Expression of the ASV src gene in hybrids between normal and virally transformed cells: Specific suppression occurs in some hybrids but not others

Dyson, Paul; Quade, Kristina; Wyke, John A.

doi:10.1016/0092-8674(82)90246-x

Cited by 39 publications

(39 citation statements)

References 47 publications

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“…It has been shown by Marshall (27) that the transformed phenotype of RSVtransformed rat cells is suppressed when the cells are hybridized with untransformed cells. The suppression of the transformed phenotype is accompanied by a decreased expression of the src gene even though the viral genome is retained in the hybrids (12,27). Therefore, it is possible that after transfection of RSV DNA into SHE cells, the expression of the v-src gene is suppressed by cellular factors.…”

Section: Resultsmentioning

confidence: 99%

Neoplastic transformation of normal and carcinogen-induced preneoplastic Syrian hamster embryo cells by the v-src oncogene.

Gilmer¹,

Annab²,

Oshimura³

et al. 1985

Mol. Cell. Biol.

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The ability of cloned Rous sarcoma virus (RSV) DNA encoding the v-src oncogene to neoplasticafly transform normal, diploid Syrian hamster embryo (SHE) cells was examined. Transfection of RSV DNA into early passage SHE cells resulted in a low but significant number of tumors when treated cells were injected into nude mice. Tumors formed with a low frequency (two tumors out of ten sites injected) and only after a long latency period (14 weeks). In contrast to the normal SHE cells, several different carcinogen-induced preneoplastic immortal SHE cell lines were highly susceptible to transformation by the v-src oncogene to the neoplastic phenotype. Tumors formed with high efficiency and a short latency period (<3 weeks). Further studies were performed to determine the basis for the inefficient transformation of the normal SHE cells. NeoR clones isolated after cotransfection of SHE cells with pSV2-neo and RSV DNAs were neither morphologically altered nor immortal and did not contain detectable levels of the v-src gene product. These results suggest that neoplastic transformation by v-src DNA in the normal cells is initially suppressed. However, cells from a v-src-induced tumor expressed v-src RNA, and antibody to v-src protein precipitated from the tumor cells a 60,000-molecular-weight protein which displayed protein kinase activity. Karyotypic analyses confirmed that the tumor was derived from Syrian hamster cells and suggested that it was clonal in nature. These results indicate that the v-src oncogene was primarily responsible for neoplastic transformation of SHE cells. In contrast to the results with the v-src oncogene, our previous studies showed that v-Ha-ras oncogene alone is unable to induce neoplastic transformation of SHE cells. Furthermore, the v-myc oncogene was able to complement v-Ha-ras to neoplastically transform SHE cells, while cotransfection with v-src plus v-myc did not increase the incidence of tumors.To understand the significance of oncogenes in neoplastic development, it is necessary to define the role of specific oncogenes in different steps of the multistep process of neoplastic progression. One experimental approach to this problem is the transfection of normal or preneoplastic cells with specific oncogenes or combinations of oncogenes to determine whether neoplastic transformation can be induced by this method. For example, Land et al. (23) To determine the universality of results obtained with a given system, it is important to compare the effects of transfection of oncogenes into different target cells. We have been studying the neoplastic progression of Syrian hamster embryo (SHE) cells in culture. This system has a number of advantages for studying the role of oncogenes in a multistep process of carcinogenesis. The normal cells have a stable karyotype and show a lower frequency of spontaneous transformation than do mouse, rat, or Chinese hamster fibroblasts (4). However, a variety of chemical carcinogens can induce morphologically transformed cells which can be isolated and cloned. The...

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Section: Resultsmentioning

confidence: 99%

Neoplastic transformation of normal and carcinogen-induced preneoplastic Syrian hamster embryo cells by the v-src oncogene.

Gilmer¹,

Annab²,

Oshimura³

et al. 1985

Mol. Cell. Biol.

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“…Transformation in the other two src-containing cell lines is suppressed in hybrids with the C-li revertant but not in hybrids with normal NIH cells. Suppression of src-related transformation in hybrids involving "normal" Swiss mouse.cells has been reported (37,38). This type of suppression may involve an inhibition of viral RNA or protein synthesis, or both, by normal mouse cells (38).. Interestingly,-Rous sarcoma virus is the only retrovirus .examined in this study that does not transform mammalian cells efficiently (45).…”

mentioning

confidence: 82%

“…It is well known that fusion of phenotypically flat cells (other than revertants) with transformed cells can often give rise to hybrid cells exhibiting a nontransformed-phenotype (22,37,38). However, Ki-MuSV is able to transform NIH/3T3 cells efficiently-at high multi, plicities of infection, essentially all of.…”

mentioning

confidence: 99%

Flat revertants isolated from Kirsten sarcoma virus-transformed cells are resistant to the action of specific oncogenes.

Noda¹,

Selinger²,

Scolnick³

et al. 1983

Proc. Natl. Acad. Sci. U.S.A.

194

129

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Two flat revertants have been isolated from mutagen-treated populations of Kirsten murine sarcoma virus (KiMuSV)-transformed NIH/3T3 cells. These revertants, which appear to be cellular variants resistant to transformation by the KiMuSV oncogene v-Ki-ras, contain Ki-MuSV-specific DNA, elevated levels of the v-Ki-ras gene product p2l, and rescuable transforming virus. Cell hybridization studies indicated that the revertant phenotype is dominant in hybrids between revertant cells and cells transformed by Ki-MuSV or the closely related Harvey MuSV and BALB MuSV. Analysis of hybrid cells resulting from the fusion of these revertants to cell lines transformed by other retroviruses showed that the action of certain oncogenes structurally unrelated to v-Ki-ras also could be suppressed. Thus, there appear to be functional relationships and diversities among transforming genes (oncogenes) not readily apparent from their structural characteristics.Recent molecular studies have defined the structure of a number of transforming genes (oncogenes) and their products in considerable detail (reviewed in ref. 1). All of the known retroviral oncogenes are closely related to sequences present in normal vertebrate cells (cellular proto-oncogenes), from which they appear to have arisen (1, 2). The viral oncogenes associated with Kirsten and Harvey murine sarcoma viruses (Ki-and Ha-MuSVs), v-Ki-ras and v-Ha-ras, for example, are known to encode similar phosphorylated 21,000-dalton proteins (designated p2ls) with guanine nucleotide-binding activities (3-6). v-Ki-ras and v-Haras are structurally related to highly conserved cellular sequences (proto-oncogenes), some of which may be associated with the etiology of certain human tumors (refs. 7 and 8; reviewed in refs. 9 and 10).In spite of the relatively large body of information concerning the molecular structure of retrovirus oncogenes and the proteins that they specify, comparatively little is known about the cellular components with which these proteins interact and the mechanism(s) by which they transform cells. The nature of the cellular components involved in the expression of transformation can be defined theoretically by the isolation and molecular characterization of flat nontransformed variants (revertants) from populations of retrovirus-transformed cells. Although a number of such flat revertants have been isolated from cells transformed by retroviruses (refs. 11-21; reviewed in ref. 22), the great majority of these has been shown to lack expression of functioning viral oncogenes. A few revertant cell lines containing apparent alterations in host cell genomes have been isolated (13, 21); however, little is known about the specific cellular factors involved in the reversion process.This report describes two cellular revertants that are resistant to transformation by Ki-MuSV and certain other retroviruses. These revertants may be used to study the mechanism of transformation by the v-Ki-ras oncogene and to reveal functional relationships among different viral oncogene...

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“…Additional experiments are required to determine whether a reduction in transforming growth factor production and secretion by flat hybrids mediates their loss of the progression phenotype. However, on the basis of the presently described studies and similar studies by other investigators (8,(15)(16)(17)37), it is clear that the effect of a specific suppressor gene from a normal cell on a tumor cell may vary from one hybrid system to another. Whether this difference is a consequence of biochemical differences in the suppressor gene products themselves or whether inherent differences exist in the cell systems analyzed remains to be determined.…”

Section: Discussionmentioning

confidence: 86%

Suppression of the progression phenotype in somatic cell hybrids occurs in the absence of altered adenovirus type 5 gene expression.

et al. 1990

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In the present study we have analyzed the genetic regulation of increased expression of transformationassociated traits, a process termed progression, in adenovirus type 5 (Ad5)-transformed secondary rat embryo cells. Somatic cell hybrids were formed between a highly progressed neomycin-resistant Ad5-transformed cloned cell line (Ell-NMT'") and an untransformed chloramphenicol-resistant rat embryo fibroblast cell line (CREFCIP). Parental Ell-NMT"e°cells grew with high efficiency in agar, exhibited reduced 125I-epidermal growth factor (EGF) binding, and were tumorigenic in nude mice. Parental CREFP cells exhibited phenotypes opposite to those of E11-NMT'e°cells. A high proportion (84%) of the presumptive hybrid cell types obtained after fusion and genetic selection (G418 and chloramphenicol) displayed a flat morphological phenotype intermediate between CREFCaP and Ell-NMTn" cells, suggesting that a trans-dominant extinction phenomenon had occurred. Two hybrids with a round morphology (R), which stil exhibited the progressed phenotype, and two hybrids with a flat morphology (F), which had lost the progressed phenotype, were chosen for detailed analysis. Both R hybrids grew efficiently in agar, exhibited low 125I-EGF binding, and were tumorigenic in nude mice, whereas both F hybrids grew poorly in agar, displayed increased 125I-EGF binding in comparison with Ell-NMTneo and R hybrids, and were nontumorigenic in nude mice. An analysis of the viral DNA integration patterns and the rates of transcription, steady-state mRNA accumulation, and relative levels of the Ad5 ElA and E1B gene products revealed no differences among the parental and hybrid cells. These studies indicate that normal CREF cells may contain a suppressor gene(s) which can inhibit the expression of specific traits of the progression phenotype in AdS-transformed cells and that this suppression is not associated with changes in the expression of AdS transforming genes.Although recent advances have led to a better understanding of the potential role of defined genetic elements in the etiology of cancer, the molecular details by which a cell becomes transformed and ultimately evolves into a population of cells possessing tumorigenic and metastatic potential have not been delineated (reviewed in references 9, 24, and 27). Transforming genes (oncogenes) have been isolated and characterized from viral and mammalian tumor cell genomes which when transferred and expressed in appropriate recipient cells display a dominant-acting phenotype (reviewed in references 2 and 4). In addition to these dominant-acting transforming genetic elements in the genomes of certain tumor cells, several lines of experimental evidence indicate that specific genes exist in normal eucaryotic cells which may function as inhibitors of expression of the transformed phenotype and tumor formation, and these have been referred to as suppressor genes, repressor genes, antioncogenes, or emerogenes (1,3,18,23,28,36). Evidence supporting the existence of suppressor genes has come from (i) the a...

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Expression of the ASV src gene in hybrids between normal and virally transformed cells: Specific suppression occurs in some hybrids but not others

Cited by 39 publications

References 47 publications

Neoplastic transformation of normal and carcinogen-induced preneoplastic Syrian hamster embryo cells by the v-src oncogene.

Neoplastic transformation of normal and carcinogen-induced preneoplastic Syrian hamster embryo cells by the v-src oncogene.

Flat revertants isolated from Kirsten sarcoma virus-transformed cells are resistant to the action of specific oncogenes.

Suppression of the progression phenotype in somatic cell hybrids occurs in the absence of altered adenovirus type 5 gene expression.

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