Search PubMed⌕ Search

Biomedical subjects

E Shtivelman

Publications and source records attributed to E Shtivelman.

At least 19 recordsLinked to original sources
PubMed2001

Metastasis suppressor CC3 inhibits angiogenic properties of tumor cells in vitro.

Resistance to apoptosis and ability to promote angiogenesis are integral features of the metastatic phenotype. Human gene CC3 is a metastasis suppressor for variant small cell lung carcinoma and a mouse melanoma in vivo. We have shown previously that metastasis-suppressing function of CC3 might be due at least in part to the ability of CC3 protein to predispose tumor cells to apoptosis. Here we demonstrate that CC3 has a previously unidentified effect on the ability of tumor cells to induce angiogenesis in vitro. Expression of CC3 in three different tumor cell lines significantly diminished their angiogenic character as manifested in the in vitro proliferation and migration assays with endothelial cells of both macro- and microvascular origin. Expression of CC3 induced changes in RNA levels of several angiogenic modulators consistent with the overall reduction in angiogenic properties. These results indicate that expression of CC3 has a dual effect on phenotype of tumor cells ultimately inhibiting their metastatic potential.

Acetyltransferases↗
PubMed2000

Alternatively spliced products CC3 and TC3 have opposing effects on apoptosis.

The human gene CC3 is a metastasis suppressor for small cell lung carcinoma (SCLC) in vivo. The ability of CC3 to impair the apoptotic resistance of tumor cells is likely to contribute to metastasis suppression. We describe here an alternatively spliced RNA of CC3, designated TC3, that encodes an unstable protein with antiapoptotic activity. TC3 and CC3 proteins share amino-terminal sequences, but TC3 has a unique short hydrophobic carboxyl terminus. Overexpression of CC3 results in massive death of rodent fibroblasts, but TC3 protects cells from CC3-induced death and from other death stimuli such as treatment with tumor necrosis factor or overexpression of Bax protein. The death-inducing activity of CC3 resides within its amino-terminal domain, which is conserved in TC3. The carboxyl terminus of TC3 is responsible for the antiapoptotic function of TC3; mutations in this domain abolish the ability of TC3 to protect cells from apoptosis. TC3 protein is short-lived due to its rapid degradation by proteasome, and it forms complexes with a regulatory subunit of proteasome known as s5alpha. The signal for the rapid degradation of TC3 resides within its carboxyl terminus, which is capable of conferring instability on a heterologous protein. The proapoptotic activity of CC3 in SCLC cells is induced by a wide variety of signals and involves disruption of the mitochondrial membrane potential (Deltapsim). The CC3 protein has sequence similarity to bacterial short-chain dehydrogenases/reductases and might represent a phylogenetically old effector of cell death similar to the recently identified apoptosis-inducing factor. CC3 and TC3 have opposing functions in apoptosis and represent a novel dual regulator of cell death.

Acetyltransferases↗
PubMed1999

Systemic gene delivery expands the repertoire of effective antiangiogenic agents.

Cationic liposome-DNA complex (CLDC)-based intravenous gene delivery targets gene expression to vascular endothelial cells, macrophages and tumor cells. We used systemic gene delivery to identify anti-angiogenic gene products effective against metastatic spread in tumor-bearing mice. Specifically, CLDC-based intravenous delivery of the p53 and GM-CSF genes were each as effective as the potent antiangiogenic gene, angiostatin, in reducing both tumor metastasis and tumor angiogenesis. Combined delivery of these genes did not increase anti-tumor activity, further suggesting that each gene appeared to produce its antimetastatic activity through a common antiangiogenic pathway. CLDC-based intravenous delivery of the human wild type p53 gene transfected up to 80% of tumor cells metastatic to lung. Furthermore, it specifically induced the expression of the potent antiangiogenic gene, thrombospondin-1, indicating that p53 gene delivery in vivo may inhibit angiogenesis by inducing endogenous thrombospondin-1 expression. CLDC-based delivery also identified a novel anti-tumor activity for the metastasis suppressor gene CC3. Thus, CLDC-based intravenous gene delivery can produce systemic antiangiogenic gene therapy using a variety of different genes and may be used to assess potential synergy of combined anti-tumor gene delivery and to identify novel activities for existing anti-tumor genes.

Angiostatins↗
PubMed1999

SCID-hu mice for the study of human cancer metastasis.

Cancer metastasis involves dynamic and multistep in vivo processes. While generation of metastatic clones requires genetic alterations in cancer cells, subsequent selection of the clones is heavily influenced by interactions with the surrounding tissue microenvironment. To reproduce the complex cellular interactions that occur in human patients is, however, difficult, and has not been achieved using currently available in vitro systems or conventional animal models. The SCID-hu mouse is generated by surgical implantation of human fetal tissues into mutant mice of the severe combined immunodeficient (SCID) phenotype. The unique feature of this model is that the implanted human tissues maintain their normal architecture and function. Therefore implanted human tissues will provide relevant microenvironments for the growth and metastasis of human cancer cells. The SCID-hu mouse model, which was specifically designed for the study of human cancer biology, enables experimental investigation of cellular events involved in cancer metastasis on the basis of interactions between human cancer cells and the human tissue microenvironment. It has been demonstrated that various types of human cancer cell lines generate tumors in implanted human bone marrow and lung, organs frequently involved in metastasis in patients, upon intravenous inoculation. Tumorigenic activity in SCID-hu mice faithfully reflects the clinical features of the original cancer. Tumor formation and selection of high tumorigenic variants occur in a species-specific manner. Furthermore, it was shown that metastatic tumor formation is regulated by both cancer cells and conditions in the host organs. Conditioning of animals by either whole-body irradiation or interleukin 1alpha treatment prior to cancer cell inoculation induced metastatic tumor formation by certain small cell lung cancer (SCLC) cell lines specifically in human bone marrow. A novel gene has been identified by comparing gene expression profiles between high and low tumorigenic SCLC cells in human lung. This gene is preferentially expressed in low metastatic lines, and transfection of the gene into highly metastatic cells results in suppression of metastasis. Recent studies have shown that the gene product is involved in the apoptosis induction pathway. Collectively, our results indicate that the SCID-hu mouse will serve as a unique platform technology with which to investigate cellular events involved in human cancer metastasis, as well as to identify genes playing important roles in the growth and metastasis of human cancer, in the context of interactions between human cancer cells and human tissue environments.

Animals↗
PubMed1997

A link between metastasis and resistance to apoptosis of variant small cell lung carcinoma.

A novel human gene CC3 with properties of a metastasis suppresor gene for small cell lung carcinoma (SCLC) is described. CC3 is an evolutionary conserved gene that is expressed ubiquitously in human tissues. CC3 RNA is absent in a subset of SCLC cell lines known as variant (v-SCLC) that are derived from tumors characterized by highly aggressive metastatic behavior. Introduction of CC3 into a variant SCLC line results in significant suppression of its metastasis in vivo. When deprived of growth factors in vitro, v-SCLC cells modified to express CC3 undergo rapid and massive cell death that at least partially could be ascribed to the activation of the apoptotic pathway. In addition, expression of CC3 in v-SCLC cells increases induction of apoptosis by chemoterapeutic drugs. Loss of CC3 in highly metastatic cells such as SCLC might render them resistant to death-inducing signals and thus help to ensure their survival under unfavorable conditions encountered in the metastatic process.

Amino Acid Sequence↗
PubMed1996

Colonization of human lung grafts in SCID-hu mice by human colon carcinoma cells.

Human colon carcinoma cell lines were examined in a colonization assay using SCID-hu mice engrafted with human fetal lung (HFL) tissues. Cell lines SW620 and COLO 320DM, derived from metastatic tumors, colonized HFL grafts after i.v. injection into SCID-hu mice. Cell lines SW480 and T34 initiated from primary colon tumors were unable to colonize HFL grafts. The ability to colonize HFL grafts but not mouse lungs of SCID-hu-L mice correctly reflects the clinical origin of these human colon carcinoma cell lines. Expression of a number of cell adhesion molecules was examined on SW480, SW620 and in vivo selected highly aggressive variants of SW620. NCAM and integrin alpha 3 expressed on the surface of SW480 cells were lost from metastatic cells, while carbohydrate ligands sialyl Lewis x and a, previously shown to be upregulated in metastatic colorectal tumors, were expressed at higher levels on colonizing cells. Unlike SW480, SW620 and its in vivo selected variants expressed RNA for calcium binding protein calbindin-D28K, a neuroendocrine marker. Acquisition of neuroendocrine features might be of potential importance in the development of the metastatic phenotype.

Animals↗
PubMed1995

Species-specific metastasis of human tumor cells in the severe combined immunodeficiency mouse engrafted with human tissue.

We have attempted to model human metastatic disease by implanting human target organs into the immunodeficient C.B-17 scid/scid (severe combined immunodeficiency; SCID) mouse, creating SCID-hu mice. Preferential metastasis to implants of human fetal lung and human fetal bone marrow occurred after i.v. injection of human small cell lung cancer (SCLC) cells into SCID-hu mice; the homologous mouse organs were spared. Clinically more aggressive variant SCLC cells metastasized more efficiently to human fetal lung implants than did cells from classic SCLC. Metastasis of variant SCLC to human fetal bone marrow was enhanced in SCID-hu mice exposed to gamma-irradiation or to interleukin 1 alpha. These data indicate that the SCID-hu mice may provide a model in which to study species- and tissue-specific steps of the human metastatic process.

Animals↗
PubMed1993

The human gene AHNAK encodes a large phosphoprotein located primarily in the nucleus.

AHNAK is a newly identified human gene notable for the exceptional size (c.a. 700 kD) and structure of its product, and for the repression of its expression in human neuroblastoma cells. Here we report the identification and partial characterization of the protein encoded by AHNAK. The protein is located principally (but not exclusively) in the nucleus and is phosphorylated on both serine and threonine. The abundance of the protein increases appreciably when cells withdraw from the division cycle, in response to either withdrawal of serum (fibroblasts) or differentiation (neuroblastoma cells). By contrast, the amount of phosphorylation appears to diminish in those settings. The considerable abundance and conjectured fibrous structure of AHNAK protein suggest a role in cytoarchitecture, but no function can yet be discerned.

Amino Acid Sequence↗
PubMed1992

A human gene (AHNAK) encoding an unusually large protein with a 1.2-microns polyionic rod structure.

We report here the identification and partial characterization of a human gene (designated AHNAK) that encodes an unusually large protein (approximately 700 kDa). AHNAK is expressed by means of a 17.5-kilobase mRNA in diverse cellular lineages but is typically repressed in cell lines derived from human neuroblastomas and in several other types of tumors. Unique-sequence domains at the two ends of the protein flank a large internal domain (approximately 4300 amino acids) composed of highly conserved repeated elements, most of which are 128 amino acids in length. The repeated elements in turn display a redundant motif, marked by the recurrence of proline at every seventh residue. Within these sequences, hydrophobic and hydrophilic residues alternate in a manner that is incompatible with a helical coiled-coil structure. Instead, we propose a structure resembling a beta-strand but with a periodicity of 2.33. The structure would engender a polyionic rod approximately 1.2 microns long. Preliminary evidence indicates that the protein resides predominantly within the nucleus, but no function has yet been discerned.

Adrenal Gland Neoplasms↗
PubMed1991

Expression of CD44 is repressed in neuroblastoma cells.

We have used cDNA subtractive cloning to identify a group of human genes that are expressed in diverse differentiated derivatives of neural crest origin but not in neuroblastoma cell lines. One of these genes was identified as CD44, which encodes an integral membrane glycoprotein that serves as the principal receptor for hyaluronate and participates in specific cell-cell and cell-extracellular matrix interactions. The repression of CD44 expression in neuroblastoma cell lines might be relevant to their high metastatic potential. We have cloned full-length cDNAs corresponding to CD44 trancscripts and identified a novel splice variant of CD44 lacking 31 amino acids of the extracellular domain. As a first step toward analysis of CD44 downregulation in neuroblastoma cells, we have mapped the CD44 RNA initiation site and analyzed the structure of the upstream regulatory region. We constructed a series of plasmids containing different amounts of CD44 upstream regulatory region linked to the bacterial chloramphenicol acetyltransferase gene and then analyzed their ability to promote transcription in neuroblastoma and melanoma cells. We found that a DNA segment including about 150 bp of the CD44 upstream region and the 5' end of the gene itself was sufficient to induce substantial transcription of the chloramphenicol acetyltransferase gene in both neuroblastoma and melanoma cells. Several upstream cis-acting elements contribute to the downregulation of CD44 in neuroblastoma cells, the most prominent being a 120-bp DNA fragment located 450 bp upstream to the RNA initiation site. Our data suggest that multiple factors might be involved in downregulation of CD44 in neuroblastoma cells.

Amino Acid Sequence↗
PubMed1990

Effects of translocations on transcription from PVT.

We have previously described a transcription unit on human chromosome 8, designated as PVT, that is consistently disrupted by the minority forms of translocations [t(2;8) and t(8;22)] in Burkitt's lymphoma. PVT begins 57 kilobase pairs downstream of the proto-oncogene MYC and is more than 200 kilobase pairs in length. In order to explore the pathogenic impact of translocations affecting PVT, we have characterized further the structure and transcription of the locus. In normal cells, PVT is transcribed into a variety of RNAs, the diversity of which remains unexplained. Alleles of PVT affected by translocations give rise to additional RNAs. These RNAs arise from a fusion of the first exon of PVT on chromosome 8 to the constant region of an immunoglobulin light chain on either chromosome 2 or chromosome 22. We have found no evidence that any of the normal or abnormal transcripts of PVT give rise to a protein. Our results suggest that the pathogenic effects of the variant translocations in Burkitt's lymphoma are not executed by a gene situated in a vicinity of the chromosomal breakpoints. Instead, our data leave open the possibility that the effects of the translocations may be mediated by activation of the relatively distant MYC gene.

Base Sequence↗
PubMed1989

Identification of a human transcription unit affected by the variant chromosomal translocations 2;8 and 8;22 of Burkitt lymphoma.

Chromosomal translocations in Burkitt lymphoma and mouse plasmacytomas typically lie within or near the protooncogene MYC. In some instances, however, these tumors contain variant translocations with breakpoints located more distant from and downstream of MYC, in a domain commonly known as pvt-1. Until now, there has been no evidence that pvt-1 marks the location of a functional gene. Here we report the identification of a large transcriptional unit in human DNA that includes pvt-1. We have designated this unit as PVT. PVT begins 57 kilobase pairs downstream of MYC and occupies a minimum of 200 kilobase pairs of DNA. Some of the translocations that occur downstream of MYC in Burkitt lymphoma transect PVT; others lie between the two genes. None of the translocations we have studied appear to enhance transcription from an intact allele of PVT (indeed, they may inactivate that transcription), but some are associated with the production of abundant and anomalous 0.8- to 1.0-kilobase RNAs that contain the 5' exon of PVT and sequences transcribed from the constant region of an immunoglobulin gene (the reciprocal participant in the translocation). Identification of PVT should facilitate the exploration of how translocations downstream of MYC and insertions of retroviral DNA in the vicinity of pvt-1 might contribute to tumorigenesis.

Base Composition↗
PubMed1989

The PVT gene frequently amplifies with MYC in tumor cells.

The line of human colon carcinoma cells known as COLO320-DM contains an amplified and abnormal allele of the proto-oncogene MYC (DMMYC). Exon 1 and most of intron 1 of MYC have been displaced from DMMYC by a rearrangement of DNA. The RNA transcribed from DMMYC is a chimera that begins with an ectopic sequence of 176 nucleotides and then continues with exons 2 and 3 of MYC. The template for the ectopic sequence represents exon 1 of a gene known as PVT, which lies 50 kilobase pairs downstream of MYC. We encountered three abnormal configurations of MYC and PVT in the cell lines analyzed here: (i) amplification of the genes, accompanied by insertion of exon 1 and an undetermined additional portion of PVT within intron 1 of MYC to create DMMYC; (ii) selective deletion of exon 1 of PVT from amplified DNA that contains downstream portions of PVT and an intact allele of MYC; and (iii) coamplification of MYC and exon 1 of PVT, but not of downstream portions of PVT. We conclude that part or all of PVT is frequently amplified with MYC and that intron 1 of PVT represents a preferred boundary for amplification affecting MYC.

Alleles↗
PubMed1988

bcr genes and transcripts.

Human chronic myelogenous leukemia (CML) is a clonal hematologic disorder. CML is characterized by the t(9:22) chromosome translocation which results in translocation of the oncogene abl from chromosome 9 into the breakpoint cluster region (bcr) gene on chromosome 22. We cloned and characterized the cDNA of the normal bcr gene. The bcr gene codes for a protein of 1271 amino acids. The open reading frame is preceded by a region high in GC. At the 5' of this region we identified several GC motifs which are probably involved in the initiation of bcr transcription. bcr transcripts of 7.0 and 4.5 kb are expressed in all cell types examined. These transcripts share all cDNA sequences analysed, including the 5' untranslated region. The latter as well as 902 or 927 amino acids are included within the CML-specific bcr-abl mRNA transcribed from the chimeric bcr-abl gene on chromosome 22. In addition to the complete bcr gene, the human genome contains 3 bcr-related genes containing the last seven exons of the intact bcr gene. One of these genes was analysed in detail and showed high sequence homology with the latter. The three bcr-related genes were probably derived from the intact gene by subsequent steps of duplication.

Base Sequence↗
PubMed1987

Mapping of four distinct BCR-related loci to chromosome region 22q11: order of BCR loci relative to chronic myelogenous leukemia and acute lymphoblastic leukemia breakpoints.

A probe derived from the 3' region of the BCR gene (breakpoint cluster region gene) detects four distinct loci in the human genome. One of the loci corresponds to the complete BCR gene, whereas the others contain a 3' segment of the gene. After HindIII cleavage of human DNA, these four loci are detected as 23-, 19-, 13-, and 9-kilobase-pair fragments, designated BCR4, BCR3, BCR2, and BCR1, respectively, with BCR1 deriving from the original complete BCR gene. All four BCR loci segregate 100% concordantly with human chromosome 22 in a rodent-human somatic cell hybrid panel and are located at chromosome region 22q11.2 by chromosomal in situ hybridization. The BCR2 and BCR4 loci are amplified in leukemia cell line K562 cells, indicating that they fall within the amplification unit that includes immunoglobulin lambda light chain locus (IGL) and ABL locus on the K562 Philadelphia chromosome (Ph1); additionally, in chronic myelogenous leukemia-derived mouse-human hybrids retaining a Ph1 chromosome in the absence of the 9q+ and normal chromosome 22, BCR2 and BCR4 loci are retained, whereas the 3' region of BCR1 and the BCR3 locus are lost, indicating that BCR3 is distal to BCR1 on chromosome 22. Similarly, in mouse-human hybrids retaining a Ph1 chromosome derived from an acute lymphoblastic leukemia-in the absence of the 9q+ and 22, only BCR2 and BCR4 loci are retained, indicating that the breakpoint in this acute lymphoblastic leukemia, as in chronic myelogenous leukemia, is proximal to the BCR1 3' region, but distal to the IGLC locus and the BCR2 and BCR4 3' loci. Thus, the order of loci on chromosome 22 is centromere----BCR2, BCR4, and IGL----BCR1----BCR3----SIS, possibly eliminating BCR2 and BCR4 loci as candidate targets for juxtaposition to the ABL gene in the acute lymphoblastic leukemia Ph1 chromosome.

Chromosome Aberrations↗
PubMed1987

bcr-abl RNA in patients with chronic myelogenous leukemia.

The major consequence of the formation of the Philadelphia (Ph1) chromosome characteristic of leukemia cells of patients with chronic myelogenous leukemia (CML) is fusion of c-abl and bcr genes. Using a sensitive RNase protection technique, we analyzed mRNA from a large number of CML patients. In most, we identified one or both species of bcr-abl chimeric transcripts. These two mRNAs vary in the specific bcr exon joined to abl exon II and are translated into slightly different proteins. The amounts of the fused mRNA within leukemia cells vary considerably between individuals and do not correlate with the phase of the disease.

Exons↗
PubMed1986

Alternative splicing of RNAs transcribed from the human abl gene and from the bcr-abl fused gene.

The primary structure of normal abl protein was determined by sequencing the coding region of its cDNA. abl contains two alternative 5' exons spliced to a common set of 3' exons to yield the two major abl RNA transcripts. These transcripts initiate in different promoter regions and give rise to proteins that vary in their N-termini. In the human cell line K562, abl is translocated from chromosome 9 to within the bcr gene on chromosome 22. Within the fused bcr-abl gene, abl exon II alternatively splices to two adjacent bcr exons. This phenomenon is seen in many patients with chronic myeloid leukemia.

Abelson murine leukemia virus↗