RESUMO
Expression of the EMT-inducing transcription factor Snail is enhanced in different human cancers. To investigate the in vivo role of Snail during progression of epithelial cancer, we used a mouse model with skin-specific overexpression of Snail. Snail transgenic mice spontaneously developed distinct histological subtypes of skin cancer, such as basal cell carcinoma, squamous cell carcinoma and sebaceous gland carcinoma. Development of sebaceous gland carcinomas strongly correlated with the direct and complete repression of Blimp-1, a central regulator of sebocyte homeostasis. Snail expression in keratinocyte stem cells significantly promotes their proliferation associated with an activated FoxM1 gene expression signature, resulting in a larger pool of Mts24-marked progenitor cells. Furthermore, primary keratinocytes expressing Snail showed increased survival and strong resistance to genotoxic stress. Snail expression in a skin-specific p53-null background resulted in accelerated formation of spontaneous tumours and enhanced metastasis. Our data demonstrate that in vivo expression of Snail results in de novo epithelial carcinogenesis by allowing enhanced survival, expansion of the cancer stem cell pool with accumulated DNA damage, a block in terminal differentiation and increased proliferation rates of tumour-initiating cells.
Assuntos
Células-Tronco Neoplásicas/metabolismo , Células-Tronco Neoplásicas/patologia , Neoplasias Cutâneas/genética , Neoplasias Cutâneas/patologia , Fatores de Transcrição/genética , Animais , Diferenciação Celular , Proliferação de Células , Progressão da Doença , Humanos , Camundongos , Camundongos Transgênicos , Metástase Neoplásica/genética , Metástase Neoplásica/patologia , Neoplasias das Glândulas Sebáceas/genética , Neoplasias das Glândulas Sebáceas/patologia , Fatores de Transcrição da Família SnailRESUMO
Transcriptional downregulation of E-cadherin appears to be an important event in the progression of various epithelial tumors. SIP1 (ZEB-2) is a Smad-interacting, multi-zinc finger protein that shows specific DNA binding activity. Here, we report that expression of wild-type but not of mutated SIP1 downregulates mammalian E-cadherin transcription via binding to both conserved E2 boxes of the minimal E-cadherin promoter. SIP1 and Snail bind to partly overlapping promoter sequences and showed similar silencing effects. SIP1 can be induced by TGF-beta treatment and shows high expression in several E-cadherin-negative human carcinoma cell lines. Conditional expression of SIP1 in E-cadherin-positive MDCK cells abrogates E-cadherin-mediated intercellular adhesion and simultaneously induces invasion. SIP1 therefore appears to be a promoter of invasion in malignant epithelial tumors.
Assuntos
Caderinas/genética , Caderinas/metabolismo , Carcinoma/patologia , Proteínas de Homeodomínio/metabolismo , Proteínas Repressoras/metabolismo , Dedos de Zinco/fisiologia , Animais , Adesão Celular/fisiologia , Linhagem Celular , Movimento Celular/fisiologia , Proteínas do Citoesqueleto/genética , Proteínas do Citoesqueleto/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/metabolismo , Regulação para Baixo/fisiologia , Células Epiteliais/citologia , Células Epiteliais/fisiologia , Regulação Neoplásica da Expressão Gênica , Proteínas de Homeodomínio/genética , Rim/citologia , Invasividade Neoplásica , RNA Mensageiro/metabolismo , Proteínas Repressoras/genética , Proteínas Smad , Fatores de Transcrição da Família Snail , Transativadores/genética , Transativadores/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Transcrição Gênica/fisiologia , Homeobox 2 de Ligação a E-box com Dedos de Zinco , beta CateninaRESUMO
Metastasin is putatively associated with cytoskeletal proteins and may influence cell motility, although its exact physiological role is not known. Because E-cadherin is an invasion suppressor molecule, and metastasin a metastasis-inducing molecule, we wondered which molecule was playing a dominant role in the balance that finally leads to noninvasiveness or invasiveness. The expression levels of E-cadherin and metastasin were monitored in two mouse tumor cell families and were found to be inversely regulated. Moreover, overexpression obtained via transfection of plasmids coding for either one of these two molecules abrogated expression of the other molecule as investigated via Northern and Western blotting experiments. Invasiveness was accordingly influenced. Expression levels of alpha- and beta-catenins were not influenced by up-regulated metastasin, but their intracellular distribution was disturbed. The present results suggest that metastasin-induced invasiveness of several malignant tumor cells is at least partially caused by down-regulation of E-cadherin.
Assuntos
Caderinas/genética , Proteínas de Ligação ao Cálcio/genética , Regulação Neoplásica da Expressão Gênica , Neoplasias Mamárias Experimentais/patologia , Proteínas S100 , Animais , Regulação para Baixo , Neoplasias Mamárias Experimentais/metabolismo , Camundongos , Invasividade Neoplásica , Proteína A4 de Ligação a Cálcio da Família S100 , Transfecção , Células Tumorais CultivadasRESUMO
Loss of E-cadherin expression has been observed both in experimental tumors and in human cancers and is related to invasiveness and poor differentiation. The E-cadherin-negative mouse mesenchymal tumor cell line MO4 was transfected with several plasmids expressing mouse E-cadherin cDNA. These plasmids differed from each other by the extent of E-cadherin-specific 3' untranslated region (UTR) sequences and by the use of different constitutive promoters. Transfectants were isolated that expressed functional E-cadherin in a homogeneous way. In syngeneic mice, such MO4-Ecad transfectants invariably produced malignant fibrosarcoma-like tumors, which were completely E-cadherin-negative at the protein level. Northern blotting revealed that E-cadherin mRNA expression was downregulated in some but not all MO4-Ecad tumors. Downregulation was caused by mRNA instability triggered by particular 3' UTR sequences. This in vivo downregulation of E-cadherin in malignant MO4-Ecad tumors turned out to be reversible and is likely to be mediated by host factors to be further identified.
