A detergent-trypsin method for the preparation of nuclei for flow cytometric DNA analysis

Characterization of the T61 human breast carcinoma established in nude mice

This paper gives a biological characterization of the T61 human breast carcinoma established in nude mice. The human origin of the tumour was verified by the demonstration of the presence of human chromosomes exclusively in the tumour cells. The tumour cells were found by chromosome analysis and flow cytometric DNA analysis to be aneuploid. By electron microscopy, the tumour cells were shown to display the characteristics of glandular epithelium; a light microscopic examination revealed morphological characteristics similar to those of an axillary metastasis of the patient from whom the T61 tumour was derived. Furthermore, the tumour was shown to contain classical receptors for oestrogen and progesterone. The growth of the tumour was characterized by gompertzian growth curves. Since the T61 tumour has a response pattern to endocrine treatment which differs from that described for other human breast tumours grown in nude mice, this tumour may provide a valuable supplement in the study of human breast cancer and endocrine treatment.

Cyclic AMP and theophylline enhance DNA synthesis in L cells stimulated with anti-actin IgG and [(IgG)2 protein A]2 complex by recruiting cells into S-phase

Surface binding of anti-actin IgG alone or in a Mr = 716 000 [(IgG)2 Protein A]2 complex results in a stimulation of DNA synthesis and cell growth in L cells. Cyclic-AMP (0.01-1.0 mM) added to such cell cultures augmented DNA synthesis as measured by incorporation of [3H]thymidine into DNA. Theophylline (0.1-1.0 mM), a phosphodiesterase inhibitor which prevents enzymatic breakdown of cAMP, had similar effects, but cGMP (0.01-1.0 microM) reversed the effects of cAMP and theophylline upon DNA synthesis. Analysis of the cell cycle by flow cytometry revealed that antibody produced a shift (7%) of cells from the G1-phase to the S-phase (DNA-synthetic) of the cell cycle at 72 hr of incubation. Addition of cAMP (0.5 mM) to cell cultures, however, produced significant shifts of antibody stimulated cells from G1-phase to S-phase at all time points measured, i.e., 24 (12%), 48 (22%), 72 hr (23%). Thus, antibody recruited cells into S-phase of the cell cycle and cAMP greatly augmented the effect. These observations suggest that the mechanism of activation of L cell growth by antibody to surface antigens involves a recruitment of cells into the DNA-synthetic phase and that the effect may be mediated by cAMP.

A method for simultaneous nuclear immunofluorescence and DNA content quantitation using monoclonal antibodies and flow cytometry

A preparative technique for the two-parameter flow cytometric study of nuclear antigen expression is reported. This method employs a brief sequential treatment of cells at 4 degrees C first with 0.5% paraformaldehyde and second with 0.1% Triton X-100 in phosphate-buffered saline followed by cellular staining with indirect immunofluorescence and propidium iodide. Using this technique, cellular morphology is preserved, cell clumping is minimized, and high-quality indirect immunofluorescence and DNA staining are obtained with a minimum of nonspecific labeling. Utilizing nuclear antigen-specific monoclonal antibodies in conjunction with this technique, the cell-cycle phase-dependent expression of such antigens is examined. From these data, the utility of two-parameter flow cytometry in the identification and quantification of cell-cycle-dependent modulation of nuclear antigens is discussed.

Cell cycles in the male accessory glands of mealworm pupae

During the pupal stage of Tenebrio molitor, the accessory reproductive glands of males grow by cell division. Within the secretory epithelium of the bean-shaped accessory glands (BAGs), cell numbers triple. In the tubular accessory glands (TAGs), the increase is 14-fold. There are two mitotic maxima in each gland. The first maximum occurs at 1-2 days while the second is at 4-5 days. The second maximum coincides with the major ecdysteroid peak described by Delbecque et al. [Dev. Biol. 64, 11-30 (1978)]. Nuclei were isolated from TAGs during the pupal mitotic bouts and during mitotic inactivity in the adult. After Feulgen or propidium iodide staining, the DNA content of these nuclear populations was measured by absorption cytophotometry or by fluorescence flow cytometry, respectively. The proportion of cells in each phase of the cycle was calculated using an iterative model. After mitoses have ended in the late pupa, the cells were arrested in G2. [3H]Thymidine was injected into 1- and 4-day pupae to pulse-label cells of the TAGs. After allowing various periods from 4 to 60 hr for cells to progress through G2 to reach mitosis, fractions of labelled mitoses were determined by autoradiography. From the combined cytometric and autoradiographic data, the duration of each phase of the cell cycle was calculated assuming the population was in exponential growth. Cell cycles in 4-day pupal TAGs take 48 hr. G1, S, G2, and, M lasted 13, 14, 17, and 4 hr, respectively.

Endocrine sensitivity of the receptor-positive T61 human breast carcinoma serially grown in nude mice

A study was made on the effect of ovariectomy, 17 beta-oestradiol, and tamoxifen on the oestrogen and progesterone receptor-positive T61 human breast carcinoma grown in nude mice. The effect of the treatment was evaluated by the specific growth delay calculated on the basis of Gompertz growth curves, and by the changes in the cell cycle distribution monitored by flow cytometric DNA analysis. The results demonstrated that both oestradiol and tamoxifen induced a temporary growth delay, whereas ovariectomy of the host had no effect on the growth of the tumour. The oestradiol-induced tumour growth delay was accompanied by a decrease in the G1 fraction, an accumulation of cells in the S-phase, and polyploidy, whereas neither treatment with tamoxifen nor ovariectomy influenced cell cycle distribution. The results indicate that oestradiol and tamoxifen have different mechanisms of action. In addition, they were interpreted as indicating different mechanisms regulating ovarian-dependent tumour growth, on the one hand, and oestrogen and tamoxifen-induced tumour growth inhibition, on the other. The results support the view that the presence of receptors may be of importance but is not a sufficiently clear marker to allow prediction of the endocrine sensitivity of individual breast tumours.

Automated recognition of atypical nuclei in breast cancer cytology specimens by iterative image transformations

In order to develop an objective grading system for nuclear atypia in breast cancer, an image analysis technique has been applied for the automated recognition of enlarged and hyperchromatic nuclei in cytology specimens. The image segmentation algorithm, based on the 'top hat' image transformation developed in mathematical morphology, is implemented on the LEYTAS automated microscope system. The performance of the segmentation algorithm has been evaluated for fifty malignant and eighty-five benign breast lesions by visual inspection of the displayed 'flagged' objects. The mean number of flagged objects per 1600 image fields for breast cancers was 887 (range 0-7920) of which 87% consisted of single, atypical nuclei. For benign lesions the mean number was 30 (range 0-307) of which 20% were single nuclei. By adaptation of the 'top hat' parameter values, a more extreme subpopulation of atypical nuclei could be discriminated. The large interspecimen variation in the breast cancer results was related to differences in DNA content distribution and mean nuclear area, determined independently with scanning cytophotometry, and to some extent with the histological type.

Disaggregation of human solid tumours by combined mechanical and enzymatic methods

Two combined mechanical and enzymatic disaggregation techniques and a simple mechanical disaggregation procedure were compared. The combined procedures involved a mechanical comminution of the tumour tissue followed by incubation in trypsin. In one method, the tissue was subjected to long-term trypsinization at 4 degrees C, and in the other procedure, repeated short-term trypsinization at 37 degrees C was applied. The results were compared in terms of the yield of viable cells, plating efficiency, the ability to produce tumours in nude mice, and DNA distribution as measured by flow cytometry. The combined techniques provided reproducible cell yields of 2-10 X 10(7) viable cells g-1 of tissue, whereas only a small number of tumour cells was produced by the mechanical method. DNA analysis demonstrated that only the long-term trypsinization procedure resulted in a representative cell yield from all the tumours tested.

Flow cytometric determination of DNA ploidy level in nuclei isolated from paraffin-embedded tissue

Nuclei, isolated from paraffin-embedded tissue, were stained with propidium iodide (PI) and found suitable for DNA analysis by flow cytometry (FCM). DNA-derived fluorescence intensity, however, was always decreased and had a much higher intersample variability as compared to results obtained with fresh material. Using chicken red blood cells (CRBC) as a model system, we found the lower fluorescence intensity to be due to the formalin fixation step in tissue processing. The intersample variability was found to be at least partly caused by variations in the duration of fixation. Overnight trypsinization improved the fluorescence intensity but did not reduce the intersample variability. Under all conditions tested PI binding to CRBC appeared to be saturable. Since fresh diploid or red blood cells could not be used to standardize DNA histograms, an alternative approach was developed in which nuclei from paraffin-embedded normal and tumor tissue of the same specimen were mixed. With this method DNA indices (DI) of 24 colorectal cancers were found to be closely correlated (r = 0.9877, P less than 0.001) with DI obtained with fresh tumor tissue from the same patients. The correlation of the percentages of S-phase nuclei between paraffin-extracted and fresh samples (r = 0.5875, P less than 0.05) was as high as could be expected, taking sampling differences into account. This method is an important tool for the retrospective analysis of FCM-derived DNA parameters in relation to diagnosis and prognosis of neoplasms.

DNA flow cytometry in primary breast carcinoma

DNA Flow cytometric values were recorded in 66 primary breast carcinomas. Twenty-six tumors were found to be diploid whereas 40 were non-diploid. About 10% of the cells belonged to the S-phase fraction. Non-diploid tumors had significantly larger S-cell fractions (greater than 10%) than diploid ones. High tumor ploidy correlated positively with high clinical stage (stage I versus stage greater than or equal to II) and with high histological grade but was unrelated to estrogen-receptor content and menopausal status.

Correlation of cell-cycle kinetics, hormone receptors, histopathology, and nodal status in human breast cancer

DNA ploidy and percent of (%S-phase) S-phase cells were determined from the DNA content distribution of 21 benign and 76 malignant (69 primary, 7 metastatic) breast tumors using flow cytometry. All of the benign tumors were diploid, whereas 89% of the malignant tumors had measurable aneuploidy. Multiple stem-lines were observed in approximately 10% of the malignant tumors. The ploidy distribution of the malignant tumors was bimodal with an increased frequency of tumors with a near diploid DNA index (DI), and a second group with DI ranging from triploid to tetraploid. The percentage of cells in S-phase ranged from less than 1% to 37.4%. DI and %S were significantly higher in poorly differentiated duct carcinomas, medullary carcinomas, and recurrent tumor metastases. DI and %S were also significantly higher in estrogen-receptor-negative tumors. There was no correlation between DI or %S and the extent of axillary nodal metastases. However, within the groups of node-negative and node-positive patients, DI and %S were not randomly distributed but were significantly correlated with degree of nuclear differentiation. Both parameters were higher in poorly differentiated tumors compared with well-differentiated tumors, indicating significant intrastage heterogeneity in tumor ploidy and proliferation characteristics. Determination of the prognostic significance of DI and %S will require a longer follow-up time.

Changes of proliferation kinetics after X-irradiation of a human malignant melanoma grown in nude mice

A human malignant melanoma grown in nude mice was exposed to single-dose X-irradiation and the effect on the proliferation kinetics was investigated by two methods. Flow cytometric DNA analysis was performed on tumour tissue obtained by sequential fine-needle aspirations after the treatment to monitor the initial cell cycle distribution changes. The technique of labelled mitoses was used to examine the kinetics of the tumours during regrowth. The results showed that the treatment initially induced a partial synchronization of small fractions of cells accumulated in the G2 phase of the cell cycle and a dose-dependent decrease of the cell generation time due to a shortening of the G1 duration time during regrowth of the tumours. Furthermore, it was shown that the calculated values of growth fraction and cell loss factor became unreliable because the tumours contained a dose-related increasing proportion of radiation-inactivated tumour cells.

Proliferation kinetics of a human malignant melanoma serially grown in nude mice

The technique of labelled mitoses and flow cytometric DNA analysis were used to determine the proliferation kinetics of a human malignant melanoma grown in nude mice. The effect of tumour volume and of long-term serial transplantation on the kinetic parameters was investigated. The results showed that the cell loss factor, which was the dominant factor in the growth of this melanoma, increased from 52 to 69% with increasing tumour size, whereas the calculated growth fraction showed no systematic changes. The cell generation time increased from 34 to 44 hr with tumour size, mainly due to a prolongation of the G1 duration time, whereas no significant changes occurred in the duration of the S and G2 phases of the cell cycle. The stability of the investigated tumour characteristics indicated that the kinetics of this melanoma remained unchanged during more than sixty serial transplantations in nude mice. The methods applied are suitable for a detailed description of tumour growth kinetics, since they provide complementary results.

Monoclonal antibody (1116 NS 19-9) defined monosialoganglioside (GICA) in colorectal carcinoma in relation to stage, histopathology and DNA flow cytometry

Immunoreactivity of 1116 NS 19-9 monoclonal antibody defined monosialoganglioside (gastrointestinal cancer-associated antigen, GICA) has been studied in a series of colorectal carcinoma patients of a multicentre prospective controlled trial in order to assess its correlation with parameters such as localization, stage histopathological characteristics and DNA flow cytometry. GICA could be detected in 60% of the carcinomas, but no correlation was observed between its status of immunoreactivity and any of the parameters studied. It is concluded that, though study of the expression of the monosialganglioside may be worth while in relation to fundamental aspects of behaviour of colorectal carcinomas, the significance of its immunohistochemical detection in a diagnostic or prognostic sense is limited.

Long-term storage of samples for flow cytometric DNA analysis

A simple procedure for long-term storage of cells for flow cytometric DNA analysis was developed and tested. The cells were stored as single cells or fine-needle aspirates suspended in a citrate buffer with dimethylsulfoxide (DMSO), or as small blocks of tissue from solid tumors. The cells were stored for up to one year by freezing at -80 degrees C. Statistical analysis of the results showed no change in the fractions of cells in the cell cycle phases as determined by deconvolution of the DNA-histograms. It was found that in addition to the intrinsic sample variation from the parameter estimation by deconvolution, there was significant intraday and interday variation. Hence the most accurate results are obtained if different aliquots of a sample are measured on different days rather than on the same day. Use of the storage method thus has the potential of increasing the accuracy of the analysis. The storage method makes sample collection independent of immediate subsequent analysis. This has enabled us to perform large internally controlled experiments, involving more samples than can be analyzed in one day, to examine tumor samples from different hospitals and to utilize fully the capacity of our flow cytometer. The method was a prerequisite for developing an accurate standardization procedure for DNA content determination.

Standardization of high-resolution flow cytometric DNA analysis by the simultaneous use of chicken and trout red blood cells as internal reference standards

Determination of nuclear DNA content by flow cytometry requires comparison with a reference standard. The use of external standards such as lymphocytes or granulocytes is time-consuming and inaccurate. Chicken red blood cells (CRBC) have a DNA content of 35% of the human diploid value and have been widely used as internal standard. The ratio calculated on the basis of the peak channel numbers of the standard and the sample and used to indicate the DNA content (DNA ratio) is, however, very sensitive to changes in the zero level adjustment of the flow cytometer. If two internal standards are used the DNA ratio becomes independent of the zero level. Rainbow trout red blood cells (TRBC) have a DNA content of 80% of human diploid cells. A mixture of CRBC and TRBC was prepared and stored in small aliquots at -80 degrees C. This mixture was added to the sample before staining. The day-to-day variation of the DNA ratio obtained by use of the two standards was smaller than that obtained by CRBC alone. The possibility of sex related differences in DNA content of CRBC and TRBC was examined. The results indicated that a new batch of standards should be tested against the old batch to avoid the introduction of a systematic error.

An analysis of histology and DNA-ploidy in primary wilms tumors and their metastases and a study of the morphological effects of therapy

In children with Wilms' tumours the length of survival is greatly influenced by success in preventing or controlling metastatic disease. The current study focuses on the morphological aspects of metastases when compared with the primary tumour. In 8 patients it appeared that blastema is the most likely component to metastasize, whereas epithelial and stromal components were hardly, if at all, represented in metastases. Furthermore, flow cytometric DNA ploidy determinations on 4 cases showed that both the primary tumours and the metastases had stemlines in the diploid and low aneuploid (hyperdiploid) range. Finally, in four cases the influence of therapy on morphology of the primary tumours was analyzed. In these cases blastema seemed to be the component most sensitive to therapy. Thus, blastema seems to play a central role in prognosis of Wilms' tumours; either reacting to therapy or, if insensitive, by metastasizing.