Integration of Myeloblastosis Associated Virus proviral sequences occurs in the vicinity of genes encoding signaling proteins and regulators of cell proliferation

AIMS: Myeloblastosis Associated Virus type 1 (N) [MAV 1(N)] induces specifically nephroblastomas in 8–10 weeks when injected to newborn chicken. The MAV-induced nephroblastomas constitute a unique animal model of the pediatric Wilms' tumor. We have made use of three independent nephroblastomas that represent increasing tumor grades, to identify the host DNA regions in which MAV proviral sequences were integrated. METHODS Cellular sequences localized next to MAV-integration sites in the tumor DNAs were used to screen a Bacterial Artificial Chromosomes (BACs) library and isolate BACs containing about 150 kilobases of normal DNA corresponding to MAV integration regions (MIRs). These BACs were mapped on the chicken chromosomes by Fluorescent In Situ Hybridization (FISH) and used for molecular studies. RESULTS: The different MAV integration sites that were conserved after tumor cell selection identify genes involved in the control of cell signaling and proliferation. Syntenic fragments in human DNA contain genes whose products have been involved in normal and pathological kidney development, and several oncogenes responsible for tumorigenesis in human. CONCLUSION: The identification of putative target genes for MAV provides important clues for the understanding of the MAV pathogenic potential. These studies identified ADAMTS1 as a gene upregulated in MAV-induced nephroblastoma and established that ccn3/nov is not a preferential site of integration for MAV as previously thought. The present results support our hypothesis that the highly efficient and specific MAV-induced tumorigenesis results from the alteration of multiple target genes in differentiating blastemal cells, some of which are required for the progression to highly aggressive stages. This study reinforces our previous conclusions that the MAV-induced nephroblastoma constitutes an excellent model in which to characterize new potential oncogenes and tumor suppressors involved in the establishment and maintenance of tumors

The Core Binding Factor CBF Negatively Regulates Skeletal Muscle Terminal Differentiation

BACKGROUND: Core Binding Factor or CBF is a transcription factor composed of two subunits, Runx1/AML-1 and CBF beta or CBFbeta. CBF was originally described as a regulator of hematopoiesis. METHODOLOGY/PRINCIPAL FINDINGS: Here we show that CBF is involved in the control of skeletal muscle terminal differentiation. Indeed, downregulation of either Runx1 or CBFbeta protein level accelerates cell cycle exit and muscle terminal differentiation. Conversely, overexpression of CBFbeta in myoblasts slows terminal differentiation. CBF interacts directly with the master myogenic transcription factor MyoD, preferentially in proliferating myoblasts, via Runx1 subunit. In addition, we show a preferential recruitment of Runx1 protein to MyoD target genes in proliferating myoblasts. The MyoD/CBF complex contains several chromatin modifying enzymes that inhibits MyoD activity, such as HDACs, Suv39h1 and HP1beta. When overexpressed, CBFbeta induced an inhibition of activating histone modification marks concomitant with an increase in repressive modifications at MyoD target promoters. CONCLUSIONS/SIGNIFICANCE: Taken together, our data show a new role for Runx1/CBFbeta in the control of the proliferation/differentiation in skeletal myoblasts

Acetonic Extract of Buxus sempervirens Induces Cell Cycle Arrest, Apoptosis and Autophagy in Breast Cancer Cells

Plants are an invaluable source of potential new anti-cancer drugs. Here, we investigated the cytotoxic activity of the acetonic extract of Buxus sempervirens on five breast cancer cell lines, MCF7, MCF10CA1a and T47D, three aggressive triple positive breast cancer cell lines, and BT-20 and MDA-MB-435, which are triple negative breast cancer cell lines. As a control, MCF10A, a spontaneously immortalized but non-tumoral cell line has been used. The acetonic extract of Buxus sempervirens showed cytotoxic activity towards all the five studied breast cancer cell lines with an IC50 ranging from 7.74 µg/ml to 12.5 µg/ml. Most importantly, the plant extract was less toxic towards MCF10A with an IC50 of 19.24 µg/ml. Fluorescence-activated cell sorting (FACS) analysis showed that the plant extract induced cell death and cell cycle arrest in G0/G1 phase in MCF7, T47D, MCF10CA1a and BT-20 cell lines, concomitant to cyclin D1 downregulation. Application of MCF7 and MCF10CA1a respective IC50 did not show such effects on the control cell line MCF10A. Propidium iodide/Annexin V double staining revealed a pre-apoptotic cell population with extract-treated MCF10CA1a, T47D and BT-20 cells. Transmission electron microscopy analyses indicated the occurrence of autophagy in MCF7 and MCF10CA1a cell lines. Immunofluorescence and Western blot assays confirmed the processing of microtubule-associated protein LC3 in the treated cancer cells. Moreover, we have demonstrated the upregulation of Beclin-1 in these cell lines and downregulation of Survivin and p21. Also, Caspase-3 detection in treated BT-20 and T47D confirmed the occurrence of apoptosis in these cells. Our findings indicate that Buxus sempervirens extract exhibit promising anti-cancer activity by triggering both autophagic cell death and apoptosis, suggesting that this plant may contain potential anti-cancer agents for single or combinatory cancer therapy against breast cancer

CCN3 modulates bone turnover and is a novel regulator of skeletal metastasis

The CCN family of proteins is composed of six secreted proteins (CCN1-6), which are grouped together based on their structural similarity. These matricellular proteins are involved in a large spectrum of biological processes, ranging from development to disease. In this review, we focus on CCN3, a founding member of this family, and its role in regulating cells within the bone microenvironment. CCN3 impairs normal osteoblast differentiation through multiple mechanisms, which include the neutralization of pro-osteoblastogenic stimuli such as BMP and Wnt family signals or the activation of pathways that suppress osteoblastogenesis, such as Notch. In contrast, CCN3 is known to promote chondrocyte differentiation. Given these functions, it is not surprising that CCN3 has been implicated in the progression of primary bone cancers such as osteosarcoma, Ewing’s sarcoma and chondrosarcoma. More recently, emerging evidence suggests that CCN3 may also influence the ability of metastatic cancers to colonize and grow in bone

Table ronde n° 5 : Démocratiser

Belorgey Jean-Michel, Camborieux Laure, Colas Hervé, Joliot Pierre, Lazar Philippe, Sève Lucien, Baulieu Étienne-Émile, Sellier Michèle, Dubois Véronique. Table ronde n° 5 : Démocratiser. In: Raison présente, n°147, 3e trimestre 2003. Pour un cadrage républicain de la bioéthique. pp. 105-130

The SWI/SNF Subunit/Tumor Suppressor BAF47/INI1 Is Essential in Cell Cycle Arrest upon Skeletal Muscle Terminal Differentiation

<div><p>Myogenic terminal differentiation is a well-orchestrated process starting with permanent cell cycle exit followed by muscle-specific genetic program activation. Individual SWI/SNF components have been involved in muscle differentiation. Here, we show that the master myogenic differentiation factor MyoD interacts with more than one SWI/SNF subunit, including the catalytic subunit BRG1, BAF53a and the tumor suppressor BAF47/INI1. Downregulation of each of these SWI/SNF subunits inhibits skeletal muscle terminal differentiation but, interestingly, at different differentiation steps and extents. BAF53a downregulation inhibits myotube formation but not the expression of early muscle-specific genes. BRG1 or BAF47 downregulation disrupt both proliferation and differentiation genetic programs expression. Interestingly, BRG1 and BAF47 are part of the SWI/SNF remodeling complex as well as the N-CoR-1 repressor complex in proliferating myoblasts. However, our data show that, upon myogenic differentiation, BAF47 shifts in favor of N-CoR-1 complex. Finally, BRG1 and BAF47 are well-known tumor suppressors but, strikingly, only BAF47 seems essential in the myoblasts irreversible cell cycle exit. Together, our data unravel differential roles for SWI/SNF subunits in muscle differentiation, with BAF47 playing a dual role both in the permanent cell cycle exit and in the regulation of muscle-specific genes.</p></div