Concomitant Secretion by A431 Cells of Tissue Plasminogen Activator and a Specific Inhibitor Masks EGF Modulation of tPA Activity

It has previously been reported that EGF enhances uPA but not tPA in the A431 squamous carcinoma cell line. To determine whether the absence of tPA modulation by EGF reflected steady levels or the action of an anti-activator, we assayed tPA, PAI-1 and tPA/PAI-1 complexes by zymography and immunological assays. Under conditions in which EGF had no effect on tPA activity, tPA antigen paradoxically increased with a concomitant rise of tPA/PAI-1 complexes. This indicated that tPA was rapidly inactivated through the formation of a complex, immunologically and electrophoretically related to tPA/PAI-1. tPA antigen and tPA/PAI-1 complexes were modulated by EGF in a time and concentration dependent manner. PAI-1 antigen was secreted into A431 medium (CM) after a lag phase of 16 h in both control andEGF-treated cultures. Evidence is presented here that two forms ofPAI-1 are present in A431 CM: an inactive form and an active form which neutralizes the tPA secreted, masking its enhancement by EGF infunctional assays.

Effects of culture passages on collagen immunostaining in human dental pulp and gingival fibroblasts

In this study, a scanning microscopic computer-assisted image analysis system was used for the immunocytochemical characterisation of collagen types I, III and V in normal human fibroblasts from pulp and gingival explants, using specific purified antibodies and peroxidase labeling. The culture conditions were standardized in order to evaluate simultaneously the expression of the three antigens in four different culture passages of the two fibroblast types. The optical density values of immunostaining intensities were quantified, the integrated optical density per cell was calculated, and the results were analyzed by a variance test. It was found that all three collagen types were present in the tissues, and in both gingival and pulp fibroblasts after three to nine culture passages. A non-parametric statistical analysis of the staining intensity variances revealed significant differences between antigenic levels depending on the tissue origin of the fibroblasts and an effect of culture passages. The results seemed to justify application of this technique at the light microscope level for the evaluation of collagen production, the principal function of fibroblasts, but the tissue origin and number of culture passages should be taken into consideration for in vitro biocompatibility testing of dental materials.

Relationship between cathepsin D, urokinase, and plasminogen activator inhibitors in malignant vs benign breast tumours

The concentrations of cathepsin D (Cath D), urokinase (uPA) and two plasminogen activator inhibitors (PAI-1 and PAI-2) were analysed in the cytosols of 130 human mammary tumours (43 benign tumours and 87 primary and unilateral breast carcinomas). uPA, PAI-1 and PAI-2 levels were measured by antigenic immunoassays and Cath D by immunoradiometric assay. The median levels of the four parameters were significantly higher in the malignant tumours than in the benign ones. Cath D and uPA increases were 4-fold and 5-fold respectively. PAI-1 and PAI-2 increases were much more important, 74-fold and 29-fold respectively. In malignant tumours, median levels of Cath D and uPA did not vary according to classical prognostic factors (histologic grade, presence or absence of axillary lymph nodes, steroid receptors, UICC stage, tumour size, age, and menopausal status). However, PAI-1 decreased in ER+ and PR+ tumours and PAI-2 increased in menopausal women's tumours. When Cath D, uPA, PAI-1 and PAI-2 levels in malignant tumours were compared, positive correlations were found for all combinations. The implication of plasminogen activator inhibitors in the phenomenon was surprising and merits further investigation using tools other than global antigen measurements in tumours.

Modulation of tPA, PAI-1 and PAI-2 antigen and mRNA levels by EGF in the A431 cell line

It has been reported that EGF treatment enhances uPA but not tPA in the A431 epidermoid carcinoma cell line. To determine whether the absence of tPA modulation by EGF could be due to the action of inhibitors, we assayed tPA, PAI-1, PAI-2 and tPA/PAI-1 complexes by immunological assays and zymography in A431 serum-free medium. We found that, under conditions in which EGF had no effect on tPA activity, tPA antigen increased with a concomitant rise of tPA/PAI-1 complexes, indicating the action of an inhibitor. Both tPA antigen and tPA/PAI-1 complexes were modulated by EGF in a time and concentration dependent manner. tPA/PAI-1 complex levels were lower than tPA levels, suggesting the presence of other inhibitors. Immunological assays detected PAI-2 in addition to PAI-1 and showed a time and dose response to EGF. Modulation of tPA and the anti-activators by the growth factor was confirmed by identification of the corresponding transcripts with cDNA probes. We conclude that the net plasminogen activator activity in A431 cells is the result of a balance between activators and inhibitors.

Concomitant secretion by A431 cells of tissue plasminogen activator and a specific inhibitor masks EGF modulation of tPA activity

It has previously been reported that EGF enhances uPA but not tPA in the A431 squamous carcinoma cell line. To determine whether the absence of tPA modulation by EGF reflected steady levels or the action of an anti-activator, we assayed tPA, PAI-1 and tPA/PAI-1 complexes by zymography and immunological assays. Under conditions in which EGF had no effect on tPA activity, tPA antigen paradoxically increased with a concomitant rise of tPA/PAI-1 complexes. This indicated that tPA was rapidly inactivated through the formation of a complex, immunologically and electrophoretically related to tPA/PAI-1. tPA antigen and tPA/PAI-1 complexes were modulated by EGF in a time and concentration dependent manner. PAI-1 antigen was secreted into A431 medium (CM) after a lag phase of 16 h in both control and EGF-treated cultures. Evidence is presented here that two forms of PAI-1 are present in A431 CM: an inactive form and an active form which neutralizes the tPA secreted, masking its enhancement by EGF in functional assays.

Helium-neon laser treatment transforms fibroblasts into myofibroblasts

The differentiation of myofibroblastic cells from normal human gingival fibroblasts in vitro has been established by transmission electron microscopy and quantitated by immunohistochemistry, using antigelsolin monoclonal antibodies. Untreated control cultures were compared to cultures exposed to Helium-Neon (He-Ne) laser irradiation. A direct and massive transformation of the cultured fibroblasts into myofibroblasts was observed as early as 24 hours after laser treatment, whereas control cultures were comprised of only resting fibroblasts and active fibroblasts. This in vitro induction of myofibroblasts may be analogous to that which occurs in vivo. Therefore we undertook a similar study using biopsies from gingival tissues after wisdom tooth extraction. Myofibroblasts were present in the connective tissue of laser-treated gums 48 hours after irradiation, but not in untreated contralateral control tissues. These data provide evidence that the primary biologic effect of the Helium-Neon laser on connective tissue is the rapid generation of myofibroblasts from fibroblasts. The induction of a phenotype with contractile properties may have clinical significance in the acceleration of the wound-healing process.

[Evaluation of the cytotoxicity of two capping materials: in vitro cell culture study]

Evaluation of the biocompatibility of a crown reconstruction material in vivo on human teeth by histologic observation of pulpal reactions is a long lasting and expensive procedure. Before to start it, a first examination can be done by testing the material on cell cultures. If the used culture cells contain antibiotics, it is necessary to combine these tests with a bacteriologic examination of the tested material. Two calcium hydroxide containing materials for dentin-pulp capping, were submitted to cytotoxicity tests using human pulpal fibroblasts cultures. The cytotoxicity of one over the two materials could be related to its lability and bacterial contamination.

Toward a new approach in tumor cell heterogeneity studies using the concept of order

A new methodology was developed to study dynamic processes topographically in biological systems by means of a graph-theoretical method. It is based upon order parameters obtained from a minimal spanning tree analysis coupled with computer simulations. The method was used to analyse the heterogeneous behavior of two neoplastic cell lines after treatment with laminin. The laminin-induced cell detachment was quantitated and shown to be inversely related to cell population density and thus to cellular interactions. Our statistical analysis is a very powerful tool to obtain information from seemingly disorderly heterogeneous biological models.

Modulation of plasminogen activator systems by matrix components in two breast cancer cell lines: MCF-7 and MDA-MB-231

We have analyzed the plasminogen activator (PA) systems of two metastatic breast adenocarcinoma cell lines, MCF-7 and MDA-MB-231, as a function of 17 beta-estradiol stimulation when the cells were cultured on purified components of extracellular matrix. Laminin enhanced PA levels in both cell lines, but this enhancement seemed to occur via different mechanisms, including dissociation of inhibitor complexes. The major effect was the marked increase in cell-associated urokinase-type PA (u-PA); the increase was independent of estrogen in hormone-insensitive MDA-MB-231 cells grown on laminin-coated surfaces. In estrogen-sensitive MCF-7 cells, 17 beta-estradiol stimulated u-PA secretion in a similar fashion on plastic, laminin, fibronectin, or collagen but acted in synergy with laminin in the production and release of tissue-type PA.

Estradiol membrane binding sites on human breast cancer cell lines. Use of a fluorescent estradiol conjugate to demonstrate plasma membrane binding systems

A fluorescent estradiol macromolecular complex was used to study and to characterize steroid binding to membranes of living target cells. Ligand binding to plasma membranes was quantitated with a sensitivity of 0.1 nM. In this way, we found two types of estradiol-binding sites on hormone sensitive MCF-7 cells. Type A sites (8000-16000 sites per cell) were rapidly saturated at low concentrations of the estradiol-bovine serum albumin-fluorescein isothiocyanate macromolecular complex (E2-BSA-FITC). They had a greater affinity for the complex than did the type B sites for which a phenomenon of cooperative fixation was shown. The complex binding was displaced by estrogenic molecules, but not by non-estrogenic compounds, such as cortisol or progesterone. We also studied complex binding on another breast cancer cell line, MDA-MB-231 (MDA), without intracellular estrogen receptors. These cells showed a specific plasma membrane binding system for estrogen, but lacked the high affinity type A binding site. Then, we report the effects of enzyme treatments (trypsin, phospholipase A2 and neuraminidase) on E2-BSA-FITC binding to MCF-7 cell membranes. The quantity of complex bound to membranes decreased after phospholipase and neuraminidase treatments and increased after trypsin. But, in the three cases, the binding was no longer specific because it could not be displaced by E2-BSA or by estradiol. The enzymatic effects were reversible and specific binding was totally restored within 24 h. However, in the presence of the protein synthesis inhibitor, cycloheximide, no restoration of specific binding occurred on trypsin-treated cells. Estrogen binding to MCF-7 and MDA cell plasma membranes thus possesses the three characteristics of all mediated transport processes across biological membranes: saturability, substrate specificity, and specific inhibition. However, the high affinity type A binding site was found only on the estrogen-sensitive cell line, MCF-7.

Early alterations at the plasma membrane of breast cancer cell lines in response to estradiol and hydroxytamoxifen

The time course of the early stage of estradiol-17 beta (E2) and hydroxytamoxifen (OHTAM) action at the plasma membrane of hormone-responsive MCF-7 and non-responsive MDA-MB-231 (MDA) breast cancer cell lines was investigated using scanning electron microscopy (SEM), electron probe X-ray microanalysis and microelectrophysiology analysis. SEM showed a marked increase in the density and the length of microvilli (MV) on MCF-7 cells treated with 1 nM estradiol for 1 min. This membrane response disappeared at 5 min. No early effect was obtained with OHTAM, but both compounds produced a similar surge of heterogeneous MV at 15 min of treatment. The morphological change induced by E2 subsided at 60 min, whereas that of OHTAM persisted. X-ray microanalysis and computer determination of peak/background ratios permitted the demonstration that these morphological alterations were concomitant with a rise in the intracellular level of potassium. Microelectrophysiology analysis showed a sharp transitory decrease in the membrane potential of MCF-7 cells in response to estradiol. In the estrogen-insensitive MDA cells, the hormone did not modify the membrane potential and K levels decreased at 1 and 5 min before rising again to control levels at minute 15 when MV appeared. With OHTAM, potassium decreased significantly at 60 min of treatment. These initial and transitory changes in surface morphology paralleled by alterations in potassium level may be consistent with the occurrence of estrogen membrane receptors on target cells, a new aspect of steroid hormone action.

Estrogen receptor immunocytochemical assay (ER-ICA): computerized image analysis system, immunoelectron microscopy, and comparisons with estradiol binding assays in 115 breast carcinomas

An estrogen receptor (ER) immunocytochemical assay (ER-ICA) was applied to 115 malignant breast carcinomas and the results were compared to those of steroid binding assays performed on cytosol extracts of the same tumors. Immunoperoxidase (peroxidase-antiperoxidase) staining was performed on frozen sections using rat monoclonal antibody to estrogen receptor H222SP gamma. A preembedding method was used for the immunoelectron microscopy study. A semiquantitative analysis and a computerized image analysis system (SAMBA 200 TITN) were used to evaluate the positive ER immunostaining. Positive immunostaining (81 of 115) was always located in the nucleus of tumor cells and of normal cells in adjacent breast tissue. The immunostaining pattern differed from one tumor to another, due to variations in either the intensity or the percentage of positive cells. When immunohistochemical staining was correlated to biochemical assay, there was an 88% correlation, and staining intensity and percentage of positive cells significantly increased (P less than 0.01) with cytosolic ER levels and were independent of cellularity. These results indicated that ER-ICA is to date the most reliable histochemical method for ER detection and correlated in 88% of the cases with ER biochemical assay; ER-ICA constitutes a method particularly valuable to screen ER negative tumors on condition that tumor fragment quality (sampling and storage) is perfectly controlled; ER-ICA provides additional information for heterogeneous ER distribution within tumors; ER-ICA as a qualitative method is unable to replace the quantitative ER determination obtained with biochemical assay although the computerized system (SAMBA 200) for image analysis of microscopic preparations constitutes a valuable improvement of immunostaining analysis; and ER-ICA based on ER antigenic site detection is complementary to biochemical assay based on ER functional site determination.

Immunohistochemical detection of laminin in 98 human breast carcinomas: a light and electron microscopic study

The distribution of laminin was studied in 98 breast carcinomas with antilaminin and the avidin-biotin-peroxidase complex method. Laminin was observed within vascular and epithelial basement membranes. Laminin displayed a continuous linear pattern in intraductal carcinomas, and it was heterogeneously distributed, with a discontinuous linear pattern, in invasive carcinomas. No intracellular laminin staining was detected. Electron microscopic study showed laminin immunostaining in the lamina densa of basement membranes in nonneoplastic breast tissue. In tumors, laminin immunostaining frequently revealed multilayered basement membranes and abnormal multilayered basement membranes in blood vessels in the tumor stroma. These data suggest that laminin immunostaining, as a new approach to the heterogeneous basement membrane changes occurring in carcinomas, should permit better understanding of cell diffusion processes and of stroma-tumor cell interactions. The consistent extracellular distribution of laminin in contact with the stroma indicates that the latter plays an important role in the assembly of basement membrane components.

Kappa casein, lactalbumin and GCDFP 70 localization in human breast carcinomas: an immunohistochemical study using the avidin-biotin-peroxidase complex method

A retrospective study of 67 human breast carcinomas of various types and grades was conducted using the avidin-biotin-peroxidase complex (ABC) to localize casein, lactalbumin, and GCDFP 70 on paraffin sections. Estrogen and progesteron receptors also were evaluated. This study demonstrated the following: (1) Casein positive cells were present in all cases with a variable distribution and degree of staining, whereas lactalbumin and GCDFP 70 were seen in only 40 and 43% of the cases, respectively. (2) No significant relationship was observed between casein, lactalbumin, GCDFP 70 and the histologic types of tumors or the extent of stromal elastosis, with the exception GCDFP 70, which was observed more often in well-differentiated ductal carcinomas. (3) No significance was established in the relationship between antigens and steroid receptor content, with the exception of casein; strong casein immunostaining was significantly related to high progestin receptor levels. (4) Lactalbumin and GCDFP 70 were significantly associated with each other, but independently so of the histologic grades and types, the extent of stromal elastosis, and the steroid receptor content of the tumor cells.

Localization of lactoferrin and nonspecific cross-reacting antigen in human breast carcinomas. An immunohistochemical study using the avidin-biotin-peroxidase complex method

A retrospective immunocytochemical study was performed on 67 human breast carcinomas to determine whether the epithelial cell-associated antigens, lactoferrin and nonspecific cross-reacting antigen (NCA), could be used as markers in the prognostic assessment of breast cancers. Fixed paraffin sections were tested with anti-lactoferrin and anti-NCA. Lactoferrin and NCA were found in 7.5% and 19% of the cases, respectively. Furthermore, the association between these two antigens in tumor cells was significant (P less than 0.05). Kappa-casein was observed in all antigen-positive cases. These antigens were observed more often in low-grade ductal carcinomas that had positive estrogen and progestin receptors, but no relationship could be established between lactoferrin or NCA and other prognostic indicators, such as histologic type and grade of the tumor, stromal elastosis, or steroid receptors. Although more antigen might have been detected in unfixed, frozen specimens, the results indicate that lactoferrin and NCA possess minimal value as epithelial cell markers and no prognostic value when detected on routinely fixed, paraffin-embedded samples.

Laminin distribution in human decidua and immature placenta. An immunoelectron microscopic study (avidin-biotin-peroxidase complex method)

An immunoelectron microscopic study was carried out on human placenta and decidua with the use of preembedding, the avidin-biotin-peroxidase complex technique, and rabbit anti-murine laminin antibody. Laminin was detected in the lamina lucida of basement membrane of placental villi, amniotic membranes, umbilical cord, endometrial glands, and blood vessels. No positive laminin immunostaining was observed in intracytoplasmic organelles. However, positive immunostaining surrounded decidual cells as a more or less continuous linear membrane. It is suggested that laminin, as a component of this basement membrane-like material that has already been reported in decidual cells, may be related to the hormonal stimulation occurring during pregnancy and trophoblastic attachment.

Estrogen response of MCF-7 cells grown on diverse substrates and in suspension culture: promotion of morphological heterogeneity, modulation of progestin receptor induction; cell-substrate interactions on collagen gels

In this study we observed the incidence of hormone sensitivity in the response of MCF-7 cells to estrogen stimulation when the cells were cultured in different contact environments (hydrophilic plastic, bovine corneal extracellular matrix, type I collagen and in suspension culture). The major purpose was to describe the influence of cell to cell and cell to substrate contacts on the morphological response to estrogen treatment. However, other parameters including growth and induction of progestin receptor were also explored, keeping in mind that the MCF-7 cell line, although representative of normal mammary epithelium in that it contains a similar hormone receptivity, was selected in vitro from a metastatic population in a pleural effusion. Although substrate conditions did not modify growth enhancement by estrogens, progestin receptor levels were significantly higher in three-dimensional spheroid cultures in which cell to cell contacts were optimal due to elimination of basal contact. A careful morphological survey of large surfaces lead to an objective opinion of the overall effect of the hormone treatment on the non-cloned cell line in which a marked heterogeneity in the response of individual cells was observed. In terms of morphofunctional differentiation, the edification of acini with dense microvillus coating was best in suspension culture. When sections were made perpendicular to the plane of cultures on collagen gel rafts two other phenomena were noted: decrease in intercellular junctions, resulting in reduced cell to cell cohesion, and accumulation biodegradation products in the collagen lattice. This suggested a hormone-mediated interaction between the metastatic cells and the fibrillar substrate, collagen I, one of the major constituents of tissue stroma. This estrogen response might be related to the metastatic phenotype and must be distinct from their hormone sensitivity in terms of growth and differentiation since hormone receptivity is generally considered to be a favorable prognosis for breast cancer.

How culture conditions modulate the morphofunctional differentiation of the human estradiol-sensitive mammary cell line (MCF-7)

The MCF-7 cell line grown on plastic surfaces is widely accepted as a model for hormone sensitivity in molecular biology. However, in vitro results concerning estrogen sensitivity remain controversial. In search of culture conditions most closely simulating the in vivo microenvironment we cultured MCF-7 cells on diverse substrates and in suspension culture. The different factors of the contact environment: (A) influence of diffusive medium, (B) influence of cell to cell contacts, and (C) influence of cell to substrate contacts were considered. Using morphological criteria:phase contrast microscopy, scanning and transmission electron microscopy we observed MCF-7 morphofunctional differentiation under the different culture conditions. Plastic, corneal endothelial cell extracellular matrix, and attached collagen gels imposed a planar medium-aggregate interface. The impermeability of the free surface and the intense basal tension antagonized epithelial polarization. Only at post-confluence did domes and clusters appear above the monolayer. On floating collagen gels and in suspension culture the cells established intimate cell-cell contacts over large surfaces and reconstituted tissular architecture. Three-dimensional growth conditions which approach the in vivo contact environment of epithelial cells should be used instead of the traditional monolayer cultures for assessing hormonal and pharmacological responses of human breast carcinomas.

Dose-related enhancement of erythropoiesis by sulfhydryl compounds and its reversal with a thiol inhibitor

Erythropoietin-mediated erythrocyte development from bone marrow of hypertransfused rats was significantly greater when the culture medium contained an optimal dose of certain sulfhydryls. This stimulatory action was attributed to the presence of SH groups because erythroblast numbers fell to control levels when the culture contained the thiol inhibitor, p-hydroxymercuribenzoate.

The role of cellular locomotion in leukemic infiltration. An organ culture study on penetration of L 5222 rat leukemia cells into the chick embryo mesonephros

The significance of cellular locomotion for leukemic infiltration was investigated using L 5222 rat leukemia cells. Previous cinemicrographic studies have shown that these cells are able to locomote only after formation of a uropod-like posterior extension. This characteristic locomotive configuration of L 5222 cells is easily recognizable in scanning electron micrographs and appropriate sections. Leukemia cells were inoculated on slices of chick embryo mesonephros incubated for 24h; at this time the fragments are completely encapsulated. Leukemic infiltration is found to begin within the first 2 h and to increase gradually up to the end of the observation period at 72 h. Spread of leukemia cells occurs mainly in the intertubular spaces; the tubular epithelium is only rarely affected. In all stages of infiltration, L5222 cells with the characteristic locomotive configuration are frequently recorded. Besides this strong although indirect indication for the significance of locomotion, further evidence was provided by experiments performed at 25 degrees C and 18 degrees C. In accordance with the previous cinemicrographic finding that at these temperatures L 5222 cells are unable to produce their posterior extension, no leukemic infiltration mesonephros fragments is recognizable at subnormal temperatures.

In vitro growth promotion of rat leukemia L5222 cells in the presence of 2-mercaptoethanol

Propagation of the transplantable acute rat leukemia L5222 in vitro was highly dependent on the reducing agent 2-mercaptoethanol (2-Me). Maximum growth promotion was obtained in the simultaneous presence of 1.25-2.5 x 10-4m 2-Me and 30% fetal bovine serum in enriched tissue culture medium NCTC 135. A short exposure to the reducing agent insured growth of the leukemia cells for 5 days, but extended culture necessitated constant presence of the thiol. After 2-8 days of culture, inoculation of the cell suspension produced widespread leukemia in inbred BD IX rats.

Masculinizing effects of a testicular interstitial cell tumour graft on female rats

An androgen-producing testicular interstitial cell tumour of rats was grafted into intact and spayed female rats. The tumour inhibited luteinization, produced follicular atresia, stimulated the uterine myometrium and endometrium, and caused vaginal mucus formation. Anoestrus set in and mating behaviour disappeared, rendering gestation impossible. After surgical removal of the tumour, the masculinization disappeared rapidly. With the return of vaginal oestrus (sometimes only 4 days after removal of the tumour) most of the rats mated and gave birth to normal young. When a palpable nodule reappeared, the reproductive function was again lost. The tumour produced similar changes in the target organs of spayed females. The inhibitory action of the endocrine tumour on pituitary gonadotrophic hormone production was shown by the absence of castration cells in the pituitary of the tumour-bearing spayed female.