Project description:Covering denuded dermal surface after injury requires migration, proliferation and differentiation of skin keratinocytes. To clarify the major traits controlling these intermingled biological events, we surveyed the genomic modifications occurring during the course of a scratch closure of cultured human keratinocytes. Using a DNA microarray approach, we report the identification of 161 new markers of epidermal repair. Expression data, combined with functional analysis performed with specific inhibitors of ERK, p38[MAPK] and PI3 kinases, demonstrate that kinase pathways exert very selective functions by precisely controlling the expression of specific genes. Inhibition of the ERK pathway totally blocks the wound closure and inactivates many early transcription factors and EGF-type growth factors. P38[MAPK] inhibition only delays “healing”, probably in line with the control of genes involved in the propagation of injury-initiated signalling. In contrast, PI3 kinase inhibition accelerates the scratch closure and potentiates the scratch-dependent stimulation of three genes related to epithelial cell transformation, namely HAS3, HBEGF and Ets1. Our results define in vitro human keratinocyte wound closure as a reparation process resulting from a fine balance between positive signals controlled by ERK and p38[MAPK], and negative ones triggered off by PI3 kinase. The perturbation of any of these pathways might lead to dysfunction in the healing process, as those observed in pathological wounding phenotypes, such as hypertrophic scars or keloids. Keywords: Transcriptome of healing keratinocytes
Project description:Pancreatic ductal adenocarcinoma is one of the most lethal cancers, with a 5 year-survival rate below 5%. Lack of curative treatment and failure of targeted therapies urge the need to identify novel efficient therapeutic strategy. Achievement of this goal will be obtained through the identification of diagnosis and prognosis biomarkers, identification of novel therapeutic targets and the knowledge of resistance mechanisms induced by these targeted therapies. PI3K/Akt/mTOR signalling, one of the most altered in cancers, is overactivated in pancreatic cancer and correlated with poor prognosis. In the Vertebrates, the family of class I phosphoinoitide-3-kinase (PI3K) includes four isoforms: p110α, p110β, p110δ and p110γ. Although they all perform the same biochemical reaction (phosphorylation of PIP2 in PIP3, a membrane lipid messenger), each isoform were demonstrated to have specific physiological roles. Global PI3K inhibitors are currently being tested in phase I/II clinical trials in advanced solid cancers, but show at maximal doses tolerated a limited therapeutic benefit. Isoform-selective PI3K inhibitors are currently the most promising agents because, at low doses, they are more efficient to inhibit one PI3K isoform, and thus, less toxic than pan-PI3K inhibitors. The objectives of this thesis are to determine isoform-specific PI3K roles and the therapeutic interest to target one or more isoforms in pancreatitis and PDAC, by the identification of isoform-specific pathways and the study of adaptive responses induced by targeting of one or all isoforms of PI3K. In a first part, my work has highlighted, validated and completed results obtained in the team, to demonstrate the significance of PI3K/Akt signalling in two physiological processes: chronic pancreatitis and initiation of pancreatic carcinogenesis. Precisely, the overactivation of PI3K/Akt pathway measured on human and murine chronic pancreatitis samples is correlated with a specific p110α activation gene expression signature. Moreover, genetic and pharmacologic inactivation of p110α during pancreatic chronic inflammation or cancerogenesis (by oncogenic Kras) prevents the formation of acino-ductal metaplasia, structures at the origin of pancreatic carcinogenesis initiation. Development of in vitro acino-ductal transdifferentiation protocol allowed me to demonstrate that only p110α is necessary at this initial step of pancreatic carcinogenesis by the regulation of Rho small GTPases, further regulating actin remodelling. In the second part, by a phosphoproteomic-based approach, I quantified PI3K downstream phosphorylation-regulated targets in a pancreatic cancer cell line treated or not by a pan- or selective PI3K inhibitor at different times. I demonstrated for the first time existence of targets, signalling pathways and adaptive responses regulated by each PI3K isoform. To conclude, all these results demonstrate the rational of combinatorial use of isoform-specific PI3K inhibitors in patients with pancreatic cancer for better clinical response
Project description:Epidermal keratinocytes respond to extracellular influences by activating cytoplasmic signal transduction pathways that change the transcriptional profiles of affected cells. To define responses to two such pathways, p38 and ERK, we used SB203580 and PD98059 as specific inhibitors, and identified the regulated genes after 1, 4, 24 and 48 hrs, using Affymetrix’ Hu133Av2 microarrays. Additionally, we compared genes specifically regulated by p38 and ERKs with those regulated by JNK and by all three pathways simultaneously. We find that the p38 pathway induces the expression of extracellular matrix and proliferation-associated genes, while suppressing microtubule-associated genes; the ERK pathway induces the expression of nuclear envelope and mRNA splicing proteins, while suppressing steroid synthesis and mitochondrial energy production enzymes. Both pathways promote epidermal differentiation and induce feedback inactivation of MAPK signaling. c-FOS, SRY and N-Myc appear to be the principal targets of the p38 pathway, Elk-1 SAP1 and HLH2 of ERK, while FREAC-4, ARNT and USF are common to both. The results for the first time comprehensively define the genes regulated by the p38 and ERK pathways in epidermal keratinocytes and suggest a list of targets potentially useful in therapeutic interventions. Human epidermal keratinocytes are grown in Keratinocyte Serum-Free Medium (Gibco) supplemented with 0.05 mg/ml bovine pituitary extract, 2.5 ng/ml epidermal growth factor, 0.09 mM CalCl2 and 1% penicillin/streptomycin (KGM). They are switched to Keratinocyte Serum Free-Media (Gibco) supplemented only with 1% penicillin/streptomycin (KBM) 24 h prior to commencing experiments. A set is left as controls, others treated with 5 uM JNK inhibitor SP600125, 15 uM p38 inhibitor SB203580, or 50 um ERK inhibitor PD98059. Timecourse of treated and parellel control samples over a 48 hr period was performed.
Project description:Dendritic epidermal T cells (DETC) reside in murine skin and participate in homeostasis and wound repair. Upon wounding, DETC become activated through the recognition of an unidentified ligand expressed by keratinocytes proximal to sites of injury. Such DETC activation is mediated through a monoclonal T cell receptor (TCR). Using a soluble form of this monoclonal TCR, we have shown that keratinocytes upregulate DETC TCR ligands in wounded tissue within 2 hours following wounding. Down-modulation of the ligand is seen 3 hours following wounding, and no expression is evident in non-wounded skin. In vitro studies on cell lines which express this unknown ligand indicate that antigen recognition by the DETC TCR is dependent upon N-linked glycosylation of the ligand. Given the glycosylation sensitivity of the ligand and the restricted expression following wounding, we are interested in pursuing microarray analysis to identify genes that are modulated in keratinocytes in response to wounding. Keratinocytes represent 90% of the cells in the epidermis (DETC and Langerhan’s cells make up the remaining 10%). As such, we propose to isolate RNA from whole epidermis under either wounded or resting conditions. In addition to comparing RNA from wounded and non-wounded epidermis, we would like to compare RNA from tissue that has been wounded for different times. Initially, we would like to analyze 4 sampes (non-wounded epidermis, and epidermal cells isolated 30 minutes, 2 hours, and 4 hours following wounding). These time points would correlate to a period prior to cell surface expression of ligand (30 minutes), during cell surface expression (2 hours), and following down regulation of cell surface expression (4 hours). In addition to providing possible identification of the unknown DETC TCR ligand, such analysis would provide novel information about early responses by keratinocytes in response to physical wounding in vivo. We propose to isolate RNA from whole epidermis under either wounded or resting conditions. In addition to comparing RNA from wounded and non-wounded epidermis, we would like to compare RNA from tissues that has been wounded for different times.
Project description:All cells and organisms exhibit stress-coping mechanisms to ensure survival. Cytoplasmic protein-RNA assemblies termed stress granules are increasingly recognized to promote cellular survival under stress. Thus, they might represent tumor vulnerabilities that are currently poorly explored. The translation-inhibitory eIF2α kinases are established as main drivers of stress granule assembly. Using a systems approach, we identify the translation enhancers PI3K and MAPK/p38 as pro-stress-granule-kinases. They act through the metabolic master regulator mammalian target of rapamycin complex 1 (mTORC1) to promote stress granule assembly. When highly active, PI3K is the main driver of stress granules; however, the impact of p38 becomes apparent as PI3K activity declines. PI3K and p38 thus act in a hierarchical manner to drive mTORC1 activity and stress granule assembly. Of note, this signaling hierarchy is also present in human breast cancer tissue. Importantly, only the recognition of the PI3K-p38 hierarchy under stress enabled the discovery of p38’s role in stress granule formation. In summary, we assign a new pro-survival function to the key oncogenic kinases PI3K and p38, as they hierarchically promote stress granule formation.
Project description:Scaffold protein IQGAP3 mediates assembly of multiprotein complexes, orchestrating intracellular signaling pathways. Earlier we have found it to be overexpressed in lesional psoriatic skin. IQGAP3 is involved in cell proliferation and chemokine signaling that are key processes in psoriasis, so we decided to investigate the molecular basis of its role in psoriatic phenotype of keratinocytes. Transcriptome profiling of HaCaT keratinocytes allowed us to identify a wide range of psoriasis-associated pathways to be altered in IQGAP3-knockdown cells. NFkB signaling, EGFR signaling, p38/MAPK and ERK1/ERK2 activation, lipid metabolism and cytokine production as well as the response to the inflammatory cytokine stimulation were altered in the knockdown cells. Real-time analysis of cell growth revealed the alterations of proliferation and wound healing. The balance between proliferation and apoptosis of skin cells was altered, as well as the skin barrier functions and the production of IL-6 and IFNg. However, the diversity of the pathway alterations in the knockdown cells led us to the conclusion that IQGAP3 may not be the best target for the therapeutic inhibition to normalize the phenotype of keratinocytes in psoriasis.
Project description:Epidermal keratinocytes respond to extracellular influences by activating cytoplasmic signal transduction pathways that change the transcriptional profiles of affected cells. To define responses to two such pathways, p38 and ERK, we used SB203580 and PD98059 as specific inhibitors, and identified the regulated genes after 1, 4, 24 and 48 hrs, using Affymetrix’ Hu133Av2 microarrays. Additionally, we compared genes specifically regulated by p38 and ERKs with those regulated by JNK and by all three pathways simultaneously. We find that the p38 pathway induces the expression of extracellular matrix and proliferation-associated genes, while suppressing microtubule-associated genes; the ERK pathway induces the expression of nuclear envelope and mRNA splicing proteins, while suppressing steroid synthesis and mitochondrial energy production enzymes. Both pathways promote epidermal differentiation and induce feedback inactivation of MAPK signaling. c-FOS, SRY and N-Myc appear to be the principal targets of the p38 pathway, Elk-1 SAP1 and HLH2 of ERK, while FREAC-4, ARNT and USF are common to both. The results for the first time comprehensively define the genes regulated by the p38 and ERK pathways in epidermal keratinocytes and suggest a list of targets potentially useful in therapeutic interventions.
Project description:All cells and organisms exhibit stress-coping mechanisms toensure survival. Cytoplasmic protein-RNA assemblies termedstress granules are increasingly recognized to promote cellularsurvival under stress. Thus, they might represent tumor vul-nerabilities that are currently poorly explored. The translation-inhibitory eIF2αkinases are established as main drivers ofstress granule assembly. Using a systems approach, we identifythe translation enhancers PI3K and MAPK/p38 as pro-stress-granule-kinases. They act through the metabolic master regu-lator mammalian target of rapamycin complex 1 (mTORC1) topromote stress granule assembly. When highly active, PI3K is themain driver of stress granules; however, the impact of p38becomes apparent as PI3K activity declines. PI3K and p38 thusact in a hierarchical manner to drive mTORC1 activity and stressgranule assembly. Of note, this signaling hierarchy is also presentin human breast cancer tissue. Importantly, only the recognition ofthe PI3K-p38 hierarchy under stress enabled the discovery of p38’srole in stress granule formation. In summary, we assign a new pro-survival function to the key oncogenic kinases PI3K and p38, as theyhierarchically promote stress granule formation
Project description:We assessed the effect of RNAi-mediated MAP kinase cascade signaling blockade in primary human keratinocytes. Two sets of siRNA targeting different regions of the Erk1/2 genes were used, enabling identification of off-target siRNA effects. Primary human keratinocytes were electroporated with scrambled control siRNA, a pair of siRNA oligomers against Erk1 and Erk2 (set A), or an independent pair of siRNA oligomers against Erk1 and Erk2 (set B). Four days after electroporation, RNA was harvested. Three biological replicates were performed for each of the three siRNA groups.
Project description:FGFR signalling is one of the most prominent pathways involved in cell growth and development, as well as cancer progression. FGFR1 amplification occurs in approximately 20% of all squamous cell lung carcinomas (SCC) - one of the most common subtypes of non-small cell lung carcinoma (NSCLC), indicating FGFR as a potential target for the new anti-cancer therapies. However, acquired resistance to this type of therapies remains a clinical issue. Here, we investigated the NSCLC cell lines response and potential mechanism of acquired resistance to novel selective FGFR inhibitor CPL304110. We found that despite significant genomic differences between CPL304110-sensitive cell lines, their resistant variants were characterized by upregulated p38 expression/phosphorylation, as well as enhanced expression of genes involved in MAPK signalling. We revealed that p38 inhibition restored sensitivity to CPL304110 in these cells. Moreover, overexpression of this kinase in parental cells led to impaired response to FGFR inhibition, thus confirming that p38 MAPK is a driver of resistance to a novel FGFR inhibitor. Taken together, our results provide an insight into the potential direction for NSCLC targeted therapy.