Project description:The study tested the hypothesis that apoptosis can prevent and control growth of neoplastic cells. Previous studies in-vitro have shown that the pro-apoptotic P2X(7) receptor regulates growth of epithelial cells. The specific objective of the present study was to understand to what degree the P2X(7) system controls development and growth of skin cancer in vivo, and what cellular and molecular mechanisms are involved in the P2X(7) action.Skin neoplasias in mice (papillomas, followed by squamous spindle-cell carcinomas) were induced by local application of DMBA/TPA. Experiments in-vitro utilized cultured epidermal keratinocytes generated from wild-type or from P2X(7)-null mice. Assays involved protein immunostaining and Western blots; mRNA real-time qPCR; and apoptosis (evaluated in situ by TUNEL and quantified in cultured keratinocytes as solubilized DNA or by ELISA). Changes in cytosolic calcium or in ethidium bromide influx (P2X(7) pore formation) were determined by confocal laser microscopy.(a) Co-application on the skin of the P2X7 specific agonist BzATP inhibited formation of DMBA/TPA-induced skin papillomas and carcinomas. At the completion of study (week 28) the proportion of living animals with cancers in the DMBA/TPA group was 100% compared to 43% in the DMBA/TPA+BzATP group. (b) In the normal skin BzATP affected mainly P2X(7)-receptor - expressing proliferating keratinocytes, where it augmented apoptosis without evoking inflammatory changes. (c) In BzATP-treated mice the degree of apoptosis was lesser in cancer than in normal or papilloma keratinocytes. (d) Levels of P2X(7) receptor, protein and mRNA were 4-5 fold lower in cancer tissues than in normal mouse tissues. (e) In cultured mouse keratinocytes BzATP induced apoptosis, formation of pores in the plasma membrane, and facilitated prolonged calcium influx. (f) The BzATP-induced apoptosis, pore-formation and augmented calcium influx had similar dose-dependence for BzATP. (g) Pore formation and the augmented calcium influx were depended on the expression of the P2X(7) receptor, while the BzATP-induced apoptosis depended on calcium influx. (h) The BzATP-induced apoptosis could be blocked by co-treatment with inhibitors of caspase-9 and caspase-3, but not of caspase-8.(a) P2X(7)-dependent apoptosis is an important mechanism that controls the development and progression of epidermal neoplasia in the mouse. (b) The P2X(7)-dependent apoptosis is mediated by calcium influx via P2X(7) pores, and involves the caspase-9 (mitochondrial) pathway. (c) The diminished pro-apoptotic effect of BzATP in mouse cancer keratinocytes is possibly the result of low expression of the P2X(7) receptor. (d) Activation of P2X(7)-dependent apoptosis, e.g. with BzATP could be a novel chemotherapeutic growth-preventive modality for papillomas and epithelial cancers in vivo.

Project description:Cancer stem cells (CSCs) have been reported in various cancers including skin squamous cell carcinoma (SCC). The molecular mechanisms regulating tumour initiation and stemness are still poorly characterized. Here, we found that Sox2, a transcription factor expressed in various types of embryonic and adult stem cells (SCs), was the most upregulated transcription factor in CSCs of squamous skin tumours. Sox2 is absent in normal epidermis and begins to be expressed in the vast majority of mouse and human pre-neoplastic skin tumours and continues to be expressed in a heterogeneous manner in invasive mouse and human SCCs. In contrast to other SCCs, in which Sox2 is frequently genetically amplified, the expression of Sox2 in mouse and human skin SCCs is transcriptionally regulated. Conditional deletion of Sox2 in the mouse epidermis dramatically decreases skin tumour formation following chemical induced carcinogenesis. Using Sox2-GFP knockin mice, we showed that Sox2 expressing cells in invasive SCC are greatly enriched in tumour propagating cells (TPCs) that further increase upon serial transplantations. Lineage ablation of Sox2 expressing cells within primary benign and malignant SCCs leads to tumour regression, consistent with the critical role of Sox2 expressing cells in tumour maintenance. Conditional Sox2 deletion in pre-existing skin papilloma and SCC leads to their regression and decreases their ability to be propagated upon transplantation into immunodeficient mice, supporting the essential role of Sox2 in regulating CSC functions. Transcriptional profiling of Sox2-GFP expressing CSC and upon Sox2 deletion uncovered a gene network regulated by Sox2 in primary tumour cells in vivo. Chromatin immunoprecipitation identified several direct Sox2 target genes controlling tumour stemness, survival, proliferation, adhesion, invasion, and paraneoplastic syndrome. Altogether, our study demonstrates that Sox2, by marking and regulating the functions of skin tumour initiating cells and CSCs, establishes a continuum between tumour initiation and progression in primary skin tumours. We used microarrays to profile tumour epithelial cells upon Sox2 deletion to uncover a gene network regulated by Sox2 in primary tumour cells in vivo. Microarray analysis was performed on FACS isolated Epcam+ a6+ TECs from 3 different biological experiments following TAM administration to K14CREER:SOX2fl/fl and control mice. Total RNA was analysed using Mouse whole genome 430 2.0 array from Affymetrix.

Project description:Cancer stem cells (CSCs) have been reported in various cancers including skin squamous cell carcinoma (SCC). The molecular mechanisms regulating tumour initiation and stemness are still poorly characterized. Here, we found that Sox2, a transcription factor expressed in various types of embryonic and adult stem cells (SCs), was the most upregulated transcription factor in CSCs of squamous skin tumours. Sox2 is absent in normal epidermis and begins to be expressed in the vast majority of mouse and human pre-neoplastic skin tumours and continues to be expressed in a heterogeneous manner in invasive mouse and human SCCs. In contrast to other SCCs, in which Sox2 is frequently genetically amplified, the expression of Sox2 in mouse and human skin SCCs is transcriptionally regulated. Conditional deletion of Sox2 in the mouse epidermis dramatically decreases skin tumour formation following chemical induced carcinogenesis. Using Sox2-GFP knockin mice, we showed that Sox2 expressing cells in invasive SCC are greatly enriched in tumour propagating cells (TPCs) that further increase upon serial transplantations. Lineage ablation of Sox2 expressing cells within primary benign and malignant SCCs leads to tumour regression, consistent with the critical role of Sox2 expressing cells in tumour maintenance. Conditional Sox2 deletion in pre-existing skin papilloma and SCC leads to their regression and decreases their ability to be propagated upon transplantation into immunodeficient mice, supporting the essential role of Sox2 in regulating CSC functions. Transcriptional profiling of Sox2-GFP expressing CSC and upon Sox2 deletion uncovered a gene network regulated by Sox2 in primary tumour cells in vivo. Chromatin immunoprecipitation identified several direct Sox2 target genes controlling tumour stemness, survival, proliferation, adhesion, invasion, and paraneoplastic syndrome. Altogether, our study demonstrates that Sox2, by marking and regulating the functions of skin tumour initiating cells and CSCs, establishes a continuum between tumour initiation and progression in primary skin tumours. We used microarrays to profile tumour epithelial cells upon Sox2 deletion to uncover a gene network regulated by Sox2 in primary tumour cells in vivo.

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Transcriptional profiles by deep sequencing (RNA-seq) of papillomas generated using the DMBA/TPA protocol from control and transgenic Nanog overexpressing mice

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