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J C Pelling

Publications and source records attributed to J C Pelling.

50 records · Page 3Linked to original sources
PubMed1988

Epidermal papillomas and carcinomas induced in uninitiated mouse skin by tumor promoters alone contain a point mutation in the 61st codon of the Ha-ras oncogene.

Previous results in a number of laboratories have demonstrated that epidermal papillomas and carcinomas induced by the two-stage protocol of initiation and promotion contain a point mutation in the 61st codon of the c-Ha-ras oncogene when the initiating agent used is 7,12-dimethylbenz[a]anthracene (DMBA). In the present report, we have analyzed DNA purified from 'spontaneously initiated' papillomas and carcinomas induced in SENCAR mouse epidermis after repetitive treatments with a tumor-promoting agent. Southern blot hybridization studies of tumor DNA digested with diagnostic restriction endonucleases demonstrated that seven of nine papillomas and carcinomas contained a point mutation in the 61st codon of one allele of the c-Ha-ras oncogene. The implications of our findings with respect to the role which a point-mutated Ha-ras proto-oncogene plays in initiation of skin tumorigenesis are discussed.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1987

Elevated expression and point mutation of the Ha-ras proto-oncogene in mouse skin tumors promoted by benzoyl peroxide and other promoting agents.

The two-stage skin carcinogenesis model of initiation and promotion in SENCAR mice has been used to examine the effects of various tumor-promoting agents on the expression of the Ha-ras oncogene in early stages of tumorigenesis in vivo. Papillomas were induced in 7,12-dimethylbenz[a]anthracene (DMBA)-initiated SENCAR mouse epidermis by (i) complete promotion with benzoyl peroxide; (ii) complete promotion with 12-O-tetradecanoyl phorbol-13-acetate (TPA); and (iii) two-stage promotion with TPA for 2 weeks followed by mezerein for 9 weeks. Results of Northern blot hybridization analyses show that early papillomas contain significantly elevated levels of Ha-ras polyadenylated [poly(A)+] RNA, irrespective of the type of tumor promotion regimen used. This pattern holds for promoters of the phorbol ester class as well as for the free radical generating agent benzoyl peroxide. Furthermore, digestion of tumor DNA with diagnostic restriction endonucleases demonstrated that 9-week-old papillomas induced by DMBA contained a point mutation in the 61st codon of one allele of the Ha-ras gene. The results represent the earliest stage in the development of a papilloma at which a Ha-ras point mutation has been reported.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1987

Benzoyl peroxide activation of protein kinase C activity in epidermal cell membranes.

We have investigated the effects of various tumor promoting agents on protein kinase C activity in adult female SENCAR mice. Topical application of benzoyl peroxide increased the calcium-independent activity of protein kinase C in the particulate fraction of basal epidermal cells while decreasing protein kinase C activity in the soluble fraction of basal epidermal cells isolated from the mice. Benzoyl peroxide apparently altered protein kinase C indirectly, as it had no direct effect on the activity of protein kinase C partially purified from bovine brain. Topical application of 12-O-tetradecanoyl phorbol-13-acetate to mouse skin resulted in increased protein kinase C activity associated with the particulate fraction of the epidermal cells with no change in the calcium-dependence of the enzyme. Since the proliferative agent ethylphenylpropiolate had no effect on protein kinase C in epidermis from SENCAR mice, the ability of benzoyl peroxide to influence protein kinase C activity in mouse skin may reflect its tumor promoting capabilities rather than its ability to induce hyperplasia.

Alkynes↗
PubMed1987

Enhanced pancreatic and skin tumorigenesis in cabbage-fed hamsters and mice.

Studies were conducted to evaluate the ability of dietary dried cabbage supplements to inhibit pancreatic carcinogenesis in hamsters and skin tumorigenesis in mice. Pancreatic cancer was induced by treatment with 40 mg/kg body wt N-nitrosobis-(2-oxopropyl)amine (BOP). Cabbage was fed from before carcinogen treatment in low fat diet and, beginning 1 week after BOP treatment, cabbage was given in low fat and high fat diets in comparison with the respective non-cabbage-containing diets. Dried cabbage was incorporated at 9 and 11% levels into the low and high fat diets. Feeding cabbage in the high fat diet elevated the yield of BOP-induced pancreatic ductular carcinoma (1.6 carcinomas/effective animal) in comparison with that observed in hamsters fed cabbage in a low fat diet or in those given a high fat diet without cabbage, 0.6-0.8 carcinomas/effective animal (P less than 0.05). Furthermore, the incidence of BOP-induced gall bladder adenocarcinoma was elevated in cabbage-fed hamsters irrespective of dietary fat intake. Effects of dietary fat and cabbage on food consumption, body weight, and serum T3 and T4 values are described. Skin tumorigenesis was induced in SENCAR mice by 10 nmol 7,12 dimethylbenz[a]anthracene (DMBA) and promoted beginning 1 week later with twice weekly applications of 2 micrograms 12-O-tetradecanoyl-13-phorbol acetate (TPA). Dried cabbage was incorporated into AIN semi-purified diets from before DMBA treatment and throughout TPA treatment. Skin papilloma yield was elevated in DMBA-initiated TPA-promoted mice that were fed diets containing 10% cabbage. Mice fed cabbage developed an average of 8.45 papillomas per mouse following 22 weeks of promotion while mice given control diet developed 7.25 papillomas per mouse (P less than 0.001). Cabbage feeding did not influence survival, food consumption or body weight of the mice. These results suggest the need for further research on the use of cabbage as a chemopreventive measure.

Animals↗
PubMed1986

The intracellular fate of [3H]benzo[a]pyrene diol epoxide diastereomers localized in vivo in SENCAR mouse epidermis: a quantitative electron microscopic study.

The intracellular localization of topically applied anti and syn diastereomers of racemic benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE) was investigated in SENCAR mouse epidermis using conventional electron microscopic (EM) autoradiography. The shaved backs of adult mice were treated in vivo with the active skin tumor initiator anti [3H]BPDE or with its stereoisomer syn [3H]BPDE, which is inactive as an initiator. After 3, 12 and 24 h of exposure, thin sections of the treated skin were prepared for high resolution autoradiography to determine the intracellular distributions of radioactivity bound within the epidermis. For each treatment and exposure time, the interfollicular area of epidermis examined by EM encompassed 350-700 keratinocytes, and extended from the basal lamina to the innermost keratinizing layer at a magnification that permitted basal and suprabasal cell populations to be distinguished in situ following autoradiography. Statistical analysis of the distributions of silver grains localized over keratinocytes at 3-, 12- and 24-h timepoints revealed that 27.2% of the carcinogenic anti [3H]BPDE grains occurred over epidermal nuclei, which was significantly more (P less than 0.001) than 20.0% of the non-carcinogenic syn [3H]BPDE grains associated with nuclei at all timepoints examined. In the basal cell population at the 3-h time point 33% of both racemic diastereomers were found within nuclei; at 12 and 24 h of exposure the nuclear association of anti [3H]BPDE grains increased (P less than 0.01) to 39% and 47% respectively, while the nuclear-associated syn [3H]BPDE grains remained at 29% and 33%. The localization of [3H]BPDE observed in our experiments suggests that the epidermal cell nucleus may be an important intracellular target for anti BPDE.

Administration, Topical↗
PubMed1986

Elevated expression of Ha-ras is an early event in two-stage skin carcinogenesis in SENCAR mice.

Alterations in the expression of the Ha-ras oncogene were investigated in SENCAR mice epidermis at various stages of initiation and promotion during two-stage skin carcinogenesis in SENCAR mice. Adult SENCAR mice were treated with 200 nmol of the (+) enantiomer of benzo[a]pyrene 7,8-diol 9,10-epoxide-anti (BPDE-anti), a potent initiating agent, followed by repetitive treatments with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA). Other mice were 'sham'-initiated with the (-) enantiomer of BPDE-anti, which is inactive as a tumor initiator. Polyadenylated RNA was isolated from pre-tumor epidermis and tumors at eight different stages of tumorigenesis and analyzed for changes in Ha-ras expression using Northern blot hybridization. Significantly enhanced levels of Ha-ras RNA were observed in TPA-promoted papillomas as early as 7 weeks after initiation. Only trace amounts of Ha-ras RNA were present in untreated epidermis or epidermis treated with the (+) or (-) enantiomer followed by 2-12 treatments with TPA (pre-papilloma stage). Southern blot hybridization of tumor DNA indicated that the increased expression of the Ha-ras oncogene was not due to gene amplification. We conclude that elevated levels of Ha-ras expression can occur at an early stage of tumor development in mouse epidermis in vivo and may play a role in tumorigenesis.

Animals↗
PubMed1985

Cellular mechanisms for tumor promotion and enhancement.

The concepts of tumor promotion discussed in this chapter demonstrate the complexity of the tumor promotion process, and illustrate the difficulty of determining which events are mechanistically important to promotion, and which ones are the result, or by-product of promotion. A number of possible mechanisms of promotion, both epigenetic and genetic, have been described on a molecular level. However, it should be stressed that none of these mechanisms is mutually exclusive; indeed, the enormous complexity of tumor promotion suggests that several of the mechanisms discussed above may very well be interrelated. The effects on epidermal differentiation, for example, may turn out to be the result of altered expression of particular oncogene whose product is actually a growth factor able to select for and amplify certain subpopulations of cells. Furthermore, the multiple steps which may occur at the molecular level, perhaps by way of sequential gene activation, serve to mirror the multiple stages which now delineate carcinogenesis in mouse skin.

Animals↗
PubMed1984

Formation and persistence of DNA, RNA, and protein adducts in mouse skin exposed to pure optical enantiomers of 7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyre ne in vivo.

The covalent binding of (+)-anti-benzo(a)pyrene-7,8-diol-9,10-epoxide [(+)-anti-BPDE], the carcinogenic metabolite of benzo(a)pyrene, and its noncarcinogenic (-) enantiomer to macromolecules was investigated in mouse skin in vivo. Levels of the adducts were measured in DNA samples isolated from the epidermis of adult Sencar mice exposed topically to (+)- and (-)-anti-BPDE for 3, 24, and 72 hr. The amount of (+)-anti-BPDE bound to epidermal DNA was approximately 3 times higher than that of the (-) enantiomer at all time points studied, with the highest level of adducts observed after 3 hr exposure. A similar time course of binding was observed in DNA purified from epidermal basal cells which were isolated from mice treated with the two enantiomers. As with the results for isolated DNA samples from whole epidermis, we also observed a 3:1 ratio of binding with (+)- and (-)-anti-BPDE in basal cell DNA. Interestingly, no significant difference in total binding between the (+) and (-) enantiomers could be detected at any time point in RNA and protein isolated from the basal cells. The formation of individual DNA adducts derived from topically applied (+)- or (-)-anti-BPDE was monitored at 3, 24, and 72 hr using high-pressure liquid chromatography. The major DNA adduct (64% of total) formed from (+)-anti-BPDE cochromatographed with marker adducts of N2-[10S-[7R,8S,9R-trihydroxy-7,8,9,10-tetrahydrobenzo(a)pyrene]yl] deoxyguanosine, while other minor adducts also were observed. With the (-)-anti-BPDE, a greater variety of DNA adducts was formed, with only 20 to 30% of the radioactivity present in high-pressure liquid chromatography chromatograms corresponding to the N2-deoxyguanosine adduct. The rate of formation and disappearance of individual adducts derived from both isomers of anti-BPDE was similar over the 72-hr time course. The results suggest that, although differences exist in total binding to DNA between the two enantiomers, they do not appear to be of sufficient magnitude to explain the marked difference in biological activity of (+)- and (-)-anti-BPDE in mouse skin.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1982

Separation of epidermal cells by density centrifugation: a new technique for studies on normal and pathological differentiation.

Murine keratinocytes, isolated by flotation trypsinization of skin, can be separated into five groups by centrifugation through Percoll, a colloidal silica gradient. Within each group a good correlation was found between density, plating efficiency, morphological appearance, DNA synthesis, and degree of keratinization/cornification. This method can be applied equally well to fetal, newborn, or adult keratinocytes and should be useful in a variety of studies including isolation of subpopulations of pathological cell types, work on chalones and hyperplastic diseases such as psoriasis, and in vitro transformation studies.

Animals↗