SV40 immortalization of adult human mesenchymal cells from neuroretina. Biological, functional and molecular characterization

Human adult mesenchymal cells from neuroretina (human choroid cells, HC) have acquired an infinite lifespan, following phenotypic transformation with a wild-type SV40. Immortalized cells (HC/SV40) contain high numbers of free circular viral DNA, and integrated molecules in a head-to-tail array in the cellular DNA. HC/SV40 cells express both the virus-coded "T" antigens and the cell-coded p53 transformation-associated protein. The transformed phenotype was further characterized by loss of contact inhibition of cell division, inability to induce the retraction of a fibrin clot and to spread within fibrin, and the existence of an altered distribution of actin cables. For the first time we also describe a coupling of the immunofluorescence and the quantitative cytofluorometric analyses, a new transformation parameter, since we show that SV40 transformation causes reorganization of the cell membrane by inducing the unmasking of the antigen recognized by the 4F2 monoclonal antibody, which is present in a "cryptic" form in the untransformed cells. Though the HC/SV40 cells have been continuously passaged over a 3-year period, they have not yet achieved a fully malignant phenotype, since they retain serum-dependency and the presence of a well developed fibronectin pericellular network, and they are not tumorigenic in nude mice. Thus this human immortal cell line constitutes a very useful tool for studying the progression toward full malignancy and the relationships between evolution of transformation parameters and changes in the viral and cellular genome interplay.

4F2 monoclonal antibody recognizes a surface antigen on spread human fibroblasts of embryonic but not of adult origin

The 4F2 monoclonal antibody (mAb) has been shown to recognize a 120-kilodalton glycoprotein expressed on the cell surface of human peripheral blood monocytes, activated (but not resting) T or B cells, and T and B lymphoblastoid cell lines. In this report we show that 4F2 mAb specifically binds to the surface of adherent human embryonic fibroblasts but fails to bind to normal adult fibroblasts. Moreover, 4F2 antigen was expressed on sarcoma-derived or SV40-transformed adult fibroblastic cells. Finally, addition of 4F2 mAb inhibited the growth of cultured HT-1080 fibrosarcoma cell line, but had no inhibitory effect on various embryonic and adult normal or transformed fibroblasts.

Abnormal behavior of cultured fibroblasts from nodule and nonaffected aponeurosis of Dupuytren's disease

Vimentin-positive, desmin-negative cells were established in culture from the nodule and from apparently normal palmar aponeurosis of a patient with Dupuytren's disease and compared with normal human embryonic and adult fibroblasts or sarcomatous cells. Cells from the nodule display in vitro biological properties that are intermediate between those expressed by normal fibroblasts and sarcoma cells or cells from the nodule transformed with SV40 virus. Thus, they represent an interesting in vitro model of partially transformed human cells. This behavior is not evolutive and justifies the classification of Dupuytren's disease among the benign mesenchymal tumors. The production of high level of plasminogen activator probably explains the local reactive pathology, and could act as a mitogenic stimulus for the proliferation of the nodule itself. Cultures derived from the apparently normal palmar aponeurosis show some but not all the abnormal growth properties of cells from nodules; this may help to explain the onset of local recurrences. Our results suggest that Dupuytren's disease is not strictly local and limited to the nodules, but affects, at least partially, the whole aponeurosis. Dupuytren's nodules could be considered as a model of tumor progression in a benign situation.

Fibrin clot retractile activity in normal, established, and tumorigenic human epithelial cells in culture

Normal and established human epithelial cell lines obtained from the same organs were compared for their capacity to retract a fibrin clot. Fibrin clot retraction was maximal in normal epithelial cells, reduced in established nontumorigenic lines, and lost in tumorigenic cancer cell lines. Fibrin clot retraction efficiency seemed to be related to the degree of cellular spreading within the clot at the end of the test. Previous works and the present study suggest that fibrin clot retraction is correlated with some steps of cell transformation in vitro.

Comparison of fibrin clot retraction with other transformation parameters after hydridization of normal and established cell lines

The expression of transformation parameters (inhibition of cell division during cell crowding, anchorage dependence, loss of fibrin clot retractile activity and secretion of plasminogen activator) was studied in a heterospecific cellular hybrid, made between established L(TK-) cells and the normal human MRC-5 cells. The hybrid nature of the cross was confirmed by the ability to incorporate [3H]-thymidine, by growth in selective HAT medium, by the identification of human chromosomes and by the expression on the surface of 100% of hybrid cells of a human glycoprotein, which is recognized by the 4F2 monoclonal antibody. The hybrid cultures showed cell cycle inhibition which became less stringent with increasing population doublings and the loss of human chromosomes. Fibrin clot retraction and anchorage dependence were absent in spite of the presence of many human chromosomes. The two properties were present or lost simultaneously in the normal parent cells and in the transformed parent or hybrid cells respectively. The human type of plasminogen activator was secreted even with very little human genetic material left, and a complete dissociation between fibrin clot retraction and production of plasminogen activator was observed. The data strengthen the hypothesis that transformation is a multistep process that involves complex genetic control and where cells progressively express different phenotypes and escape growth control.

Comparison between proliferative changes and nuclear events during ageing of human fibroblasts in vitro

Age-related alterations in nucleoproteins were examined in resting human embryonic fibroblasts at various population doubling levels (PDL) with three techniques for electron microscopy. Conventional glutaraldehyde fixation showed nuclear modifications consistent with previously published studies. Miller's technique permitted the detection of transcription complexes in young as well as in old cells. The technique involving the ultrathin sectioning of partially loosened nucleoproteins revealed at high PDL a marked rarefaction of the chromatin threads and the appearance of large parts of the lamina densa devoid of attached threads. In addition, the nucleolar filamentous masses were considerably less tufty than at earlier PDL, suggesting a decrease in the ribosomal transcriptional activity. These changes in nucleoprotein organization were rare before the 40th PDL, then increased to about 5% of the nuclei when the percentage of cells initiating DNA during the first 24 h remained at low levels. They were the rule for the last 6 to 7 PDL and coincided with the time when the maximal densities started to fall rapidly. They appeared after treatment with a loosening medium at neutral and at alkaline pH.

Relationship between fibrin clot retraction and tumorigenesis in C3H/10T1/2 cells

Fibrin clot retraction (FCR) was studied in C3H/10T1/2 murine fibroblasts. These cells were able to induce FCR with high efficiency during resting phase as well as during active growth. C3H/10/T1/2 cells which became tumorigenic after X-irradiation lacked FCR activity. Non-tumorigenic revertant clones regained the capacity to induce FCR, while revertants which progressively back-reverted to the neoplastic state showed intermediate FCR activity. These unstable revertants, when again fully tumorigenic, completely lost FCR activity.

Fibrin clot retraction in normal and transformed avian fibroblasts

Normal avian embryo fibroblasts induced retraction of a fibrin clot. The expression of high levels of this activity was associated with the exponential growth phase of the cell division cycle. Cells transformed by avian sarcoma virus (ASV) and other agents lost this activity regardless of the cell cycle phase. Cultures infected with transformation-defective ASV mutants retained a high level of fibrin clot retraction. However, this activity could not be recovered when temperature-sensitive, virus-transformed cells were shifted to a nonpermissive temperature (41 degrees C). The results indicated that, in this cell system, loss of fibrin clot retraction could be considered a reliable parameter of cell transformation.

Stimulation of spreading of trypsinized human fibroblasts by lysozymes from Staphylococcus aureus, hen egg white, and human urine

The effect of lysozyme from three different sources--Staphylococcus aureus, hen egg white, and human urine--on adhesion to substrate and spreading of trypsinized human fibroblasts was studied. Several fibroblast strains were tested under various conditions. It was found that the different cell strains did not show the same capability of spreading and stably attaching to substrates when resuspended in media not containing serum. Some strains did not spread, whereas others spread even in the absence of serum. Cell spreading in these strains did not occur when the cells were pregrown for 5 weeks in media supplemented with 1% fetal bovine serum. Lysozyme from S. aureus allowed stable adhesion to substrate and spreading of all the fibroblast strains unable to elongate in nonsupplemented minimal essential medium. This enzyme accelerated and augmented spreading of the strains capable of elongating in the absence of serum. S. aureus lysozyme also allowed spreading and stable adhesion to substrates of all these strains when they were pregrown for 5 weeks in the presence of 1% fetal bovine serum. Furthermore, hen egg white lysozyme and the lysozyme purified from human urine were both capable of stimulating anchorage to substrate and spreading of trypsinized fibroblasts although their effect was less pronounced than that of the S. aureus lysozyme. Some tentative hypotheses for the mechanism of cell spreading in the presence of lysozyme are made. The possibility that lysozymes, virtually ubiquitous enzymes, may play a specific role in nature in the regulation of cell differentiation and tissue development is finally raised and discussed in light of several previous observations and findings.

Effect of low dose rate irradiation on the division potential of cells in vitro. VII. Human fibroblasts from young and adult donors

Lung and skin fibroblasts from young and adult donors were irradiated with low dose rate ionizing radiation. Experiments show that in fibroblastlike cells from human adult donors there are three main types of response: irradiation can decrease only the total number of cells produced, it can also decrease the number of subcultures, and in some instances it can prolong the growth potential. Previous experiments suggested that these responses are genetically determined. They may have implications concerning the donor's proneness to cancer.

Effects of Staphylococcus aureus lysozyme on human fibroblasts

The purified lysozyme excreted by Staphylococcus aureus strains promotes elongation and spreading on plastic surfaces and stimulates DNA synthesis of human fibroblasts (WI38). This enzyme also raises twofold the saturation density level of cultures of these cells. It is suggested that the primitive and main effect of lysozyme on fibroblasts is the triggering of morphogenesis.