Determination of TGFbeta1 protein level in human primary breast cancers and its relationship with survival

Transforming growth factor-beta (TGFbeta)1 is thought to be implicated in breast cancer progression. However, data about the influence of TGFbeta1 on breast cancer development are conflicting. To clarify the clinical relevance of TGFbeta1, TGFbeta1 protein level has been measured by enzyme-immunoassay in 193 breast tumour samples. We found that 94.3% of patients expressed TGFbeta1 with a range of 0-684 pg mg(-1) protein. In the overall population, an increase of tumoral TGFbeta1 was observed in premenopausal patients when compared to postmenopausal subgroup (P=0.0006). When patients were subdivided according to nodal status, TGFbeta1 was correlated to type-1 plasminogen activator inhibitor in the node-negative subgroup (P=0.040). Multivariate analysis revealed that, after lymph node status (P=0.0002) and urokinase-type plasminogen activator (P=0.004), TGFbeta1 was an independent prognostic marker for DFS (P=0.005) in the overall population. In the node-negative population, TGFbeta1 was the prominent prognostic factor (P=0.010). In the same population, Kaplan-Meier curves demonstrated that high TGFbeta1 level was correlated with a shorter disease-free survival (P=0.020). These data suggest that the measurement of tumoral TGFbeta1 protein level, especially for node-negative patients, might help to identify a high-risk population early in tumour progression.

Frequency and genome load of Epstein-Barr virus in 509 breast cancers from different geographical areas

Since the few data exploring a possible association between Epstein-Barr virus (EBV) and breast cancer are conflicting, we investigated this association together with the influences of geographical areas. 509 breast cancers were sampled from areas with varying risks of nasopharynx carcinoma (NPC) such as North Africa (Algeria and Tunisia, high-risk area); southern France (Marseille, intermediate-risk area); and northern Europe (northern France, the Netherlands and Denmark; low-risk areas). Polymerase chain reaction (PCR) of a subregion of EBV BamHIC encoding the EBERs demonstrated that 31.8% of the tumours contained the viral genome. No significant differences were observed among the geographical areas. However, positive samples showed higher loads of the EBV genome in the NPC high- and intermediate-risk areas than in the low-risk areas. EBV type 1 was the dominant strain. In situ hybridization studies using a(35)S-labelled riboprobe for EBER1 and a laser capture microdissection, combined with quantitative PCR, showed that EBV localization was restricted to some tumour epithelial cell clusters. EBV could not be detected in the stroma. Considering the whole population covered, the presence of the EBV genome was not correlated with age, menopausal status, tumour, size, nodal status or histological grade.

Morphological evidence for a subpopulation selection effect by estrogen and antiestrogen treatments in the heterogeneous MCF-7 cell line

Recently, we developed a method to quantitatively study tumour cell heterogeneity in terms of both nuclear size and estrogen receptor (ER) content by image cytometry. The method, previously used to analyse the proliferation of the breast cancer cell line MCF-7, was applied here to analyse the growth of this cell line under estradiol (E2), hydroxytamoxifen (OH-TAM), and both E2 and OH-TAM treatments. The method extracts characteristic parameters of single nuclei and features that measure the global and local organisation of the cells in their growing phase. Modifications of the heterogeneity of the cell line are emphasised through phenotypic changes and modifications of the spatial organisation of the cells. The hormone (E2) generates a very fast growth of cells with small nuclei that became ER negative in the long term. The antihormone (OH-TAM) produces a gradual selection of ER negative or poorly positive cells with large nuclei. These modifications are reversed when E2 and OH-TAM are simultaneously used. Moreover, estradiol induces a permissive context of proliferation, whereas hydroxytamoxifen acts only on some subpopulations. The combination of cell count, cytomorphology, and cell organisation revealed the magnitude of the potential of structuration of hormones or antihormones on in vitro growing cells.

A minimal model for calcium signal generated by tyrosine kinase and G protein linked receptors; a stochastic computer simulation with CALSIM

A software was designed to simulate the calcium signal following hormone or growth factor stimulation in epithelial cells. The software written in C runs on a PC under Windows environment. It is based on a Markov process where the dynamic of the system is characterised by phenomenological transition probabilities. Moreover a minimal model is proposed to analyse the role of plasma channels and IP3 receptors, together with the opposite action of the CaATPase pumps, in the cytosolic and endoplasmic reticulum (ER) calcium signal control. The simulation is applied on the calcium response following stimulation by carbacol (protein G coupled receptors) or epidermal growth factor (tyrosine kinase type receptors) in A431 epithelial cells. The experimental calcium signals can be grouped in three classes; a spike and a return to the basal level (signal A), a spike and a decrease to a plateau level (signal B) or a slow increase to a plateau (signal C). Epidermal growth factor induces signal A and B while carbacol gives signal B and C. When a 'pseudo' steady state is reached oscillations occur. Computer simulations show that signal A can result from the activation of IP3 receptors while signal C would result from the activation of the plasma channels; signal B appears as the additive contribution of both channels, while oscillations are compatible with a calcium induced calcium release mechanism. Simulations suggest that the calcium dynamic in the ER is a mirror of cytosolic calcium but that a simple way to produce similar calcium elevation in these two compartments is to activate plasma channels. Implications of such a mechanism is discussed.

[Contribution of the topographical analysis to quantitative microscopy in cultured cell systems: application to the evaluation of hormone therapy]

Quantitative microscopy by image analysis allows not only to measure various parameters on each cell but also to consider the global population as a whole. In the hypothesis that cell position is reflecting the relational and dynamical structure of the system, spatial arrangement analysis may help to show up intercellular communication (interactions and control systems via contact or diffusible factors). We describe a topographical analysis method used to study these neighbour relationships, and thus the sociological behaviour of the cells. It is applied to the study of the effect of estrogenic and antiestrogenic treatments on a breast cancer cell line (MCF-7). It shows up that estrogens increase proliferation and induce an unusual topographical behaviour, notably in cell cycle phases: cells in S phases are very randomly distributed. It points out the role of estrogens on the cells neighbour relationships inducing the way to a permissive proliferation context. This effect is reversed by antiestrogenic treatment after a few days. Antiestrogenic treatment alone increases the proliferation constraint.

Topographical analysis of spatial patterns generated by a cellular automaton model of the proliferation of a cancer cell line in vitro

A well-suited model to simulate cellular population dynamics is the two-dimensional cellular automaton model, which consists of a lattice of sites, the value ai,j of each site being updated in discrete time steps according to an identical deterministic rule depending on a neighbourhood of sites around it. A cellular automaton is described which mimics cell population proliferation by replacing the site values by the age and the cycle phase of cells. The model takes into account the size of the cells. It is used to simulate the proliferation of the human breast cancer cell line MCF-7 and the results of the simulation are compared with experimental data obtained from a light microscopic image analysis of the proliferation process. The initial configuration of the cellular automaton is obtained from the discretization of the results of the initial stage of the image processing. After each day of proliferation the pattern obtained from the simulation is compared to the experimental result of the corresponding image analysis. The comparison is made from a topographical point of view through the concept of the minimal spanning tree graph. The agreement between experiment and model is a good starting point to complex models such as cell proliferation under growth effectors or drugs.

Distribution of estrogen receptor heterogeneity in growing MCF-7 cells measured by quantitative microscopy

The existence of interactive subpopulations is a biological feature that can modulate the proliferation of tumor cells. The hormone-responsive breast cancer cell line MCF-7 has been described as heterogeneous in terms of density. In this study we describe a quantitative image analysis methodology that we developed for the in situ detection of different subpopulations in MCF-7 cell cultures. Using this technology, we demonstrate the heterogeneity of the MCF-7 cell line in terms of both nuclear size and estrogen-receptor content. Analysis of the organization (topography) of the different subpopulations in culture reveals a nonrandom distribution of cells. When studying the development of these cell subpopulations as a function of time of culture, we observe modifications of their topography associated with an increase of estrogen-receptor-expressing cells. Moreover, the use of cluster analysis allows study of the local organization of these subpopulations. These changes appear to be independent of cell proliferation.

Image cytometry and topographical analysis of proliferation of endothelial cells in vitro during Bartonella (Rochalimaea) infection

Bartonella quintana and Bartonella henselae are clinically associated with proliferative neovascular lesions. The effect of Bartonella infection on human endothelial cells was evaluated in vitro by quantitative image analysis. Particular emphasis is placed on reporting the methodologies employed. Human umbilical vein endothelial cells were infected in vitro with the two Bartonella species. Cell proliferation (cell density), cell morphology (cell surface, form and elongation factors) and spatial reorganization (global topographical analysis and hierarchical cluster detection) were monitored over a 3-day period of infection. Firstly, infection stimulated endothelial cell proliferation. Secondly, infection induced obvious morphological changes; infected cells became larger, more elongated and spindle-shaped. Cytoskeletal reorganization was confirmed by staining of F actin. Thirdly, infection altered the spatial organization of cells within the monolayer; this could not have been due solely to the morphological modifications they experienced. This model demonstrates that Bartonella infection provoked endothelial cell proliferation, topographical rearrangements and morphological changes because of modifications of the cytoskeleton. These experimental findings provide a physiopathological explanation to the abnormal angiogenesis observed in bacillary angiomatosis.

Mode of EGF action on cell cycle kinetics in human breast cancer cell line MCF-7: some evidence that EGF acts as a "progression factor"

EGF is known to play a very important role in the growth regulation of tumor cells. We have determined the effect of EGF in the absence and in the presence of serum on the cell cycle of MCF-7 cells synchronized in the G1 phase by serum deprivation. In the presence of 1% serum, EGF was found to increase DNA synthesis to 120% of control (P < 0.02), but did not modify the transition time from G1 into S phases, nor the cell doubling time during the first generation following the cell synchronization. The autoradiography analysis of 3H-thymidine labeled cells indicated that, following 24 h of EGF treatment, a constant additional number of cells (11 +/- 1.5%, P < 0.002) were recruited into the S phase in the presence as well as in the absence of serum. These data indicate that EGF exerts its mitogenic effect on MCF-7 cells by increasing the percent of S phase cells without modulating the cell doubling time. However, in the absence of serum a significant increase of thymidine incorporation in whole cells required 12 h of EGF treatment, whereas a 6 h-incubation with EGF was sufficient to stimulate DNA synthesis when synchronized cells were pretreated with serum for 6 h, suggesting that EGF sensitivity is dependent on the cell advance into the G1 phase at the moment of EGF addition. Topographical analysis of 3H-thymidine-labeled cells aimed at determining the spatial distribution of cells in culture revealed that EGF-stimulated cells were disposed near proliferative cells, indicating the local influence on cell proliferation. Taken together, our results suggest that in the MCF-7 cell line, EGF acts in the G1 phase by increasing the proportion of S cells without affecting the duration of the cell cycle. In our model, EGF seems to act as a "progression factor", in that it stimulates only cells already traversing a certain stage in the G1 phase under the action of serum factors, cell secreted diffusible products and cell-cell contact.

Electron micrography and x-ray study of dip-lacquered LiF (220)

It has been proposed to use the 220 reflection of LiF with a multilayer deposited upon the top for simultaneous spectroscopy near Fe-k and O-k and below the C-k absorption edge (284 eV) in x-ray astronomy. We demonstrate that a substantial reduction of surface roughness is obtained by dip lacquering state-of-the-art polished LiF(220) surfaces. Using a microdensitometer analysis of electron micrographs of surface replicas and x-ray reflection, we have measured approximately 10-A rms roughness of Au-coated dip-lacquered LiF(220) crystals, as opposed to approximately 60 A measured on the bare LiF(220) crystal surface.

Abortive intermediates in transcription by wheat-germ RNA polymerase II. Dynamic aspects of enzyme/template interactions in selection of the enzyme synthetic mode

At constant enzyme concentration and with the full set of nucleotide substrates dictated by template sequence, the chain-length distribution of polymeric product varies with template concentration in reactions catalysed by wheat-germ RNA polymerase II. Under the same conditions, but in the presence of a single ribonucleoside triphosphate, the rate of condensation of the triphosphate substrate to a dinucleotide primer also exhibits a complex dependence with the template concentration. This effect is observed using poly[d(A-T)] as a template. For both reactions there are two extreme types of behaviour in each of which transcription appears to involve a single enzyme synthetic mode, characterized by either a high (at low template concentration) or a low (at high template concentration) probability of releasing the transcripts. A strong correlation is found between these two pathways, such that conditions favouring the abortive release of trinucleotide products in the single-step addition reaction are associated with the synthesis of short-length RNA species in productive elongation, and reciprocally. A model previously developed by Papanicolaou, Lecomte & Ninio [(1986) J. Mol. Biol. 189, 435-448] to account for the kinetics of polymerization/excision ratios with Escherichia coli DNA polymerase I, and by Job, Soulié, Job & Shire [(1988) J. Theor. Biol. 134, 273-289] for kinetics of RNA-chain elongation by wheat-germ RNA polymerase II provides an explanation for the observed behaviour with the plant transcriptase. The basic requirement of this model is a slow equilibrium between two states of the polymerization complex with distinct probabilities of releasing the product. In the presence of Mn2+, and under conditions allowing the synthesis of poly[r(A-U)], one of these states is involved in the formation of oligonucleotides shorter than 15 bases, whereas the other catalyses the polymerization of chains longer than 40 bases.

Molecular organization and clustering of cell-wall-bound enzymes as a source of kinetic apparent co-operativity

When fixed charges and enzyme molecules are not homogeneously distributed in a matrix, the degree of organization of charges, of enzyme molecules and of charges with respect to enzyme molecules modulate the enzyme reaction rate. The overall reaction velocity of the bound enzyme system may be expressed in terms of monovariate moments of the charge density distribution and of the bivariate moments of the charge and enzyme density distributions. With respect to the situation where fixed charges and enzyme molecules are randomly distributed in the matrix, the molecular organization, as expressed by the monovariate and bivariate moments results in an increase or a decrease, of the overall reaction rate, as well as in the appearance of a kinetic cooperativity. The degree of spatial organization of objects may be expressed quantitatively through the concept of minimal spanning tree. This concept may thus be applied to the quantification of the degree of order that may exist in the bidimensional distribution of enzyme molecules in a charged matrix. Primary walls of isolated plant cells in sterile culture behave as a polyanion and contain different enzymes. The spatial distribution in sycamore cell walls of an acid phosphatase has been studied through the concept of minimal spanning tree and shown to be non-randomly distributed in the polyanionic matrix, but clustered in that matrix. This spatial organization results in a modulation of the reaction rate of the cell-wall-bound phosphatase reaction. Both the theoretical and experimental results presented in this study leave little doubt as to the validity of the idea that in situ the organization of fixed charges and enzyme molecules modulate the overall dynamics of enzyme reactions.

Extreme UV and x-ray scattering measurements from a rough LiF crystal surface characterized by electron micrography

XUV and x-ray scattering by a LiF crystal is measured. The angular distribution of the scattered radiation (ADSR) reveals characteristic features, side peaks or asymmetry. The surface of the sample is statistically characterized by a microdensitometer analysis of electron micrographs resolving the short spatial wavelengths of the surface roughness. This analysis shows that the surface has a large microroughness with an autocovariance function which is Gaussian in its initial portion. The first-order perturbation vector theory of the roughness-induced scattering leads to an interpretation of the ADSR features in terms of the modulation of the surface power spectral density function associated with the microroughness by an optical factor. The possibility of obtaining short scale roughness characterization from XUV or x-ray measurements is discussed.

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.

Minimal spanning tree analysis of biological structures

A new approach to study order and disorder in biological membranes and more generally in biological structures is developed. It is based on a graph constructed on the set points representing the position of particles. From this graph, which is called the minimal spanning tree, it is possible to deduce two parameters, namely the average length m and the standard deviation sigma which are characteristic of the repartition to be studied. The use of a diagram involving both m and sigma makes it possible to determine the degree of order by taking a simple reading in the (m, sigma) plane.

Quantitative characterization of a biological membrane by means of its spatial autocovariance

Profiles for the exoplasmic face (EF) of the freeze-fractured plasma membrane from the root storage tissue of red beets are reconstructed by microdensitometry of micrographs of surface-shadowed-platinum carbon replicas. Autocovariance functions (ACFs) are computed from those profiles. The initial portions of the ACFs have a Gaussian form whose parameters (root mean square surface roughness and autocovariance length) are estimated. The parameter estimates are used to show that the pits on the EF faces are in good complementarity with the intramembrane particles seen on the complementary protoplasmic fracture faces.