophageal reflux (mixed reflux) or acid reflux in rats. The influence of reflux on esophageal glutathione levels was also examined. Mixed reflux caused more gross mucosal injury than acid reflux. Gross mucosal injury occurred in the mid-esophagus. Total glutathione (GSH) in the esophageal mucosa of control rats was highest in the distal esophagus. The time course of esophageal GSH in rats treated by mixed reflux showed a significant decrease 4 hr after initiation of reflux, followed by a significant increase from the 12th hour on. Mucosal GSH was increased in both reflux groups after 24 hr but significantly more so in the mixed than in the acid reflux group. The free radical scavenger superoxide dismutase (SOD) prevented esophagitis and was associated with decreased GSH levels. GSH depletion by buthionine sulfoximine (BSO) prevented esophagitis and stimulated SOD production in the esophageal mucosa. It is concluded that gastroesophageal reflux is associated with oxidative stress in the esophageal mucosa. The lower GSH levels in the mid-esophagus may predispose to damage in this area. Duodenogastroesophageal reflux causes more damage than pure acid reflux. Oxidative stress leads to GSH depletion of the esophageal mucosa in the first few hours following damage but then stimulates GSH production. GSH depletion by BSO does not worsen esophagitis since it increases the esophageal SOD concentration.

Dietary vitamin E modulation of cytokine production by splenocytes and thymocytes from alcohol-fed mice

As vitamin E enhances immune responses, it may reduce dietary ethanol (EtOH)-induced immune suppression, thereby favorably affecting host disease resistance. The effects of dietary vitamin E at higher level in alcohol-fed female C57BL/6 mice was determined via in vitro cytokine production by splenocytes and thymocytes, and some other immune functions. A 15-fold increase of vitamin E (160 IU/liter) in a liquid diet (National Council Research), with or without EtOH (4.5%, v/v), was fed to mice for 10 weeks. Vitamin E supplementation restored production of interleukin-2, -5, -6, -10, and interferon-gamma by concanavalin A (Con A)-stimulated splenocytes and interleukin-6 and tumor necrosis factor-alpha by lipopolysaccharide-stimulated splenocytes, which were suppressed by dietary EtOH. However, it had no effect on interleukin-4 secretion, which was also reduced by splenocytes from EtOH-fed mice. Vitamin E supplementation also restored EtOH-suppressed, mitogen-induced splenocyte proliferation, but not thymocyte proliferation, although it slightly increased production of immunoglobulin A and G by lipopolysaccharide-stimulated splenocytes, which were suppressed by dietary EtOH. Dietary vitamin E, furthermore, significantly increased interleukin-2 and -6 secretion by Con A-stimulated thymocytes, which were suppressed by dietary EtOH, although it had no effect on interleukin-4 and interferon-gamma production by Con A-stimulated thymocytes from EtOH-fed mice. These data suggest that dietary vitamin E supplementation can modulate dysregulation of cytokines initiated by dietary EtOH and restore immune dysfunctions induced by EtOH ingestion.

Ethanol, immune responses, and murine AIDS: the role of vitamin E as an immunostimulant and antioxidant

Excessive alcohol consumption is a major health problem in the United States. Prolonged consumption of alcohol results in alterations of immune responses, ultimately manifested by increasing susceptibility to infectious agents. Such changes can be due to the direct effects of alcohol or its metabolites on immune cells, as well as to nutritional deficiency, oxidative stress, and neutrophil dysfunctions. This ETOH-induced immunosuppression could be a potential cofactor in the progression to AIDS. As vitamin E supplementation has been associated with enhancement of immune response and improvement of host defense, it may provide a useful therapeutic approach for treatment of alcoholics to improve host defense. This article is a review of alcohol-related immunosuppression as a possible cofactor in the development of AIDS, and vitamin E-related immunoenhancing roles in animals and humans, showing why vitamin E supplementation could be used as a useful adjunct agent in alcoholics' treatment. Since there is little information available regarding nutritional therapy with alcohol users, our purpose is to provide evidence from animal models of the potential therapeutic role of vitamin E supplementation in the treatment of alcoholics.

Esophageal carcinogenesis in the rat: a model for aerodigestive tract cancer

A number of chemical carcinogens have been used to study the process of esophageal carcinogenesis. Among the most prominent of these models is the induction of cancer of the esophagus in the rat by the nitrosamine N-nitrosomethylbenzylamine (NMBA). In the rat, tumors can occur within 15 weeks of carcinogen administration. The rat model has been used to investigate the mechanism of action of several chemopreventive agents. Among these, the garlic-derived agent diallyl sulfide has been shown to be a specific inhibitor of NMBA metabolism. Other investigators have used the model to seek out the relationship of dietary factors and alcohol in esophageal tumorigenesis. With striking histologic parallels to human esophageal carcinoma, the NMBA model provides useful information to study this cancer.

Ethanol-mediated promotion of oral carcinogenesis in hamsters: association with lipid peroxidation

Pouches of male Syrian Golden hamsters were painted with 1% 7,12-dimethylbenz[a]anthracene (DMBA) three times for one week. One week after DMBA treatment, hamsters were fed an ethanolic diet and continued on this diet until they were killed 22 and 35 weeks after the start of the experiment. Phospholipids, cholesterol, indexes of lipid peroxidation (malondialdehyde, diene and triene conjugates, lipid fluorescence), and the antioxidants glutathione and vitamin E were determined in the buccal mucosa, as was the incidence of tumors. At 22 weeks, the relative proportion of cholesterol to phospholipids in ethanol-consuming hamsters was significantly increased. At 35 weeks, most of the treatments showed a return of cholesterol vs. phospholipids toward that of untreated mucosa at 22 weeks. Ethanol consumption also increased the indexes of lipid peroxidation at 22 weeks; the largest increases occurred when ethanol use was combined with DMBA treatment. However, at 35 weeks such increases in lipid peroxidation had either returned to intermediate levels or were not different from the untreated controls at 22 weeks. Glutathione decreased in pouches of hamsters fed ethanol diets at 22 weeks, but at 35 weeks there was no appreciable difference. However, vitamin E increased significantly with ethanol consumption at 22 weeks, which increased further when combined with DMBA treatment, but at 35 weeks these values were intermediate. No tumors were seen at 22 weeks. At 35 weeks, DMBA-treated ethanol-fed hamsters had a significantly higher incidence of tumors, more multiple tumors per hamster with tumors, and more of the larger tumors than DMBA-treated control-fed hamsters. The results suggest that an increase in lipid peroxidation occurs with ethanol-related tumor promotion processes, but this lipid peroxidation declines when tumors appear to be preceded by increases in cholesterol relative to phospholipids and increases in vitamin E.

Alcohol stimulation of lipid peroxidation and esophageal tumor growth in mice immunocompromised by retrovirus infection

Tumor appearance can be accelerated in the immunodeficient and immunosuppressed animal. The role of lipid peroxidation and immune dysfunction induced by retrovirus and ethanol treatments on cancer promotion were investigated. Following the initiation of esophageal cancer by methylbenzylnitrosamine, ethanol consumption and retrovirus infection individually and concomitantly increased growth of esophageal tumors. Dietary supplementation with vitamin E reduced the size and frequency of the developed tumors. Tumor growth modifications in the vitamin E supplemented animals may be due to changes in T-cell numbers and functions stimulated by vitamin E. In addition, increased production of free radicals following ethanol treatment and retrovirus infection, and the suppression of these formations lipid peroxide by vitamin E is accompanied by lower incidence and size of tumors. Thus, the mechanisms of tumor enhancement observed in immunocompromised animals may include a combination of immunomodulation and modification of oxidant production by ethanol consumption and retrovirus infection.