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G Shklar

Publications and source records attributed to G Shklar.

At least 37 records · Page 2Linked to original sources
PubMed1993

p53 in the anticancer mechanism of vitamin E.

Immunohistochemical techniques were used to study the expression of "wild type" p53 and "mutant" p53 in experimental cancer inhibition by vitamin E. The cancer model used was the squamous cell carcinoma of hamster buccal pouch induced by the carcinogen 7,12 dimethylbenz(a)anthracene (DMBA). Cancer development was studied sequentially for 8-14 weeks and specimens prepared for histological and immunohistochemical interpretation. Primary antibodies used were monoclonal antibodies for "wild type" and "mutant" p53. Specificity of antibodies was confirmed by flow cytometry. Peroxidase-antiperoxidase staining was used on the tissue specimens. In those animals receiving vitamin E the buccal pouch tumour development was significantly inhibited and there was a notable expression of "wild type" p53. There was also a relative absence of "mutant" p53 in the buccal pouch lesions of animals receiving vitamin E. These observations suggest that vitamin E may inhibit cancer formation by stimulating the expression of a cancer suppressor gene.

Animals↗
PubMed1993

Inhibition of oral carcinogenesis by glutathione.

Forty young adult Syrian hamsters (Mesocricetus auratus) were divided into four groups of 10 animals each. In Group 1 (tumor control), the right buccal pouches were painted three times per week with a 0.5% solution of 7,12-dimethylbenz[a]anthracene (DMBA) in heavy mineral oil (USP) with a no. 4 sable brush. In Group 2 (experimental group), the right buccal pouches were painted with DMBA, as in Group 1. In addition, Group 2 received 1 mg of reduced glutathione in 0.5 ml of mineral oil three times per week on days alternate to the DMBA application. The glutathione was administered systemically by mouth with a pipette. Group 3 received only glutathione, and Group 4 was untreated (control groups). Animals were sacrificed after 14 weeks, and tumors were counted and measured. Both right and left pouches were photographed, excised, fixed in formalin, sectioned in paraffin, and studied histologically. The animals receiving glutathione demonstrated significantly fewer and smaller tumors. The mean tumor burden was 315 mm3 in the glutathione-treated group and 3,040 mm3 in the untreated group. The statistical significance by Student's t test was < or = 0.0001. Histological study also revealed significantly fewer areas of dysplastic leukoplakia in the group treated with glutathione. This study represents the first demonstration of the anticancer effect of systemically administered reduced glutathione.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1993

The effectiveness of a mixture of beta-carotene, alpha-tocopherol, glutathione, and ascorbic acid for cancer prevention.

Previous studies have shown that beta-carotene and alpha-tocopherol can act synergistically to inhibit the growth of experimentally induced oral cancer. The initial studies on the synergistic anticancer activity of antioxidants have been extended to include reduced glutathione and ascorbic acid. Sixty male hamsters (4-5 wks old) were divided into six equal groups. Groups 1-6 were treated with 7,12-dimethylbenz[a]anthracene (DMBA) (0.5% solution). Group 2 received a mixture containing equal amounts of beta-carotene, dl-alpha-tocopherol (vitamin E), glutathione, and l-ascorbic acid (vitamin C) (12.5 micrograms) delivered orally by pipette. Groups 3-6 were treated with beta-carotene alone (50 micrograms), vitamin E alone (50 micrograms), glutathione (50 micrograms) alone, and vitamin C alone (50 micrograms). Animals were euthanized at 12 and 14 weeks. Tumors were counted and measured, and tumor burden was calculated for each experimental group. The mixture of antioxidants significantly reduced tumor burden, whereas the beta-carotene, vitamin E, and reduced glutathione treatments also reduced tumor burden. beta-Carotene and glutathione provided greater levels of chemoprevention than vitamin E as single agents. In contrast, vitamin C treatment produced no antitumor effect but increased tumor burden by Week 14. This mixture of antioxidants produced a significant synergistic chemoprevention of oral cancer.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1992

The selective cytotoxic effect of carotenoids and alpha-tocopherol on human cancer cell lines in vitro.

This study compares the toxic effects of the carotenoids, beta-carotene and canthaxanthin, and alpha-tocopherol (vitamin E) on human tumor cells and their normal counterparts in vitro. Seven different malignant cell lines were examined: oral carcinoma (two cell lines), breast (two cell lines), lung carcinoma (two cell lines), and malignant melanoma. The in vitro cell culture assays showed a consistent morphologic change in the affected tumor cells following treatment with carotenoid or vitamin E. A rounding of the tumor cells and eventual lifting off the tissue culture plate were observed. These changes were apparent after 1 to 5 hours of treatment depending on the tumor cell line. Associated with these observable cellular changes were quantitative reductions in proliferation (3H-thymidine proliferation) and succinic dehydrogenase activity (MTT assay). In addition, there was a noticeable change in protein expression, with an increased expression of a 70-kD protein following treatment with beta-carotene. This protein was associated with tumor cells showing a decrease in proliferation (oral carcinoma, malignant melanoma) but not with normal keratinocytes or melanocytes. These studies substantiate a selective cytotoxic effect on human tumor cell growth by carotenoids and alpha-tocopherol in vitro, and may provide an explanation of the therapeutic activity of these agents and their possible use in the treatment of premalignancy or early oral carcinoma.

Breast Neoplasms↗
PubMed1991

Sequential mast cell infiltration and degranulation during experimental carcinogenesis.

Mast cell density, distribution, and ultrastructure were studied by light and electron microscopy in hamster buccal pouches undergoing chemically induced carcinogenesis. Epidermoid carcinomas in the pouches were induced by three topical applications per week of 0.5% 7,12-dimethylbenz[a]anthracene (DMBA) in oil using a brush. Four experimental, DMBA-treated and two normal, untreated hamsters were sacrificed after 8, 10, 12, 14, and 16 weeks. After 8 weeks of DMBA treatment, the epithelium showed the pathological signs of dysplasia and hyperkeratosis. In the dermis an increased number of mast cells were evident, some of which showed degranulation. A few mast cells had started to migrate upwards towards the dysplastic epithelium after 10 weeks of DMBA treatment. Rapid degranulation was also apparent in some mast cells. These processes of upward migration and degranulation continued progressively during the 12- and 14-week periods of DMBA application in correlation with the progression of the tumor. By 16 weeks of treatment with the carcinogen, more mast cells had migrated closer to the invasive carcinoma, and many had degranulated. In the connective tissue mast cells were fully packed with many granules, and some mast cells were in proximity to macrophages and eosinophils. Our observations demonstrate that there is a positive correlation between developing carcinomas and mast cell density. Mast cell migration towards the carcinoma and degranulation were also evident.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1991

Directed lysis of experimental cancer by beta-carotene in liposomes.

The purpose of this study was to extend the knowledge of the antitumor activity of liposomes and to identify, for the first time, the antitumor effect of liposomes with the antioxidant beta-carotene. The administration of the carotenoid encapsulated in in liposomes has the advantages of quantitation, facilitation, and most importantly an increased therapeutic response, resulting in the accentuation of regression of carcinoma in the hamster pouch. Tumors induced after the application of the carcinogen 7,12-dimethylbenz[alpha]anthracene (0.5%) were injected with liposomes composed of phosphatidylcholine, phosphatidylserine, and phosphatidylethanolamine in a ratio of 1:1:1 (large unilamellar vesicles). Tumor-bearing animals were divided into four groups, each containing 10 hamsters. The group treated with the liposomes of beta-carotene exhibited a significantly lower tumor burden (approx 5,000-fold difference) than the control tumor group. Electron- and light-micrographic analyses were used to substantiate the gross observations of tumor regression. It was noted that the carcinoma cells endocytozed liposomes in increased numbers compared with normal mucosa treated with liposomes. In addition, non-tumor-bearing hamsters injected with beta-carotene liposomes or liposomes alone did not exhibit any pathological change to the normal mucosa. An inflammatory infiltrate consisting of mononuclear cells, mast cells, and some polymorphonuclear leukocytes was noted, and degranulating polymorphonuclear leukocytes and mast cells and eosinophils predominated in the tumor controls (7,12-dimethylbenz[alpha]anthracene treated only). Notably, not all areas of degenerating dysplasia or early carcinoma exhibited a dense inflammatory response adjacent to the mucosa after the injection of beta-carotene liposomes. The results demonstrate a selective nontoxic therapy to regress experimental oral cancer.

Animals↗
PubMed1990

Induction of a 70 kD protein associated with the selective cytotoxicity of beta-carotene in human epidermal carcinoma.

Beta-carotene and canthaxanthin at concentrations of 70 or 300 microM were shown to inhibit the proliferation of cultured human squamous cells (SK-MES lung carcinoma and SCC-25 oral carcinoma) in a 5 hr cell density assay. Responses were similar for both tumor cell lines, ranging from 71-84% inhibition. In contrast, equimolar concentrations of alpha-tocopherol gave only 19-36% inhibition of SCC-25, but 50-75% inhibition of SK-MES cell density. Equimolar reduced glutathione resulted in 4-15% stimulation of SCC-25 and 22-25% inhibition of SK-MES cell proliferation. With cultured normal keratinocytes, treated final cell densities did not differ significantly from those of controls. Two additional assays measuring the metabolic generation of formazan (MTT assay) and [5-3H]thymidine incorporation were in substantial agreement with the growth inhibition pattern. Thus both continuous and cyclic cellular processes are involved in the tumor-specific response. Onset of the response to beta-carotene alone or in combination with alpha-tocopherol is signalled within 1-2 hours of treatment by the appearance of a unique 70 kD heat-shock protein.

Canthaxanthin↗
PubMed1990

The administration of beta carotene to prevent and regress oral carcinoma in the hamster cheek pouch and the associated enhancement of the immune response.

In the past four years this laboratory has utilized the hamster cheek pouch tumor model to investigate the anticancer activities of antioxidants, such as beta carotene. These molecules, which have exhibited no evidence of toxicity, have been administered systemically (oral ingestion), and locally to the tumor site in the hamster cheek pouch. The results have been either the inhibition of tumor growth, or the regression of tumor. Adjacent to the degenerating tumors a dense inflammatory infiltrate was observed. Specifically, the cytokines, tumor necrosis factor alpha, and beta, have been immunohistochemically localized to the site of regressed oral carcinoma. Recently, liposomes composed of phosphaditylcholine, phosphaditylserine, and phosphodityelanolamine were combined with beta carotene and injected locally to oral squamous cell carcinoma of the hamster. The results indicated that tumor cells accumulated the liposomes and were lysed while normal mucosal cells did not demonstrate this effect. Therefore antioxidants such as beta carotene can be localized to a tumor site, without a toxic response. Future studies on the anticancer activity of the antioxidants need to focus on the cellular and molecular changes produced in the immune effectors and in the mucosal cells following administration of the antioxidants.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1990

An animal model for mucositis induced by cancer chemotherapy.

Mucositis induced by chemotherapy is a painful and often dose-limiting side effect of cancer therapy. Furthermore, loss of the integrity of the oral epithelium often provides a microbial portal of entry and leads to sepsis. The present study describes the first animal model for chemotherapy-induced mucositis. The combination of three intraperitoneal injections of 5-fluorouracil at 5-day intervals and superficial mechanical mucosal irritation resulted in clinical breakdown of the oral mucosa characterized by ulcerative mucositis in Golden Syrian hamsters. Both clinical and histologic evaluation demonstrated that these changes were similar to those described in human beings and followed a pattern influenced by the degree of myelosuppression. This model should be of significance in establishing the stomatotoxicity of new chemotherapeutic agents, in evaluating medicaments to treat mucositis, and in studying the influence of oral mucosal breakdown on sepsis in myelosuppressed persons.

Animals↗
PubMed1990

Prevention of experimental cancer and immunostimulation by vitamin E (immunosurveillance).

Eighty young adult male Syrian hamsters were divided into four equal groups. Group 1 animals had the right buccal pouches painted with a 0.1% solution of 7,12 dimethylbenz(a)anthracene (DMBA) three times per wk for 28 wk. Group 2 animals were similarly painted with DMBA for 28 wk but were also given 140 micrograms vitamin E in 0.4 ml mineral oil three times weekly on days alternate to DMBA painting. Group 3 animals were used as DMBA-vehicle controls. Group 4 animals were vitamin E controls. Animals were killed after 28 wk, the pouches photographed and tumors counted, measured. The pouches were fixed in formalin, sectioned in paraffin and studied histologically and histochemically for tumor necrosis factors alpha and beta. All animals in Group 1 and 3 had gross tumors of the right buccal pouch. None of the animals in Group 2 had grossly visible tumors. Microscopic studies revealed that, while no gross tumors were seen in the Group 2 animals, there was histologic evidence of dysplasia and early carcinoma-in-situ undergoing degeneration. Immunohistochemical staining revealed a dense infiltrate of mononuclear cells adjacent to tumor sites with a large number of cytotoxic T lymphocytes and macrophages. Vitamin E appears to prevent tumor formation by stimulating a potent immune response to selectively destroy tumor cells as they begin to develop into recognizable microscopic foci of carcinoma.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

Detection of Ki-ras messenger RNA in normal and chemically transformed hamster oral keratinocytes.

The cheek pouch of the Syrian hamster is an excellent model for the experimental study of oral carcinogenesis. The carcinogenic chemical 7,12-dimethylbenz[a]anthracene consistently produces epidermoid carcinomas in the cheek pouch of the Syrian hamster, giving rise to characteristic histopathological lesions in a time-dependent manner. We now present experimental evidence that c-Ki-ras mRNA can be detected in all 7,12-dimethylbenz[a]anthracene-induced tumors examined (in vivo and in vitro) in this experimental oral cancer model while no detectable c-Ki-ras mRNA can be found in the normal hamster cheek pouch epithelium. Cellular synchronization experiments using a cell line (hamster cheek pouch carcinoma cell line 1) derived from one of these 7,12-dimethylbenz[a]anthracene-induced hamster oral tumors revealed that the c-Ki-ras protooncogene is expressed during the G1 phase of the cell cycle (proliferation dependent). Serum starvation and RNA synthesis inhibition experiments using hamster cheek pouch carcinoma cell line 1 cells suggest that the c-Ki-ras protooncogene is indeed quiescent in the normal hamster cheek pouch epithelium and that failure to detect its mRNA is not related to the slower proliferation of the normal epithelial cells. These results suggest that the transcription of the c-Ki-ras protooncogene is associated with malignant transformation in the cheek pouch of the Syrian hamster.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

Regression of experimental cancer by oral administration of combined alpha-tocopherol and beta-carotene.

alpha-Tocopherol (vitamin E) and beta-carotene have been shown to be capable of regressing established epidermoid carcinomas of hamster buccal pouch when injected locally into the tumor site. Neither has yet been shown to be effective in regressing cancer when administered by oral route. However, a combination of both alpha-tocopherol and beta-carotene was shown to be effective in regressing epidermoid carcinomas of hamster buccal pouch when the mixture was administered orally in vegetable oil. The epidermoid carcinomas were induced in the right buccal pouch of 100 Syrian hamsters by painting three times weekly for 14 weeks with a 0.5% solution of 7,12-dimethylbenz[a]anthracene in mineral oil. The animals were then divided into five equal groups of 20 animals. Group 1 animals received no further treatment and represented tumor controls. Group 2 animals received 200 micrograms beta-carotene and 200 micrograms dl-alpha-tocopherol acid succinate combined in 0.2 ml vegetable oil. Animals received the mixture daily by mouth using a 1-ml syringe. Groups 3 and 4 received beta-carotene and alpha-tocopherol individually in double amounts (400 micrograms in 0.2 ml vegetable oil). Group 5 animals received only the vegetable oil (0.2 ml daily) and were controls for vehicle. The animals in Groups 1, 3, 4, and 5 were killed after 22 weeks because the tumors were extensive, large, and necrotic and the animals were weak and cachectic. After 22 weeks, the tumors in Group 2 animals were small in 15 out of 20 animals. The tumors were reduced in size compared with tumor burden at 14 weeks, the point at which the beta-carotene/alpha-tocopherol was started.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

Prevention and inhibition of oral cancer in the hamster buccal pouch model associated with carotenoid immune enhancement.

Beta carotene, canthaxanthin, and a carotenoid mixture from an extract of algae were shown to prevent or inhibit the gross development of squamous cell carcinoma induced in the hamster buccal pouch by 7,12-dimethylbenz(a)anthracene. The carotenoids, dissolved in mineral oil, were administered by oral ingestion on days alternate to the carcinogen. Animals fed similar amounts of canthaxanthin, beta carotene or algae extract exhibited a statistically significant reduction in the development of tumors, both in number and size. The feeding of carotenoids, besides inhibiting gross tumor development, also produced a histologically unique picture. Microscopic areas of dysplasia, carcinoma in situ histologically unique picture. Microscopic areas of dysplasia, carcinoma in situ, or early carcinoma showed areas of tumor lysis and an inflammatory infiltrate consisting of lymphocytes and histiocytes. Characterization of this infiltrate disclosed a significant increase in cytotoxic lymphocytes, and cytotoxic macrophages producing tumor necrosis factor alpha. To confirm the presence of cytotoxic lymphocytes and macrophages a 51Cr release assay was performed. The results indicate that the immune response of the hamster was directed to the developing areas of dysplasia and carcinoma and was associated with the observations of prevention and inhibition of the growth of oral squamous cell carcinoma.

Administration, Oral↗
PubMed1988

Transforming growth factor alpha in chemically transformed hamster oral keratinocytes.

The cheek pouch of the Syrian hamster is an excellent tissue for the experimental induction of oral cancer by carcinogenic chemicals. Lysate prepared from a cell line (HCPC-1) derived from one of these hamster oral tumors greatly increased the growth of these oral tumor cells in vitro. We now show that the mitogenic substance, transforming growth factor alpha (TGF-alpha), is present in all of the chemically transformed hamster oral tumors examined (in vitro and in vivo). In no adult normal tissue of the Syrian hamster can we detect expression of TGF-alpha. TGF-alpha could be partly or wholly responsible for the mitogenic activity detected in the lysate of the chemically transformed hamster oral keratinocytes. Both normal and chemically transformed hamster oral keratinocytes express the receptor to epidermal growth factor. The consistent detection of TGF-alpha and epidermal growth factor receptor mRNAs in these hamster oral tumor cells suggests that an autocrine growth mechanism might be operative. This hamster cheek pouch oral cancer model can be used for the molecular analysis of how TGF-alpha and epidermal growth factor receptor might be involved in the malignant transformation of epithelial tissues.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1988

Tumor necrosis factor in experimental cancer regression with alphatocopherol, beta-carotene, canthaxanthin and algae extract.

Regression of established hamster buccal pouch carcinoma has recently been demonstrated in association with an induction of tumor necrosis factor alpha in macrophages. Regression of hamster buccal pouch tumors has also been demonstrated following the local injection of alphatocopherol, canthaxanthin and an extract of Spirulina-Dunaliella algae. The current study demonstrates that cancer regression is also accompanied by a significant induction of tumor necrosis factor in macrophages in the tumor area, suggesting a possible mechanism of tumor destruction. One hundred and forty young, male adult hamsters were divided into seven equal groups of 20 animals. Epidermoid carcinomas were induced in right buccal pouches by 14 weeks of painting, three times per week, of a 0.5% solution of 7,12-dimethylbenz(a)anthracene. Groups 1 and 2 were untreated and sham injected controls. Groups 3-7 had injected twice weekly into the right buccal pouches 0.1 ml (1.9 mg/ml of 13-cis-retinoic acid, canthaxanthin, algae extract, beta-carotene and alphatocopherol. After 4 weeks the tumors in groups 3-7 demonstrated varying degrees of regression and the animals were sacrificed and the right buccal pouches excised. Tumor necrosis factor alpha (TNF-alpha) was demonstrated by immunohistochemical techniques. A very significant increase in TNF-alpha positive macrophages was found in the tumor-bearing pouches of animals in groups 5-7. Smaller numbers of TNF-alpha-positive macrophages were found in group 4 pouches and a very slight increase in group 3 pouches.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1988

A light and electron microscope study of aging parotid and submandibular salivary glands of Swiss-Webster mice.

Light and electron microscope comparisons were made of parotid and submandibular glands from male Swiss-Webster white mice 3, 13, and 18 months old. The glands from the 13- and 18-month-old mice were less organized and the parenchyma was not as dense. Fibrous connective tissue, intracellular lipofuscin granules, and residual body formation increased with age. In the cells of the parotid glands of 18-month-old mice, the nucleus-to-cytoplasm ratio was greater than in the specimens from the younger two ages. The granular convoluted tubules in submandibular glands of 18-month-old mice were the smallest of all age groups. The age changes appear comparable to those of rat and human salivary glands, yet this is an inexpensive animal model that achieves old age in less time than other animal models.

Aging↗
PubMed1988

Regression of experimental oral carcinomas by local injection of beta-carotene and canthaxanthin.

Regression of 7,12-dimethylbenz[a]anthracene (DMBA)-induced epidermoid carcinomas of hamster buccal pouch was accomplished by local injections of beta-carotene and canthaxanthin. One-hundred male hamsters (2-3 months old) were divided into five groups of 20 animals. All animals had the right buccal pouches painted three times weekly for 14 weeks with a 0.5% solution of DMBA in mineral oil, at which time all animals exhibited gross tumors of variable size and number. Group 1 animals were then injected locally into the right buccal pouch twice weekly for 4 weeks with 250 micrograms-carotene in 0.1 ml minimal essential medium (MEM) per injection. Group 2 animals were similarly injected with 250 micrograms canthaxanthin in 0.1 ml MEM. Group 3 animals were similarly injected with 250 micrograms 13-cis-retinoic acid in 0.1 ml MEM. Group 4 animals were injected only with MEM; Group 5 animals were untreated controls. Animals were killed in a carbon dioxide chamber, and buccal pouches were photographed. Tumors were counted and measured. Tumor burden in each group was compared, and statistical significance between groups was recorded. beta-Carotene was more effective than canthaxanthin in tumor regression. 13-cis-Retinoic acid had no effect in this system.

9,10-Dimethyl-1,2-benzanthracene↗