afimoxifene and Hyperplasia

Raf is one of the downstream effectors of Ras GTPases, and plays a key role in regulating cell proliferation and differentiation through the activation of MAPK. We have previously demonstrated that temporal induction of Raf in the epidermis of K14-Raf:ER transgenic mice results in epidermal hyperplasia resembling squamous cell carcinoma and psoriasis. It has been demonstrated that epidermal Stat3 activation is required for psoriasis development, since keratinocyte-specific Stat3 activation in a mouse model elicits a psoriasis-like phenotype, which is reversed by inhibition of Stat3 signaling.. The aim of this study was whether Stat3 signaling is involved in Raf-MAPK-dependent epidermal hyperplasia.. K14-Raf:ER transgenic mice, in which the 4-hydroxytamoxifen (4OHT)-responsive mutant estrogen receptor ligand binding domain-Raf fusion gene is expressed under control of the keratin 14 promoter, were mated with epidermis-specific Stat3 null mice (K5-Cre.Stat3(flox/flox)). K5-Cre.Stat3(flox/flox) mice were used to define the impact of Stat3 deficiency on Raf-induced epidermal hyperplasia.. Over-expression of Raf by 4OHT treatment in K14-Raf:ER;K5-Cre.Stat3(flox/flox) mice greatly attenuated the epidermal hyperplasia and dermal cell infiltrates compared with K14-Raf:ER;K5-Cre.Stat3(flox/WT) mice. Also, up-regulation of psoriasis-associated cytokine profiles, including VEGF, was inhibited in the skin from K14-Raf:ER;K5-Cre.Stat3(flox/flox) mice following 4OHT treatment.. These results clearly indicate that Raf-MAPK-dependent psoriatic-like epidermal hyperplasia requires Stat3 signaling in keratinocytes.

Topics: Animals; Carcinoma, Squamous Cell; Cell Differentiation; Epidermis; Gene Expression Regulation; Humans; Hyperplasia; Keratinocytes; Ligands; MAP Kinase Signaling System; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Transgenic; Mutation; Phenotype; Psoriasis; raf Kinases; Receptors, Estrogen; Signal Transduction; STAT3 Transcription Factor; Tamoxifen

Raf is one of the downstream effectors of Ras GTPases. The induction of Raf in the epidermis causes the proliferation of keratinocytes and epidermal hyperplasia. However, skin inflammation accompanying Ras-induced epidermal reactions has not been fully delineated.. The aim of this study was to characterize inflammatory reactions induced by epidermal-specific Raf expression and to elucidate its role in skin inflammation.. K14-Raf:ER transgenic mice, in which the 4-hydroxytamoxifen (4OHT)-responsive mutant estrogen receptor (ER) ligand binding domain-Raf fusion gene was expressed under control of the keratin 14 promoter, were used to characterize inflammatory reactions induced by Raf expression in the epidermis.. A single topical application of 4OHT induced the expression of phosphorylated extracellular signal-related kinase 1/2 and elicited neutrophil-dominant inflammatory infiltrates in the skin. The Raf expression also rapidly induced the production of several cytokines and chemokines, including VEGF and CXCL1, by keratinocytes and inmouse skin in vivo. Furthermore, CD4-positive cells from regional lymph nodes had the potential to differentiate into IFNg- and IL17-producing cells. Treatment with an anti-Gr-1 antibody diminished the Raf-induced cutaneous inflammation and partially reversed the epidermal hyperplasia and hyperkeratosis.. Activation of the Raf signaling pathway is involved in the epidermal hyperplasia and the neutrophil-dominant cutaneous inflammatory reactions which are characteristics of psoriasis.

Topics: Animals; CD4 Antigens; Chemokine CXCL1; Epidermis; Extracellular Signal-Regulated MAP Kinases; Humans; Hyperplasia; Interferon-gamma; Interleukin-17; Keratin-14; Lymph Nodes; Mice; Mice, Inbred C57BL; Mice, Transgenic; Neutrophils; Promoter Regions, Genetic; Psoriasis; raf Kinases; Receptors, Estrogen; Tamoxifen; Vascular Endothelial Growth Factor A

Phenotypic switching of smooth muscle cells (SMCs) plays a key role in vascular proliferative diseases. We previously showed that Krüppel-like factor 4 (Klf4) suppressed SMC differentiation markers in cultured SMCs. Here, we derive mice deficient for Klf4 by conditional gene ablation and analyze their vascular phenotype following carotid injury. Klf4 expression was rapidly induced in SMCs of control mice after vascular injury but not in Klf4-deficient mice. Injury-induced repression of SMC differentiation markers was transiently delayed in Klf4-deficient mice. Klf4 mutant mice exhibited enhanced neointimal formation in response to vascular injury caused by increased cellular proliferation in the media but not an altered apoptotic rate. Consistent with these findings, cultured SMCs overexpressing Klf4 showed reduced cellular proliferation, in part, through the induction of the cell cycle inhibitor, p21(WAF1/Cip1) via increased binding of Klf4 and p53 to the p21(WAF1/Cip1) promoter/enhancer. In vivo chromatin immunoprecipitation assays also showed increased Klf4 binding to the promoter/enhancer regions of the p21(WAF1/Cip1) gene and SMC differentiation marker genes following vascular injury. Taken together, we have demonstrated that Klf4 plays a critical role in regulating expression of SMC differentiation markers and proliferation of SMCs in vivo in response to vascular injury.

Topics: Animals; Carotid Artery Injuries; Cell Differentiation; Cell Division; Crosses, Genetic; Cyclin-Dependent Kinase Inhibitor p21; Gene Expression Regulation; Humans; Hyperplasia; Kruppel-Like Factor 4; Kruppel-Like Transcription Factors; Ligation; Mice; Mice, Inbred C57BL; Mice, Knockout; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Recombinant Fusion Proteins; Tamoxifen; Transcription, Genetic; Tunica Intima

Various common signaling pathways maintain tissue stem cells, including Notch and Wnt/beta-catenin signals. Phosphoinositide-3 kinase (PI3K)/Akt signaling regulates the 'stemness' of several stem cells in culture, specifically in maintaining embryonic stem and neural stem cells, and in deriving embryonic germ cells from primordial germ cells. We examined the effect of Akt signaling in epidermal cells in transgenic mice expressing an Akt-Mer fusion protein whose kinase activity was conditionally activated by treatment with 4-hydroxytamoxifen (4OHT). The topical application of 4OHT to adult skin of the transgenic mice induced new hair growth in resting phase follicles. In addition, the mice showed hyperplasia in interfollicular epidermis (IFE) and hair follicles, which was presumably caused by the extensive proliferation of keratinocytes in basal layer of IFE and outer root sheath of hair follicles, respectively. The progenitor cell population increased consistently in 4OHT-treated transgenic mice. Our results show that PI3K/Akt signaling induces epidermal hyperplasia and proliferation of epidermal progenitors.

Topics: Animals; Animals, Newborn; Antigens, CD34; Binding Sites; Cell Proliferation; Enzyme Activation; Epidermis; Ethanol; Flow Cytometry; Hair Follicle; Hyperplasia; Integrin alpha6; Keratinocytes; Mice; Mice, Transgenic; Proto-Oncogene Proteins c-akt; Receptors, Estrogen; Recombinant Fusion Proteins; Signal Transduction; Skin; Stem Cells; Tamoxifen

The protooncogene c-myc regulates cell growth, differentiation, and apoptosis, and its aberrant expression is frequently observed in human cancer. However, the consequences of activating c-Myc in an adult tissue, in which these cellular processes are part of normal homeostasis, remain unknown. In order to achieve this, we have targeted expression of a switchable form of the c-Myc protein to the skin epidermis, a well characterized homeostatic tissue. We show that activation of c-MycER in adult suprabasal epidermis rapidly triggers proliferation and disrupts differentiation of postmitotic keratinocytes. Sustained activation of c-Myc is sufficient to induce papillomatosis together with angiogenesis--changes that resemble hyperplastic actinic keratosis, a commonly observed human precancerous epithelial lesion. All these premalignant changes spontaneously regress upon deactivation of c-MycER.

Topics: Animals; Cell Differentiation; Cell Division; Epidermis; Estrogen Antagonists; Gene Expression Regulation, Neoplastic; Hair Follicle; Humans; Hyperplasia; Keratinocytes; Male; Mice; Mice, Inbred C57BL; Mice, Inbred CBA; Mice, Transgenic; Neovascularization, Pathologic; Papilloma; Phenotype; Proto-Oncogene Proteins c-myc; Skin Neoplasms; Tamoxifen