Characterization of the differentiation of human colorectal cancer cell lines by means of Voronoi diagrams

Limits of Applicability of the Voronoi Tessellation Determined by Centers of Cell Nuclei to Epithelium Morphology

It is well accepted that cells in the tissue can be regarded as tiles tessellating space. A number of approaches were developed to find an appropriate mathematical description of such cell tiling. A particularly useful approach is the so called Voronoi tessellation, built from centers of mass of the cell nuclei (CMVT), which is commonly used for estimating the morphology of cells in epithelial tissues. However, a study providing a statistically sound analysis of this method's accuracy is not available in the literature. We addressed this issue here by comparing a number of morphological measures of the cells, including area, perimeter, and elongation obtained from such a tessellation with identical measures extracted from direct imaging acquired by staining the cell membranes. After analyzing the shapes of 15,000 MDCK II epithelial cells under several conditions, we find that CMVT reasonably well reproduces many of the morphological properties of the tissue with an error that is between 10 and 15%. Moreover, cross-correlations between different morphological measures are reproduced qualitatively correctly by this method. However, all of the properties including the cell perimeters, number of neighbors, and anisotropy measures often suffer from systematic or size dependent errors. These discrepancies originate from the polygonal nature of the tessellation which sets the limits of the applicability of CMVT.

Encapsulated Cd3P2 quantum dots emitting from the visible to the near infrared for bio-labelling applications

Quantum dot composites (PS@Cd₃P₂, SiO₂@Cd₃P₂) were prepared and employed for the first time as fluorescent probes for biological imaging.

A tool for the quantitative spatial analysis of complex cellular systems

Spatial events largely determine the biology of cells, tissues, and organs. In this paper, we present a tool for the quantitative spatial analysis of heterogeneous cell populations, and we show experimental validation of this tool using both artificial and real (mammary gland tissue) data, in two and three dimensions. We present the refined relative neighborhood graph as a means to establish neighborhood between cells in an image while modeling the topology of the tissue. Then, we introduce the M function as a method to quantitatively evaluate the existence of spatial patterns within one cell population or the relationship between the spatial distributions of multiple cell populations. Finally, we show a number of examples that demonstrate the feasibility of our approach.

Upregulation of galectins-1 and -3 in human colon cancer and their role in regulating cell migration

To probe the potential contribution of beta-galactoside-contributing epitopes and receptor proteins (gal-1 and gal-3) to colon malignancy, we first examined the expression of galectins and binding sites in clinical specimens by lectin and immunohistochemistry. Sixty-seven colonic surgical resections were studied, including 10 normal, 10 mild dysplasias, 10 severe dysplasias and 37 cancers. gal-1 and gal-3 were expressed in variable amounts in the epithelial cells and the connective tissue of normal colon. Their expression significantly increased with the degree of dysplasia, suggesting that gal-1 and gal-3 and their binding sites are related to malignant progression, while gal-8 has been associated with suppressor activity. To study the functional aspects, the influence of these galectins on the migration of 4 human colorectal cancer cell lines (HCT-15, LoVo, DLD-1, CoLo201) was studied. In agreement with histopathologic monitoring, these tumor cells were found to produce gal-3, while only CoLo201 was positive for gal-1. Except for DLD-1 and gal-1, the lines exhibited gal-1 binding sites on the surface, prompting study by computer-assisted videomicroscopy of the effect on cell migration of the presence of galectin on the culture substrate. The level of cell migration for HCT-15, LoVo and CoLo201 cells was significantly reduced by 0.15 microg/cm(2) gal-1, and the presence of a blocking antibody at least reduced this effect. gal-3 significantly reduced cell migration in all 4 of the in vitro cell lines.

Evidence for stimulation of tumor proliferation in cell lines and histotypic cultures by clinically relevant low doses of the galactoside-binding mistletoe lectin, a component of proprietary extracts

The toxic galactoside-specific lectin from mistletoe, a component of proprietary extracts with unproven efficacy in oncology, exhibits capacity to trigger enhanced secretion of proinflammatory cytokines at low doses (ng/ml or ng/kg body weight) and reductions of cell viability with increasing concentrations. To infer any tumor selectivity of this activity, cytofluorimetric and cell growth assays with a variety of established human tumor cell lines were performed. Only quantitative changes were apparent, and the toxicity against tumor cells was within the range of that of the tested fibroblast preparations from 5 donors. No indication for any tumor selectivity was observed. In kinetic studies with 8 sarcoma and 4 melanoma lines, this evidence for quantitative variability of the response in interindividual comparison was further underscored. At 50 pg lectin/ml x 10(5) cells, even a growth-stimulatory impact was noted in 5 of 12 tested cases. To mimic in vivo conditions with presence of cytokine-secreting inflammatory and stromal cells, exposure to the lectin was extended to histotypic cultures established from 30 cases of surgically removed tumor. As salient result, 5 specimens from 4 of the 8 tested tumor classes responded with a significant increase of [3H]-thymidine incorporation relative to controls during the culture period of 72 hours, when the lectin was present at a concentration in the described immunomodulatory range (1 ng/ml). A relation of this activity to the extent of the actual proliferative status of the reactive samples could not be delineated. Therefore, a non-negligible percentage of the established tumor cell lines (e.g., 3 from 8 sarcoma lines) can be markedly stimulated by the lectin at a very low dose and with dependence on the cell type. Furthermore, the feasibility to elicit a significant growth enhancement is likewise documented for human tumor explants in 16.6% of the examined cases. In view of the uncontrolled application of lectin-containing extracts in alternative/complementary medicine, the presented results on unquestionably adverse lectin-dependent effects in two culture systems call for rigorous examination of the clinical safety of this unconventional, scientifically entirely experimental treatment modality.

Segmentation of tissue architecture by distance graph matching

BACKGROUND

Characterization of tissues can be based on the topographical relationship between the cells. Such characterization should be insensitive to distortions intrinsic to the acquisition of biological preparation. In this paper, a method for the robust segmentation of tissues based on the spatial distribution of cells is proposed.

MATERIALS AND METHODS

The neighborhood of each cell in the tissue is modeled by the distances to the surrounding cells. Comparison with an example or prototype neighborhood reveals topographical similarity between tissue and prototype. Processing of all cells in the tissue extracts the regions with tissue architecture similar to the given example.

RESULTS

Comparison with other topographical-segmentation methods shows that the proposed method is better suited for partitioning tissue architecture. As an example, the quantification of the structural integrity in rat hippocampi after ischemia is demonstrated. In contrast to other methods, the algorithm correlates well with expert evaluation.

CONCLUSIONS

The present method reduces the nonbiological variation in the analysis of tissue sections and thus improves confidence in the result. The method can be applied to any field where regular patterns have to be detected, as long as the directional distribution of neighbors may be neglected.

Lectin histochemistry of astrocytic tumors and in vitro characterization of lectin-induced modifications on the proliferation of the SW1088, U373 and U87 human astrocytic cell lines

The role of lectins as biosignalling molecules or as markers of human astrocytic tumors remains relatively unexplored. The aim of the present work is to investigate (1) whether or not human astrocytic tumors express specific glycans, evidenced experimentally by means of lectin histochemistry, and (2) whether, in turn, these lectins can significantly modulate astrocytic tumor cell proliferation. Using a cell image processor, we therefore began by quantitatively measuring the histochemical binding pattern of 5 lectins (WGA, PNA, PHA-L, GSA-IA4 and Con A) in 5 astrocytomas, 5 anaplastic astrocytomas and 5 glioblastomas. Secondly, we measured the influence of these 5 lectins on the proliferation of 3 astrocytic tumor cell lines (SW1088, U373 and U87) growing in vitro as monolayers. Cell proliferation was assessed by means of the colorimetric MTT assay. The histochemical lectin staining markedly varied intra- and inter-group. However, some constant results were obtained. Indeed, the staining increased markedly from GSA-IA4 and PHA-L through WGA and PNA to ConA in the three histopathological groups. The assessment of cell proliferation demonstrated that WGA, Con A and PHA-L very significantly decreased proliferation in the 3 astrocytic cell lines in a dose-dependent manner. Astrocytic tumor cells in the confluent growth phase were less sensitive to the WGA, Con A and PHA-L lectin-induced effects than cells in the log growth phase. The GSA-IA4 and PNA lectins had globally very weak effects on the proliferation of the astrocytic tumor cell lines. Increasing the fetal calf serum from 1% to 10% in the culture media significantly antagonized the WGA-, Con A- and PHA-L-induced cell proliferation decrease in the 3 astrocytic cell lines. In conclusion, the present data strongly suggest that some lectins (including WGA, Con A and PHA-L) significantly influence the proliferation of astrocytic tumor cells.

Computer-assisted microscope characterization of BCNU-induced modifications in the collective behavior of 12 human brain cancer cell lines

The aim of our study is to characterize the disturbance induced by repeated BCNU treatments in 12 human brain tumor cell lines in terms of their collective behavior. This collective behavior was characterized by means of the Delaunay triangulation and Voronoi mathematical paving techniques combined with the computer-assisted microscope analysis of Feulgen-stained nuclei. This methodology enabled growth to be characterized in terms of cell colony size and density. In addition to this colony pattern characterization, the DNA ploidy level was assessed by means of DNA histogram typing. The cell proliferation level was also determined. Ten astrocytic and two medulloblastoma cell lines treated weekly with BCNU were analyzed. Study of the cell colony architecture and cell proliferation revealed specific BCNU-induced modifications in connection with the origins of the cell lines, i.e. astrocytoma (AST), glioblastoma (GBM), or medulloblastoma (MED). The BCNU-induced effect on GBM (the more malignant of the cell lines) was very different in that proliferation was weakened, but the cell colony density increased after a latency phase. The decrease in cell colony density and cell proliferation of MED seems to indicate that they are more sensitive to BCNU than GBM, but relatively tolerant of this type of chemotherapy in comparison with AST.

In vitro characterization of prolactin-induced effects on proliferation in the neoplastic LNCaP, DU145, and PC3 models of the human prostate

BACKGROUND

Proliferation of normal and tumoral prostate tissue is regulated by androgens and various growth factors. We characterized the in vitro proliferative influence of prolactin (PRL) in androgen-sensitive and androgen-insensitive human prostate cancers.

METHODS

The biologic models employed included the androgen-sensitive LNCaP and the androgen-insensitive DU145 and PC3 cell lines. PRL-induced influences (0.1-10 mIU/ml of medium) on proliferation were assessed using the colorimetric methylthiotetrazole assay. Androgen sensitivity in the three cell lines was determined by assessing the proliferative influence of dihydrotestosterone (DHT) (0.1-10 nM). PRL-induced modifications in PC3 cell kinetics were assessed using Feulgen-stained nuclear image cytometry.

RESULTS

Although DHT markedly stimulated LNCaP proliferation, it had no proliferative effect on the DU145 and PC3 cell lines. By contrast, PRL significantly modulated the proliferation of the DU145 and PC3 lines, but exerted weak, if any, effect on the proliferation of the LNCaP cell line. PRL increased the percentage of PC3 proliferating cells (i.e., cells in the S/G2 phases of the cell cycle) at low doses (0.1 mIU/mL) and decreased this percentage at high doses (10 mIU/ml).

CONCLUSIONS

Proliferation of androgen-insensitive human prostate cell lines can be significantly modulated by prolactin.

Influence of dihydrotestosterone, epidermal growth factor, and basic fibroblast growth factor on the cell kinetics of the PC3, DU145, and LNCaP prostatic cancer cell lines: relationship with DNA ploidy level

The cell kinetics (percentage of cells in the S+G2 phases of the cell cycle) and the DNA ploidy levels (nuclear DNA content) were determined in 108 samples each of the PC3, DU145, and LNCaP prostate cancer models. This was carried out by means of the digital cell image analysis of Feulgen-stained nuclei. Two to three hundred cell nuclei were analyzed for each of the 324 samples under study. The three cell lines were submitted to experimental conditions including the addition of dihydrotestosterone (DHT), epidermal growth factor (EGF), and basic fibroblast growth factor (bFGF), either alone or in combination, to the culture media. The results show that under the present culture conditions, the PC3 cell line was DHT-, EGF- and bFGF-insensitive. In contrast to what is generally reported in the literature, the DU145 cell line was DHT- and EGF-sensitive under the present culture conditions, but bFGF-insensitive. The LNCaP cell line was DHT-sensitive, but EGF- and bFGF-insensitive. While mainly tetraploid, the three cell lines nevertheless exhibited a significant level of heterogeneity in their nuclear DNA content distributions. Indeed, the proportions of non-tetraploid (diploid, hyperdiploid, triploid, hypertriploid, hypertetraploid, polymorphic) DNA histograms were 14% in the PC3, 16% in the DU145, and 29% in the LNCaP cell lines. These results suggest that the DNA ploidy level would not influence the hormone sensitivity level in the cell lines since they had significantly distinct hormone sensitivity profiles while remaining mainly tetraploid.

Relationship between DNA ploidy level and tumor sociology behavior in 12 nervous cell lines

Cell population sociology was studied in two medulloblastomas and 10 astrocytic human tumor cell lines by means of the characterization of the structure of neoplastic cell colonies growing on histological slides. This was carried out via digital cell image analysis of Feulgen-stained nuclei, to which the Delaunay triangulation and Voronoi paving mathematical techniques were applied. Such assessments were compared to the DNA polidy level (assessed by means of DNA histogram typing). The results show that the cell colony architecture characteristics differed markedly according to whether the cell lines were euploid (diploid or tetraploid) or aneuploid (hyperdiploid, triploid, hypertriploid, or polymorphic). In fact, the cell colonies from the euploid cell nuclei populations were larger and more dense than those from the aneuploid ones. Furthermore, for an identical period of culture, the cell lines from high-grade malignant astrocytic tumors (glioblastomas) exhibited cell colonies that were larger and more dense than those in cell lines from low-grade astrocytic tumors (astrocytomas). In each of these two groups, the diploid cell nuclei populations exhibited cell colonies larger and more dense than the nondiploid colonies. The present methodology is now being applied in vivo to histological sections of surgically removed human brain tumors in order to distinguish between high-risk clinical subgroups and medium-risk subgroups in clearly circumscribed histopathological groups.

Characterization of the influence of anti-hormone and/or anti-growth factor neutralizing antibodies on cell clone architecture and the growth of human neoplastic astrocytic cell lines

The influence of five anti-hormone and/or anti-growth factor neutralizing antibodies on the in vitro proliferation of four human astrocytic tumor cell lines (U87, U138, U373, H4) is quantitatively described by means of a new tool which makes it possible to evaluate cell growth and cell clone architecture concomitantly. This tool relies upon the combined use of the digital cell image analyses of Feulgen-stained nuclei and the Delaunay and Voronoi mathematical triangulation and paving techniques. Of the five anti-hormone and/or anti-growth factors tested here, the anti-luteinizing hormone-releasing hormone (LHRH) antibody induced the most marked perturbation in the U138 and U373 cell lines, whereas this role was played by the anti-epidermal growth factor (EGF) antibody in the U87 and H4 cell lines. The anti-gastrin (G) antibody significantly modified the growth and/or cell clone architecture of the U138, U87 and H4 cell lines, as did the anti-transforming growth factor alpha (TGFalpha) antibody. The anti-transforming growth factor beta (TGFbeta) antibody modified the growth and/or cell clone architecture of the four cell lines under study. If the five antibodies are taken into consideration, the results strongly suggest that four (the anti-G, the anti-EGF, the anti-LHRH and the anti-TGFalpha) act as inhibitory agents on some glioma cell line proliferation, while the fifth one, i.e. the anti-TGFbeta, act as a stimulator of cell proliferation, perhaps by abrogating the inhibitory effects of TGFbeta on proliferation. A comparison of cell growth data with cell clone architecture characteristics provided further evidence of some specific influence exercised by a given hormone and/or growth factor on glioma cell proliferation. Indeed, the anti-LHRH antibody caused the most pronounced perturbations in the U138 and U373 cell clone architecture; this feature was observed in the H4 cell line and, to a lesser extent in the U87 one after the anti-EGF antibody had been used.