bromochloroacetic-acid and Cocarcinogenesis

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Benzoyl Peroxide; Cheek; Cocarcinogenesis; Cricetinae; Hyperplasia; Keratins; Mesocricetus; Mouth Mucosa; Mouth Neoplasms; Precancerous Conditions; Tetradecanoylphorbol Acetate

Protein kinase C epsilon (PKCepsilon) overexpressing transgenic (PKCepsilon Tg) mice develop papilloma-independent squamous cell carcinomas (SCC) elicited by 7,12-dimethylbenz[a]anthracene (DMBA) tumor initiation and 12-O-tetradecanoylphorbol-13-acetate (TPA) tumor promotion. We examined whether epidermal cell turnover kinetics was altered during the development of SCC in PKCepsilon Tg mice. Dorsal skin samples were fixed for histological examination. A single application of TPA resulted in extensive infiltration of polymorphonuclear neutrophils (PMNs) into the epidermis at 24 h after TPA treatment in PKCepsilon Tg mice while wild-type (WT) mouse skin showed focal infiltration by PMNs. Complete epidermal necrosis was observed at 48 h in PKCepsilon Tg mice only; at 72 h, epidermal cell regeneration beginning from hair follicles was observed in PKCepsilon Tg mice. Since the first TPA treatment to DMBA-initiated PKCepsilon Tg mouse skin led to epidermal destruction analogous to skin abrasion, we propose the papilloma-independent phenotype may be explained by death of initiated interfollicular cells originally destined to become papillomas. Epidermal destruction did not occur after multiple doses of TPA, presumably reflecting adaptation of epidermis to chronic TPA treatment. Prolonged hyperplasia in the hair follicle may result in the early neoplastic lesions originally described by Jansen et al. (2001) by expanding initiated cells in the hair follicles resulting in the subsequent development of SCC.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Carcinoma, Squamous Cell; Cell Death; Cell Differentiation; Cell Proliferation; Chemotaxis, Leukocyte; Cocarcinogenesis; Disease Models, Animal; Epidermis; Female; Hair Follicle; Hyperplasia; Keratin-10; Keratinocytes; Keratins; Mice; Mice, Transgenic; Neutrophils; Phenotype; Precancerous Conditions; Protein Kinase C-epsilon; Skin; Skin Neoplasms; Tetradecanoylphorbol Acetate; Time Factors

The erbB family of receptor tyrosine kinases, which consists of the epidermal growth factor receptor (EGFr/erbB1), erbB2 (neu), erbB3 and erbB4, has been shown to be important for both normal development as well as neoplasia. The expression of rat erbB2 was targeted to the basal layer of mouse epidermis with the bovine keratin 5 promoter. Overexpression of wild type rat erbB2 in the basal layer of epidermis led to alopecia, follicular hyperplasia and sebaceous gland enlargement as well as hyperplasia of the interfollicular epidermis. Spontaneous papillomas, some of which converted to squamous cell carcinomas, arose in homozygous erbB2 transgenic mice as early as 6 weeks of age with >90% incidence by 6 months. Analysis of several proliferation/differentiation markers indicated that erbB2 overexpression led to epidermal hyperproliferation and a possible delay in epidermal differentiation. Transgenic mice were also hypersensitive to the proliferative effects of the skin tumor promoter, 12-0-tetradecanoylphorbol-13-acetate (TPA) and were more sensitive to two-stage carcinogenesis. Elevations in EGFr and erbB2 protein as well as erbB2:EGFr and erbB2:erbB3 heterodimers were observed in skin of the erbB2 transgenic mice. Phosphotyrosine levels of the EGFr, erbB2 and erbB3 proteins were also elevated. These results indicate an important role for erbB2 signaling in epidermal growth, development and neoplasia. Oncogene (2000) 19, 4243 - 4254

Topics: Animals; Carcinogens; Carcinoma, Squamous Cell; Cattle; Cell Differentiation; Cell Division; Cell Transformation, Neoplastic; Cocarcinogenesis; Dimerization; Disease Progression; Epidermis; ErbB Receptors; Female; Gene Expression Regulation; Gene Expression Regulation, Neoplastic; Genes, erbB-2; Genes, ras; Genes, Synthetic; Hyperplasia; Keratins; Male; Mice; Mice, Inbred ICR; Mice, Transgenic; Neoplasm Proteins; Papilloma; Phosphorylation; Promoter Regions, Genetic; Protein Processing, Post-Translational; Rats; Receptor, ErbB-2; Receptor, ErbB-3; Recombinant Fusion Proteins; Signal Transduction; Skin Neoplasms; Tetradecanoylphorbol Acetate; Transgenes

Carcinogenesis involves the accumulation of genetic changes within a single cell. Tumor promotion functions in the initial clonal expansion of an initiated cell but is generally not considered to influence later stages. To investigate whether tumor promotion can influence later stages of carcinogenesis we developed a two-hit 7, 12-dimethylbenz[a]anthracene (D) protocol designed to enrich for keratinocytes that contain at least two D-induced genetic alterations. FVB/N mice were initiated with D and promoted with 12-O-tetradecanoylphorbol-13-acetate (T) or treated with acetone (A) vehicle for 6 weeks. At 7 weeks after the start of promotion, but before visible papilloma development, groups of mice were treated with a second dose of D or A and 1 week later T promotion was resumed. D/T/A/T mice developed 2.8 papillomas/mouse and D/A/D/T mice demonstrated an additive tumor response and developed 5.8 papillomas/mouse. Importantly, D/T/D/T mice developed 12.4 papillomas/mouse, thereby demonstrating a synergistic tumor response compared with D/A/D/T and D/T/A/T mice. D/T/D/T papillomas exhibited increases in suprabasal S phase cells and keratin 13 expression when compared with D/T/A/T papillomas. D/T/D/T mice developed squamous cell carcinomas (SCCs) 10 weeks earlier than D/T/A/T mice and demonstrated a 96% malignancy incidence and 1.71 SCC/mouse compared with D/T/A/T mice, which demonstrated a 28% malignancy incidence and 0.32 SCC/mouse. Greater than 90% of D/T/A/T and D/T/D/T papillomas and SCCs contained mutant Ha-ras, while a normal Ha-ras allele persisted in all cases, indicating that a gene other than the remaining normal allele of Ha-ras was a target gene for the second D hit. These data demonstrate that: (i) promotion between the first and second hits has a profound outcome on carcinogenesis, presumably by increasing the probability that a second hit will occur in a previously initiated cell; (ii) continued promotion after the second hit is required for full expression of malignancy; (iii) the classic initiation-promotion protocol can be extended to a multihit, multistage model.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Acetone; Animals; Carcinogens; Carcinoma, Squamous Cell; Cell Transformation, Neoplastic; Cocarcinogenesis; DNA Mutational Analysis; DNA, Neoplasm; Female; Gene Expression Regulation, Neoplastic; Genes, ras; Keratinocytes; Keratins; Mice; Models, Biological; Neoplasm Proteins; Papilloma; Polymerase Chain Reaction; Polymorphism, Single-Stranded Conformational; S Phase; Skin Neoplasms; Tetradecanoylphorbol Acetate

The keratin cytoskeleton is formed in different epidermal compartments by distinct polypeptides. Basal, proliferative keratinocytes express keratin (K) 5 and K14, whereas, suprabasal, post-mitotic keratinocytes express K1 and K10. Changes in this keratin pattern have been found to occur in hyperproliferative skin disorders and, in particular, throughout mouse epidermal carcinogenesis. Whereas some keratins not found in normal epidermis (K6, K16, K13, and K8) are induced at different stages of tumor development, K1 and K10 expression is lost. To determine whether K1 and K10 loss is just a consequence of the altered differentiation program or an event required for tumor progression, we generated transgenic mice carrying the human keratin 10 gene (hK10) under the control of a bovine keratin 6 gene regulatory region, which is silent in normal skin but is induced and drives transgene expression in hyperproliferative skin keratinocytes and, therefore, in skin tumors. Transgenic animals subjected to a complete carcinogenesis protocol developed tumors that contained various amounts of transgenic hK10. Although no significant difference was found in tumor number or malignancy, tumor onset was significantly delayed in transgenic mice, indicating that the presence of K10 actually impairs tumor development.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Carcinogens; Carcinoma, Squamous Cell; Cattle; Cell Division; Cocarcinogenesis; Gene Expression; Humans; Keratin-10; Keratins; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Transgenic; Skin; Skin Neoplasms; Skin Physiological Phenomena; Transgenes

Topics: Animals; Carcinogens; Cocarcinogenesis; Crosses, Genetic; DNA-Binding Proteins; Gene Expression Regulation; Genes, ras; Genetic Vectors; Keratinocytes; Keratins; Mice; Mice, Transgenic; Oncogene Protein p21(ras); Oncogene Proteins, Viral; Organ Specificity; Proto-Oncogene Proteins c-fos; Recombinant Fusion Proteins; Skin Neoplasms

XB2 cells, a teratocarcinoma derived cell line of keratinocyte lineage, have been shown to proliferate and differentiate in low calcium medium (0.03 mM Ca2+) at a density of 500 cells/9.6 cm2 without the need for fibroblast feeder layers or conditioned medium. The degree of differentiation can be assessed by measurements of keratin production and stratification of colonies of cells. Both of these parameters, as well as the proliferative capacity of the cells, can be altered by treatment of the cultures with various promoting agents and non-genotoxic carcinogens. Treatment with teleocidin and 12-O-tetradecanoyl phorbol-13-acetate induced large increases in proliferation, stratification and keratinization; mezerein-treated cells showed increased stratification at higher doses; butylated hydroxyanisole treatment resulted in hyperkeratinization and hyperstratification to lower levels than that seen with the phorbol-ester-like promoters; butylated hydroxytoluene had purely hyperproliferative effects. We suggest that this culture system may provide a useful model for studies of the mechanism of promotion and non-genotoxic carcinogenesis in epithelial tissues.

Topics: Animals; Butylated Hydroxyanisole; Butylated Hydroxytoluene; Calcium; Carcinogens; Cell Differentiation; Cell Division; Cocarcinogenesis; Diterpenes; Keratins; Lyngbya Toxins; Mice; Teratoma; Terpenes; Tetradecanoylphorbol Acetate; Tumor Cells, Cultured

Papillomas induced by standard initiation-promotion protocols progress to carcinomas at a low frequency. Experimental protocols were developed to elicit papillomas with a higher probability of malignant conversion. SENCAR mice initiated by 7,12-dimethylbenz[a]anthracene were promoted by treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) for 5, 10, 20 or 40 weeks. With promotion for 10 weeks or more, a peak of papilloma incidence at 16-20 weeks was followed by a 35-40% decrease within 3 months. A much lower papilloma response was seen in mice promoted for 5 weeks, but these papillomas persisted. The yield of malignant tumors was similar in all four groups, with 20-25 carcinomas per group of 30 mice. Thus, the papillomas induced by the first few TPA treatments are much more likely to progress to carcinomas than those which appear later. In a separate study, initiated Charles River CD-1 mice were promoted with TPA for either 12 or 52 weeks. Acetone solvent treatment was begun at Week 13 in the group treated 12 weeks with TPA. At Week 16, the papilloma incidence was identical in the two groups of mice. However, by Week 28, the papilloma yield in the continuous TPA group had increased and was twice that of the acetone group, in which papillomas had regressed. The first carcinoma arose 14 weeks earlier with continuous TPA, but the final number of carcinomas per group of 40 mice was 17 with TPA and 20 with acetone. Neither the increase in papillomas in TPA-treated mice nor the regression of papillomas after cessation of promotion with TPA affected the final carcinoma yield. This result suggests that TPA-dependent papillomas are very unlikely to progress to carcinomas. In a third experiment, promotion of initiated SENCAR mice with mezerein resulted in a small number of papillomas which had a much higher probability of progression to carcinomas than the large number of papillomas promoted by TPA. The ability to induce papillomas promoted by TPA. The ability to induce papillomas with a known probability of conversion to carcinomas will facilitate the identification of markers associated with malignant progression.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; Carcinoma; Cocarcinogenesis; Diterpenes; DNA; Female; Keratins; Mice; Mice, Inbred Strains; Papilloma; Probability; Terpenes; Tetradecanoylphorbol Acetate; Time Factors