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Biomedical subjects

G Symonds

Publications and source records attributed to G Symonds.

At least 19 recordsLinked to original sources
PubMed1992

An in vitro fibroblast model system to study myc-driven tumour progression.

We have utilized fibroblast cell lines to investigate myc-mediated cell transformation and tumour progression. Deregulated myc alleles were introduced into the rat fibroblast cell line, Rat-1, and a partially-transformed derivative of this cell line termed Rat-1 (PT). A human c-myc gene coupled to the Moloney murine leukemia virus long terminal repeat was introduced into both cell lines by transfection. The avian MC29 v-myc gene was introduced into the Rat-1 cell line by retroviral infection using a Moloney murine leukemia recombinant retrovirus. For both cell lines, the introduction of exogenous myc genes resulted in an increased degree of transformation. For the non-tumorigenic Rat-1 cell line, this also resulted in the acquisition of tumorigenicity, while for the Rat-1 (PT) cell line the degree of tumorigenicity was increased. Various clones were isolated and, for both human c-myc and avian v-myc, the level of myc expression correlated with the degree of transformation and the tumorigenic potential of the cell lines. In addition, both these parameters could be increased by passaging through syngeneic recipients. Our data show that tumour progression may be driven by the deregulated expression of myc genes; that transformation and tumorigenicity correlate with the level of exogenous myc expression; that additional events involving both in vitro and in vivo selection are involved in this process; and that myc expression may increase the cells' metastatic capacity.

Animals↗
PubMed1992

Both myeloproliferative disease and leukemia are induced by transplantation of bone marrow cells expressing v-myc.

An in vivo system has been established to investigate v-myc-induced hematopoietic neoplasia in mice. A Moloney murine leukemia virus (Mo-MLV)-derived recombinant retrovirus containing v-myc was used to infect immature bone marrow cells, and these cells were then transplanted into lethally irradiated recipients. All provirus-positive reconstituted mice were found to develop hematopoietic proliferative disorders and, in certain cases, overt leukemia--myeloblastic, myelomonocytic and T lymphocytic. In all cases expression of v-myc was high and the disease type did not correlate with the level of expression. We have isolated immortalized monocytes, myeloid progenitors and T lymphocytes from several of these mice and shown tumorigenicity in secondary syngeneic recipients. This system provides a model for investigating the progression from a pre-leukemic disease to malignancy. In addition, we describe a recombinant v-myc-containing retrovirus that directs high-level v-myc expression from the Mo-MLV promoter in all the hematopoietic cell types examined.

Animals↗
PubMed1992

Germ-line splicing mutation of the p53 gene in a cancer-prone family.

Li-Fraumeni syndrome is a rare autosomal dominant susceptibility to a variety of cancers including carcinomas of the breast and the adrenal cortex, tumors of brain and muscle tissue, and leukemias. Affected individuals develop cancer at a young age and often at multiple primary sites. A study has been conducted into the genetic basis of cancer in a particular Li-Fraumeni syndrome family. Examination of p53 as a candidate susceptibility gene revealed that, in two affected individuals, there was an aberrant larger transcript of 3.6 kilobases present in both tumor and constitutional material in addition to the normal-sized 2.8-kilobase transcript. The additional transcript was not found in three unaffected family members. S1 nuclease mapping localized the insertion toward the 5' end of the p53 transcript near exons 4 and 5, and sequencing revealed a point mutation in the splice donor site of intron 4 in the germ-line of the two affected individuals, which accounted for the presence of the larger transcript. The same splicing mutation was also detected in two obligate carriers and was not found in two unaffected individuals. As no mutations were detected in exons 5-8 in either tumor examined, the second p53 allele was most likely lost during tumorigenesis in both tumors. The demonstration of a germ-line splicing mutation in affected individuals from a Li-Fraumeni syndrome family provides for a novel mechanism of p53 inactivation not seen previously in other affected families, in whom the mutations have all been missense.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Cortex Neoplasms↗
PubMed1992

Constitutive expression of exogenous myc in myelomonocytic cells: acquisition of a more transformed phenotype and inhibition of differentiation induction.

The effects of deregulated expression of the human c-myc and MC29 v-myc oncogenes have been examined in a murine myelomonocytic cell line J774 (c-myc) and in a variety of myelomonocytic cell lines of different degrees of maturity generated from primary hematopoietic tissue (v-myc). Introduction of a Moloney murine leukemia virus long terminal repeat (LTR) c-myc construct into J774 cells resulted in constitutive expression of the exogenous myc gene and a concomitant increase in the degree of transformation and tumorigenicity of the cells. In addition, constitutive expression of exogenous myc inhibited induced differentiation of these cells by a variety of treatments including addition to the medium of lipopolysaccharide (LPS) or the phorbol ester 12-O-tetradecanoyl phorbol 13-acetate (TPA) as well as complete withdrawal of serum from the medium. The degree of increased transformation, tumorigenicity and inhibition of terminal differentiation was dependent upon the level of exogenous myc expression. For the v-myc-generated myelomonocytic cell lines, introduction of v-myc resulted in a high degree of transformation and, irrespective of the differentiation status of the cells, a block of induced differentiation. These results indicate that the level of constitutive myc expression can affect the transformed phenotype, tumorigenicity and differentiation inducibility of myelomonocytic cells.

Animals↗
PubMed1992

Transformation of murine pre-B-lymphocytes by v-erb-B: progression to growth factor independence and tumorigenicity.

v-erb-B is the principal transforming gene of avian erythroblastosis virus, a replication defective retrovirus that transforms erythroid and fibroblast cells in vitro and causes erythroleukemia and fibrosarcoma in vivo. We have used a recombinant murine retrovirus, based on the truncated genome of Moloney murine leukemia virus and containing a chimeric gag-v-erb-B gene, to determine the murine hematopoietic cells transformed by v-erb-B. Infection of day 16.5 murine embryonal cells in liquid culture with this virus resulted in the outgrowth of foci of loosely to non-adherent hematopoietic cells which grew in close association with an adherent monolayer. After several weeks in culture a clonal population of transformed pre-B-lymphocytes emerged from this transformation initiated, though still growth factor dependent, population. These transformed cells were growth factor independent, and were tumorigenic in syngeneic mice. The results indicate that although v-erb-B can initiate transformation of murine hematopoietic cells, additional events are required for establishment of the fully transformed growth factor independent, tumorigenic phenotype. This v-erb-B induced progression from growth factor dependence to independence provides an in vitro model system for analysing events involved in the initiation and maintenance of leukemia.

Animals↗
PubMed1991

Establishment in culture and characterization of a strain with mast cell and monocytic properties from the bone marrow of a child with diffuse cutaneous mastocytosis.

Bone marrow was isolated from a child with congenital mastocytosis. Upon prolonged in vitro culture, initially in the presence of interleukin-3 (IL-3), a population of relatively large fusiform, strongly adherent cells grew out plus a subpopulation of smaller nonadherent cells. The morphology of the adherent cells was not typical of fibroblasts, epithelial cells, nor of standard hematopoietic cell types, whereas the morphology of the nonadherent cells resembled mast cells. Neither cell type required the presence of IL-3 nor a feeder layer of fibroblasts for continued growth. Attempts to isolate the two populations were unsuccessful. This cell strain comprised of both cell populations has been termed human bone marrow-derived mastocytosis cells (HBM-M). These cells were found to possess some of the cytochemical, ultrastructural, and surface phenotypic features of degranulated mast cells. They reacted with the mast cell marker, monoclonal antibody YB5.B8, but not with the basophil specific monoclonal antibody Bsp-1 and released the inflammatory mediators histamine, leukotriene C4, prostaglandin D2, and platelet-activating factor constitutively. This release was not potentiated by immunologic- or nonimmunologic-activating stimuli. In addition, they exhibited cytochemical and surface phenotypic features of monocytes. Our results indicate that a population of abnormal proliferative cells exist in the marrow of this patient; that these cells may be responsible for the patient's pronounced systemic proliferation of mast cells and the associated symptoms; and that the cell's mast cell, monocyte properties may be indicative of a common bone marrow-derived mast cell/monocyte precursor.

Antibodies, Monoclonal↗
PubMed1991

Stage-specific expression of intracisternal A-particle sequences in murine myelomonocytic leukemia cell lines and normal myelomonocytic differentiation.

The levels of intracisternal A-particle (IAP) mRNA were analyzed in a variety of myelomonocytic leukemia cell lines, peritoneally derived macrophages, and normal hemopoietic progenitors induced to differentiate. In both normal and leukemic cells, the highest level of IAP message was found in cells at an intermediate stage of myelomonocytic differentiation, namely, the promyelomonocyte. These results indicate that IAP sequence transcription is regulated differentially during myelomonocytic cell development and that in general, the expression pattern is preserved in leukemic cell lines in vitro. In addition, Northern (RNA) analysis detected only type I IAP transcripts as the major IAP message and the expressed IAP subtypes varied in certain cell lines. This is the first comprehensive study of IAP expression in the myelomonocytic lineage and provides a useful system to study the biology of IAPs.

Animals↗
PubMed1991

Tumor progression following transformation of murine monocytes by v-myc: acquisition of immortalization and tumorigenicity.

Monocyte transformation by the v-myc oncogene has been used to study myelomonocytic tumor progression in vitro. Murine monocytes transformed by a recombinant retrovirus containing MC29 v-myc were found to exhibit a proliferative burst to day 28-40 post-infection. There-after growth slowed and cell number remained relatively static to day 80-90 post-infection. During both the proliferative and quiescent periods, the cells were dependent on the myelomonocytic growth factor CSF-1 for growth and viability. Analysis of this transformation revealed that the initial transformants were polyclonal, non-immortal, and non-tumorigenic in syngeneic mice. At day 80-90 post infection, a fresh round of cellular proliferation occurred and, in contrast to the initial burst, growth was sustained allowing the establishment of cell lines. These lines were found to be monoclonal, immortal, growth factor independent and, in certain cases, tumorigenic in syngeneic mice. Associated with the establishment of growth factor independent cell lines was the constitutive synthesis of the myelomonocytic growth factor, CSF-1. Proto-oncogene screening of the initial transformants and the cell lines also revealed the expression of c-raf and the CSF-1 receptor, c-fms. Our results indicate that, following transformation by v-myc, monocytes can progress in vitro to become growth factor independent and immortal and that both monocyte transformation and immortalization can be dissociated from tumorigenicity.

Animals↗
PubMed1991

Overexpression of the retinoblastoma gene in a familial adrenocortical carcinoma.

Tumors derived from a Li-Fraumeni syndrome cancer-susceptible family were examined for expression of the retinoblastoma susceptibility gene (RB). Whereas RB expression was normal in a primary breast carcinoma and its metastases from one member of this family, overexpression of RB was found in an adrenocortical carcinoma from another family member. This was in contrast to normal RB expression in normal tissue of this patient, the adrenocortical adenocarcinoma cell line SW-13, and the fibroblast cell line MRC-5, and low level RB expression in normal adrenal tissue. The overexpression in the adrenocortical carcinoma resulted in increased synthesis of the RB-encoded protein and did not appear to be associated with RB amplification or rearrangement. This result is novel as it is usually the loss of expression or production of an altered RB transcript exhibiting deletions that is associated with carcinogenesis. In light of the recent discovery of p53 point mutations in the affected Li-Fraumeni syndrome family members tested, RB overexpression may constitute a secondary event in Li-Fraumeni syndrome tumorigenesis.

Adrenal Cortex Neoplasms↗
PubMed1991

Inducible transformation of fibroblasts using a metallothionein-v-myc gene construct.

An inducible oncogene construct has been engineered by coupling the MC29 v-myc oncogene to the sheep metallothionein promoter. Transfection of this plasmid, which also contains the neomycin resistance gene, into Rat-1 cells, has resulted in the isolation of independent clones resistant to G418. Certain of these clones were found to exhibit inducible transformation in response to ZnSO4. Transformation was graded with increasing ZnSO4 levels and was reversible when ZnSO4 was removed from the media. By analyzing v-myc mRNA levels, the inducible alterations in cellular morphology and growth were found to be associated with increased v-myc expression. The metallothionein promoter exhibited negligible constitutive expression of v-myc and none of the clones isolated exhibited spontaneous transformation. Our results show that the use of a metallothionein promoter v-myc construct facilitates the study of inducible fibroblast transformation.

Animals↗
PubMed1990

Tumour-induced host stromal-cell transformation: induction of mouse spindle-cell fibrosarcoma not mediated by gene transfer.

Tumour-induced host-cell transformation has been addressed by examining human tumours in situ and following xenograft to nude mice. We have found evidence for the transformation of host stromal fibroblasts both in vivo and following the introduction of the tumours to in vitro culture. The in vitro culture of one such xenograft--derived from a human prostatic adenocarcinoma--resulted in the outgrowth of a transformed aneuploid mouse cell line. This transformed line was tumourigenic both in BALB/c nu/nu (nude) mice and in heterozygous nu/+mice, with the morphology of a spindle-cell sarcoma. The cell line did not express human isozymes or human histocompatibility antigens, nor were human chromosomes present. Moreover, human DNA sequences were not detected by human Alu repeat sequence element probing in the transformed cell line grown either in vitro or in vivo. The line contained retroviral long terminal repeat sequences but there was no evidence of proviral activation. These findings indicate that tumour cells may cause transformation of neighbouring stromal cells; that this transformation may proceed in the absence of DNA transfer or activation of endogenous proviruses; and that the means of this observed transformation may involve humoral factors elaborated by the tumour cells.

Adenocarcinoma↗
PubMed1990

Transformation of early erythroid precursor cells (BFU-E) by a recombinant murine retrovirus containing v-erb-B.

Avian erythroblastosis virus (AEV) is a replication-defective retrovirus that transforms erythroid and fibroblast cells in vitro and in vivo. The transforming ability of AEV is due primarily to the oncogene v-erb-B. A recombinant murine retrovirus has been constructed by inserting a chimeric gag-v-erb-B gene into a Moloney murine leukemia virus based vector. This retrovirus was used to examine v-erb-B-induced transformation of murine hematopoietic cells. Infection of murine primary fetal liver, adult bone marrow or adult spleen cells with the recombinant virus generated large hemoglobinized erythroid colonies in the absence of exogenous growth factors. Generation of such colonies usually requires the presence of erythropoietin (Epo) and interleukin-3 (IL-3). These growth-factor independent colonies were shown to be derived from early (BFU-E) and not late (CFU-E) erythroid progenitor cells, and the effect was not attributable to growth factors elicited by the virus-producing cell lines. In order to confirm that the recombinant virus was responsible for this transformation of BFU-E to growth factor independence, bone marrow cells from post 5-fluorouracil treated mice were infected and used to repopulate lethally-irradiated mice. Growth factor-independent BFU-E were obtained in up to 30% of day-13 spleen colonies and it was shown by DNA analysis that cells from these colonies contained integrated provirus. Our results indicate that v-erb-B transforms early erythroid progenitors to growth factor independent growth and subsequent differentiation to erythrocytes -a process that normally requires Epo plus either IL-3 or granulocyte-macrophage colony stimulating factor (GM-CSF).

Alpharetrovirus↗
PubMed1989

Transformation of murine myelomonocytic cells by myc: point mutations in v-myc contribute synergistically to transforming potential.

The v-myc oncogenes of chicken retroviruses (including MC29) bear point mutations relative to chicken c-myc. These mutations result in several amino acid differences in the encoded proteins. We have used recombinant murine retroviruses containing various myc alleles to analyse the myelomonocytic transforming potential of the myc oncogene. The myc alleles used were MC29 v-myc, chicken c-myc, chimeric genes combining 5' sections of v- or c-myc with 3' sections of c- or v-myc, and mouse c-myc. The same retroviral vector (based on the genome of Moloney leukemia virus) was used for each allele and the genes were translated from genomic message. By infecting the primary mouse tissues, bone marrow, peritoneal-derived macrophages and mixed embryonic tissue with the recombinant viruses, variation was found in the transforming efficacy of these alleles: v-myc was most effective, followed by the two chimeric genes, whereas c-myc (chicken or mouse) was least effective in eliciting myelomonocytic transformation. Viral gag sequences were not necessary for this transformation. In each case, the transformed monocytes were growth factor-dependent and non-immortal. However, v-myc transformed monocytes (though not monocytes transformed by other myc alleles) were able to progress to an immortal, growth factor-independent phenotype. Our results indicate that v-myc is far more effective than c-myc in eliciting myelomonocytic transformation; that this is due to combinatorial effects of 5' and 3' mutations in the v-myc gene; and that secondary events in addition to these mutations are required for transformation of myelomonocytic cells to an immortal, tumorigenic phenotype.

Animals↗
PubMed1988

Impact of staff education on pressure sore development in elderly hospitalized patients.

To test the hypothesis that an educational program alone without the introduction of new technology could result in both higher quality care and cost savings, the incidence of development of pressure sores among patients over the age of 65 years was concurrently reviewed before and after an education program developed and disseminated by a skin care team composed of physicians and nurses. Before the education program, 18 (14.6%) of 123 patients with no pressure sores developed pressure sores during their hospital admission. After the education program, only six (5.4%) of 105 patients who entered the hospital with intact skin developed a pressure sore during their hospital stay. The data show that an educational program was effective in decreasing by 63% the development of pressure sores in an elderly hospitalized population. Furthermore, a cost savings of $74,372 in the use of special care beds was realized.

Aged↗
PubMed1986

Dispersed chromosomal localization of the proto-oncogenes transduced into the genome of Mill Hill 2 or E26 leukemia virus.

Both Mill Hill 2 and E26 retroviruses have transduced two cellular genes--c-myc and c-mil/mht (Mill Hill 2) and c-myb and c-ets (E26). We localized the genes transduced by these viruses to different chromosomes: c-myc and c-myb to relatively large chromosomes and c-mil/mht and c-ets to microchromosomes. Thus, like avian erythroblastosis virus, each of these retroviruses has transduced two cellular genes unlinked in the chicken genome.

Animals↗