Showing papers on "Cell growth published in 1990"

Progressive development of the rat osteoblast phenotype in vitro: Reciprocal relationships in expression of genes associated with osteoblast proliferation and differentiation during formation of the bone extracellular matrix

Abstract: The relationship of cell proliferation to the temporal expression of genes characterizing a developmental sequence associated with bone cell differentiation was examined in primary diploid cultures of fetal calvarial derived osteoblasts by the combined use of autoradiography, histochemistry, biochemistry, and mRNA assays of osteoblast cell growth and phenotypic genes. Modifications in gene expression define a developmental sequence that has 1) three principle periods–;proliferation, extracellular matrix maturation, and mineralization–;and 2) two restriction points to which the cells can progress but cannot pass without further signal–;the first when proliferation is down-regulated and gene expression associated with extracellular matrix maturation is induced, and the second when mineralization occurs. Initially, actively proliferating cells, expressing cell cycle-and cell growth-regulated genes, produce a fibronectin/type I collagen extracel-lular matrix. A reciprocal and functionally coupled relationship between the decline in proliferative activity and the subsequent induction of genes associated with matrix maturation and mineralization is supported by 1) a temporal sequence of events in which there is an enhanced expression of alkaline phos-phatase immediately following the proliferative period, and later, an increased expression of osteocalcin and osteopontin at the onset of mineralization; 2) increased expression of a specific subset of osteoblast phenotype markers, alkaline phosphatase and osteopontin, when proliferation is inhibited by hydroxyurea; and 3) enhanced levels of expression of the osteoblast markers as a function of ascorbic acid-induced collagen deposition, suggesting that the extracellular matrix contributes to both the shutdown of proliferation and the development of the osteoblast phenotype.

Proliferating cell nuclear antigen (PCNA) immunolocalization in paraffin sections: An index of cell proliferation with evidence of deregulated expression in some, neoplasms

Abstract: Proliferating cell nuclear antigen (PCNA) is a 36 kD nuclear protein associated with the cell cycle A monoclonal antibody, PC10, that recognizes a fixation and processing resistant epitope has been used to investigate its tissue distribution Nuclear PCNA immunoreactivity is found in the proliferative compartment of normal tissues PCNA immunoreactivity is induced in lectin stimulated peripheral blood mononuclear cells in parallel with bromodeoxyuridine incorporation and the number of cells with PCNA immunoreactivity is reduced by induction of differentiation in HL60 cells In non-Hodgkin's lymphomas a linear relation between Ki67 and PCNA staining was demonstrated These data suggest that in normal tissues and lymphoid neoplasms, PCNA immunolocalization can be used as an index of cell proliferation However, in some forms of neoplasia, including breast and gastric cancer and in vitro cell lines, the simple relation between PCNA expression and cell proliferation is lost In some breast and pancreatic tumours there is apparent deregulation of PCNA with increased expression in tissues adjacent to the tumours The over-expression in some tumours and in adjacent morphologically normal tissue may represent autocrine or paracrine growth factor influence on PCNA gene expression

Progressive Development of the Rat Osteoblast Phenotype In Vitro: Reciprocal Relationships in Expression of Genes Associated With Osteoblast Proliferation and Differentiation During Formation of the

Abstract: The relationship of cell proliferation to the temporal expression of genes characterizing a developmental sequence associated with bone cell differentiation was examined in primary diploid cultures of fetal calvarial derived osteoblasts by the combined use of autoradiography, histochemistry, biochemistry, and mRNA assays of osteoblast cell growth and phenotypic genes. Modifications in gene expression define a developmental sequence that has 1) three principle periodsproliferation, extracellular matrix maturation, and mineralization-and 2) two restriction points to which the cells can progress but cannot pass without further signals-the first when proliferation is down-regulated and gene expression associated with extracellular matrix maturation is induced, and the second when mineralization occurs. Initially, actively proliferating cells, expressing cell cycleand cell growth-regulated genes, produce a fibronectinhype I collagen extracellular matrix. A reciprocal and functionally coupled relationship between the decline in proliferative activity and the subsequent induction of genes associated with matrix maturation and mineralization is supported by 1) a temporal sequence of events in which there is an enhanced expression of alkaline phosphatase immediately following the proliferative period, and later, an increased expression of osteocalcin and osteopontin at the onset of mineralization; 2) increased expression of a specific subset of osteoblast phenotype markers, alkaline phosphatase and osteopontin, when proliferation is inhibited by hydroxyurea; and 3) enhanced levels of expression of the osteoblast markers as a function of ascorbic acid-induced collagen deposition, suggesting that the extracellular matrix contributes to both the shutdown of proliferation and the development of the osteoblast phenotype.

Relationship of cell growth to the regulation of tissue-specific gene expression during osteoblast differentiation.

Abstract: The relationship of cell proliferation to the temporal expression of genes characterizing a developmental sequence associated with bone cell differentiation can be examined in primary diploid cultures of fetal calvarial-derived osteoblasts by the combination of molecular, biochemical, histochemical, and ultrastructural approaches. Modifications in gene expression define a developmental sequence that has 1) three principal periods: proliferation, extracellular matrix maturation, and mineralization; and 2) two restriction points to which the cells can progress but cannot pass without further signals. The first restriction point is when proliferation is down-regulated and gene expression associated with extracellular matrix maturation is induced, and the second when mineralization occurs. Initially, actively proliferating cells, expressing cell cycle and cell growth regulated genes, produce a fibronectin/type I collagen extracellular matrix. A reciprocal and functionally coupled relationship between the decl...

Deregulated Bcl-2 gene expression selectively prolongs survival of growth factor-deprived hemopoietic cell lines.

Abstract: The t(14;18) of human follicular B cell lymphoma translocates the Bcl-2 gene into the Ig H chain locus and markedly deregulates Bcl-2 expression. We sought to determine if Bcl-2 could be directly implicated in a growth-factor pathway. Consequently, we introduced a retrovirus containing the murine Bcl-2 gene (N2-M-Bcl-2) or the parental retrovirus (N2) into a series of factor-dependent hemopoietic cell lines. Overexpressed Bcl-2 resulted in no long term IL-2, IL-3, or IL-6 independent clones, indicating that Bcl-2 could not spare the need for a specific ligand-receptor interaction. However, Bcl-2 did extend the short term survival of IL-3-dependent cell lines after factor deprivation. Although viable, IL-3-deprived pro B lymphocytes (FL5.12) bearing N2-M-Bcl-2 were in Go, and deregulated Bcl-2 did not obviously influence cell-cycle progression. Bcl-2 predominant effects were to delay the onset of cell death and to modestly augment viable cell growth in the first 48 h after IL-3 deprivation. This death sparing was associated with increased levels of Bcl-2 RNA and protein in factor-deprived cells possessing N2-M-Bcl-2. This result was not restricted to prolymphocytes because an IL-3-dependent mast cell line (32D) as well as a promyeloid line (FDC-P1) demonstrated the same response to Bcl-2. Moreover, the effect was not limited to the IL-3/IL-3R signal transduction pathway in that promyeloid cells maintained in granulocyte-macrophage-CSF or IL-4 displayed a similar response. Yet, Bcl-2-enhanced cell survival was not universal as an IL-2-dependent T cell line, and an IL-6-dependent myeloma line demonstrated no consistent effect upon IL withdrawal. Thus, Bcl-2 appears to interfere with cell death but in a cell type and/or factor-restricted fashion.

Novel primitive lymphoid tumours induced in transgenic mice by cooperation between myc and bcl -2

Abstract: The putative oncogene bcl-2 is juxtaposed to the immunoglobulin heavy chain (Igh) locus by the t(14;18) chromosomal translocation typical of human follicular B-cell lymphomas. The bcl-2 gene product is not altered by the translocation, but its expression is deregulated, presumably by the Igh enhancer E mu. Constitutive bcl-2 expression seems to augment cell survival, as infection with a bcl-2 retrovirus enables certain growth factor-dependent mouse cell lines to maintain viability when deprived of factor. Furthermore, high levels of the bcl-2 product can protect human B and T lymphoblasts under stress and thereby confer a growth advantage. Mice expressing a bcl-2 transgene controlled by the Igh enhancer accumulate small non-cycling B cells which survive unusually well in vitro but do not show a propensity for spontaneous tumorigenesis. In contrast, an analogous myc transgene, designed to mimic the myc-Igh translocation product typical of Burkitt's lymphoma and rodent plasmacytoma, promotes B lymphoid cell proliferation and predisposes mice to malignancy in pre-B and B lymphoid cells. Previous experiments have suggested that bcl-2 can cooperate with deregulated myc to improve in vitro growth of pre-B and B cells. Here we describe a marked synergy between bcl-2 and myc in doubly transgenic mice. E mu-bcl-2/myc mice show hyperproliferation of pre-B and B cells and develop tumours much faster than E mu-myc mice. Suprisingly, the tumours derive from a cell with the hallmarks of a primitive haemopoietic cell, perhaps a lymphoid-committed stem cell.

Increased cell division as a cause of human cancer

Abstract: Carcinogenesis research is increasingly focused on chemicals that are not genotoxic and yet, at high doses, can induce cancer, apparently by increasing cell proliferation. We hypothesize that increased cell division per se stimulated by external or internal factors is also associated with the development of many human cancers. Although this hypothesis is well substantiated in the experimental literature, it has not been generalized as an important mechanism for carcinogenesis in human populations. Under this increased cell division model, the pathogenesis of cancer may result from molecular genetic errors induced during the process of cell division and from altered growth control of malignant or premalignant cells. Molecular genetic analysis of human cancers has shown that tumor cells contain multiple genetic defects including mutations, translocations, and amplifications of oncogenes and are reduced to homozygosity for putative tumor suppressor genes; these phenomena all require cell division for their occurrence and fixation. Increased cell division increases the risk of such events occurring. An accumulation of a combination of such genetic errors leads to a neoplastic phenotype. Examples are discussed of human cancers in which increased cell division, which drives the accumulation of genetic errors and can lead to neoplastic transformation, is caused by hormones, drugs, infectious agents, chemicals, physical or mechanical trauma, and other chronic irritation.

p53 functions as a cell cycle control protein in osteosarcomas.

Abstract: Mutations in the p53 gene have been associated with a wide range of human tumors, including osteosarcomas. Although it has been shown that wild-type p53 can block the ability of E1a and ras to cotransform primary rodent cells, it is poorly understood why inactivation of the p53 gene is important for tumor formation. We show that overexpression of the gene encoding wild-type p53 blocks the growth of osteosarcoma cells. The growth arrest was determined to be due to an inability of the transfected cells to progress into S phase. This suggests that the role of the p53 gene as an antioncogene may be in controlling the cell cycle in a fashion analogous to the check-point control genes in Saccharomyces cerevisiae.

Monoclonal antibody analysis of the proliferating cell nuclear antigen (PCNA). Structural conservation and the detection of a nucleolar form.

Abstract: The proliferating cell nuclear antigen, PCNA, has recently been identified as the polymerase delta accessory protein. PCNA is essential for cellular DNA synthesis and is also required for the in vitro replication of simian virus 40 (SV40) DNA where it acts to coordinate leading and lagging strand synthesis at the replication fork. The cDNA for rat PCNA was cloned into a series of bacterial expression vectors and the resulting protein used to immunize mice. Eleven new monoclonal antibodies to PCNA have been isolated and characterized. Some of the antibodies recognize epitopes conserved from man to fission yeast. Immunocytochemical analysis of primate epithelial cell lines showed that the antibodies recognized antigenically distinct forms of PCNA and that these forms were localized to different compartments of the nucleus. One antibody reacted exclusively with PCNA in the nucleolus. These results suggest that the PCNA protein may fulfil several separate roles in the cell nucleus associated with changes in its antigenic structure.

Scatter factor: molecular characteristics and effect on the invasiveness of epithelial cells.

Abstract: The generation of invasiveness in transformed cells represents an essential step of tumor progression. We have previously shown that MDCK epithelial cells, which are deprived of intracellular adhesion by the addition of anti-Arc-1/uvomorulin antibodies, become invasive for collagen gels and embryonal heart tissue (Behrens, J., M. M. Mareel, F. M. Van Roy, and W. Birchmeier. 1989. J. Cell Biol. 108: 2435-2447.). Here we examined whether invasiveness is also induced by scatter factor, which is known to dissociate epithelial cells (Stoker, M., E. Gherardi, M. Perryman, and J. Gray. 1987. Nature (Lond.). 327:239-242.). Scatter factor was purified to homogeneity from conditioned medium of human fibroblasts by heparin-Sepharose chromatography, followed by cation exchange chromatography, gel filtration, or preparative SDS gel electrophoresis. We found that scatter factor represents a 92,000 mol wt glycoprotein which, apparently, is converted by limited proteolysis into disulfide-linked 62,000 and 34/32,000 mol wt subunits. Reversed phase HPLC and sequence analysis of tryptic peptides confirmed the suggested molecular structure, and revealed further that scatter factor exhibits sequence similarities to hepatocyte growth factor and to plasminogen. Purified scatter factor in fact induces the invasiveness into collagen matrices of MDCK epithelial cells, and induces or promotes the invasiveness of a number of human carcinoma cell lines. Apparently, the effect on the human cells depends on their respective degree of differentiation, i.e., cell lines with a less pronounced epithelial phenotype were more susceptible to the factor. Scatter factor does not seem to influence synthesis, steady-state level, and phosphorylation of the cell adhesion molecule Arc-1/uvomorulin. Thus, scatter factor represents a clearly defined molecular species which induces, in vitro, the progression of epithelial cells to a more motile, i.e., invasive phenotype.

Physiology and Biochemistry of Plant Cell Walls

Abstract: The role of the cell wall in the life of the plant. The molecular components of the wall. Cell wall architecture and the skeletal functions of the wall. Cell-wall formation. The cell wall and control of cell growth. The cell wall and intracellular transport. The cell wall and interactions with other organisms. The cell wall and reproduction. Cell-wall degradation and biotechnological applications. Cell walls in diet and health. Outstanding problems for future research.

Progestin Regulation of Cellular Proliferation

Abstract: I. Introduction THE control of cellular proliferation is known to involve a delicate balance between the effects of different regulatory molecules including hormones and growth factors which provide, in the immediate environment of the cell, signals to stimulate or inhibit cellular replication (1). The past decade has seen significant progress in the identification and characterization of novel regulatory molecules, generally referred to as growth factors, and definition of their molecular mechanisms of action (2, 3). With the recent emphasis on peptide growth factors it is perhaps less well appreciated that some of the largest physiological changes (both positive and negative) in rates of growth and cell proliferation are mediated by steroid hormones. Recent studies on breast cancer cells (4) and immature rat uterus (5, 6), illustrating estrogenic control of autocrine and paracrine growth factor production, support the view that some of these steroid-induced responses are intimately linked to growth fact...

Distinct mechanisms of suppression of murine T cell activation by the related macrolides FK-506 and rapamycin.

Abstract: FK-506 and the structurally related macrolide rapamycin (RAP) were investigated in comparison with cyclosporin A (CsA) for their immunosuppressive effects on murine T cells. All three agents suppressed the proliferation of splenic T cells triggered by lectins or antibodies to CD3 and Ly-6C. FK-506 or CsA also inhibited proliferation, IL-2 production, and IL-2R expression in splenic T cells activated with ionomycin + PMA. However, RAP minimally affected IL-2 production and IL-2R expression in these cells, although it reduced proliferation. Similarly, FK-506 and CsA, but not RAP, suppressed IL-2 production by activated DO.11.10 T hybridoma cells. In such a system, as well as in normal T cells stimulated with high ionomycin concentrations, FK-506 and CsA enhanced proliferation, indicating that they both abrogate negative signals associated with T cell activation. On the contrary, RAP diminished the autonomous proliferation of hybridoma cells, whereas FK-506 and CsA had little effect. The proliferative response induced in D10.G4 cells by IL-1 + ionomycin but not that induced by IL-1 + PMA was sensitive to inhibition by FK-506 and CsA. In contrast, RAP inhibited equally well both types of stimulation. Finally, T cell proliferation driven by IL-2 or IL-4 was found to be relatively resistant to FK-506 or CsA but sensitive to RAP. Altogether, these data demonstrate that FK-506 and CsA alter similar calcium-associated events of T cell activation and block T cell proliferation primarily by suppressing lymphokine production. RAP interferes with a different set of events and inhibits T cells by impairing their response to growth-promoting lymphokines.

Cell proliferation in human coronary arteries.

Abstract: Despite the lack of direct evidence for cell multiplication, proliferation of smooth muscle cells in human atherosclerotic lesions has been assumed to play a central role in ontogeny of the plaque. We used antibodies to cell cycle-related proteins on tissue sections of human arteries and coronary atherosclerotic plaques. Specific cell types were identified by immunochemical reagents for smooth muscle, monocyte-macrophages, and other blood cells. Low rates of smooth muscle cell proliferation were observed. Macrophages were also observed with rates of proliferation comparable to that of the smooth muscle. Additional replicating cells could not be defined as belonging to specific cell types with the reagents used in this study. These findings imply that smooth muscle replication in advanced plaques is indolent and raise the possibility of a role for proliferating leukocytes.

Fibronectin controls capillary endothelial cell growth by modulating cell shape.

Abstract: An in vitro system has been developed to study the mechanism by which fibronectin (FN) regulates capillary endothelial cell growth in the presence of soluble angiogenic mitogens. Endothelial cells were cultured in chemically defined medium containing a constant, saturating amount of basic fibroblast growth factor. Formation of cell-FN contacts was then varied in a controlled fashion by three different techniques: (i) nonadhesive, bacteriological dishes were precoated with increasing densities of FN; (ii) soluble RGD peptides were used to progressively inhibit binding of cell-surface integrin receptors to adsorbed FN; and (iii) FN-coated surfaces were covered with increasingly thick layers of polyhydroxyethylmethacrylate (a nonadhesive polymer) to physically restrict cell access to FN binding sites. Endothelial cells became more extended and proliferated more rapidly as FN coating concentrations were raised from approximately 250 to approximately 10,000 FN molecules per micron 2. Computerized morphometric analysis confirmed that cell shape (projected cell areas) was determined by the density of FN contacts and that DNA synthetic levels were tightly coupled to the extent of cell spreading, regardless of the method used to perturb cell adhesion. In contrast, neither soluble FN nor cell-surface binding of FN-coated microbeads (diameter, 4.5 microns) had any effect on growth when cells were grown in suspension and cell spreading was prohibited. These results suggest that FN controls capillary endothelial cell proliferation based on its ability to support tension-dependent alterations of cell shape--i.e., both by binding to cell-surface integrins and by resisting mechanical loads that are applied to these receptors.

Negative growth regulation in a glioblastoma tumor cell line that conditionally expresses human wild-type p53.

Abstract: To investigate the effect that human wild-type p53 (wt-p53) expression has on cell proliferation we constructed a recombinant plasmid, pM47, in which wt-p53 cDNA is under transcriptional control of the hormone-inducible mouse mammary tumor virus promoter linked to the dominant biochemical selection marker gene Eco gpt. The pM47 plasmid was introduced into T98G cells derived from a human glioblastoma multiforme tumor, and a stable clonal cell line, GM47.23, was derived that conditionally expressed wt-p53 following exposure to dexamethasone. We show that induction of wt-p53 expression in exponentially growing cells inhibits cell cycle progression and that the inhibitory effect is reversible upon removal of the inducer or infection with simian virus 40. Moreover, when growth-arrested cells are stimulated to proliferate, induction of wt-p53 expression inhibits G0/G1 progression into S phase and the cells accumulate with a DNA content equivalent to cells arrested in the G0/G1 phase of the cell cycle. Taken together, these studies suggest that wt-p53 may play a negative role in growth regulation.

Programmed cell death during regression of PC-82 human prostate cancer following androgen ablation.

Abstract: To study the mechanism of regression of human prostatic cancer following androgen ablation, the androgen-responsive PC-82 human prostatic adenocarcinoma xenograft was used as a model system Castration of male nude mice bearing PC-82 xenografts results in a 50% tumor regression by 2 wk following androgen ablation This regression is due to a sequence of biochemical and morphological events that results in both the cessation of cell proliferation and activation of programmed death or apoptosis of the androgen-dependent prostatic cancer cells Associated with this response are an enhanced expression of the transforming growth factor beta 1 gene, a potent inhibitor of cell proliferation, and testosterone-repressed prostatic message 2 (designated TRPM-2), a programmed cell death-associated gene Fragmentation of tumor DNA into nucleosomal oligomers and histological appearance of apoptotic bodies are characteristic early events that preceded the dramatic reduction in tumor volume following androgen ablation These results suggest that androgen-dependent human prostatic cancer cells, like normal prostatic cells, retain the ability to inhibit proliferation and to activate programmed cell death in response to androgen ablation Clarification of the biochemical pathway involved in the activation of this programmed cell death should identify new targets of therapy for even androgen-independent human prostatic cancer

Cell-cycle-dependent regulation of phosphorylation of human retinoblastoma gene product

Abstract: In the field of regulation of cell proliferation, a method of inhibiting or preventing cell proliferation is disclosed. Rb, a stable protein encoded by the retinoblastoma gene (RB1), is synthesized at all phases of the cell cycle. Newly synthesized Rb is underphosphorylated during the G0 and G1 phases but is phosphorylated at multiple sites at the G1/S boundary and during S phase. HL-60 cells lose their ability to multiply phosphorylate newly synthesized Rb when induced to terminally differentiate by chemicals such as dimethylsulfoxide, retinoic acid and butyric acid. A method of using these chemicals to inhibit or prevent cell proliferation in cells containing Rb is disclosed.

AIDS Kaposi sarcoma-derived cells produce and respond to interleukin 6.

Abstract: Cell lines derived from Kaposi sarcoma lesions of patients with AIDS (AIDS-KS cells) produce several cytokines, including an endothelial cell growth factor, interleukin 1 beta, and basic fibroblast growth factor. Since exposure to human immunodeficiency virus increases interleukin 6 (IL-6) production in monocytes and endothelial cells produce IL-6, we examined IL-6 expression and response in AIDS-KS cell lines and IL-6 expression in AIDS Kaposi sarcoma tissue. The AIDS-KS cell lines (N521J and EKS3) secreted large amounts of immunoreactive and biologically active IL-6. We found both IL-6 and IL-6 receptor (IL-6-R) RNA by slot blot hybridization analysis of AIDS-KS cells. The IL-6-R was functional, as [3H]thymidine incorporation by AIDS-KS cells increased significantly after exposure to human recombinant IL-6 (hrIL-6) at greater than 10 units/ml. When AIDS-KS cells (EKS3) were exposed to IL-6 antisense oligonucleotide, cellular proliferation decreased by nearly two-thirds, with a corresponding decrease in the production of IL-6. The decrease from IL-6 antisense in AIDS-KS cell proliferation was reversed by the addition of hrIL-6. We confirmed that AIDS-KS cells produced IL-6 in vivo by preparing RNA and tissue sections from involved and uninvolved skin from a patient with AIDS Kaposi sarcoma. We detected immunoreactive IL-6 in the involved tumor areas and to a lesser extent in the surrounding normal epidermis. Slot blot hybridization showed a great excess of IL-6 and IL-6-R RNA in involved skin compared to uninvolved skin. These results show that both IL-6 and IL-6-R are produced by AIDS-KS cells and that IL-6 is required for optimal AIDS-KS cell proliferation, and they suggest that IL-6 is an autocrine growth factor for AIDS-KS cells.

Identification and characterization of an inhibitor of haemopoietic stem cell proliferation.

Abstract: THE haemopoietic system has three main compartments: multi-potential stem cells, intermediate stage progenitor cells and mature cells. The availability of simple reproducible culture systems1 has made possible the characterization and purification of regulators of the progenitor cells, including colony-stimulating factors and interleukins. In contrast, our knowledge of the regulators involved in the control of stem cell proliferation is limited. The steady-state quiescent status of the haemopoietic stem cell compartment is thought to be controlled by locally acting regulatory elements present in the stromal microenvironment2, but their purification has been hampered by the lack of suitable culture systems. We have recently developed a novel in vitro colony assay that detects a primitive cell (CPU-A) 3 which has similar proliferative charac-teristics, in normal and regenerating bone marrow, to the CFU-S (haemopoietic stem cells, as defined by the spleen colony assay4) and which responds to CFU-S-specific proliferation regulators. We have now used this assay to purify to homogeneity a macrophage-derived reversible inhibitor of haemopoietic stem cell proliferation (stem cell inhibitor, SCI). Antibody inhibition and sequence data indicate that SCI is identical to a previously described cytokine, macrophage inflammatory protein-lα ( MIP-lα), and that SCI/MIP-lα is functionally and antigenically iden-tical to the CFU-S inhibitory activity obtained from primary cultures of normal bone marrow cells5. The biological activities of SCI/MIP-lα suggest that it is a primary negative regulator of stem cell proliferation and that it has important therapeutic appli-cations in protecting haemopoietic stem cells from damage during cytotoxic therapies for cancer.

Developmental mechanisms underlying pathology of arteries

Abstract: This review tries to provide a general, and very speculative, view of growth control mechanisms that may be common to the development of blood vessels and to pathological processes including cell proliferation. From a developmental point of view, vascular growth is most likely to include local autocrine or paracrine mechanisms that permit the two cells of the vessel wall to grow, organize into the characteristic tubular and layered structures of the vessel wall, and eventually achieve a return to quiescence. The "real" mechanisms controlling growth in vivo are difficult to ascertain from studies in culture. For example, a large list of angiogenesis molecules must be able to generate endothelial replication, but in culture many of these molecules are inhibitory for each endothelial replication. Similarly, in culture, we have a long list of smooth muscle mitogens, but none of these have as of yet been proven to control smooth muscle growth in vivo. Endothelial growth control has been attributed to the presence of membrane molecules able to inhibit endothelial replication and to the actions of soluble growth factors and their receptors. Unfortunately for the former hypothesis we still lack specific molecules with the properties of contact inhibition of replication. The data discussed here, however, suggest that modulation of expression or function of cell-cell adhesive molecules could be critical both to morphogenic changes and to mitogenesis by release of cells from cell-cell contact. Moreover, our data and data from other laboratories suggest that angiogenic factors, including the HBGFs and TGF-beta, may function in angiogenesis by altering cell-cell and cell-cell substrate interactions rather than via a primary effect on cell replication. This view of angiogenesis is consistent with the absence of a mitogenic effect of some angiogenic factors. Although endothelial cell replication is obviously necessary to angiogenesis, the lack of mitogenic effect of some factors suggests a need for a more general explanation of the actions of angiogenic factors. Endothelial injury may be interrelated with smooth muscle growth. The simplest possibility is that a failure of the endothelial cell barrier function, due either to denudation or an increase in adhesivity for leukocytes, would permit access of platelets or leukocytes to the vessel wall. These extrinsic cells, in turn, would stimulate smooth muscle cell replication by release of growth factors. The second possibility is that the endothelial cell may itself release growth factors into the vessel wall.(ABSTRACT TRUNCATED AT 400 WORDS)

Fibroblast-mediated acceleration of human epithelial tumor growth in vivo

Abstract: Transformed fibroblasts coinoculated with epithelial cells accelerated the growth and shortened the latency period of human epithelial tumors in athymic mice. Addition of NbF-1 fibroblasts caused epithelial tumors to grow from five marginally tumorigenic or "nontumorigenic" (nontumor-forming) human tumor cell lines or strains: PC-3 (prostate), WH (bladder), MDA-436 (breast), and cells derived from the ascites fluids of patients with metastatic renal pelvic or prostate cancers. Evidence for the human and epithelial nature of these experimental tumors was provided by histologic, immunohistochemical, Southern and dot-blot hybridization, and cytogenetic analyses. Transformed fibroblasts induced predominantly carcinosarcomas, whereas nontumorigenic fibroblasts (NIH 3T3) and lethally irradiated transformed fibroblasts induced exclusively carcinomas. The fibroblast-epithelial interaction appears to occur bidirectionally and does not result from cell fusion. Because coculture experiments in vitro did not demonstrate an increased cell proliferation, it appears that undefined host factors can influence tumor growth. This tumor model may be useful in drug-screening programs and in mechanistic studies of factors regulating human tumor growth and progression.

Transforming growth factors and the regulation of cell proliferation.

Abstract: Mechanisms of growth regulation by polypeptides include endocrine, paracrine and autocrine systems. Factors, such as hormones, which enter the circulatory system and effect target cells or tissues distant from their site of synthesis, are endocrine in nature. It has been postulated that some growth factors may function in an endocrine manner. Insulin-like growth factor, which is synthesized in the liver and enters the blood stream to affect distal tissues, is an example of endocrine action of a specific growth factor [1,2]. The paracrine mechanism of action suggests that growth factors synthesized by one cell type diffuse through the extracellular spaces to act on neighboring target cells. Finally, autocrine growth regulation may occur when cells are able to both synthesize and respond to a specific growth signal. The autocrine model of growth regulation was originated as a concept to explain the abnormal growth of cancer. This model hypothesizes that affected cells over-produce a stimulatory growth factor to which they respond, thus resulting in sustained, self-stimulated proliferation [3]. Although initially postulated to explain the unregulated growth of cancer cells, the autocrine mechanism of growth regulation, in addition to paracrine and endocrine systems, is likely to play an important role in normal cellular processes, including development, differentiation and proliferation [4, 5]. Thus local concentrations of growth factors and numbers of specific cell-surface receptors, will affect the biological response of cells to a particular growth factor. It is apparent, therefore, that regulated growth requires the complex interaction of many growth signals and that this interaction may be influenced by the synthesis and delivery of growth factors to target tissues. Of particular interest in the study of the regulation of cell proliferation are the transforming growth factors (TGF), for which paracrine and autocrine mechanisms have been postulated.

Spontaneous transformation and immortalization of human endothelial cells.

Abstract: A new cell line from the human umbilical vein has been established and maintained for more than 5 yr (180 generations; 900 population doublings). This strain, designated ECV304, is characterized by a cobblestone monolayer growth pattern, high proliferative potential without any specific growth factor requirement, and anchorage dependency with contact inhibition. Karyotype analysis of this cell line reveals it to be of human chromosomal constitution with a high trisomic karyotype (mode 80). Ultrastructurally, endothelium-specific Weibel-Palade bodies were identified. Although one of the endothelial cell markers, Factor VIII-related antigen (VIIIR:Ag) was negative in this cell line, immunocytochemical staining for the lectin Ulex europaeus I (UEA-I), and PHM5 (anti-human endothelium as well as glomerular epithelium monoclonal antibody) was positive, and angiotensin-converting enzyme (ACE) activity was also demonstrated. In addition, ECV304 displayed negativity for alkaline and acid phosphatase and for the epithelial marker keratin. All of these findings suggest that ECV304 cells originated from umbilical vein endothelial cells by spontaneous transformation. Ultrastructurally, no viruslike particles have been detected intracellularly. Nude mouse tumorigenicity and rabbit cornea tests were both positive. This is a report on a novel case of phenotypic alteration of normal venous endothelial cells of human origin in vitro, and generation of a transformant with indefinite life spans. This line may be useful in studies of some physiologically active factors available for medical use.

Transforming growth factor beta 1 suppression of c-myc gene transcription: role in inhibition of keratinocyte proliferation.

Abstract: Transforming growth factor beta 1 (TGF-beta 1) is a potent growth inhibitor for many cell types, including most epithelial cells. However, the mechanism of growth inhibition is unknown. In skin keratinocytes, TGF-beta 1 has been shown to inhibit growth and to rapidly reduce c-myc expression. It has been demonstrated that protein synthesis is required for TGF-beta 1 regulation of c-myc in keratinocytes. Here we present evidence that treatment of mouse BALB/MK keratinocyte cells with either antisense c-myc oligonucleotides or TGF-beta 1 inhibited cell entry into S phase. These results suggest that TGF-beta inhibition of c-myc expression may be essential for growth inhibition by TGF-beta 1. The block in c-myc expression by TGF-beta 1 occurred at the level of transcriptional initiation. Studies with a series of 5' deletion c-myc/chloramphenicol acetyltransferase constructs indicated that a cis regulatory element(s), which resides between positions -100 and +71 relative to P1 transcription start site, is responsible for the TGF-beta 1 responsiveness. Based on these data, it is proposed that the mechanism of TGF-beta 1 growth inhibition involves synthesis or modification of a protein that may interact with a specific element(s) in the 5' regulatory region of the c-myc gene, resulting in inhibition of transcriptional initiation.