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T J Slaga

Publications and source records attributed to T J Slaga.

At least 127 records · Page 7Linked to original sources
PubMed1986

Critical genetic determinants and molecular events in multistage skin carcinogenesis.

Carcinogenesis can be operationally and mechanistically divided into at least three major stages--initiation, promotion, and progression. Variations among stocks and strains of mice to susceptibility to multistage skin and liver carcinogenesis appear to be more related to alterations in tumor promotion than tumor initiation; however, the critical events have not been determined. In the mouse skin model the first stage is thought to involve the interaction of a tumor initiator with the genetic material of stem cells leading to an alteration in some aspect of growth control, differentiation, or both. The major effect of tumor promoters, regardless of the type, is the specific expansion of the initiated stem cells in the skin. This appears to occur by both direct and indirect mechanisms that involve the loss of glucocorticoid receptors, differentiation alterations, a direct growth stimulation of the initiated cells, or selective cytotoxicity. The progression stage is characterized by a high level of genetic instability that produces a number of chromosomal alterations. These changes may be responsible for the loss of the high-molecular-weight keratin proteins and filaggrin, increase in gamma-glutamyl-transpeptidase activity, and changes in oncogene expression in squamous cell carcinomas. We have found that a high percentage of squamous cell carcinomas have a trisomy in chromosome 2 that carries both src and abl genes and an increased expression of src and abl. We have also found increased Ha-ras on RNA expression in both papillomas and squamous cell carcinomas. We suggest that the genetic instability of the initiated cells is responsible for most observed changes during skin carcinogenesis.

Animals↗
PubMed1986

Evidence that a slowly cycling subpopulation of adult murine epidermal cells retains carcinogen.

The distribution and persistence of radioactively labeled benzo(a)pyrene [B(a)P] in the skin of adult female SENCAR mice were investigated by autoradiography of epidermal whole mounts and cross-sections at intervals following a single initiating application of 200 nmol of either [3H]B(a)P (2 mCi) or [14C]B(a)P (23 muCi). One day after treatment, the entire thickness of the skin was labeled; the grain density was greatest over hair follicles, sebaceous glands, and interfollicular epidermis. At 1 and 2 weeks, decreases in the nuclear grain density were consistent with the overall pattern of epidermal renewal. One month after treatment, carcinogen label-retaining cells made up approximately 2% of the interfollicular basal cells. They were also present in the hair follicles, approximately 4 and 5% of basal cells in the infundibulum and external root sheath, respectively. They were rare in the germ region and dermal papilla. Carcinogen label-retaining cells were compared with slowly cycling [3H]thymidine label-retaining cells and "maturing" basal cells, two distinct proliferative subsets of adult murine epidermis. Carcinogen label-retaining cells were found to have characteristics of the slowly cycling cells: (a) most of the carcinogen labeled nuclei were found in the central regions of the epidermal proliferative units; (b) treatment of the carcinogen label-retaining cells with 2 micrograms of 12-O-tetradecanoylphorbol-13-acetate elicited labeled mitoses within 1 day, and a general decrease in grain density over basal nuclei. In contrast, maturing basal cells 4 days after a single injection of [3H]thymidine were found at the periphery of the epidermal proliferative units. Within 1 day after treatment with 2 micrograms of 12-O-tetradecanoylphorbol-13-acetate, maturing basal cells were displaced to the suprabasal layers. Double isotope-double emulsion autoradiographs demonstrated doubly labeled cells 1 month after continuous labeling with [3H]thymidine and [14C]B(a)P and provide evidence that the radioactive carcinogen is retained by the slowly cycling [3H]thymidine label-retaining cells. These observations suggest that a slowly cycling population of epidermal cells may be relevant to the initiation phase of two-stage carcinogenesis.

Animals↗
PubMed1986

Cytogenetic evidence for gene amplification in mouse skin carcinogenesis.

Using our recently developed methodology for cytogenetic evaluation of solid tumors, we analyzed the occurrence of double minutes (DM) in chemically induced mouse skin carcinomas and papillomas. These studies revealed that DM were observed in 10% of the squamous cell carcinomas and in none of the papillomas screened. In addition, we analyzed four cell lines derived from mouse skin papillomas and one spontaneously transformed mouse epidermal cell line. The presence of DM was a consistent feature in all the studied cell lines. In the papilloma cell lines, the degree that DM occurred correlated with the cell line's capacity to form malignant tumors in immunosuppressed mice. DM were also observed in direct chromosomal preparations from tumors induced by one of the papilloma cell lines. Homogeneously staining regions were also present in metaphases from the spontaneously transformed cell line. We have shown here, for the first time, DM and homogeneously staining regions in mouse skin tumors and transformed cells derived from mouse skin. Since DM and homogeneously staining regions are the cytogenetic equivalents of gene amplification, which is a mechanism of increased expression of normal or altered gene products, these findings may play a relevant role in mouse epidermal carcinogenesis.

Animals↗
PubMed1985

Retinoyl-phorbol-acetate is a complete skin tumor promoter in SENCAR mice.

The semi-synthetic phorbol ester 12-O-retinoyl phorbol 13-acetate (RPA) was tested for activity as a complete tumor promoter, as well as for first or second stage promotion activity, in the skin of SENCAR mice. Unlike in NMRI mice where RPA has been reported to act only as a second stage promoter, in SENCAR mice it has moderate complete promoting activity as well as second stage activity. RPA also induces epidermal hyperplasia and an increase in the number of dark basal keratinocytes.

Animals↗
PubMed1985

Survival curves and incidence of neoplastic and non-neoplastic disease in SENCAR mice.

The survival curves and the incidence of spontaneous diseases were studied in a population of SENCAR mice, a stock derived by a selected breeding protocol for enhanced susceptibility to chemical carcinogenesis in the skin. SENCAR mice proved to be as long-lived as other mouse strains or stocks, including one of their parental lines, Charles River CD-1. The most frequently occurring neoplasias in SENCAR mice were lymphoma, myeloid leukemia and reticulum cell sarcoma. Other frequently occurring neoplastic diseases included lung adenomas and carcinoma and mammary gland carcinoma. However, the incidence of these tumors was not higher than the incidence in CD-1 mice or other mouse strains or stocks. A variety of non-neoplastic diseases, both inflammatory and degenerative, were also observed in old mice. The most common were liver, spleen and kidney amyloidosis, pyelonephritis and papillary necrosis. These data indicate that selective breeding for susceptibility to chemical carcinogenesis has not produced a concomitant increase in the incidence of spontaneous neoplastic and non-neoplastic disease.

Animals↗
PubMed1985

Effects of ellipticine, flavone, and 7,8-benzoflavone upon 7,12-dimethylbenz[a]anthracene, 7,14-dimethyldibenzo[a,h]anthracene and dibenzo[a,h]anthracene initiated skin tumors in mice.

Varying doses of ellipticine (EL), flavone (FL), or 7,8-benzoflavone (78BF) were applied to mouse skin 5 min before an initiating dose of 10 nmol 7,12-dimethylbenz[a]anthracene (DMBA), 47.5 nmol 7,14-dimethylbenzo[a,h]anthracene (DDBA), or 200 nmol dibenzo[a,h]anthracene (DBA) and the development of skin tumors in the mice then promoted by topical applications of 2 micrograms 12-O-tetradecanoylphorbol-13-acetate (TPA). As expected, treatment with 78BF (37 nmol or 370 nmol) markedly inhibited the skin tumor initiation by DMBA (greater than 70%). High doses of FL (4500 nmol) or EL (410 nmol) also inhibited DMBA tumorigenesis (52% and 82%, respectively) but lower doses of FL (450 nmol) or EL (4.1 nmol) stimulated DMBA tumorigenesis (greater than 40%). As was the case with DMBA initiation, the higher doses of FL or EL inhibited DDBA skin tumorigenesis and the lower doses of these two modifiers stimulated the DDBA tumorigenesis. In contrast with the results with DMBA initiation, treatment with 78BF (370 nmol or 3700 nmol) slightly enhanced DDBA tumorigenesis (22% and 6%, respectively). Treatment with EL and FL at all doses tested stimulated DBA tumorigenesis (range 4-51%), while treatment with 370 nmol 78BF slightly stimulated DBA tumorigenesis (19%) and treatment with 3700 nmol slightly inhibited DBA tumorigensis (9%). The effects of a range of 78BF doses upon skin tumor initiation by 40 nmol DMBA were also investigated. While all doses of 78BF tested (0.37-370 nmol) inhibited the DMBA tumorigenesis, the dose response was not linear; treatment with 3.7 nmol 78BF resulted in more papillomas per mouse (12.20) than did treatment with either 0.37 nmol 78BF (8.70) or 37 nmol 78BF (5.97). It is concluded that modifiers such as 78BF, FL and EL may have a variable, dose-dependent effect upon skin tumor initiation by carcinogenic polycyclic arylhydrocarbons. Some implications of this proposal are discussed.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1985

The first stage and complete promoting activity of retinoic acid but not the analog RO-10-9359.

Retinoic acid has the ability to act as either a weak first stage promoter or a weak complete promoter in the initiation-promotion protocol for skin carcinogenesis in the SENCAR mouse. The retinoid analog RO-10-9359 lacks this tumor promoting activity. Both retinoids however inhibit 12-O-tetradecanoylphorbol-13-acetate (TPA) promotion. Additional comparisons revealed that retinoic acid alone can induce dark keratinocytes, a characteristic of tumor promoters, while RO-10-9359 cannot. Retinoic acid but not RO-10-9359 can induce an immediate chemiluminescence response in human polymorphonuclear cells. Both retinoids, however, inhibit a TPA-induced response. Since the chemiluminescence response is believed to be due to oxygen free radical generation, the data suggest that the ability of retinoic acid but not RO-10-9359 to promote tumors and induce dark cells may be due to initial oxidative reactions at the cell membrane.

Animals↗
PubMed1985

Evidence that the centrally and peripherally located cells in the murine epidermal proliferative unit are two distinct cell populations.

The purpose of this investigation was to characterize the [3H]thymidine label-retaining and the "maturing" classes of basal cells from the dorsal epidermis of adult SENCAR mice and to compare their early cellular kinetic responses to topical application of the tumor promoter, 12-O-tetradecanoylphorbol-13-acetate (TPA). Autoradiography of epidermal whole mounts and cross sections demonstrated that injection of [3H]thymidine every 6 h for 1 week labeled 95% of the basal nuclei, including those in the central region of the epidermal proliferative units. One month later, the labeling index was reduced to 2%; 90% of the label-retaining cells were within a nuclear diameter of the central suprabasal column of the proliferative units. When mice were treated with 2 micrograms of TPA 1 month after labeling, mitotic label-retaining cells were found within 22 h after treatment. Seventy-five percent of the label-retaining cells remained on the basal layer through the 28-h experimental period. In contrast, the basal labeling index following a 1-h pulse of [3H]thymidine was 5%. Eighty-five percent of the labeled cells were found in the periphery of the proliferative units. By 4 days after pulse labeling, most of the originally labeled cells had divided, although vertical cross sections indicated that 92% remained on the basal layer. When mice were treated with TPA on day 4, labeled cells were rarely found in mitosis. Instead, about 60% of the labeled cells were displaced to the suprabasal layers. These observations suggest that 2 classes of epidermal basal cells have different early responses to TPA treatment: the label-retaining cells proliferate, and most of the "maturing" cells continue to differentiate.

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↗
PubMed1985

Cutaneous changes during prolonged application of 12-O-tetradecanoylphorbol-13-acetate on mouse skin and residual effects after cessation of treatment.

The epidermal and dermal effects of protracted 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment (2 micrograms TPA twice weekly) of Sencar mouse skin were studied using cell kinetics and morphometric techniques. In addition, regression of TPA-induced changes was evaluated after cessation of 56 topical applications. During the first week of treatment a reactional hyperplasia, characterized by cell damage, edema, and acute inflammation in both epidermis and dermis, occurred. This picture changed gradually during the following 3 weeks: an epidermal hyperplasia devoid of involutional or inflammatory features was accompanied by a moderate to mild chronic inflammation of the dermis and a hyperplasia of the hair follicles. This remained throughout the experimental period until the topical TPA treatment ceased. Although TPA induced papillomas in only 5% of the animals (maximum = 2 papillomas/animal and no carcinomas), all sustained marked epidermal hyperplasia of approximately 4 to 5 times the normal thickness, and increased the number and volume of hair follicles. The [3H]thymidine pulse-labeling index of the basal layer was approximately 32% (normal congruent to 6%). The level of dark keratinocytes remained constant; i.e., 8% of the basal cells were identified as dark cells during the entire experiment. At the subepidermal level the dermal thickness and total cellularity increased, although the proportion of the different cell types changed during the treatment. The mast cell population increased remarkably. After TPA treatment ceased, most of these parameters regressed abruptly during the first 2 weeks. Two to 4 months later, the epidermis was slightly thinner, and the labeling index was 50% lower than normal (2.8%). This study shows that prolonged repetitive TPA applications induced a steady-state hyperplasia without tachyphylaxis, and that this alteration regressed rapidly after treatment ceased. In addition, labeling-index values lower than normal were reached soon after normalization, suggesting that a possible selection of keratinocytes, dependent on TPA for proliferation, took place during the chronic administration of topical TPA. The number of hair follicle, capillary vessels, mast cells, and the dermal thickness never reached normal values after treatment. These important changes in the dermis and hair follicles indicate that the target cells for tumor promoters are not confined to the epidermis alone, and that these tissues could participate actively in carcinogenesis directly, either as tumor-originating tissues (hair follicles), or as inducers or helpers of neoplastic growth (connective tissue cells).

Animals↗
PubMed1984

Tumor initiating activities of 1-nitropyrene and its nitrated products in SENCAR mice.

The environmental mutagens, 1-nitropyrene, 1,3-dinitropyrene, 1,6-dinitropyrene and 1,8-dinitropyrene were evaluated for their ability to initiate skin tumors in male and female SENCAR mice. 1-Nitropyrene (greater than 99.5% purity) did not induce papilloma formation over a dose range of 0-3.0 mg/mouse after 30 weeks of promotion with 12-O-tetradecanoylphorbol-13-acetate (TPA). Systemic administration of 1-nitropyrene by i.p. injection over a dose range of 0-8.0 mg/mouse followed by topical treatment with TPA also did not induce papilloma formation. A mixture of dinitropyrenes (1,3-dinitropyrene, 1,6-dinitropyrene and 1,8-dinitropyrene (1:1.94:1.95] (99% purity) was dermally applied to SENCAR mice over a dose range of 0-2.0 mg/mouse and the mice subsequently promoted with TPA. A significant induction of papillomas was observed at 30 weeks (0.37-0.39 papillomas/mouse, 26-29% of the mice bearing tumors) at 2.0 mg/mouse. Comparison of this data with that obtained from the same mouse strain using diesel exhaust particulate extracts containing 1-nitropyrene and its nitrated products indicate that these nitrated polynuclear aromatics do not significantly contribute to the mouse skin tumorigenic activity of diesel exhaust particulate extracts.

Administration, Topical↗
PubMed1984

Mouse skin tumor-initiating activity of benz[e]aceanthrylene and benz[l]aceanthrylene in SENCAR mice.

Benz[e] aceanthrylene (B[e]A) and benz[l] aceanthrylene (B[l]A), cyclopenta-fused derivatives of benz[a]anthracene, have been reported to be active bacterial cell and mammalian cell gene mutagens. In this study they were evaluated as skin tumor initiators in both male and female SENCAR mice. Both polycyclic aromatic hydrocarbons (PAHs) induced papilloma formation in the range of 50-1000 nmol/mouse. B[l]A was the most active, being approximately 4 times as active as benzo[a]pyrene (B[a]P) while B[e]A had activity approximately equivalent to B[a]P. These results are in contrast to those reported for the air pollutant, cyclopenta[cd]pyrene, another cyclopenta-fused PAH, which is a weak mouse skin tumor initiator. We postulate that these cyclopenta-PAHs are formed by pyrosynthetic routes similar to other environmental cyclopenta-PAHs and that they may be of importance as contributors to air pollution carcinogenesis.

Air Pollutants↗
PubMed1984

The growth of cultured human foreskin keratinocytes is not stimulated by a tumor promoter.

The tumor promoter 12-O-tetradecanoyl phorbol-13-acetate (TPA) does not stimulate the growth of human epidermal cells in foreskin explant cultures; a dose-dependent inhibition is seen at doses higher than 10(-5) micrograms/ml. TPA also inhibits epidermal growth factor-stimulated growth and does not induce ornithine decarboxylase activity or increase polyamine levels. This is not due to the rapid breakdown of TPA, since TPA is not metabolized to any appreciable extent.

Cell Division↗
PubMed1984

The reduction of tumor initiating activity and cell mediated mutagenicity of dimethylbenz[a]anthracene by a copper coordination compound.

Cu(II) (3,5-diisopropyl salicylate)2 (CuDIPS) which is an anti-inflammatory copper coordination compound (mol. wt. 503) possessing superoxide dismutase (SOD) activity was tested to determine its effect on 7,12-dimethylbenz[a]anthracene (DMBA)-induced initiation of tumors in mouse skin and on mutagenicity to 6-thioguanine resistance in a mouse keratinocyte mediated Chinese hamster V-79 cell system. A single application of CuDIPS (0.4 mg/mouse) administered at a short interval before DMBA application when followed by 20 weeks of promotion by TPA reduced the mouse skin tumor yield by 55%. When DMBA-induced cell-mediated mutagenesis was tested in the presence of CuDIPS a significant reduction in the number of V-79 6-thioguanine resistant mutants was observed.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1984

Murine susceptibility to two-stage skin carcinogenesis is influenced by the agent used for promotion.

Several approaches were employed to investigate whether murine stock and strain differences in susceptibility to two-stage skin carcinogenesis are due to differences in the metabolism of the initiating aromatic hydrocarbons, or the consequences of the agents used for promotion. A cell-mediated mutagenesis assay was used to quantitatively compare the abilities of cultured newborn SENCAR, DBA/2, C57BL/6 and BALB/c keratinocytes to metabolize dimethylbenz[a]anthracene (DMBA) to mutagenic and cytotoxic metabolites. At equivalent concentrations of DMBA, throughout a 25-fold range in promutagen concentration, C57BL/6, BALB/c and SENCAR keratinocyte-dependent mutant frequencies were very similar and approximately twice DBA/2 keratinocyte-dependent mutant frequencies. In in vivo tumor studies, C57BL/6 mice were more sensitive than SENCAR mice to complete skin carcinogenesis protocols employing repetitive weekly treatments with DMBA and benzo[a]pyrene (BP). At equivalent concentrations of either DMBA or BP, C57BL/6 mice developed carcinomas sooner, and had a greater number of carcinomas per animal. SENCAR mice were very sensitive to two-stage skin carcinogenesis protocols employing BP and DMBA as initiators and benzoyl peroxide and 12-O-tetradecanoylphorbol-13-acetate (TPA) as promoters. C57BL/6 mice were relatively refractory to TPA promotion but sensitive to promotion with benzoyl peroxide. These findings suggest that murine stock and strain-dependent differences in sensitivity to two-stage skin carcinogenesis may not be due to major differences in the metabolism of the initiating hydrocarbons, but are partially the consequences of the agents used for promotion.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1984

Effects of the antiandrogen, cyproterone acetate, on the induction of papillomas, DNA synthesis and ornithine decarboxylase activity in mouse skin.

The antiandrogen, cyproterone acetate (CPA), applied simultaneously with 12-O-tetradecanoylphorbol-13-acetate (TPA) to the dorsal skin of male and female SENCAR mice initiated with 7,12-dimethylbenz[a]anthracene inhibited the production of papillomas of the skin. Although 125 and 250 micrograms of CPA had no effect on the incidence of papillomas per mouse, 500 micrograms of CPA inhibited papilloma production by 95% and 91% in female mice after 20 and 37 weeks of promotion, respectively. Testosterone propionate only partially blocked the inhibitory effect of CPA. In male mice 500 micrograms and 1 mg of CPA inhibited papilloma production by 77% and 88%, respectively. In the two-stage promotion protocol 500 micrograms of CPA was ineffective as an inhibitor when it was applied with TPA during the 1st stage but inhibited papilloma production by 71% when it was applied with mezerein during the 2nd stage. CPA was also observed to inhibit TPA-stimulated epidermal DNA synthesis and inflammation but had no effect on TPA-induced epidermal ornithine decarboxylase activity.

Androgen Antagonists↗