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427 result(s) for "Humbert, P."
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Control of tumourigenesis by the Scribble/Dlg/Lgl polarity module
The neoplastic tumour suppressors, Scribble, Dlg and Lgl, originally discovered in the vinegar fly Drosophila melanogaster, are currently being actively studied for their potential role in mammalian tumourigenesis. In Drosophila , these tumour suppressors function in a common genetic pathway to regulate apicobasal cell polarity and also play important roles in the control of cell proliferation, survival, differentiation and in cell migration/invasion. The precise mechanism by which Scribble, Dlg and Lgl function is not clear; however, they have been implicated in the regulation of signalling pathways, vesicle trafficking and in the Myosin II–actin cytoskeleton. We review the evidence for the involvement of Scribble, Dlg, and Lgl in cancer, and how the various functions ascribed to these tumour suppressors in Drosophila and mammalian systems may impact on the process of tumourigenesis.
Loss of human Scribble cooperates with H-Ras to promote cell invasion through deregulation of MAPK signalling
Activating mutations in genes of the Ras-mitogen-activated protein kinase (MAPK) pathway occur in approximately 30% of all human cancers; however, mutation of Ras alone is rarely sufficient to induce tumour development. Scribble is a polarity regulator recently isolated from a Drosophila screen for events that cooperate with Ras mutation to promote tumour progression and cell invasion. In mammals, Scribble regulates directed cell migration and wound healing in vivo ; however, no role has been identified for mammalian Scribble in oncogenic transformation. Here we show that in human epithelial cells expressing oncogenic Ras or Raf, loss of Scribble promotes invasion of cells through extracellular matrix in an organotypic culture system. Further, we show that the mechanism by which this occurs is in the regulation of MAPK signalling by Scribble. The suppression of MAPK signalling is a highly conserved function of Scribble as it also prevents Raf-mediated defects in Drosophila wing development. Our data identify Scribble as an important mediator of MAPK signalling and provide a molecular basis for the observation that Scribble expression is decreased in many invasive human cancers.
The tumour-suppressor Scribble dictates cell polarity during directed epithelial migration: regulation of Rho GTPase recruitment to the leading edge
Altered expression of human Scribble is associated with invasive epithelial cancers, however, its role in tumour development remains unclear. Mutations in Drosophila Scribble result in loss of polarity, overproliferation and 3D-tumourous overgrowth of epithelial cells. Using complementation studies in Drosophila we recently demonstrated that expression of human Scribble can also regulate polarity and restrict tissue overgrowth. Here, we have undertaken a detailed study of human Scribble function in the polarized mammary cell line, MCF10A. We show that although Scribble does not seem to be required for apical-basal polarity or proliferation control in MCF10A cells, Scribble is essential for the control of polarity associated with directed epithelial cell migration. Scribble-depleted MCF10A cells show defective in vitro wound closure and chemotactic movement. The cells at the wound edge fail to polarize, show reduced lamellipodia formation and impaired recruitment of Cdc42 and Rac1 to the leading edge. Furthermore, we show that this function is relevant in vivo as Scribble mutant mice show defective epidermal wound healing. This data identifies an essential role for mammalian Scribble in the regulation of the polarity specifically involved in directed epithelial migration.
Scrib heterozygosity predisposes to lung cancer and cooperates with KRas hyperactivation to accelerate lung cancer progression in vivo
Lung cancer is the leading cause of cancer deaths worldwide with non small-cell lung cancer (NSCLC) accounting for 80% of all lung cancers. Although activating mutations in genes of the RAS-MAPK pathway occur in up to 30% of all NSCLC, the cooperating genetic lesions that are required for lung cancer initiation and progression remain poorly understood. Here we identify a role for the cell polarity regulator Scribble (Scrib) in NSCLC. A survey of genomic databases reveals deregulation of SCRIB in human lung cancer and we show that Scrib +/− mutant mice develop lung cancer by 540 days with a penetrance of 43%. To model NSCLC development in vivo , we used the extensively characterized LSL-KRas G12D murine model of NSCLC. We show that loss of Scrib and activated oncogenic KRas cooperate in vivo, resulting in more aggressive lung tumors, likely due to a synergistic elevation in RAS–MAPK signaling. Finally, we provide data consistent with immune infiltration having an important role in the acceleration of tumorigenesis in KRas G12D lung tumors following Scrib loss.
Autophagy suppresses Ras-driven epithelial tumourigenesis by limiting the accumulation of reactive oxygen species
Activation of Ras signalling occurs in ~30% of human cancers; however, activated Ras alone is not sufficient for tumourigenesis. In a screen for tumour suppressors that cooperate with oncogenic Ras ( Ras V12 ) in Drosophila , we identified genes involved in the autophagy pathway. Bioinformatic analysis of human tumours revealed that several core autophagy genes, including GABARAP , correlate with oncogenic KRAS mutations and poor prognosis in human pancreatic cancer, supporting a potential tumour-suppressive effect of the pathway in Ras-driven human cancers. In Drosophila, we demonstrate that blocking autophagy at any step of the pathway enhances Ras V12 -driven epithelial tissue overgrowth via the accumulation of reactive oxygen species and activation of the Jun kinase stress response pathway. Blocking autophagy in Ras V12 clones also results in non-cell-autonomous effects with autophagy, cell proliferation and caspase activation induced in adjacent wild-type cells. Our study has implications for understanding the interplay between perturbations in Ras signalling and autophagy in tumourigenesis, which might inform the development of novel therapeutics targeting Ras-driven cancers.
Scribble acts as an oncogene in Eμ-myc-driven lymphoma
Scribble complex proteins maintain apicobasal polarity, regulate cell fate determination and function as tumour suppressors in epithelial tissue. Despite evidence that the function of Scribble is maintained in the lymphocyte lineage, we still understand little about its role as a tumour suppressor in haematological malignancies. Using the Eμ-myc model of Burkitt’s lymphoma we investigated the role of Scribble in lymphomagenesis. We found that contrary to its well-documented tumour suppressor role in epithelial tissue, loss of Scribble expression delayed the expansion of peripheral B cells and delayed the onset of Eμ-myc-driven lymphoma. This was despite upregulated ERK phosphorylation levels in Scribble-deficient tumours, which are associated with loss of Scribble expression and the development of more aggressive Burkitt’s lymphoma. Interestingly, the developmental stage of lymphoma was unaffected by Scribble expression challenging any role for Scribble in fate determination in the haematopoetic lineage. These data provide evidence for oncogenic properties of Scribble in Myc-driven B-cell lymphomagenesis, reinforcing recent findings that overexpression of a mutant form of Scribble can act as an oncogene in epithelial cells. Our results support the growing appreciation that the tumour regulatory functions of Scribble, and other polarity protein family members, are context dependent.
Evaluation of the Performance and Tolerance of the Combination of an HA-based Filler with Tri-Hyal Technology and a Skin Biorevitalizer on Skin Aging Parameters
Biorevitalization solutions contain numerous nutritive compounds to improve skin quality. Dermal fillers like HA (hyaluronic acid), depending on rheological characteristics, are used to fill large static defaults with a sustained long-term efficacy. Treatments with either dermal filler or biorevitalization solutions alone are not enough to bring a global facial aging approach. To demonstrate the anti-aging performance and safety of a new protocol, BIONUTRILIFT, which combined an HA-based filler with Tri-Hyal technology and a skin biorevitalizer, to target the skin quality and wrinkles correction at the same time. Eligible subjects were enrolled based on a score of 2, 3, 4, or 5 on Bazin cheek folds wrinkle scale. Safety outcomes measured were immediate and local tolerability. Performance outcomes measured included: proportion of subjects in whom the severity of cheeks folds, nasolabial folds, marionette lines, upper lip wrinkles and skin radiance remained at least one point below the baseline measurement (Bazin scale) Global Aesthetic Improvement Scale scores by subjects and investigators. In performance analyses with the combined protocol, skin radiance and cheek folds wrinkle correction sustained during the four-month study and decrease by 61% and 55%, respectively. 96% and 77% of subjects respectively showed at least a one-point decrease in the mean skin radiance score and Bazin score compared with baseline. Interestingly, the BIONUTRILIFT protocol showed the distance effect of vector A (cheek injection) and vector B (mandibular injection) on perioral zone and remained significant even 120 days after injections. Adverse events (AEs) were consistent with the expected AEsthat occurred after dermal injections. No serious AEswere recorded. BIONUTRILIFT may satisfy the subjects' demand by obtaining in the same session a simple, personalized, noninvasive, atraumatic, and reproductible technique.
Topically applied vitamin C enhances the mRNA level of collagens I and III, their processing enzymes and tissue inhibitor of matrix metalloproteinase 1 in the human dermis
Ascorbic acid (vitamin C) is a cofactor required for the function of several hydroxylases and monooxygenases. It is not synthesized in humans and some other animal species and has to be provided by diet or pharmacologic means. Its absence is responsible for scurvy, a condition related in its initial phases to a defective synthesis of collagen by the reduced function of prolylhydroxylase and production of collagen polypeptides lacking hydroxyproline, therefore, they are unable to assemble into stable triple-helical collagen molecules. In fibroblast cultures, vitamin C also stimulates collagen production by increasing the steady-state level of mRNA of collagen types I and III through enhanced transcription and prolonged half-life of the transcripts. The aim of the experimental work has been to evaluate the effect on dermal cells of a preparation of vitamin C topically applied on one side vs placebo on the other side of the dorsal face of the upper forearm of postmenopausal women. Biopsies were collected on both sides and the level of mRNA measured by non competitive reverse transcription-polymerase chain reaction made quantitative by the simultaneous transcription and amplification of synthetic RNA used as internal standards. The mRNA of collagen type I and type III were increased to a similar extent by vitamin C and that of three post-translational enzymes, the carboxy- and amino-procollagen proteinases and lysyloxidase similarly increased. The mRNA of decorin was also stimulated, but elastin, and fibrillin 1 and 2 were not modified by the vitamin. The expression of matrix metalloproteinases 1, 2, and 9 was not significantly changed, but an increased level of tissue inhibitor of matrix metalloproteinase 1 mRNA was observed without modification of tissue inhibitor of matrix metalloproteinase 2 mRNA. The stimulating activity of topical vitamin C was most conspicuous in the women with the lowest dietary intake of the vitamin and unrelated to the level of actinic damage. The results indicate that the functional activity of the dermal cells is not maximal in postmenopausal women and can be increased.
Can leg ulcer fibroblasts phenotype be influenced by human amniotic membrane extract?
Prevalence of leg ulcer in general population is important and new efficient treatments are now needed, especially for chronic leg ulcers. Human amniotic membrane (HAM) can be used as an alternative treatment for recalcitrant leg ulcers. The aim of this study is to investigate the effects of a HAM extract on normal fibroblasts (NF) and ulcer fibroblasts (UF). NF and UF were obtained from biopsies by explants technique. HAM extract was used at 10 μg of total proteins per ml. Single patient-matched NF and UF were compared, without or with HAM extract. Studied parameters were proliferation rate, retraction of free-floating lattices, alpha smooth muscle actin expression by flow cytometry, and synthesis of elastin, glycosaminoglycans (GAGs), pro-collagen I, MMP-1 and TIMP-1. Our results show that UF had a specific phenotype compared to NF: low proliferation, high expression of alpha-SM actin and high synthesis of MMP-1, TIMP-1 and elastin. HAM extract significantly increased the synthesis of GAGs, pro-collagen I and MMP-1 in NF and decreased retraction of free lattices. HAM extract transiently increased UF proliferation, slowed down lattices retraction and decreased elastin synthesis. In conclusion, HAM extract has little effect on UF for the parameters studied and NF are more responsive than UF. However, clinical beneficial effect of HAM application on leg ulcers was previously observed and might rather be related to an action on keratinocytes and/or a modulation of the highly inflammatory environment of these chronic wounds.