Quantitative evaluation of heterochromatin in epithelial atypia by an image processing method

Chromatin organization and breast cancer prognosis. Two-dimensional and three-dimensional image analysis

BACKGROUND

The assessment of breast cancer prognosis still relies on clinical staging and histologic grading. Among the different prognostic parameters, attention has been focused on features of chromatin structure. Although data from two-dimensional (2-D) analysis of chromatin structure show significant correlation with the survival, their biologic interpretation remains difficult. In this respect, insights into the spatial organization of chromatin appear important.

METHODS

The authors performed computerized three-dimensional (3-D) reconstructions of Feulgen-stained tumor cell nuclei, correlating the results with those of 2-D image analysis. Forty-nine ductal-invasive carcinomas with 10-18 years follow-up were investigated.

RESULTS

The 2-D analysis demonstrated that along with nuclear size and shape, chromatin features such as marginal concentration of condensed chromatin are of prognostic importance. As 3-D analysis revealed, chromatin changes concern ordered organization and were associated with the increase of spatial entropy.

CONCLUSIONS

The 3-D description of chromatin structure by means of spatial models provides evidence that tumor aggressiveness correlates with events of clustering and randomization. These indicate disturbances of ordered chromatin organization.

Quantitative features of chromatin structure in the prognosis of breast cancer

In prognosis of breast cancer different parameters are in current use. Along with clinical staging the most important parameter appears to be histologic grading. Features of the grading such as nuclear pleomorphism proved to correlate closely with the proliferative activity and aggressiveness of the tumors. Because of difficulties in assessing and classifying the degree of nuclear pleomorphism by usual microscopy, the authors applied methods of digital image analysis. The study is a retrospective analysis of paraffine slides from the primary lesions of 60 breast cancers with 10 to 16 years of follow-up evaluation. Using large sets of different parameters defining nuclear morphology and chromatin structure the authors extracted criteria with prognostic importance. These included nuclear area in micron 2, eccentricity, integral optical density per micron 2, average area of a chromatin region, integral optical density of a chromatin region per micron 2, and the number of central chromatin regions per micron 2. The results demonstrate that the criteria used enable prediction of prognosis with an accuracy of 92%.

Quantitative nuclear morphology in the diagnosis of ovarian tumors of low malignant potential (borderline)

Ovarian tumors of low malignant potential or of borderline malignancy are characterized histologically by the association of malignant type of epithelial proliferation with a noninvasive pattern of growth. Because epithelial proliferation relates to features of nuclear morphology and chromatin structure and because of the difficulties to distinguish nuclear atypism seen in borderline malignancy from that in frankly invasive tumors by usual microscopic study, the authors concentrated their studies exclusively on computerized analysis of cell nuclei images. Using specially developed methods of analysis the authors described geometrical, optical, and structural differences among the epithelial and stromal cell nuclei of benign, borderline, and malignant ovarian tumors. The structural differences concern the pattern of chromatin condensation and suggest that the cytokinetic properties of the borderline tumors are intermediate to those of benign and malignant. The results demonstrate that the quantitative evaluations provide objective and reproducible data useful in the differential diagnostic of the borderline malignancy.

A model of chromatin-dependent DNA replication sequences based on the decondensation units hypothesis

A model of chromatin-dependent DNA replication sequences was developed on the previously reported "decondensation units" hypothesis and its kinetic properties were examined by way of calculating various numerical indices using a Monte Carlo procedure. The model has much in common with the previous one but a fundamental difference is that the unit is assumed to consist of linearly arranged H-, D-, A- and S-zones each containing genes of different functional categories which are called H-, D-, A- and S-genes, respectively. The units are decondensed by the action of D-factors, i.e. decondensation factors, from H-zone to the end of S-zone and the genes in decondensed regions release signals to produce housekeeping enzymes, D-factors, A-factors and S-factors. These products are stored and at the same time degraded. A-factors activate replication origins in the decondensed regions and S-factors induce DNA synthesis at the activated origins. Replicated DNA is recondensed and gene activities are shut down in the recondensed chromatin. The factors are produced under the control of chromosome cycle and in turn affect chromosomes. Thus, dual control mechanism operates as Mazia and Prescott have argued. Biochemical and cytogenetic basis of this model was reviewed briefly and some results of simulation presented which include DNA synthesis rate vs. DNA content relationships. An outstanding characteristic of the model is the constancy of cellular state in A-subphase located in the late G1.

Quantitative description of nuclear morphology in assessing resistance of sarcoma 180 to adriamycin

Resistance to adriamycin generally is explained through changes of cell/drug interactions that possibly reflect structural alterations of intracellular targets. One of the main targets of adriamycin is believed to be nuclear chromatin. In order to recognize chromatin alterations, we studied cell nuclei morphology and chromatin structure by means of digital image analysis. The studies were performed in both adriamycin-sensitive and -resistant Sarcoma 180 cell lines which were cultured under growth-stimulated and nonstimulated conditions. Using specially developed methods, we extracted parameters characterizing geometrical, optical, and structural properties of the cell nuclei from light microscopical images. The latter parameters concerned microscopical appearances of condensed chromatin and were described by features of high-optical-density regions. The results demonstrated that the quantitative criteria applied enabled the discrimination of sensitive and resistant cells. The most important parameters are the nuclear size, number, distribution, and optical density of condensed chromatin regions. In addition, the criteria permit recognition of changes related to differences in the growth conditions of the cells. The data of the image analysis suggest that adriamycin resistance in Sarcoma 180 cells is associated with characteristic patterns of cell nuclear morphology which can be described with a sufficient number of appropriate parameters. The advantages of image analysis are evident when these results are compared with the flow cytometric findings. The conclusion is that structural features of nuclear chromatin provide information essential for the assessment of drug resistance.