Flow cytometry of human colorectal tumors: nuclear isolation by detergent technique

A robust flow-cytometric protocol for assessing growth rate of hatchery-reared barramundi Lates calcarifer larvae

In this study, a flow-cytometric cell cycle analysis method to assess instantaneous growth rate of whole larvae of the Australian barramundi Lates calcarifer was developed and validated. High-resolution DNA measurements of either fresh, frozen or RNAlater-preserved larvae (gap0-gap1, G(0) -G(1), coefficient of variation (c.v.) < 3, 4 and 5%, respectively) enabled the deconvolution of the DNA histogram and assignment of the proportion of nuclei into cell cycle compartments G(0) -G(1), S (DNA synthesis) and G(2) -M (Gap2-Mitosis). This technique can be also used for individual fish tissues such as brain, liver, fin and muscle. For the first time, the combined proportion of replicating nuclei (into S and G(2) -M phases) of whole fish larvae and absolute growth rate in length (mm day(-1)) has been correlated in commercial aquaculture conditions. Fast growing L. calcarifer larvae had an overall hyperplasia advantage as indicated by a greater proportion of cells in the S+G(2) -M phase compared with slow growing larvae, which might explain the increasing differences in size during culture. In a fasting trial, larvae ceased growth while maintaining the constant initial rates of cell division throughout a 6 day period. For a highly fed fast growing control group, cell division rates significantly increased after day 4. Flow-cytometric cell cycle analysis of whole fish larvae may provide fish biologists and aquaculturists with a better understanding of how cell division rates influence early growth in natural and artificial environments.

Heterogeneity of squamous cell carcinomas of the head and neck in relation to clinicopathological variables

We analysed 32 primary, 8 recurrent and 16 metastatic squamous cell carcinomas of the head and neck by flow cytometry to assess tumoural heterogeneity. Intratumoural heterogeneity was found in 9 of 30 primary tumours (30%). All heterogeneous tumours had diploid and aneuploid cell lines. DNA indices were different from those of the primary tumours in 3 of the 8 recurrent lesions (38%) and in 8 of the 12 metastatic lesions (67%). The results indicate that new cell lines evolve during the process of recurrence and metastasis. The incidence of recurrence, metastasis, and heterogeneity increased with the size of the tumour. Histologically, there were tumours in which the degree of differentiation and mode of invasion of primary lesions were not consistent with the results of flow cytometry in both homogeneous and heterogeneous tumours. In conclusion, multiple sampling for flow cytometric analysis is essential for better characterization of oral carcinomas.

The implication of DNA content and S-phase fraction in oral carcinomas with and without metastasis

Flow cytometry DNA analysis was performed on fresh tissue samples of 90 primary lesions and 32 metastatic lymph nodes of squamous cell carcinomas of the oral cavity and related regions to elucidate the characteristics of tumors with metastatic potency. The incidence of aneuploidy for carcinomas with metastasis was 67%, which was significantly higher than the 44% of carcinomas without metastasis, and aneuploid carcinomas (39%) had a higher tendency to metastasis than diploid carcinomas (20%). The incidence of aneuploidy and metastasis was related to the T classification, the degree of differentiation, and the histologic grade of malignancy. The incidence of aneuploidy and mean DNA index of metastatic lesions were 31% and 1.12, respectively, and the values were significantly lower than the 67% and 1.30 of the corresponding primary lesions. The results indicate that the chance of evolution of metastatic cell lines is higher in aneuploid carcinomas than diploid carcinomas, possible because the former is more heterogeneous than the latter, but most of the cell lines causing lymph-node metastasis are diploid cell lines. Metastatic lesions had a lower S-phase fraction than primary lesions, indicating that a high S-phase fraction does not always reflect the presence of metastatic cell lines.

DNA ploidy pattern in human chronic liver diseases and hepatic nodular lesions. Flow cytometric analysis on echo-guided needle liver biopsy

BACKGROUND

Significantly elevated fractions of diploid hepatocytes and reduction in the polyploid populations have been reported in human and experimentally induced hepatocellular carcinomas (HCC). This study was conducted to determine how these changes are related to conditions that often precede HCC, such as chronic hepatitis, cirrhosis, and premalignant focal nodules in cirrhotic livers.

METHODS

Ultrasound-guided needle biopsy specimens of the liver were obtained from patients with chronic hepatitis, cirrhosis, or ultrasonographically diagnosed nodules within cirrhotic livers; biopsy specimens also were taken from patients without hepatic disease. DNA flow cytometry was performed on isolated nuclei to determine the percentages of diploid, tetraploid, and octaploid hepatocytes; the S-phase fraction for each diploid peak and the diploid/polyploid (tetraploid + octaploid) ratio also were calculated. Part of each specimen was reserved for evaluation of hepatocyte binuclearity.

RESULTS

Chronically hepatitic (18 patients) and cirrhotic (18 patients) livers showed significantly increased diploid/polyploid ratios, with respect to normal livers, that were significantly correlated with decreases in hepatocyte binuclearity. This trend was even more marked in euploid nodules (4 premalignant and 5 malignant), in which the S-phase fractions were significantly higher than those of normal liver; aneuploidy was found in 6 of 11 malignant and 2 of 6 premalignant nodules.

The effect of oestrogen ablation on the phospholipid metabolite content of primary and transplanted rat mammary tumours

The concentration of phospholipid metabolites was determined in chemical extracts from two types of rat mammary tumours and compared with proliferation data (S-phase fraction). One of the tumours was an oestrogen-sensitive transplanted tumour. In this tumour the concentration of phosphocholine (PC) and glycerophosphorylcholine (GPC) correlated strongly with the S-phase fraction but not with the number of cells actively synthesizing DNA. Oestrogen ablation resulted in tumour regression. Regressing tumours contained less PC and more GPC than those actively growing. The other tumour was induced in rats by intravenous administration of N-methyl N-nitrosourea. Phosphoethanolamine (PE), PC and GPC levels were not associated with the S-phase fraction in this tumour. Oestrogen ablation resulted in tumour regression. There was no significant difference between the regressing and growing tumours in PE, PC or GPC content.

Flow cytometric analysis of squamous cell carcinomas of the oral cavity in relation to lymph node metastasis

Nuclear DNA content and cell kinetics were studied in 40 squamous cell carcinomas of the oral cavity by flow cytometry to evaluate the diagnostic significance of the method in predicting lymph node metastasis. The presence of lymph node metastasis was confirmed histologically in 20 carcinomas. The incidence of metastasis was 36% in group A (22 carcinomas of the tongue and floor of the mouth) and 67% in group B (18 carcinomas of the alveolus and gingiva). On flow cytometric analysis, DNA aneuploidy was observed in 23 tumors (58%). The incidence of lymph node metastasis in the aneuploid tumors was 70%, which was significantly higher than the 24% for the diploid tumors. This also was the case for both of the subgroups. The incidence of aneuploidy and the DNA index for tumors with metastasis were 80% and 1.58, respectively. These values were significantly higher than the 35% and 1.16 for tumors without metastasis, but there were no significant differences in the S phase and G2M phase fractions between the tumors with and without metastasis. The incidence of aneuploidy in tumors with metastasis was also higher in group A (75% versus 36%) and group B (83% versus 33%). In terms of histologic differentiation, the incidence of metastasis and aneuploidy increased as the degree of differentiation decreased. Similar relationships were found between the histologic grade of malignancy and the incidence of metastasis and aneuploidy. The results indicate that nuclear DNA content analysis by flow cytometry is useful as a supplement to clinical and histologic evaluation in predicting the tendency of squamous cell carcinomas of the oral cavity to metastasize to regional lymph nodes.

Chromosome number distribution and cellular DNA content in colorectal adenomas from polyposis and nonpolyposis patients

Ploidy analyses of colorectal adenomas were performed by combined flow cytometric DNA analysis of unfixed isolated nuclei and direct chromosome preparation after Colcemid incubation for 9-20 hours. Ten of 18 adenomas from nonpolyposis patients and 4 of 13 adenomas from patients with familial adenomatous polyposis yielded a mean of 25 countable metaphases (range 7-44) per tumor. Of 343 metaphases, only 38% had 46 chromosomes, and 62% were nondiploid. All but one adenoma had diploid or peridiploid modes in the range of 46-50 chromosomes. One adenoma was hyperploid, with a mode of 74 chromosomes and a correspondingly increased nuclear DNA content. In another two adenomas, the DNA analyses showed small hyperploid populations constituting 6% and 2% of the cells. The most striking difference between the DNA analyses and chromosome number distributions was that 13% of all metaphases were hyperploid with chromosome numbers outside the perimodal range but, except in one adenoma, without indication in the DNA histogram of corresponding hyperploid cell populations. We propose that these aberrant metaphases indicate an early acquired genetic instability of the neoplastic epithelium, which may be instrumental in generation of hyperploid, invasive clones, which constitute most colorectal carcinomas.

A comparison between stereological estimates of mean nuclear volume and DNA flow cytometry in bladder tumours

The correlation between stereological estimate of mean nuclear volume and DNA-content was studied in 55 human urinary bladder tumours. The DNA-content was determined by flow cytometry on isolated nuclei stained with ethidium bromide. Trout erythrocytes were used as a biological internal standard providing an accurate determination of the DNA-histogram. An unbiased estimate of the mean nuclear volume (vv) was obtained after standard formaline fixation, paraffin-embedding, sectioning and hematoxylin-eosin staining using the equation vv = pi/3.l3(0). Here l0 is the length of an intercept measured in a random direction through a test point, which hit a nucleus. A highly significant correlation was found between vv and mean DNA-content of nuclei (2p = 0.0004). A highly significant correlation was also found between vv and the highest DNA-content present in tumours having cell populations with different DNA content (2p = 0.0016). The mean nuclear volume and the DNA-content also correlated well with the pathologic grade. Although significant the correlations were far from perfect, which indicates that DNA content and mean nuclear volume may provide partly independent biological information. The methods provide objective, unbiased and reproducible data which may improve the possibility of grading and predicting the disease course of human urinary bladder tumours.

Binding of wheat and peanut lectins to human transitional cell carcinomas. Correlation with histopathologic grade, invasion, and DNA ploidy

The binding of peanut (PNA) and wheat germ (WGA) lectins to tissue sections was examined in biopsy specimens from normal urothelium (ten patients) and from tumor tissue of noninvasive (17 patients) and invasive bladder (31 patients) carcinomas. The results were correlated to DNA content, histopathologic grade, and the presence or absence of invasion. Significant alterations in lectin binding associated with the development of cancer were found. A gradual loss of both PNA and WGA binding was found to correlate with higher grades of atypia (P less than 0.001). The loss of WGA binding was significantly correlated with both tumor aneuploidy (P less than 0.001) and the presence of invasion (P less than 0.05), whereas no significant correlation was found between loss of PNA binding and these variables. We concluded that the loss of WGA binding structures associated with bladder cancer shows a better correlation with known risk factors (aneuploidy and invasion) than the loss of PNA binding does.

Flow cytometric analysis of benign and malignant tumors of the oral and maxillofacial region

One hundred eight fresh tissue samples obtained from normal tissues, benign tumors, and malignant tumors of the oral and maxillofacial region were analyzed for nuclear DNA content and cell kinetics by flow cytometric analysis (FCM). Mean DNA indices for 22 normal tissues and 18 benign tumors were 1.00 and 1.02, respectively, and all samples but one showed diploid pattern. On the other hand, the value for 68 malignant tumors was 1.38, and 66% of them showed an aneuploid pattern. The S phase and G2 + M phase cell populations for malignant tumors were 17.2% and 7.0%, respectively. With the exception of G2 + M phase cell population, all values for malignant tumors were significantly higher than those of normal tissue and benign tumors. Although statistical differences were not observed in most of the values, they were higher in squamous cell carcinomas than in malignant salivary gland tumors. The incidence of aneuploidy and DNA index showed a tendency to increase with the increase of T classification, in N2 and N3 tumors, and in the group of patients with recurrence or who died. The DNA index and the type of DNA ploidy were well correlated to malignancy grade determined by six histologic parameters, whereas the S phase cell population was correlated to mitosis. The analysis by the two-dimensional diagnostic supporting system showed that more than 80% of malignant tumors can be correctly diagnosed by combined values of DNA index and S phase cell population. The results indicate that nuclear DNA analysis by FCM is quite useful as a supplement to histologic diagnosis and evaluation of malignancy grade.

Solid tumor preparation for flow cytometry using a standard murine model

The application of flow cytometry (FCM) to solid human tumors has been hindered by the difficulty in producing high yield, viable, unaltered single cell suspensions. Carcinomas containing a high desmosomal content, such as well-differentiated squamous cell (SCC) cancers of the head and neck (H&N) region, are particularly difficult to prepare. The desire to employ FCM to study cellular DNA parameters of these tumors led to the use of a 3-methylcholanthrene induced murine SCC for the comparative testing of preparative techniques. Dissociation techniques, including mechanical, enucleation, chemical, single and combination enzymes methods, were comparatively tested. Of these, the combination enzyme treatment employing trypsin and collagenase produced the highest cell yields in the shortest time with the highest dye exclusion viability and the least expense. Several fixation systems including glutaraldehyde, paraformaldehyde, acetic acid, and ethanol were comparatively tested using percent of cell loss and quality of the DNA histograms produced as end points. Ethanol-water systems with added fetal calf serum provided minimal cell loss and high quality histograms which were stable for extended periods of time. A murine tumor, closely mimicking the histology of the human tumor of interest, may be used as a model for the determination of optimum techniques of solid tumor preparation for flow cytometric analysis.

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.

A comparison between flow cytometric ploidy investigation and chromosome analysis of 32 human colorectal tumors

The correlation between flow cytometric ploidy investigation and classic chromosome analysis was studied in 32 human colorectal tumors. Flow cytometry was performed by nuclei isolation and DNA staining with ethidium bromide. Chromosome analysis was done after incubation with colcemid. In 12 cases, chromosome identification was possible by grouping according to the Denver system or by Q-banding. Generally, the measured DNA content corresponded well with the content expected from chromosome analysis, giving an average difference of 4%. In nine tumors, the measured DNA content was 4-18% higher than expected. Some of these discrepancies could be due to difficulties in identifying the corresponding cell populations in heterogeneous tumors. However, in general the number of cell populations and their quantitative representation by the two methods were statistically well correlated. The results indicate that flow cytometric ploidy investigation of colorectal tumors with the present technique is a reliable method, but also that a combination of both techniques may yield additional information about tumor cytogenetics.