The use of trout erythrocytes and human lymphocytes for standardization in flow cytometry

Simple Field Storage of Fish Samples for Measurement of DNA Content by Flow Cytometry

Flow cytometry is an effective and widely used tool for determination of ploidy in fish, but it is not always possible to access the fresh samples for analysis. We investigated the potential for extended storage of fish tissue with sterlet and tench as representative species of Chondrostei and Teleostei, using blood and fin of subadult/adult specimens and tail of larvae. Thirteen procedures for extending storage, selected for rapidity and simplicity in both field and laboratory conditions, were tested for each tissue sample. Flow cytometry was applied to fresh tissue immediately after sampling and to tissue subjected to experimental protocols, always along with species-specific standard, after 1, 5, and 10 days storage at 0-4°C or freezing at -80°C. The fluorochrome 4',6-diamidine-2'-phenylindole dihydrochloride was used with excitation/emission maximum 358/461 nm. Based on the measurability of stored samples, evaluation of directly measured coefficients of variation of their DNA peaks and the changes in fluorescence intensity compared to fresh tissue, optimal procedures for extended storage of the selected tissue types of the model species are suggested. © 2020 The Authors. Cytometry Part A published by Wiley Periodicals LLC. on behalf of International Society for Advancement of Cytometry.

Three-dimensional DNA image cytometry by optical projection tomographic microscopy for early cancer diagnosis

Aneuploidy is typically assessed by flow cytometry (FCM) and image cytometry (ICM). We used optical projection tomographic microscopy (OPTM) for assessing cellular DNA content using absorption and fluorescence stains. OPTM combines some of the attributes of both FCM and ICM and generates isometric high-resolution three-dimensional (3-D) images of single cells. Although the depth of field of the microscope objective was in the submicron range, it was extended by scanning the objective's focal plane. The extended depth of field image is similar to a projection in a conventional x-ray computed tomography. These projections were later reconstructed using computed tomography methods to form a 3-D image. We also present an automated method for 3-D nuclear segmentation. Nuclei of chicken, trout, and triploid trout erythrocyte were used to calibrate OPTM. Ratios of integrated optical densities extracted from 50 images of each standard were compared to ratios of DNA indices from FCM. A comparison of mean square errors with thionin, hematoxylin, Feulgen, and SYTOX green was done. Feulgen technique was preferred as it showed highest stoichiometry, least variance, and preserved nuclear morphology in 3-D. The addition of this quantitative biomarker could further strengthen existing classifiers and improve early diagnosis of cancer using 3-D microscopy.

Triploidy in rainbow trout determined by computer-assisted analysis

This study was designed to assess the use of a computer-assisted system based on erythrocyte measurements as a possible alternative to flow cytometry for identifying triploid rainbow trout (Oncorhynchus mykiss). Blood smears were prepared from 26 triploid and 26 diploid specimens, as determined by flow cytometry after staining blood cells with propidium iodide. The cell and nucleus lengths of 10 erythrocytes were determined in each fish. This was followed by discriminatory analysis to distinguish between diploids and triploids based on their score profiles. Triploid trout showed significantly larger erythrocyte cell and nucleus measurements than their diploid counterparts (N=52; P<0.0001). Erythrocyte length correctly identified 100% of the fish specimens as diploid or triploid, while nucleus length was a less accurate predictor of the level of ploidy. Our findings validate the potential use of computer-assisted analysis for this purpose.

DNA index, genome size, and electronic nuclear volume of vertebrates from the Miami Metro Zoo

BACKGROUND

Flow cytometry is a rapid and reliable method for measuring nuclear DNA content and genome size. Fluorochrome binding characteristics, sample preparation and differences in DNA condensation, and availability of binding sites can cause variations in results obtained.

METHODS

Blood samples from 82 vertebrate species were collected in 10% dimethyl sulfoxide and stained with propidium iodide/hypotonic citrate or 4,6-diamidino-2-phenylindole dihydrochloride for analysis of DNA content and electronic nuclear volume (ENV). Trout red blood cells (TRBCs), human peripheral blood lymphocytes, and human buccal cavity cells were used as internal standards.

RESULTS

Mean fluorescence channel (MFC) values of TRBC and buccal cavity cells used as internal standards were stable at 15 to 120 min of propidium iodide staining. TRBCs mixed with other cells especially human peripheral blood cells showed an increase in MFC. ENV and MCF values were less variable in different species of birds than in reptiles or mammals. Genome size based on use of buccal cavity cells as the internal standard showed a high degree of correlation with previous reports.

CONCLUSIONS

Proper selection and use of internal standards and sample preparation are essential for reliable determination of DNA content and genome size in vertebrates by flow cytometry.

Genetic heterogeneity and ploidy level analysis among different gynogenetic clones of the polyploid gibel carp

BACKGROUND

Some triploid and tetraploid clones have been identified in the gynogenetic gibel carp, Carassius auratus gibelio Bloch, by karyotypic and cytologic analyses over many years. Further, 5-20% males and karyotypic diversity have been found among their natural and artificial populations. However, the DNA contents and the relation to their ploidy level and chromosome numbers have not been ascertained, and whether normal meiosis occurs in spermatogenesis needs to be determined in the different clones.

METHODS

The sampled blood cells or sperms were mixed with blood cells from chicken or individual gibel carp and fixed in 70% pre-cooled ethanol overnight at 4 degrees C. The mixed cell pellets were washed 2-3 times in 1x phosphate buffered saline and then resuspended in the solution containing 0.5% pepsin and 0.1 M HCl. DNA was stained with propidium iodide solution (40 microg/mL) containing 4 kU/ml RNase. The measurements of DNA contents were performed with Phoenix Flow Systems.

RESULTS

Triploid clones A, E, F, and P had almost equal DNA content, but triploid clone D had greater DNA content than did the other four triploid clones. DNA content of clone M (7.01 +/- 0.15 pg/nucleus) was almost equal to the DNA content of clone D (5.38 +/- 0.06 pg/nucleus) plus the DNA content of common carp sperm (1.64 +/- 0.02 pg/nucleus). The DNA contents of sperms from clones A, P, and D were half of their blood cells, suggesting that normal meiosis occurs in spermatogenesis.

CONCLUSIONS

Flow cytometry is a powerful method to analyze genetic heterogeneity and ploidy level among different gynogenetic clones of polyploid gibel carp. Through this study, four questions have been answered. (a) The DNA content correlation among the five triploid clones and one multiple tetraploid clone was revealed in the gibel carp, and the contents increased with not only the ploidy level but also the chromosome number. (b) Mean DNA content was 0.052 pg in six extra chromosomes of clone D, which was higher than that of each chromosome in clones A, E, F, and P (about 0.032 pg/chromosome). This means that the six extra chromosomes are larger chromosomes. (c) Normal meiosis occurred during spermatogenesis of the gibel carp, because DNA contents of the sperms from clones A, P, and D were almost half of that in their blood cells. (d) Multiple tetraploid clone M (7.01 +/- 0.15 pg/nucleus) contained the complete genome of clone D (5.38 +/- 0.06 pg/nucleus) and the genome of common carp sperm (1.64 +/- 0.02 pg/nucleus).

Flow cytometry measurement of the DNA contents of G0/G1 diploid cells from three different teleost fish species

BACKGROUND

Although there is a lot information in the literature about genome size in fish, a high variability among data for the same species is reported, being mainly related to methodological aspects. Flow cytometry-based fluorescence measurements of intercalating dyes is the most attractive approach due to its precision, objectivity, high speed, and relative simplicity.

METHODS

We analyze the DNA content of G0/G1 diploid nuclei of three teleost species (Carassius auratus, Tinca tinca, and Danio rerio) using flow cytometry. Forty-three animals were used and up to 50,000 retinal cells were analyzed per sample. Propidium iodide-associated fluorescence was assessed using a FACSCalibur flow cytometer. Standard human leukocytes were used as a reference.

RESULTS

Our results show that C. auratus (3.584 +/- 0.058 pg per nucleus) and D. rerio (3.357 +/- 0.074 pg per nucleus) showed similar DNA contents per cell, whereas it was significantly lower (2.398 +/- 0.038 pg per nucleus) in T. tinca. Interestingly, a low intraspecies variability was observed, the coefficient of variation being 1.608%, 2.198%, and 1.573% for C. auratus, D. rerio, and T. tinca, respectively.

CONCLUSIONS

The methodology used in this study provides an accurate and easy measurement of the genome size of a species.

Endometrial carcinomas--flow cytometric DNA content and S-phase values

The purpose of the investigation was to determine the DNA content and S-phase value in a large material of fresh tumour tissue from endometrial carcinomas and to correlate these parameters to tumour type, grade of differentiation, depth of myometrial invasion and stage. The prospective study consisted of 290 unselected cases of endometrial carcinomas, FIGO stage I-IV where flow cytometry was performed on fresh tumour tissue blocks from hysterectomy specimens. 223 cases had more than 10% tumour tissue in tissue blocks taken adjacent to the blocks for flow cytometry. Non-diploidy was defined as 0.9 > or = DNA index > 1.10 and high S-phase value was defined as > 15%. Non-diploidy was found in 46% of the endometrioid adenocarcinoma and in 85% of the non-endometrioid carcinomas (clear cell adenocarcinoma, serous adenocarcinoma and malignant mixed mesodermal tumour) (p < 0.001). S-phase value was > 15% in 39% of the endometrioid adenocarcinoma and in 100% of the non-endometrioid carcinomas (p < 0.0001). In endometrioid adenocarcinoma there was a statistical significant relation between non-diploidy and grade of histological differentiation (p < 0.006), as well as with depth of myometrial invasion (p < 0.05). There was no relation between non-diploidy and the presence of squamous differentiation, whether benign or malignant or to FIGO stage. High S-phase values (> 15%) was related to the grade of differentiation (p < 0.002). No relation was demonstrated between S-phase > 15% and squamous differentiation, depth of myometrial invasion or FIGO stage. In conclusion, 50% of all the endometrial carcinomas were non-diploid and 43% had S-phase value > 15%. Ploidy correlated with histologic tumour types, grade of differentiation and depth on myometrial invasion while S-phase values only correlated with histologic tumour types and grade of differentiation.

Numerical aberrations of chromosomes 1 and 7 in renal cell carcinomas as detected by interphase cytogenetics

Alcohol-fixed single cell suspensions of 37 renal cell carcinomas (RCCs) were assessed by both flow cytometry (FCM) and the fluorescence in situ hybridization (FISH) technique, using chromosome 1- and chromosome 7-specific centromere DNA probes. DNA diploidy or near-diploidy was observed in 30 of the 37 RCCs and only 12 of these (near-)diploid tumours were disomic for both chromosomes 1 and 7. Numerical aberrations of chromosome 1 and/or chromosome 7 were present in 18 of the 30 (near-)diploid RCCs and five of these cases showed monosomy for chromosome 1 in more than 50 per cent of the tumour cells. A double target FISH, with a centromeric and a telomeric specific probe for 1p36, excluded misinterpretation on the basis of clustering of 1q12, and suggested a complete loss of chromosome 1. All these five (near-)diploid RCCs with monosomy for chromosome 1 were eosinophilic chromophilic cell carcinomas, according to the Thoenes classification of RCC. This observation is of special interest, because it was recently concluded from cytogenetic studies that the diagnosis of chromophilic renal cell carcinoma must be considered as obsolete. Monosomy for chromosome 1 seems to be a non-random numerical aberration of (near-)diploid eosinophilic chromophilic cell carcinomas, and a gain of one or more chromosomes 1 appeared to be a common phenomenon in RCCs, especially in the DNA aneuploid tumours. As these chromosomal abnormalities were not found in the earlier classical cytogenetic studies, we conclude that in situ hybridization techniques are required in addition to chromosome banding techniques to obtain a complete characterization of the chromosome imbalances in RCCs.

Sources of error associated with sample collection and preparation of nucleated blood cells for flow cytometric analysis

Analysis of cellular DNA content by flow cytometry has been used to detect genetic changes associated with exposure to environmental contaminants. In lower vertebrates, nucleated red blood cells can be collected for analysis without harm to the animal. Because erythrocytes sampled from an individual should have identical amounts of DNA, the coefficient of variation (CV) around the G0/G1 peak should be small. Increases in CV can indicate genetic aberrations, but may also be caused by sample handling and preparation or problems with instrumentation. To increase confidence in associating increases in CV with external causes, artifactual changes in CV due to sample treatment and instrument parameters should be identified and minimized. We assessed the effects of various sampling and handling protocols on the CV of nucleated blood cells collected from largemouth bass (Micropterus salmoides). We also compared the distribution of cells among the G0/G1, S, and G2/M phases of the cell cycle to see whether these were affected by sampling or treatment protocols. Groups of 7 fish were bled on 7 consecutive days, and blood from each fish was analyzed by flow cytometry when freshly collected, and after freezing for 1 hour or 10 days. The same fish were bled again over a consecutive 7-day period, and the experiment was repeated. CV and cell cycle distribution were not affected by our freezing protocol. Repeat sampling from the same individual did not affect CV, but altered the distribution of cells in the cell cycle, suggesting increased hemopoiesis in response to blood sampling.(ABSTRACT TRUNCATED AT 250 WORDS)

Differences in relative DNA content between human peripheral blood and bone marrow subpopulations--consequences for DNA index calculations

By sequentially staining for leukocyte differentiation antigens with monoclonal antibodies and for stainable DNA content with propidium iodide, we have evaluated the DNA ratios of normal peripheral blood and bone marrow subpopulations. In 19 peripheral blood samples the relative DNA content of the monocytes was higher than that of other subpopulations, with highly significant differences between the DNA ratios of the CD14+ monocytes, on the one hand, unlabeled controls, CD3+ T-lymphocytes, and CD20+ B-lymphocytes, on the other. In bone marrows from 16 healthy volunteers, the relative DNA content of the myelomonocytic subpopulations was higher than that of the T-lymphocytes with significant differences between the CD3+ lymphocytes, on the one hand, and the CD14+ monocytes, the CD13+ and CD33+ immature myeloid, the NAT9+ mature myeloid, and the AS-E1+ nucleated erythroid subpopulation, on the other. Since a mixture of peripheral blood mononuclear cells or T lymphocytes from healthy volunteers is often used as an external standard for DNA ploidy determinations, these data suggest that such a procedure could result in an overestimation of the DNA indices of most of the bone marrow subpopulations. Instead, we suggest the use of the DNA ratio of the CD14+ subpopulation from peripheral blood as standards for ploidy determinations for the myeloid bone marrow subpopulations.

A comparison of flow cytometric and absorption cytometric DNA values as prognostic indicators for pancreatic carcinoma

BACKGROUND

The DNA content of 30 adenocarcinomas of the head of the pancreas was measured by flow and absorption cytometric analysis.

METHODS

Each of the patients in this study had curative pancreatoduodenectomy. The absorption cytometric measurements were done in a research laboratory, and the flow cytometric measurements were performed in a commercial laboratory. The DNA measurements were done on nuclei disaggregated from pancreatic cancer tissue blocks without the examiner knowing whether the patient had survived.

RESULTS

Twenty-one of the 30 cancers were found to be aneuploid by absorption cytometric analysis, whereas only 1 of the 30 cancers was aneuploid by flow cytometric analysis. This difference was statistically significant (P < 0.001).

CONCLUSIONS

Univariate and multivariate analyses showed that the absorption cytometric DNA measurements were stronger prognostic determinants for patient survival than were the flow cytometric DNA measurements, indicating that some caution may be warranted in the interpretation of commercially obtained DNA distributions of pancreatic carcinomas.

Prediction of lymph node metastases in patients with early squamous cell carcinoma of the cervix uteri by histopathological grading and flow cytometry

The present study comprises a retrospective investigation of 126 patients with stage IB squamous cell carcinoma of the cervix, and a similar prospective investigation of 53 patients with stage IB and 6 patients with stage IIA disease. Tumour biopsies from these patients were analysed by means of flow cytometry and a semiquantitative histological grading system. The study showed that a combination of a low tumour cell DNA index and a low score value of the grading system indicated a very low risk of regional lymph node metastases (0% lymph node metastases in patients with low scores vs. 24-46% metastases in patients with high scores, P < 0.001). In order to study the reproducibility of the histological grading 20 randomly selected cases were studied blindly by three of the participating pathologists and after discussion of the grading criteria. A kappa coefficient of 722 demonstrated a substantial agreement between the observers. These results suggest that by combining flow cytometry with semiquantitative histological grading, a subgroup of patients with early squamous cell cancer of the cervix uteri may be selected that could be sufficiently treated with simple hysterectomy instead of radical hysterectomy including lymphadenectomy, which, in many oncology centres, is the standard treatment of this patient category.

Use of mouse hepatocytes for the flow cytometric determination of DNA levels of nuclei extracted from fresh tissue of hybrid larch (Larix x eurolepis Henry)

A rapid and reliable method is presented to release intact nuclei from small amounts (100 mg) of fresh plant tissue. Further, an accurate and readily accessible new standard is proposed. Both techniques have potential application for many plant systems. The system chosen as a standard (inbred mouse strain Balb/C or B6/AF1 hepatocyte nuclei) contains both diploid and polyploid cells. This system was applied in the flow cytometric determination of absolute nuclear DNA values of female gametophytes and in vitro propagated shoots of hybrid larch (Larix x eurolepis Henry). The amount of DNA in 2C nuclei of in vitro grown larch is 32.48 +/- 4.04 or 31.97 +/- 6.14 pg/nucleus, respectively, when calculated using the mouse hepatocyte 4C or 8C nuclear peak as a reference standard. The amount of DNA in female gametophyte nuclei is 17.47 +/- 1.33 pg DNA/nucleus when these haploid larch nuclei were analyzed with trout red blood cell nuclei as the standard. When hepatocyte 4C nuclei were used as a standard, the absolute value of DNA per haploid larch nucleus was estimated as 16.8 +/- 0.53 pg. Plant tissue with as little as 4-6 pg DNA/nucleus up to as much as 35 pg DNA/nucleus can be tested using mouse hepatocytes as a standard while retaining an optimal sample/standard ratio.

DNA content in Eurasian sturgeon species determined by flow cytometry

The nuclear DNA content in 10 species of chondrostean fishes was measured by flow cytometry. The sterlet Acipenser ruthenus blood cells were used as an internal standard. The sterlet DNA content was calculated on the basis of comparison with the Xenopus laevis blood cells, 2C = 6.30 pg. In the tetraploid A. ruthenus and A. stellatus the DNA content comprises 3.74 pg/nucleus and is practically invariant; in Huso dauricus it is almost the same, 3.74-3.81 pg; and in A. nudiventris it is a little higher, 3.88-4.04 pg. In the oldest chondrostean, Pseudoscaphirhynchus kaufmanni, the nuclear DNA content is slightly lower, 2C = 3.46-3.48 pg, and in the American paddlefish Polyodon spathula it is lower still, 3.17 pg. In two octoploid sturgeons, A. baeri and A. gueldenstaedti, the DNA content is twice as high as that of the sterlet, 8.29-8.31 and 7.86-7.88 pg, respectively; a very similar amount, 8.24-8.42 pg, was determined in the hybrid Huso huso x A. ruthenus. In the Sakhalin sturgeon, A. medirostris (= A. mikadoi), the DNA content is two times higher than in the octoploids, 13.93-14.73 pg; therefore its ploidy may be 16n and the number of chromosomes could be 500.

In situ detection of supernumerary aberrations of chromosome-specific repetitive DNA targets in interphase nuclei in human melanoma cell lines and tissue sections

The use of non-radioactive in situ hybridization (ISH) with chromosome-specific repetitive DNA probes to study genomic changes, aneuploidy, and heterogeneity during melanocytic tumor progression, relies on its applicability to non-mitotic interphase nuclei, present in cell suspensions and tissue sections. Therefore, we studied the feasibility of detecting numerical aberrations with respect to the (peri-) centromere regions of chromosomes 1 and 7 in intact nuclei of two human melanoma cell lines with different metastatic behavior in nude mice. In addition, we used paraffin sections from xenograft lesions, obtained by inoculation of these cell lines in nude mice (subcutaneous tumors and spontaneous lung metastases). Paraffin sections from the original primary cutaneous melanoma (with a subepidermal and a dermal part) and two loco-regional metastases were also studied, one of which was the source for the cell lines. These cells and tissues represent examples of materials used in different approaches to the study of melanocytic tumor progression. Regarding the targeted sequences, ISH analysis showed that both cell lines were heterogeneous and aneuploid. The results correlated well with those obtained by ISH on metaphase spreads. Differences between the lines, which could not be detected by flow-cytometric or conventional karyotyping analysis, included data suggestive of a polyploid subpopulation and an extra copy of chromosome 7 in the metastasizing cell line. The polyploid population could be detected also in the paraffin sections of the corresponding subcutaneous xenografts and lung metastases in the mice. Both areas in the patients' primary melanoma could be evaluated separately and showed similar supernumerary aberrations of the chromosome-specific targets. These abnormalities matched those found in both metastases. Our results demonstrate that ISH can be used to visualize genomic abnormalities at the single-cell level in melanocytic nuclei in their natural context, which makes it a promising tool in the histopathology of melanocytic lesions and in the study of melanocytic tumor progression.

DNA level and stereologic estimates of nuclear volume in squamous cell carcinomas of the uterine cervix. A comparative study with analysis of prognostic impact

Grading of malignancy in squamous cell carcinomas of the uterine cervix is based on qualitative, morphologic examination and suffers from poor reproducibility. Using modern stereology, unbiased estimates of the three-dimensional, volume-weighted mean nuclear volume (nuclear vv), were obtained in pretreatment biopsies from 51 patients treated for cervical cancer in clinical Stages I through III (mean age of 56 years, follow-up period greater than 5 years). In addition, conventional, two-dimensional morphometric estimates of nuclear and mitotic features were obtained. DNA indices (DI) were estimated by flow cytometry. Finally, the semiquantitative malignancy grade score value (MGS) was determined according to previously published methods. Estimates of nuclear vv were on average increased in euploid lesions (2P = 0.01), but the overall relationship between nuclear vv and DI was poor. Different clinical stages of disease did not differ with regard to nuclear vv (2P = 0.99) and DI (2P = 0.56). No relationship was disclosed between MGS and nuclear vv (2P = 0.85). Single-factor analysis showed prognostic impact of clinical stage of disease (2P = 0.0001) and DI (2P = 0.04), whereas estimates of nuclear vv were only of marginal prognostic significance (2P = 0.07). However, Cox multivariate regression analysis showed independent prognostic value of patient age and nuclear vv along with clinical stage and DI. All other investigated variables were rejected from the model. A prognostic index with highly distinguishing capacity between prognostically poor and favorable cases was constructed (2P = 1.9 x 10(-7)). It is concluded that realistic estimates of nuclear volume are independent of nuclear DNA content and are of prognostic value for objective malignancy grading in patients with squamous cell carcinoma of the uterine cervix.

Establishment and characterization of a human melanoma cell line (MV3) which is highly metastatic in nude mice

To select human melanoma cells that are highly tumorigenic and metastatic in nude mice we have implanted fragments of a fresh human melanoma metastasis subcutaneously (s.c.) into a nude mouse. After 3 passages in nude mice, part of the xenograft was cultured and a new melanoma cell line, MV3, was established. After intravenous (i.v.) inoculation of 2 x 10(6) MV3 cells, 95% of the nude mice (n = 20) developed lung colonies within 6 weeks. S.c. inoculation of 2 x 10(6) MV3 cells resulted in 95% tumor take, while 90% of the mice (n = 20) showed spontaneous metastases in the lungs within 7 weeks. Histological and immunohistological features of the original tumor of the patient were largely retained in the tumors of the mice and in the cell line in vitro. As shown by Alcian blue staining, MV3 cells contain large quantities of glycosaminoglycans (GAGs) and/or proteoglycanes (PGs), both in vivo and in vitro. The cells showed a marked expression of transferrin receptor, ICAM-1, EGF-receptor, and VLA-2 integrin. As only few human melanoma cell lines are available that frequently show metastasis in nude mice, the highly metastatic MV3 cell line represents a useful tool for studying the expression and regulation of molecules on human melanoma cells involved in the process of metastasis.

Use of diploid and triploid trout erythrocytes as internal standards in flow cytometry

DNA content determination requires the use of standards. Vindelov has shown the need to use two standards. Chicken and trout erythrocytes are commonly used, but they are not ideal standards. On the one hand, their DNA contents rarely frame the studied sample DNA content, and, on the other hand, as their base compositions are different in terms of A + T/G + C, their relative indices change according to the stains used. Use of triploid trout erythrocytes instead of chicken erythrocytes allows elimination of these two drawbacks; however, diploid trout must be differentiated from triploid trout. The present paper shows that an anatomic malformation is found with the triploid trout and so justifies the use of paired diploid and triploid trout as standards to measure nuclear DNA content.

Is radical hysterectomy always necessary in early cervical cancer?

A semiquantitative histopathologic grading system was used in combination with flow cytometric measurements of tumor cell DNA content to predict the risk of lymph node metastases in early cervical cancer. A retrospective study of 126 stage IB patients showed that a group with no risk of lymph node involvement could be identified by the use of both the histopathologic score and the DNA index. The results were confirmed in a prospective investigation of 59 new patients. Simple hysterectomy may be advised in low-risk patients.

Endometrial carcinoma: current concepts and future perspectives

Endometrial carcinoma is increasing worldwide and, in most of western Europe and the U.S., it is now the most common malignancy in the female pelvis. The most common parameters in deciding therapy are staging, according to the International Federation of Gynecologists and Obstetricians (FIGO) and histopathological grading, and evaluation of myometrial invasion. The treatment results in terms of a 5-year survival rate, are about 90% for well and moderately differentiated stage I to II endometrial carcinomas, whereas that for poorly differentiated ones is about 70%. The latter figures point towards the need for further prognostic parameters to identify subgroups with a fatal form of the disease. One such parameter might be the concentration of steroid receptors and promising results have been published recently but still better prognostic parameters have been proposed recently. It is known that the DNA content in individual tumor cells is a prognostic parameter. Due to the development of flow cytometry such determinations are rapid and more precise, and the prognostic significance has been proved to be superior to the more commonly used parameters.

Reference standards for flow cytometry and application in comparative studies of nuclear DNA content

Nuclear DNA mass in cells from a reference species can be used to obtain high-resolution estimates of DNA mass from a target species. In our study of DNA mass in cells from 45 selected species, representing each of the major vertebrate classes, we have obtained values of from 1.5 to 110.0 pg of DNA. Because values in or near this range would be expected in the study of nuclear DNA mass in vertebrates and other organisms, the species in this report can provide a useful catalogue of references for comparative studies of DNA.

Flow cytometry and phytoplankton

Flow cytometry and sorting are now an important technology in aquatic research. Simultaneous measurements of individual particle cell size, fluorescence, and light scatter properties are directly applicable to current topics in aquatic research. Flow sorting may be employed to obtain subsets of cells for analysis by conventional methods. The manner in which rapid, precise measurements of single cells are made is complex, and the application of this technology to aquatic samples is subject to many analytical constraints. Flow cytometric measurements of algal cell size and pigment autofluorescence are relative and are therefore dependent on the optical configuration and variability of the instrument. Specific types of reference materials are used to establish the validity of analyses: 1) instrument standards, 2) fluorescence controls, and 3) internal stain standards. The selection and application of standards and controls are discussed in the context of allometric (cell size versus pigment fluorescence) and ataxonomic (pigment color groups) methods. The widespread acceptance of particular reference materials among research groups will result in comparable data sets describing aquatic particle distributions.

Differences in the flow and absorption cytometric DNA distributions of mouse hepatocytes and tumor cells

We have determined the DNA content, the ploidy levels, and the percentages of different cell types present in small and large mouse mammary tumors as well as in young and old mouse livers by using absorption and flow cytometry. Absorption cytometry data indicated a significant increase in the proportion of transformed G0/G1 cells in the tumors as compared to that of the stromal G0/G1 cells with progressive tumor growth. This increase was not detected by flow cytometry. In both young and old mouse livers, a small number of cells of higher ploidy (8C and 16C) were detected by absorption cytometry but were not apparent in histograms obtained by flow cytometry. Furthermore, changes in the proportions of liver cells of different ploidy with age were apparent in absorption cytometry data but not in flow cytometry data. In one mouse liver experiment, a 6C cell peak appeared in the flow cytometry histogram, but a direct measurement of DNA content by absorption cytometry failed to detect cells with such a peak. We therefore believe that some caution may be warranted in the use of flow cytometry alone for evaluation of DNA distributions and of the proportions of different types of cells in complex solid tissues.

Flow cytometric measurements of DNA and other cell components in human tumors: a critical appraisal

Fundamental principles of flow cytometry with emphasis on DNA measurements and cell cycle analysis in human cells and tissues are summarized. Some of the pitfalls of cell preparation techniques and histogram interpretation are discussed at length. While consensus has been reached for some organs and tumors that DNA quantitation by flow cytometry (or image cytometry) may be of prognostic value, for most cancers studied to date the information remains incomplete. Thoroughly lacking are well-structured prospective studies because retrospective studies, while suggestive, may not necessarily be of the same value. Potential usefulness of other tumor markers is briefly discussed. Many fundamental questions concerning definitions of "diploid" and "aneuploid" tumors have not been satisfactorily settled. While the goal of "objective measurements" is worthy of further pursuit, the interpretation of results is often highly subjective. The biologic reasons for behavioral differences between diploid and aneuploid tumors are still totally obscure.

DNA index and karyotype analysis in myelodysplasia

DNA index (DI) determined by flow cytometry and karyotype determined by conventional methods were obtained on bone marrow samples from 43 haematologically normal subjects and 54 patients with myelodysplastic syndrome (MDS). Twenty one patients had a clonal karyotype abnormality but an additional five had a DI outside the normal range, showing evidence of aneuploidy that was not available from chromsome preparations. When patients were grouped into those with excess chromosomal material, those with diploid karyotypes, and those with a loss of chromosomal material, there was a significant difference among the mean DIs of each group, normal subjects being different from all patient groups. In these patients DI measurements were of value when carried out together with conventional chromsomal analysis in gaining the maximum amount of genetic information when a satisfactory karyotype might not be available or where failure of an abnormal cell population to proliferate might give an incomplete cytogenetic picture. The contribution of non-clonal chromsome loss to the DI is probably significant but has not been quantitated.

Assessment of DNA content and cell cycle distribution of erythroid and myeloid cells from bone marrow

A method is described for the measurement of DNA index and cell cycle distribution in purified erythroid and myeloid populations from human bone marrow. Erythroid cells were prepared after complement mediated lysis of non-erythroid marrow cells. Myeloid cells were obtained by fluorescence activated cell sorting by forward and wide angle light scatter. Mononuclear marrow cells were prepared with a density gradient. Nuclei prepared from the separated populations were stained with propidium iodide. Myeloid cells had a higher DNA index than erythroid cells, and the mononuclear preparation had an intermediate value. There were more erythroid than myeloid cells in the S and G2M phases of the cell cycle. These lineage differences are particularly relevant when considering data derived from unseparated bone marrow cells, and further experiments are needed to determine the origin of these anomalies.

Flow cytometric analysis of DNA content differences in blood samples obtained by leucoconcentration

The leucoconcentration technique allows rapid obtainment of cellular suspensions from total blood or bone marrow for flow cytometric analysis. The technique is based on picric acid in ethyl alcohol fixation and saponin red cell lysis, followed by mithramycin staining for DNA. It gives a good resolution of DNA distributions that allow detection of slight variations in DNA content. These results were obtained with cellular suspensions differing only in one X or Y chromosome (male, female, Klinefelter and Turner syndromes). In these studies the ratio of the DNA content of X and Y chromosomes agrees with the chromosomal mass ratio already reported by other authors, but the "absolute values" are 10-fold more compared to these same works. Our conclusion is that leucoconcentration technique followed by DNA staining with mithramycin increases the difference in the dye's penetration and binding between X and Y chromosomes.

Prognostic influence of ploidy level and histopathologic differentiation in cervical carcinoma stage Ib

Flow-cytometric DNA analysis and extended histopathologic grading were performed in specimens from 126 patients with squamous cell carcinoma of the uterine cervix stage Ib. Archival material was used for the measurements and the ploidy level was analysed according to the method described by Hedley with some modifications. The histopathologic grading was based on eight well-defined parameters all scored 1-3. The results showed that the ploidy level held significant prognostic information about the 10 year survival according to a division of DNA indices above and below 1.5. Further prognostic information appeared from a combination of DNA index and histopathologic score value. The combination held its prognostic importance in subgroups of patients with different tumour sizes. It is concluded that flow-cytometric analysis and histopathologic grading can identify subsets of patients who need more aggressive treatment.

Predictive value of flow cytometric DNA-analysis on fresh retinoblastoma tissue

The cellular DNA content and the distribution of tumour cells in different phases of the cell cycles has been analysed in 8 consecutive enucleated eyes with retinoblastoma. All tumours had abnormal ploidy levels. The analysis did not reveal any specific pattern in 2 tumours which had metastasized compared to 6 local tumours. The flow cytometric analysis alone or in combination with histopathology appeared not to improve the classification of large retinoblastomas.

Prognostic value of the flow cytometric DNA index in human ovarian carcinoma

Flow cytometric measurements were done on 51 ovarian carcinoma specimens collected from consecutive patients in a prospective study. The ploidy status was related to the course of the disease. The tumors from 26 (52%) of 50 evaluable patients had DNA aneuploidy. Patients with diploid tumors were more often considered disease-free after initial operation (P less than 0.01). Patients with aneuploid tumors had a more aggressive course of the disease in all respects of comparison. The median survival of patients with diploid tumors was 18 months as compared to 8 months for those with aneuploid tumors (P less than 0.0005). Flow cytometric DNA measurements give important prognostic information and such analyses should be included in future clinical trials. Through the development of high-speed instrumentation they also may become feasible in routine clinical work.

Technique and staining optimization leucoconcentration

In cytometric clinical application, it is important to obtain cell suspensions rapidly with as little cytological alteration as possible. A procedure has been achieved to prepare cell suspensions for flow cytometric analysis. The leucoconcentration technique, first described by Herbeuval for cytologic analysis, has been modified to be applied in cytometry. This technique involves Saponin lysis of red cells of peripheral blood or bone marrow samples that have been previously fixed with picric acid alcohol solution. Cells in suspension are not shifted and tinctorial affinity is not modified. Then cells have been stained with Mithramycin. Each parameter defined by Crissman has been analyzed to define the best staining conditions. The availability of Leucoconcentration with Mithramycin-DNA-staining permits determination of cell cycle with a fine resolution.

Characterization of an intraocular retinoblastoma-like tumour

A transplantable intraocular retinoblastoma-like tumour growing in F 344 rat eyes and tissue cultures suitable for therapeutic experiments is characterized. The tumours grew in the vitreous and infiltrated the internal layers of the retina. Feeder vessels from the retina supplied the tumours. Few and often incomplete rosettes were seen, and calcification was sparse in areas of necrosis. Stainings for glial fibrillary acidic protein, S-100 protein, neuron-specific enolase and desmin were negative. Ultrastructural analysis brought out a close correspondence between the tumour cell and the human retinoblastoma and other virus-induced retinoblastoma-like tumours. The experimental tumour cells lacked cilia, but had neurosecretory granules. Chromosome analysis showed a modal chromosome number in the triploid range, and 6 marker chromosomes were demonstrated. Flow-cytometric analysis showed a S-phase cell fraction of 42%, and chromosome stability was suggested by a tumour-cell DNA index which remained stable for more than 3 months.

Ploidy assessment of benign and malignant ovarian tumors by flow cytometry. A clinicopathologic study

In a prospective study, 112 fresh ovarian tumor samples were collected from 83 consecutive patients. Cellular DNA content was measured by flow cytometry. All the benign (n = 24) and semimalignant (n = 6) tumors were diploid. Of 50 malignant tumors, 24 (48%) were diploid and 26 (52%) were aneuploid. Aneuploidy was more frequent in the advanced stages of the disease, in tumors of low degree of differentiation, and in older patients. The patients with aneuploid tumors had smaller primary tumors and more often ascites. The fraction of cells with S-phase DNA content was higher in the aneuploid tumors. No association was seen to the tumor type. Ploidy determination is objective and reproducible. Aneuploidy associates to most negative prognostic factors in ovarian carcinoma and may reflect the aggressiveness of the tumor. The ploidy status may be taken into consideration in the stratification of patients of comparable risk for treatment studies.

Tissue-specific markers in flow cytometry of urological cancers. III. Comparing chromosomal and flow cytometric DNA analysis of bladder tumors

Thirty-seven transitional-cell carcinomas (TCC) of the urinary bladder were analyzed by DNA flow cytometry (FCM). After labelling of the cell suspensions with antibodies to cytokeratin, the cytokeratin-positive cells and the non-epithelial cytokeratin-negative cells could be analyzed separately. After estimation of S- and G2M phase, 3/17 cases (18%) with a normal DNA index showed elevated proliferative levels, among cytokeratin-labelled suspensions only. Of these 17 cases, 14 showed chromosomal abnormalities. The remaining 20 cases were abnormal, irrespective of the technique used. Although immuno-labeling of tumor cells for cytokeratin in FCM increases the sensitivity of this method in detecting aneuploid tumors or tumors with high proliferation fractions, the discriminating power of chromosomal analysis of TCC is greater than FCM.

Trout and salmon erythrocytes and human leukocytes as internal standards for ploidy control in flow cytometry

Control of technique and use of biological standards in flow cytometry have become increasingly important due to the wider use of the method for ploidy determination of malignant tumors in clinical research. Trout (TRBC) and salmon erythrocytes and human buffy coat leukocytes were selected for a study of factors influencing the DNA stainability. Whether standard and test cells were mixed before or after enzymatic treatment and staining was found to be critical for the ploidy comparisons. Otherwise, artifactual differences of at least 20% may be noted, leading to an overestimation of DNA aneuploidy. The time from staining to analysis had minimal effect, with some exceptions. The proportions of different cells in the sample had no influence, and nonlinearity of measurements was negligible. Diploid cells in normal endometrium and benign ovarian tumors, as well as the diploid fraction of aneuploid tumor cells, were systematically measured to have a DNA staining 5-7% above human leukocytes.

Methanol fixation permits flow cytometric analysis of immunofluorescent stained intracellular antigens

Fixation and immunofluorescent staining methods were developed for analyzing intracellular antigens with the cell flow cytometer. Fixing cell suspensions with 100% methanol provided best preservation of morphology, lowest fluorescent background staining and most intense specific immunofluorescence. Immunoglobulins present in B cell lines that were representative of different developmental stages could be distinguished quantitatively. Fluorescence histograms were compared with fluorescence microscope presentation of stained cells. Intracellular antigens that reacted with monoclonal antibodies could also be evaluated by flow cytometry. This method was utilized to assess plasmacyte development in mouse spleen cell cultures after stimulation with lipopolysaccharide.

Interphase cell flow cytometry as a means of monitoring genomic size in normal and neoplastoid cell cultures

The DNA specific fluorescence of mass cultures and clones derived from human skin and bladder tumor tissue was assayed by flow cytometry. In order to detect and quantitate small fluorescence intensity changes, cytogenetically defined triploid or diploid human fibroblast strains were cocultivated, harvested, and stained with the cell strain of unknown karyotype. The triploid standard (derived from human abortus tissue) proved chromosomally unstable at high passage level. Fifteen male, female, and 45,X strains displayed target-to-standard cell fluorescence ratios commensurate with their respective chromosome constitutions. Interstrain variation was highest among the 45,X strains, although mosaicism could not be detected by conventional cytogenetics. Interclonal fluorescence variation was two- to ten-fold higher among the tumor-derived clones tested. Chromosome counts and subcloning experiments indicate that this increased fluorescence variation is due to genome size variation. The clonal evolution of genome size differences was observed in subclones of chromosomally divergent parental clones. These observations suggest that well controlled flow cytometry can adequately resolve subtle degrees of genome size variation in cultivated human cells. The technique is especially suited for monitoring genome size changes in cultivated tumor cells.

Comparison of tissue disaggregation techniques of transitional cell bladder carcinomas for flow cytometry and chromosomal analysis

DNA index (DI) measurements and chromosomal analysis of 42 transitional cell carcinomas were done after mechanical and enzymatical disaggregation of the tumor specimens. The results obtained with these different disaggregation techniques were compared in the 33 cases (79%) that showed recognizable chromosomes. The enzymatically obtained cell suspensions could not be used for chromosomal analysis after short-term culture of 24 hours. In four cases, the DI after enzymatical treatment could not be estimated. In most cases, the DI obtained from the tumor cells was similar for both aggregation techniques, with the exception of four cases of enzymatically treated cell suspensions in which the DI could not be estimated. The average DI of the aneuploid tumors was 13% higher than the corresponding chromosome count. In 19% of the aneuploid tumors the proportion of aneuploid cells could not be measured after enzymatical treatment. In the remaining suspensions the proportion of diploid cells was higher after enzymatical disaggregation than after mechanical treatment. It is concluded that for flow cytometric and direct chromosomal analysis of bladder tumors, the mechanical disaggregation technique is most suitable.

Accuracy and reliability of flow cytometric DNA analysis using a simple, one-step ethidium bromide staining protocol

Sources of variation and error were investigated for a simple flow cytometric analysis of DNA content of detergent-isolated nuclei stained with ethidium bromide. Using the ploidy classes of mouse liver nuclei, deviations from linearity were assessed for three different instruments. In more extreme settings, the maximum deviations for a FACS instrument were up to 6 to 9%, but in general deviations were around 1% or lower for all instruments. As biological DNA standards, human peripheral lymphocytes and trout erythrocytes appeared to be suitable and easy to store frozen. The erythrocytes had dye-binding characteristics similar to those of human lymphocytes and a 20% lower fluorescence, thus being well suited as an internal standard, as was demonstrated in tumor ploidy analyses performed with varied tissue concentration. Staining homogeneity was improved when staining time was extended to 24 h, at which time male and female lymphocytes were completely separated with an average difference in DNA content of 1.9%. A small difference in fluorescence between mitogen-stimulated and unstimulated lymphocytes was reduced to less than 1% after 24 h of staining. In general, the manipulations of the conditions for the analysis resulted in maximum variations of around 1%, indicating the robustness and reliability of the technique.

Binding of Hoechst 33258 to chromatin in situ

The binding of Hoechst 33258 to rat thymocytes, human lymphocytes, and NHIK 3025 tissue culture cells was studied by measuring the fluorescence and light scattering of the cells as functions of dye concentration using flow cytometry. The results indicated that there were two different modes of binding of Hoechst 33258 to chromatin in situ at physiological pH. Type 1 binding, which dominated at total dye/phosphate ratios below 0.1 (0.15, M), was characterized by a binding constant of the order 10(7) M-1 and fluorescence with high quantum yield. Further binding of the dye resulted in a reduced blue/green fluorescence ratio, indicating that secondary sites were occupied. Binding at secondary sites above a certain density (0.1 less than or equal to bound dye/phosphate less than or equal to 0.2) induced strong quenching of fluorescence and precipitation of chromatin. Precipitation was quantitated by measuring the large-angle (greater than or equal to 15 degrees) light scattering of the cells above 400 nm, i.e., outside the Hoechst 33258/DNA absorption spectrum, as a function of dye concentration. In contrast, the light scattering at 365 nm, i.e., within the absorption spectrum of Hoechst 33258/DNA, was independent of the total dye/phosphate ratio. The coefficient of variation of the light-scattering (greater than or equal to 400 nm) histograms decreased with Hoechst 33258 concentration. Type 2 binding to histone-depleted chromatin was cooperative (Hill-coefficient approximately 2) and the apparent binding constant was 2-3 X 10(5) M-1 as determined from quenching and precipitation data.(ABSTRACT TRUNCATED AT 250 WORDS)

DNA content and cell cycle analysis of bone marrow cells in myelodysplastic syndromes (MDS)

DNA distribution in bone marrow cells from 10 normal subjects and 34 patients with MDS (24 with refractory anaemia (RA) and 10 with excess blasts (RAEB] was determined by flow cytometry using a FACS III. DNA histograms were resolved into G0/1, S and G2/M compartments by fitting Gaussian distributions and the DNA content of G0/1 cells, expressed as DNA index (DI), was determined. In 19 MDS patients the DI was outside the normal range, those with RA tending to be hyperdiploid. Two patients with RAEB had a second G0/1 peak. In five cases of RA the number of cells in G0/1 was below the normal range and the mean value was significantly lower than normal for this group as a whole (P = 0 X 018). Eleven (RA) patients had a higher percentage of cells in G2/M than normal (P = 0 001). In RAEB patients there is a suggestion of increased numbers in G0/1 and a decrease in S phase and G2/M cells. All three of the deaths amongst RA patients and four out of the five deaths in RAEB patients since the beginning of this study were associated with an abnormal DI at the initial investigation.

Short-term cryopreservation of human breast carcinoma cells for flow cytometry

A procedure is described for short-term cryopreservation of primary human tumor cells and tissue slices for later analysis by flow cytometry. Cells were mechanically dispersed into a freezing medium, which was then frozen at either -20 degrees C or -70 degrees C for delayed cell cycle analysis. The results show that a correlation coefficient of greater than 0.95 exists between cell cycle kinetic analyses performed immediately after surgical excision of the tumor and on cells frozen from 1 to 30 days at -70 degrees C in this freezing solution. Somewhat lower levels of correlation exist for cells frozen at -20 degrees C in this freezing medium. This procedure has also been successfully used to preserve freshly isolated breast carcinoma cells shipped from distant laboratories for analysis in the flow cytometer, thus expanding the data base on certain types of breast carcinoma.

Cell DNA content--correlation with clonogenicity in the human tumour cloning system (HTCS)

Thirty-six ovarian and renal-cell tumours were analyzed by flow cytometry (FCM) for DNA content and in parallel were assayed for colony formation in a human tumour cloning system (HTCS). While 15/19 (79%) tumours with an abnormal (aneuploid) DNA stemline formed colonies in the HTCS, only 2/17 (12%) of diploid tumours formed colonies. All samples contained tumour cells as assessed by routine cytological examination. The capacity to form colonies in the HTCS was not correlated in these tumours with grade or stage of disease or tumour type. The level of aneuploidy expressed as the FCM DNA index did not correlate with the cloning efficiency in HTCS. These findings suggest that tumour growth in the HTCS reflects a biologically important potential, related in at least some tumours to an abnormal DNA stemline.

Clinical and biological significance of aneuploidy in human tumours

Aneuploidy is a well recognised feature of human tumours, but the investigation of its biological and clinical significance has been hampered by technological constraints. Quantitative DNA analysis reflects the total chromosomal content of tumour cells and can now be determined rapidly and reliably using flow cytometry; this has resulted in renewed interest in its potential clinical applications. This article reviews the accumulating evidence that tumour ploidy reflects the biological behaviour of a large number of tumour types and that diploid tumours in particular have a relatively good prognosis. The measurement of tumour ploidy is likely to become a valuable adjunct to the clinical and histopathological assessment of cancers.

Practical breast carcinoma cell kinetics: review and update

The S-phase fraction (SP) measured by flow cytometry of DNA and the thymidine labeling index (TLI) measured autoradiographically indicate the proportion of carcinoma cells currently synthesizing DNA and reflect the rate of proliferation. The TLI and SPF are lognormally distributed. The median TLI performed to maximize precursor uptake is near 5% (5 labeled carcinoma cells per 100) the mean near 7%, and the range from less than 1% to near 40%. Corresponding values for the SPF measured by DNA flow cytometry are slightly higher when appropriate measures are taken to reduce background debris counts and other artefacts. Residual elevation of SPF above TLI may result from S-phase arrested cells. Flow cytometric histograms show that clearly aneuploid cell lines exist in 50-80% of primary breast carcinomas. Aneuploid breast carcinomas have higher mean TLI than diploid breast carcinomas, and therefore proliferate more rapidly. They also more frequently lack estrogen receptor (ER). Carcinomas with minimal nuclear anaplasia, particularly those of tubular, mucinous, infiltrating lobular and adenocystic types have low TLI and SPF, whereas carcinomas with highly anaplastic nuclei, including medullary carcinomas, have high TLI and SPF. TLI and SPF correlate inversely with ER and PgR content, have no relationship to axillary lymph nodal status, and have a weak positive correlation with tumor size and a weak negative correlation with age. High TLI predicts a high risk of early relapse after primary therapy for both node-negative and node-positive carcinomas. Carcinomas that produce brain metastases have particularly high TLI. Current evidence suggests that high SPF and aneuploidy may prove to have prognostic significance like TLI.