Proviral rearrangements and overexpression of a new cellular gene (nov) in myeloblastosis-associated virus type 1-induced nephroblastomas.

Abstract

Histological and anatomopathological studies performed on 152 independent myeloblastosis-associated virus type 1 (MAV1)-induced nephroblastomas allowed us to precisely define the chronology of tumor development in chickens. Three tumors representing increasing developmental stages were used to construct genomic libraries and to study both the state of proviral genomes and the sites of MAV1 integration in genomic DNA. We established that increasing levels of proviral rearrangement, eventually leading to the elimination of infectious MAV genomes, were associated with tumor progression and that 22 individual tumors, representative of different developmental stages, did not contain any common MAV1 integration site. Cloning of cellular fragments flanking the MAV1-related proviruses in tumor DNA showed that each one of eight nephroblastomas tested expressed a high level of an as yet unidentified cellular gene (nov) whose transcription is normally arrested in adult kidney cells. Cloning of the normal nov gene established that in one tumor, fused long terminal repeat-truncated nov mRNA species were expressed, indicating that at least in that case, the high level of nov expression was under the control of the MAV long terminal repeat promoter. The normal nov gene encodes a putative 32-kDa secreted polypeptide, which is a member of a new family of proteins likely to be involved in cell growth regulation. We also showed that the expression of an amino-terminal-truncated nov product in chicken embryo fibroblasts was sufficient to induce their transformation.The avian nephroblastoma induced by myeloblastosisassociated virus (MAV) is generally considered a good model for the human Wilms' tumor because of their histological similarities (i.e., embryonic tissues consisting of a heterogeneous mixture of immature and differentiated renal elements) (18,23). It is now well established that nephroblastoma development in humans is associated with deletion of at least one of two distinct genetic loci assigned to chromosome 11: llpl3 (11,27,33,40), lip15 (26,37), and alteration of a locus outside of llp (16,21,43). There is also a growing body of evidence to suggest that recessive alleles at these loci are involved in tumorigenesis. Recently, one of the candidate Wilms' tumor genes, located at the chromosome llpl3 locus within the WAGR complex, was reported to encode a potential zinc finger protein (7,13).We believe that studying MAV-induced nephroblastoma may lead to the characterization of molecular events associated with tumor development which might not be directly accessible in the human system. MAV is a replicationcompetent retrovirus responsible for the induction of nephroblastoma, osteogenic osteoblastoma (osteopetrosis), and, less frequently, lymphoid leukemia and sarcoma in chickens (48). On the basis of differences in their pathogenicity, two strains of MAV2 were identified as inducing preferentially osteopetrosis [MAV2 (0) for these two viral strains confirmed that they were genetically distinct (54), but the molecular basi...

CCN3/NOV small interfering RNA enhances fibrogenic gene expression in primary hepatic stellate cells and cirrhotic fat storing cell line CFSC

“…CCN3/NOV expression in fibroblasts was found to either negatively influence chick embryo fibroblasts or positively regulate 3T3 cell proliferation (Joliot et al 1992;Liu et al 1999). In our analysis, we demonstrated that CCN3/NOV siRNA inhibits PDGFinduced DNA synthesis in CFSC without influencing PDGF signalling and cell numbers (cf.…”

“…CCN3/NOV was originally isolated from myeloblastosisassociated virus 1-induced avian nephroblastoma (Soret et al 1989;Joliot et al 1992), representing a well established animal model of pediatric Wilms tumor. Early expression analysis of embryonic and adult livers demonstrated ccn3/ nov transcripts to be virtually absent in liver (Joliot et al 1992).…”

“…Early expression analysis of embryonic and adult livers demonstrated ccn3/ nov transcripts to be virtually absent in liver (Joliot et al 1992). Based on its expression profile, it was first speculated that ccn3/nov is a novel proto-oncogene overexpressed in nephroblastoma while the expression is probably not transforming in all tissues per se.…”

Human CYR61-mediated enhancement of bFGF-induced DNA synthesis in human umbilical vein endothelial cells

“…These secreted, cysteine-rich proteins have been named members of the`CCN family' (for Cyr61/Cef10, CTGF/Fisp12, and Nov; Bork, 1993) and include at least three distinct members: cyr61/cef10 (Simmons et al, 1989;O'Brien et al, 1990), CTGF/®sp12 (Bradham et al, 1991;Ryseck et al, 1991) and nov Joliot et al, 1992). Members of this protein family share a high level of sequence homology, including complete conservation of 38 cysteine residues in their secreted portion.…”

“…CTGF is also mitogenic for ®broblasts in culture and is expressed in dermal ®broblasts during wound healing (Igarashi et al, 1993;Frazier et al, 1996). nov was ®rst identi®ed in chicken as an aberrantly expressed gene in retrovirus-induced avian nephroblastomas (Joliot et al, 1992). An N-terminal deletion of Nov is able to transform chicken embryo ®broblasts (Joliot et al, 1992), and the human ortholog novH was found to be associated with various human tumors such as Wilm's tumor (Martinerie et al, 1994).…”