Sorting out of normal and virus-transformed cells in cellular aggregates.

Gershman, Howard; Drumm, Judith; Culp, Lloyd A.

doi:10.1083/jcb.68.2.276

Cited by 18 publications

(8 citation statements)

References 28 publications

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“…Formation of three-dimensional cell aggregates by rotation-mediated aggregation of single cell suspensions of cultured cells has been 169 used in developmental biology for many years as a tool for studying adhesive and cognitive interaction between embryonic cells (94). More recently, aggregates prepared in this way, and the closely related three-dimensional cell spheroid system, have been used as in vitro models of tumor invasion (95,96) and infiltration of host inflammatory cells into neoplastic tissue (97). It has been argued that cell penetration into three-dimensional structures of thiskind better approximates tumor invasion in vivo than the highly simplified two-dimensional cell monolayer system.…”

Section: A Invasion Of Host Tissuesmentioning

confidence: 99%

Experimental systems for analysis of the malignant phenotype

Poste

1982

Cancer Metast Rev

109

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Identification of the cellular and subcellular alterations responsible for the metastatic behavior of malignant tumor cells and development of reliable screening programs for detecting new therapeutic agents for improved treatment of metastatic disease both depend crucially on the availability of experimental systems that can serve as relevant models of human cancer. Recent advances in our understanding of the pathogenesis of cancer metastasis have raised serious doubts about the usefulness of many of the experimental approaches that have long been used in the study of metastasis. Recent findings showing that metastases are caused by specific subpopulations of metastatic tumor cells, and that not all cells in a malignant primary tumor possess metastatic properties, are of profound importance for experimental efforts to understand the mechanism of metastatic phenotype among cells from the same tumor means that the traditional, and widely used, approach of analyzing primary tumors and cultured cell lines containing multiple, phenotypically heterogeneous, subpopulations of cells may provide little or no insight into the properties of the metastatic subpopulations, particularly if they represent only a minor fraction of the entire population. Similarly, the practice of screening potential therapeutic modalities for their ability to reduce the mass and/or growth rate of a primary tumor may be inadequate in predicting the responsiveness of metastatic lesions. Solution of these problems requires that new methods must be devised to isolate and characterize the specific subpopulations of tumor cells endowed with metastatic potential. In addition, knowledge of how the extraordinary phenotypic diversity found in tumor cell subpopulations from the same tumor is generated and how subpopulation diversity is regulated during progressive growth of both the primary tumor and its metastases are of fundamental importance if we are to design meaningful experimental systems for studying the metastatic process. This article reviews our current understanding of these complex issues and their implications for the experimental analysis of the malignant phenotype. The merits and shortcomings of different experimental systems are discussed in detail together with the identification of areas in which new experimental strategies and models are now needed.'

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Section: A Invasion Of Host Tissuesmentioning

confidence: 99%

Experimental systems for analysis of the malignant phenotype

Poste

1982

Cancer Metast Rev

109

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“…ethylene glycol bis(#-aminoethyl ether)-NN'-tetraacetic acid (EGTA) (0.5 mM, in phosphate-buffered saline) and were formed into cellular masses or aggregates in one of two ways. Under these conditions, both cell types were previously shown to display viability comparable to the same cells maintained as confluent monolayers (11,12). One method of aggregate formation consisted of allowing 3 X 106 cells to aggregate in 3 ml of medium in 10-ml flasks on a gyratory water bath shaker as previously described (13).…”

mentioning

confidence: 99%

Division of BALB/c mouse 3T3 and simian virus 40-transformed 3T3 cells in cellular aggregates

Carrino

Gershman

1977

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

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The phenomenon of density-dependent regulation of growth is widely accepted as a measure of a cell line's ability to display "normal" in vitro growth properties. Although this phenomenon was originally referred to as "contact inhibition of growth," recent findings have cast doubt on the hypothesis that cell-cell contact mediates this inhibition of cell division. For instance, when cultured in low concentrations of serum, mouse 3T3 cells, which display normal in vitro growth properties, cease growth as sparse cultures in which there is virtually no cell contact (1, 2). It has also been shown that breaking contacts between confluent 3T3 cells is not sufficient to stimulate incorporation of thymidine into the cells. Serum must also be present in order for thymidine incorporation to take place (3). In addition, the final cell density attained by 3T3 cells is proportional to the concentration of serum in the culture medium (4).Serum also plays a role in the alteration of growth properties upon transformation of cells. Well-established among the growth properties of transformed cells are growth to high density (5), growth in the absence of anchorage to an artificial substrate (6, 7), and formation of colonies on top of monolayers of normal cells (8). In addition, transformed cells, but not normal cells, are able to grow in 1% serum (4), in serum depleted by nontransformed growing cells (4, 9), or in gamma-globulin-free serum depleted by incubation with confluent nontransformed cells (10).The results described above suggest that intercellular contact is not the mediator of growth regulation. It should be noted, however, that all of these experiments were carried out with cells grown attached to solid artificial surfaces (glass or polystyrene). In this report we have examined the growth properties of BALB/c 3T3 cells and cells of a line, SVT-2, transformed by simian virus 40 (SV40), cultured as masses or aggregates in agitated liquid medium. These spherical masses consist of 1000 to 5000 cells and contain no artificial surfaces. In these cellular aggregates, most of the cells are completely surrounded by other cells and are therefore in a situation of three-dimensional cell-cell contact, in contrast to the two-dimensional intercellular contact that obtains in conventional flat culture. This system provides a high density of cell-cell interactions that approximates in vivo conditions more closely than does conventional flat culture. (0.4 ,tCi/ml of culture medium, [18][19][20] Ci/ mmol). After the 2-hr pulse period, the cells were removed from the dishes with trypsin (Difco 1:250, 0.05%, 37°, 10 min). The dishes were rinsed twice with 2 ml of serum-free culture medium, and the rinses were combined with the trypsin suspenAbbreviation: SV40, simian virus 40. 3874The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.

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“…This work stimulated many other studies comparing the adhesive behavior of a variety of normal and tumorigenic cells, and of cell lines repeatedly selected for high or low metastatic capacity. In some cases, the transformed or highly metastatic cells were found to display reduced adhesiveness (20)(21)(22)(23)(24)(25)(26)(27)(28)(29), while in other studies, the adhesiveness of these cells was increased (30)(31)(32)(33)(34). Finally, still other studies found no differences or subtle differences (35)(36)(37)(38)(39)(40).…”

Section: Cell Adhesiveness and Cancermentioning

confidence: 76%

Molecular mechanisms of cell adhesion in normal and transformed cells

Brackenbury

1985

Cancer Metast Rev

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Alterations in the adhesive mechanisms of cancer cells are likely to play an important role in determining the invasive or metastatic potential of these cells. An understanding of these alterations at the molecular level is now within reach, due to recent progress in the identification and characterization of several cell adhesion molecules (CAMs). Two of these molecules, the neural cell adhesion molecule N-CAM and the liver cell adhesion molecule L-CAM, are expressed on a variety of cell types from early embryos and throughout adult life, and appear to play several important roles in early inductive events, formation of specific intercellular connections, and maintenance of adult tissues. Two other molecules, the neuron-glia adhesion molecule Ng-CAM and a molecule involved in the specific adhesion of lymphocytes, appear to be more restricted in their developmental expression and function. The molecular characterization of N-CAM made possible for the first time an examination of the effects of transformation on the expression of a defined cell adhesion molecule. In both established cell lines from rat cerebellum and embryonic chick neuroepithelial cells, transformation by Rous sarcoma virus caused a large reduction in expression of N-CAM. In both cases, the N-CAM-mediated adhesion was correspondingly reduced. The neuroepithelial cells also became more highly motile after transformation. The decrease in N-CAM coupled with this increase in cell motility may significantly enhance the invasiveness of these cells. Other surface antigens have also been identified that may be involved in essential steps of invasion and metastasis. Such studies represent the initial step toward a detailed understanding of the role of CAMs in the various steps of metastasis. The accessibility of CAMs on tumor cell surfaces, and the availability of specific antibodies to these components suggests that reagents may become available in the near future that will offer new opportunities for preventing the formation of metastases.

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Sorting out of normal and virus-transformed cells in cellular aggregates.

Cited by 18 publications

References 28 publications

Experimental systems for analysis of the malignant phenotype

Experimental systems for analysis of the malignant phenotype

Division of BALB/c mouse 3T3 and simian virus 40-transformed 3T3 cells in cellular aggregates

Molecular mechanisms of cell adhesion in normal and transformed cells

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