Bivariate analysis of cellular DNA versus RNA content by laser scanning cytometry using the product of signal subtraction (differential fluorescence) as a separate parameter.

BACKGROUND: The cytometric methods of bivariate analysis of cellular RNA versus DNA content have limitations. The method based on the use of metachromatic fluorochrome acridine orange (AO) requires rigorous conditions of the equilibrium staining whereas pyronin Y and Hoechst 33342 necessitate the use of an instrument that provides two-laser excitation, including the ultraviolet (UV) light wavelength. METHODS: Phytohemagglutinin (PHA)-stimulated human lymphocytes were deposited on microscope slides and fixed. DNA and double-stranded (ds) RNA were stained with propidium iodide (PI) and protein was stained with BODIPY 630/650-X or fluorescein isothiocyanate (FITC). Cellular fluorescence was measured with a laser scanning cytometer (LSC). The cells were treated with RNase A and their fluorescence was measured again. The file-merge feature of the LSC was used to record the cell PI fluorescence measurements prior to and after the RNase treatment in list mode, as a single file. The integrated PI fluorescence intensity of each cell after RNase treatment was subtracted from the fluorescence intensity of the same cell measured prior to RNase treatment. This RNase-specific differential value of fluorescence (differential fluorescence [DF]) was plotted against the cell fluorescence measured after RNase treatment or against the protein-associated BODIPY 630/650-X or FITC fluorescence. RESULTS: The scattergrams were characteristic of the RNA versus DNA bivariate distributions where DF represented cellular ds RNA content and fluorescence intensity of the RNase-treated cells, their DNA content. The distributions were used to correlate cellular ds RNA content with the cell cycle position or with protein content. CONCLUSIONS: One advantage of this novel approach based on the recording and plotting of DF is that only the RNase -specific fraction of cell fluorescence is measured with no contribution of nonspecific components (e.g., due to the emission spectrum overlap or stainability of other than RNA cell constituents). Another advantage is the method's simplicity, which ensues from the use of a single dye, the same illumination, and the same emission wavelength detection sensor for measurement of both DNA and ds RNA. The method can be extended for multiparameter analysis of cell populations stained with other fluorochromes of the same-wavelength emission but targeted (e.g., immunocytochemically) for different cell constituents.

Multiparameter analysis of progeny of individual cells by laser scanning cytometry.

BACKGROUND: Effectiveness of antitumor drugs to suppress unrestricted proliferation of cancer cells is commonly measured by cell clonogenicity assays. Assays of clonogenicity are also used in studies of stem/progenitor cells and in analysis of carcinogenic transformation. The conventional assays are limited to providing information about frequency of colonies (cloning efficiency) and do not reveal the qualitative (phenotype) attributes of individual colonies that may yield clues on mechanisms by which cell proliferation was affected by the studied agent. METHODS: Laser scanning cytometry (LSC) was adapted to identify and characterize size and phenotype of colonies of MCF-7 cells growing in microscope slide chambers, untreated and treated with the cytotoxic ribonuclease, onconase (Onc). Individual colonies were located and data representing each colony were segmented based on >650-nm fluorescence excited by a He-Ne laser of the cells whose protein was stained with BODIPY 630/650-X. The DNA of the cells was stained with propidium iodide (red fluorescence) whereas specific proteins (estrogen receptor [ER] or tumor suppressor p53) were detected immunocytochemically (green fluorescence), each excited by an Ar ion laser. RESULTS: A plethora of attributes of individual colonies were measured, such as (a) morphometric features (area, circumference, area/circumference ratio, DNA or protein content per area ratio), (b) number of cells (nuclei), (c) DNA content, (d) protein content and protein/DNA ratio, and (e) expression of ER or p53 per colony, per total protein, per nucleus or per DNA, within a colony. Also cell cycle distribution within individual colonies and heterogeneity of colonies with respect to all the measured features could be assessed. The colonies growing in the presence of Onc had many of the above attributes different than the colonies from the untreated cultures. CONCLUSIONS: Analysis of the features of cell colonies by LSC provides a wealth of information about the progeny of individual cells. Changes in colony size and phenotype, reflecting altered cell shape, cell size, colony protein/DNA ratio, and expression of individual proteins, may reveal mechanisms by which drugs suppress the proliferative capacity of the cells. This may include inducing growth imbalance and differentiation and modulating expression of the genes that may be associated with cell cycle, apoptosis, or differentiation in a progeny of individual cells. Extensions of LSC may make it applicable for automatic analysis of cloning efficiency and multiparameter analysis of cell colonies in soft agar. Such analyses may be useful in studies of the mechanisms and effectiveness of antitumor drugs, in the field of carcinogenesis, and for analyzing primary cultures and assessing tumor prognosis and drug sensitivity. The assay can also be adapted to analysis of microbial colonies.

Multiparameter analysis of DNA content and cytokeratin expression in breast carcinoma by laser scanning cytometry.

OBJECTIVE: The objective of this study was to test a new laboratory technology, laser scanning cytometry, for the purpose of performing multiparameter DNA content analysis of breast carcinomas. DESIGN: We developed a simplified method of multiparameter DNA content analysis using cytokeratin expression to positively gate epithelial cells. Over 300 consecutive cases of breast carcinoma were analyzed by multiparameter laser scanning cytometry. The first 73 cases were analyzed in parallel by single parameter flow cytometry. SETTING: The Department of Pathology, Christ Hospital and Medical Center, Oak Lawn, Ill. SPECIMENS: Three hundred eighteen consecutive cases of breast carcinoma presenting between March 1994 and December 1995. MAIN OUTCOME MEASURES: Outcome measures included the percentage of cases for which DNA content analysis could be successfully performed given the limitations of specimen size. Additionally, for the first 73 cases, laser scanning cytometry results were compared with flow cytometry results. RESULTS: All of the first 73 cases were successfully analyzed by laser scanning cytometry, but for 8 cases (11%) there was insufficient material for flow cytometry. Correlation of DNA content for the remaining 65 cases analyzed in parallel by the two methods was nearly perfect (p = .994). Five seemingly discrepant cases highlighted the importance of cytokeratin gating of epithelial cells by any technique, as well as other advantages specific to laser scanning cytometry, such as the ability to examine individual cells microscopically and correlate cytologic morphology with DNA content results. CONCLUSIONS: Laser scanning cytometry is a promising new technology for DNA content analysis of solid tissue tumors. Further work needs to be performed to validate the prognostic potential of the laser scanning cytometric assay results and to generate methodologies aimed at providing highly objective determinations of tumor cell S-phase fraction.

Methods for automatic multiparameter analysis of fluorescence in situ hybridized specimens with a laser scanning cytometer.

Multiparameter laser scanning cytometry has been applied to the automatic counting of probe spots and the simultaneous measurement of cellular DNA for fluorescence in situ hybridization (FISH) prepared specimens counterstained with propidium iodide. Relatively low resolution imaging, highly variable probe fluorescence, spectral overlap of probe with counterstain fluorescence, and autofluorescence required the development of an image processing method to detect and isolate FISH probe spots. Inability to properly apportion detected probe spots because of overlapping probe spot images in the same cell required development of a method to eliminate cell data whenever spots in that cell could not be reliably isolated. Laser scanning cytometry incorporating these methods to determine per cell probe spot count and DNA is demonstrated on tissue cultures and peripheral blood cells using different centromeric FISH probes with either FITC or Spectrum Green labeling.

Slide-based laser scanning cytometry.

OBJECTIVE: To show that laser scanning cytometry (LSCM) can provide data equivalent to flow cytometry (FCM) data and furnish a number of benefits, including cell relocation for visualization and several additional measurement features that may make it more suitable than FCM for pathology laboratories. STUDY DESIGN: A laser scanning cytometer, the LSC, was developed. Several instruments, at sites in the United States and Japan during the last two years, provided data characterizing the instrument and its usefulness. RESULTS: Data describing the sensitivity, precision, accuracy, utility of added measurement features and cell relocation capabilities of the LSC are presented. The data illustrate the applicability of the LSC to multiparameter DNA ploidy studies, resolution of phases of the cell cycle and cytogenetics. CONCLUSION: Because it is microscope based and measures cells on a slide, not in a flow chamber; records the position of each cell on the slide; and has higher resolution, LSCM provides a number of benefits that may make it more suitable than FCM for pathology laboratories.

Immunophenotypic analysis of hematologic malignancy by laser scanning cytometry.

The authors tested a newly-developed computerized laser scanning cytometer (LSC) as a means of performing immunophenotypic analysis of hematologic specimens within their community hospital. Results were compared on a case-by-case basis with parallel flow cytometric and immunohistochemical data. A total of 71 specimens analyzed include 22 excised lymph nodes or other tissue biopsies, 18 peripheral bloods, 17 bone marrow aspirates, 7 body fluids, and 7 fine-needle aspiration biopsies of lymphoid tissue. The LSC proved to be a useful instrument capable of generating simultaneous two-color immunofluorescent data directly analogous to that obtained via conventional flow cytometry. However, laser scanning cytometric analysis provides advantages over flow cytometric analysis, because the LSC measures cells on a slide rather than in a fluid stream. Specifically, cells can be microscopically examined at any time--before, during, or after automated immunofluorescent analysis. In addition, specimen preparation techniques are less restricted and more cost efficient. Lastly, even extremely small and/or hypocellular specimens (such as body fluids and fine-needle aspiration biopsies) can be successfully analyzed.

Resolution of mitotic cells using laser scanning cytometry.

A microscope-based laser scanning cytometer (LSCM) has been developed that automatically measures multiple wavelength fluorescence and light scattering of cells on a microscope slide and generates lists of cytochemical and morphological features for each of thousands of cells in a typical sample. For a sample stained with a DNA stain, among the features generated are the value (DNA content), peak (chromatin condensation), and area (nuclear size), as well as the location of the cell on the slide. When combined with each other, these features give detailed resolution of the mammalian cell cycle, including the separation of mitotic from interphase cells. This is demonstrated under a variety of conditions, including cells that were fixed while in suspension and then adhered to a microscope slide, cytocentrifuge preparations, adherent cells fixed in situ on a microscope slide, on viable adherent cells, and on pathological tissue material. Galleries are shown of images of cells that were identified by the instrument as belonging to specific stages of the cell cycle, based on their biochemical staining, and were automatically relocated for viewing. The images are either epifluorescence images of the cells stained with the DNA fluorochrome or brightfield images of cells from slides that were restained with chromatic dyes.

Evaluation of a new slide-based laser scanning cytometer for DNA analysis of tumors. Comparison with flow cytometry and image analysis.

DNA measurements generated by a new automated slide-based cytometer, the laser scanning cytometer (LSC), were compared with those produced by commercial flow cytometry (FCM) and image analysis (IA) devices. Laser scanning-cytometric analysis was performed by scanning alcohol-fixed, propidium iodide-stained tumor imprints with a 5-microns spot laser beam. Fifty-three malignant tumors (51 breast carcinomas and 2 lung carcinomas) were studied. Ploidy concordance rates for FCM versus LSC, IA versus LSC, and FCM versus IA were 96%, 91%, and 91%, respectively. Statistically significant agreement between methods was determined by linear regression analysis of DNA indices. Synthesis-phase fractions generated by FCM and LSC also were comparable, as demonstrated by linear regression (r = .83). Mean coefficients of variation for the LSC compared favorably with those for FCM and IA. The few discrepancies in ploidy status between methods could be explained by sampling error, the presence of possible near-diploid aneuploid populations that could not be effectively resolved by one or another modality, and the visual selection bias with IA when small aneuploid cell populations were present. The LSC shares many useful features with FCM, including automation, accuracy of quantitation, rapidity, and generation of reliable information regarding cell proliferation (synthesis-phase fraction). In addition, it has some of the advantages of IA, such as minimal tissue requirement, no need for special preparation, and the potential for visual selection of the cells measured. The LSC holds great promise for use in the clinical laboratory because of these combined characteristics.

Microscope-based multiparameter laser scanning cytometer yielding data comparable to flow cytometry data.

We describe a computer-controlled 10 microns spot size laser scanning cytometer for making multiple wavelength fluorescence and scatter measurements of unconstrained cells on a surface such as a microscope slide. Designated areas of slides placed on a microscope stage are automatically scanned, and cells which generate above-threshold scatter or fluorescence values are found and individually processed to determine a list of measurement parameters. For each fluorescence or scatter measurement parameter, this list contains the integrated and peak values and bit pattern images of a scan window centered on the cell. The measurement time, the position of the cell on the slide, and two segmentation indices are also included in the list. Measurement time, cell position, and properties derived from the bit patterns are used interchangeably with integrated or peak measurement values as coordinates of multiproperty displays. Cells may be selected for counting, data display in various forms, or visual observation based on their meeting complex criteria among a chain of two property screens. Cells with selected properties may be viewed during an experiment or retrospectively. A designated specimen field may be repeatedly remeasured to perform kinetic cell studies. An argon ion and a HeNe- based laser instrument have been constructed and software has been written and evaluated with the specific goal of increasing the precision of propidium iodide-stained cellular DNA measurements. Some of the capabilities of the instrument and its current performance are described.

Objective measures of information from blood cells.

An answer to the question, "The blood cell: what to measure? why?" is considered by proposing the use of indices derived from flow cytometric measurements. Indices derived from laser light scatter and fluorescence measurements of red cells, platelets, reticulocytes and leukocytes are described. To answer the "why" part of the question, I have proposed a statistical measurement evaluation technique based on information theory. This is illustrated by an example using indices to predict patient infection.

Estimation of membrane potentials of individual lymphocytes by flow cytometry.

The membrane potentials of individual cells can be estimated by flow cytometric quantitation of the cells' uptake of the fluorescent lipophilic cationic dye 3,3'-dihexyloxacarbocyanine iodide. Human lymphocytes separated from peripheral blood on Hypaque-Ficoll gradients are uniformly depolarized by gramicidin and hyperpolarized by valinomycin. Concanavalin A and phytohemagglutinin depolarize only a fraction of the lymphocytes. The flow cytometric technique allows precise detection of heterogeneous membrane potential responses to stimuli such as lectins; it could also provide a basis for sorting cells that respond differently to a given stimulus.