Degradation of apoptotic cells and fragments in HL-60 suspension cultures after induction of apoptosis by camptothecin and ethanol

Early indicators of apoptosis in mammalian cells are membrane potential breakdown (loss) in mitochondria (MPLM), chromatin condensation, DNA degradation, and phosphatidylserine exposure (PSE) on the outside plasma membrane. One aim of the present study was to determine the kinetics of these characteristics. These changes were measured by flow cytometry using the following methods: membrane potential of mitochondria was analysed using Mito Tracker Green and Red, PSE was analysed using annexin-V-FITC staining simultaneously with propidium iodide (PI) to detect membrane permeability; chromatin condensation was measured using the acid denaturation Acridine Orange (AO) method; DNA degradation was studied by the sub G1 method and the terminal transferase dUTP nick end-labelling (TUNEL) assay (labelling of strand breaks). HL-60 cells were induced to apoptosis by 3% ethanol and 1.5 microM camptothecin (CAM) and the kinetics of the apoptotic cells were measured. The same kinetics were found for chromatin condensation and DNA degradation indicating that these changes appeared at approximately the same time after induction. The MPLM and PSE kinetics showed a considerably later increase indicating that MPLM occurred downstream of DNA degradation and that plasma membrane changes occurred downstream of MPLM. The main aim of the study was to follow the fate of apoptotic cells after the appearance of the initial characteristics. The lifetime of apoptotic cells was studied by chase experiments. The inducing drug was removed after 4 h treatment and the disappearance of apoptoses recorded. An exponential decay was measured with a half life (T(1/2)) of 17.8 h. As a corollary from these experiments, camptothecin was found to induce apoptosis also in G1 and G2 phase cells, however, it took much longer to occur than in S phase cells. Using labelling of the plasma membrane with a fluorescent cell membrane linker, it was possible to show that the majority of apoptotic bodies as well as condensed apoptotic cells contain DNA and membrane. The degradation of these apoptotic bodies follows similar kinetics as those of the condensed apoptotic cells. The membrane remained considerably stable, there was no further loss in the next 7 days, after the first day when the apoptotic characteristics develop. It is concluded that the apoptosis programme is completed within a day and no further steps follow.

Relationship between cell kinetics and apoptotic effects in TNF-alpha and IFN-gamma-treated human tumour cell lines

TNF-alpha is a potent inducer of apoptosis and also affects the transit of cells through the phases of the cell cycle. It is thought that the proliferation signalling pathway is related to the apoptosis pathway, the details of this cross-talk are not yet fully understood. In this report, the effects of tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) on human tumour cell lines with respect to proliferation and apoptosis are examined. The TNF-alpha-sensitive cell lines Me-180 and MCF-7, the resistant cell line TCC-Sup, and the intermediate line 5637 were used. After a one day treatment, the transit through all phases of the cell cycle slowed down and after 3 days stopped completely, as measured with the BrdU-assay and flow cytometry. During the same time however, the levels of c-Myc and Ki-67 expression and the number of cells becoming apoptotic increased. Combined treatment with TNF-alpha and IFN-gamma augmented both the effects on the cell cycle and on apoptosis in the sensitive lines, and had only a minor additional effect on the resistant cell line as compared to single TNF-alpha treatment. The cells becoming apoptotic detached from the culture flask bottom and floated in the medium. Several apoptosis assays were used to prove that the floating cells were indeed apoptotic. As a subsidiary result of receptor measurement, we observed complexes of TNF-alpha receptors I with TNF-alpha receptors II using the related blocking antibodies and I125-TNF-alpha as ligand. The association of proliferative parameters and apoptosis became obvious by plotting the levels of c-Myc expression versus remaining live cells after apoptotic cells were detached. Our data revealed a good linear correlation indicating that high levels of c-Myc render cells sensitive to apoptosis, independent of the treatment, TNF-alpha alone or TNF-alpha in combination with IFN-gamma. The quantitative linear correlation may point to a threshold mechanism.

Impact of preirradiation of the tumour bed on cell production rate and cell loss of human FaDu squamous cell carcinoma growing in nude mice

PURPOSE

To explore whether the tumour bed effect (TBE) in FaDu squamous cell carcinoma growing in nude mice is caused by a reduced tumour cell production rate and/or by increased tumour cell loss.

MATERIALS AND METHODS

Human FaDu tumours were studied in NMRI nude mice. The volume doubling time (VDT) between 100 and 400 mm3 was determined for tumours in unirradiated subcutaneous (sc) tissues (group 1), tumours in sc tissues preirradiated with 12.5 Gy (group 2), tumours irradiated in situ with 12.5 Gy (group 3), and tumours from group 3 re-transplanted into unirradiated sc tissues (group 4). Labelling index (LI), potential doubling time (Tpot), relative necrotic area and apoptotic index (AI) were evaluated in tumours from groups 1 and 2.

RESULTS

The median VDT were 2.6 days (95% CI 2-4) in group 1 and 7.0 days (4-15) in group 2 (p<0.001). The VDT were not significantly different between groups 2 and 3, and group 1 and 4. In groups 1 and 2, the Tpot values (3.1 +/- 0.6 days (SD) versus 2.9 +/- 0.5 days) and the LI were identical (10 +/- 1.5%). The median relative necrotic area was significantly larger in group 2 (37% [23-42]) compared with group (6% [0.3-27]). The apoptotic index was low (0.2%) and did not differ between groups 1 and 2.

CONCLUSIONS

The results indicate that the TBE in FaDu squamous cell carcinoma is not caused by a reduced cell production rate in the viable tumour compartment. Rather, the TBE reflects a decreased viable tumour cell compartment due to increased cell loss. Necrosis appears to be the major component of the tumour bed induced cell loss in FaDu tumours, whereas apoptosis has no impact on the TBE in this model.

Impact of overall treatment time on local control of slow growing human GL squamous cell carcinoma in nude mice treated by fractionated irradiation

BACKGROUND AND PURPOSE

The impact of overall treatment time of fractionated irradiation on local control of slow growing human GL squamous cell carcinoma (SCC) was determined.

MATERIALS AND METHODS

Moderately well differentiated and keratinizing human GL SCC with a volume doubling time of 8 days were transplanted subcutaneously into the right hindleg of NMRI (nu/nu) mice and irradiated with 30 fractions under ambient conditions over 2, 3, 4.5, 6 and 10 weeks. Endpoint of the experiments was local tumor control at day 180 after end of treatment.

RESULTS

The tumor control dose 50% (TCD50) increased from 40 to 57 Gy when the treatment time was extended from 2 to 10 weeks. The data can be well described by a linear increase in TCD50 with time. The recovered dose per day (D(r)) was 0.28 Gy (95% confidence interval 0.06; 0.48). The fit to the data was not significantly improved by assuming a biphasic (dog-leg) time course with constant TCD50 values in the initial part of treatment followed by a more rapid increase of TCD50 thereafter.

CONCLUSIONS

D(r) in GL SCC was significantly less than the value of 1.0 Gy (0.7; 1.3) previously reported for poorly differentiated, non-keratinizing and fast growing human FaDu SCC (Baumann M, Liertz C, Baisch H, Wiegel T, Lorenzen J, Arps H. Impact of overall treatment time of fractionated irradiation on local control of human FaDu squamous cell carcinoma in nude mice. Radiother. Oncol. 1994:32:137-143), indicating important heterogeneity of the time factor between different tumors of the same histological type.

Growth of human prostate carcinomas with and without hormone alpha- dehydrotestosterone in nude mice

OBJECTIVES

The dependence of human prostate carcinoma growth on hormone was studied in xenotransplants in nude mice. The objective was to determine differences in cell kinetic parameters and volume growth of tumors growing with alpha-dehydrotestosterone (alphaDHT) and without alphaDHT. These differences could be used as arguments pro and contra the adaptation versus the clonal selection hypothesis.

METHODS

Human prostate carcinomas were xenotransplanted into nude mice. Growth of tumors was observed in castrated male mice without and with implanted osmotic pumps secreting alphaDHT. In a further series of experiments the alphaDHT tubes were removed when the tumors had reached a volume of 0.3 cm3. Tumor volume was measured to determine tumor doubling time with and without alphaDHT. Detailed cell kinetics were analyzed using the bromodeoxyuridine (BrdUrd) method with flow cytometry. Applying the relative movement (RM) and a simulation analysis to parallel single and multiple BrdUrd labelling experimental data we determined transit times through the phases of cell cycle, potential doubling time Tpot, growth fraction (GF) and cell loss.

RESULTS

Five human prostate carcinomas were xenotransplanted into nude mice. Tumor take was only achieved when androgen hormone was present. However, when alphaDHT was removed when the tumors had grown to a volume of 0.3 cm3, they continued to grow at nearly the same Td as those tumors with continued alphaDHT application. The BrdUrd experiments, on the other hand, showed considerable increase of Tc and Tpot upon withdrawal of alphaDHT in 4 out of 5 tumors. The GF and labelling index (LI) were maintained at about the same level as alphaDHT consuming tumors.

CONCLUSION

While small transplanted tumor pieces do not grow without alphaDHT, larger tumors grow with the same Td after removal of alphaDHT. The slower proliferation shown by the increased Tc and Tpot is balanced by less cell loss. Since GF and LI were maintained at about the same level, we conclude that in our tumors the majority of cells adapted to hormone independence. There was no evidence for the selection model since the tumors continued to grow at about the same speed after hormone depletion. All cell kinetic parameters showed a considerable inter- and intratumoral heterogeneity. A clinical implication may be that hormone ablation therapy should always be supplemented by some other therapy.

Assessing genetic markers of tumour progression in the context of intratumour heterogeneity

This is a report from the Kananaskis working group on quantitative methods in tumour heterogeneity. Tumour progression is currently believed to result from genetic instability and consequent acquisition of new genetic properties in some of the tumour cells. Cross-sectional assessment of genetic markers for human tumours requires quantifiable measures of intratumour heterogeneity for each parameter or characteristic observed; the relevance of heterogeneity to tumour progression can best be ascertained by repeated assessment along a tumour progressional time line. This paper outlines experimental and analytic considerations that, with repeated use, should lead to a better understanding of tumour heterogeneity, and hence, to improvements in patient diagnosis and therapy. Four general principles were agreed upon at the Symposium: (1) the concept of heterogeneity requires a quantifiable definition so that it can be assessed repeatably; (2) the quantification of heterogeneity is necessary so that testable hypotheses may be formulated and checked to determine the degree of support from observed data; (3) it is necessary to consider (a) what is being measured, (b) what is currently measurable, and (c) what should be measured; and (4) the proposal of working models is a useful step that will assist our understanding of the origins and significance of heterogeneity in tumours. The properties of these models should then be studied so that hypotheses may be refined and validated.

Heterogeneous cell kinetics in tumors analyzed with a simulation model for bromodeoxyuridine single and multiple labeling

Bromodeoxyuridine (BrdUrd) labeling of DNA and flow cytometry measurement of bivariate BrdUrd-DNA content distributions yield proportions of cells in the cycle phases. After application of BrdUrd, with time, these proportions change according to the cell kinetic parameters of the investigated cell line or tumor. In a previous study of S-phase transit time using the relative movement method, we obtained better fits with S-duration distributions rather than constant values (Baisch and Otto: Cell Prolif 26:439-448, 1993). Now, we have developed a simulation model using asymmetric phase duration distributions in all phases of the cell cycle to fit the experimental data after single or multiple BrdUrd labeling. The model includes transit of cells from proliferating to quiescent compartments in all phases. The results yield the phase duration distributions, mean and median percentages of quiescent cells in all phases, growth fraction, and potential doubling time. The model was used to fit data of five renal cell carcinomas xenotransplanted into nude mice that were obtained after single and multiple labeling up to 93 hours. The estimated phase duration distributions varied from narrow to extremely asymmetric. In particular, TG2M duration and asymmetry were nearly as large as those of G1 phase in some tumors. The contribution of inter- and intratumoral heterogeneity cannot be separated by the simulation model, but evidence of intratumoral heterogeneity is provided by DNA content distributions at extended time spans after BrdUrd labeling.

Impact of overall treatment time of fractionated irradiation on local control of human FaDu squamous cell carcinoma in nude mice

A series of experiments were performed to determine the impact of overall treatment time on local control of human FaDu squamous cell carcinoma irradiated with 30 fractions under ambient conditions in nude mice. The TCD50 increased with treatment time between 15 days and 10 weeks from 43 Gy to 102 Gy. The data can be well described by a single linear function. The dose recovered per day is 1.0 Gy. However, the data can also be adequately fitted by two components with an initial delay of about 30 days followed by a steep increase at a rate of 1.5 Gy per day. Assuming that the increase of TCD50 is solely caused by repopulation of clonogenic tumor cells, and that the cellular radiation sensitivity in vitro reflects the radiation sensitivity of FaDu cells in vivo, the doubling time of clonogenic tumor cells during treatment is estimated to be approximately 1.8 days for the one-component model and, after an initial delay, approximately 1.2 days for the two-component model. Both values are shorter than the doubling time of clonogenic cells in untreated FaDu tumors and similar to the potential doubling time determined by flow cytometry after BrdUrd labelling. It is concluded that the dose necessary to control FaDu squamous cell carcinoma increases considerably with increasing time of a fractionated radiation treatment. It appears most likely that this increase is caused by repopulation of clonogenic tumor cells; however, other mechanisms such as an increasing fraction of hypoxic tumor cells can not be ruled out at present.

Intratumoral heterogeneity of S phase transition in solid tumours determined by bromodeoxyuridine labelling and flow cytometry

Cell kinetics of human renal cell carcinomas xenotransplanted into nu/nu mice were analysed using the bromodeoxyuridine (BrdUrd) labelling method. Tumours were removed 0.5-14 h after injection of the BrdUrd solution. The tumour cells were stained with fluorescein isothiocyanate conjugated anti-BrdUrd antibodies and propidium iodide (DNA content). From the flow cytometry data the relative movement was calculated. Relative movement data of variable intervals after BrdUrd labelling were subjected to a fit procedure using log-normal distributions for S phase transition (T(s)). The log-normal distributions were modified by inflation factors in order to get extremely asymmetric distributions. The best fits to the experimental data were obtained using wide asymmetric T(s) distributions, indicating that progression through S phase in solid human tumours is considerably heterogeneous. This implies that the potential doubling time (T(pot)) is longer than calculated from a single measured relative movement value obtained a few hours after BrdUrd labelling.

Nuclear DNA content in 27 pancreatic endocrine tumours: correlation with malignancy, survival and expression of glycoprotein hormone alpha chain

Paraffin-embedded tissue from resection specimens of 14 functioning and 13 nonfunctioning pancreatic endocrine tumours (PET) was analysed for nuclear DNA content by image cytometry. Data on follow-up (mean 5.5 years) were available in all patients. DNA histograms with a diploid pattern were found in 13 (48%) tumours, while an aneuploid pattern was seen in the remaining 14 tumours (52%). Six (40%) of the diploid tumours and 9 (60%) of the aneuploid tumours were malignant. Survival was shorter in patients with malignant and aneuploid PET (mean 3.5 years, range 0.5-7) than in those with malignant and diploid PET (mean 5.7 years, range 3-8). Human chorionic gonadotropin-alpha was expressed in 3 of 12 benign PET, with 1 being aneuploid, and 6 of 15 malignant PET, with 4 being aneuploid. We conclude from these results that the ploidy pattern of PET allows no discrimination between benign and malignant tumours but may provide prognostic information on the aggressiveness of malignant PET.

Sensitivity of urinary quantitative immunocytology with monoclonal antibody 486 P3/12 in 241 unselected patients with bladder carcinoma

We investigated the sensitivity of quantitative immunocytology with our monoclonal antibody 486 P3/12 in 241 unselected patients with transitional cell carcinoma. Immunocytology yielded a sensitivity of 91.8%, 89.4% and 92.9% for grade 1, 2 and 3 tumors, respectively. Standard cytology was positive in 59.2%, 63.8% and 84.7%, respectively. Deoxyribonucleic acid flow cytometry, used in the first 69 patients, was positive in only 27.7%, 48.6% and 57.1%, respectively.

Decreased binding of HIV-1 and vasoactive intestinal peptide following plasma membrane fluidization of CD4+ cells by phenytoin

Plasma membrane fluidity of intact peripheral blood lymphocytes (PBL) of phenytoin-treated nonepileptic patients and phenytoin-treated CD4+ lymphoid cells H9 and K37 was determined by fluorescence anisotropy measurements. Anisotropy values of the membrane probe 6-(9-anthroyloxy) stearic acid were decreased in all cell types as compared with controls, indicating increased plasma membrane fluidity of phenytoin-treated cells. Specific binding of 125I-labeled vasoactive intestinal peptide (VIP) to its cellular receptor CD4 on PBL was decreased in PBL of phenytoin-treated patients as compared with untreated, healthy subjects. Adsorption of a different ligand to the CD4 receptor on PBL, the human immunodeficiency virus type 1 (HIV-1), was likewise abolished to PBL of phenytoin-treated patients and phenytoin-treated CD4+ H9 and K37 cells, as assessed by indirect immunofluorescence. Subsequent HIV-1 infection of phenytoin-treated H9 and K37 cells was reduced as measured by indirect immunofluorescence and p24 antigen production. These data indicate that CD4 receptor availability for VIP and HIV-1 was reduced in phenytoin-treated cells. Using the DNA-specific dye Hoechst 33258, we examined cell cycle phase distributions of HIV-1 adsorbing and nonadsorbing H9 cells, as separated by flow cytometry. The majority of HIV-1 adsorbing cells were found to be in the G2/M phase, while nonadsorbing cells were mainly in the G0/G1 phase, during which plasma membrane fluidity is supposed to be increased. This study indicates that plasma membrane fluidization by phenytoin may serve to disrupt CD4 receptor function and emphasizes the impact of plasma membrane properties on HIV-1 adsorption and infection.

Antiproliferative and cytotoxic effects of single and combined treatment with tumor necrosis factor alpha and/or alpha interferon on a human renal cell carcinoma xenotransplanted into nu/nu mice: cell kinetic studies

A human renal cell carcinoma serially transplanted into nude mice was treated with recombinant human tumor necrosis factor alpha (TNF-alpha), recombinant human alpha interferon (IFN-alpha), and a combination of both. All treatments resulted in a significantly reduced tumor growth. The greatest effect was obtained with the combination of TNF-alpha and IFN-alpha. This latter treatment completely eradicated tumors which were smaller than 50 mm3 at the beginning of treatment. Cell kinetic analysis using the bromodeoxyuridine technique and flow cytometry revealed a prolongation of the transition time through S-phase from 7.9 h in the case of control tumors to 10.5 h for tumors treated with IFN-alpha and TNF-alpha. Single treatment with either TNF-alpha or IFN-alpha had only minor effects. The bromodeoxyuridine labeling index was unaffected by IFN-alpha (16.6%; control, 15.2%) but was reduced to 12.1 and 11.7% when tumors were treated with TNF-alpha and IFN-alpha plus TNF-alpha, respectively. The calculated potential doubling times were 2.3 and 2.8 days, respectively, for tumors treated with TNF-alpha or IFN-alpha plus TNF-alpha. When treated with IFN-alpha, the potential doubling time (1.7 days) was similar to that of the control (1.6 days), indicating that the main effect of TNF-alpha was antiproliferative. Conversely, the calculated cell loss factors increased after IFN-alpha and combined treatment but not after TNF-alpha treatment. Combined treatment augmented cytotoxicity, but the cell kinetic characteristics of surviving cells remained similar to those of tumors treated with TNF-alpha alone. Histological analysis showed a distinctly reduced mitotic activity but no coagulative necroses after treatment with TNF-alpha. IFN-alpha and, in particular, IFN-alpha plus TNF-alpha induced cytoplasmic vacuolization, nuclear pyknosis, and cell death, which resulted in tumor regression. These data suggest that, in this particular tumor model, TNF-alpha produces mainly antiproliferative effects, whereas IFN-alpha acts via cytotoxic mechanisms.

Combined treatment of rat rhabdomyosarcoma R1H with mitomycin C and X-rays

The effects of mitomycin C (MTC) alone and in combination with radiation on R1H rhabdomyosarcomas in WAG/Rij rats were studied. Growth delay was determined from tumor volume growth curves and proportion of tumor and host cells from flow cytometry measurements. Only minor growth delays were obtained with MTC at doses near the toxic level while irradiation applied in three fractions of 10 Gy in three weeks yielded growth delays of 27, 44, and 51 days measured at volumes of 2, 5, and 10 cm3, respectively. The combination of 1 micrograms/kg b.w. MTC and 10 Gy irradiation given in three weekly fractions resulted in 21, 28, and 29 days growth delay for the above tumor volumes. The lower effect of combination as compared to irradiation alone is discussed with the flow cytometry data. These data show that early after start of treatment the proportion of tumor cells remains constant in contrast to radiation alone where the fraction of tumor cells decreases because of influx of granulocytes and macrophages into the tumor. In contrast to the reduced effect on tumors the combination treatment was considerably more toxic for the animals than the single treatments.

DNA ploidy and cell-cycle analysis in pancreatic and ampullary carcinoma: flow cytometric study of formalin-fixed paraffin-embedded tissue

The cellular DNA content of formalin-fixed, paraffin-embedded specimens from 47 ductal adenocarcinomas of the pancreas and 5 adenocarcinomas of the ampulla of Vater was analysed using flow cytometry. Ploidy and the fraction of cells in the S and G2M phases were determined and correlated with tumour stage and grade as well as patients' survival. Cell populations with aneuploid DNA content were observed in 15% of the tumours. The S + G2M fractions ranged between 1% and 10%. Compared to non-neoplastic tissue of the pancreas the S + G2M fraction was significantly higher in the carcinomas. Cox regression analysis revealed the S + G2M fraction as an independent prognostic factor (p less than 0.05). Ploidy was of no prognostic value for survival, but correlated weakly with tumour stage and tumour grade. All patients without lymph node metastases at time of surgery had diploid tumours. Aneuploidy was restricted to tumours in advanced stages and tended to be more frequent in high-grade tumours.

Increased deoxyribonucleic acid synthesis of autonomously functioning thyroid adenomas: independent of but further stimulable by thyrotropin

The percentage of cells in the S/G2M fraction and the cytosol deoxythymidine kinase activity (TKA) were measured in autonomously functioning thyroid adenomas (AFTA) and paranodular tissue (PNT), with special regard to the impact of the patient's serum TSH concentration on DNA synthesis. The S/G2M fraction was determined by means of DNA flow cytometry, and TKA was determined by radioenzyme assay. The S/G2M fraction of AFTA (n = 15, median; 7.1%; range, 3.2-9.2%) exceeded the S/G2M fraction of normal thyroid tissue (n = 8; median, 2.8%; range, 2.3-4.0%; P = 0.008) and in 12 of 13 AFTA was 1.2- to 2.3-fold higher than the S/G2M fraction in the corresponding PNT (median, 4.0%; range, 2.5-6.7%; P = 0.0022). TKA of AFTA (n = 15; median, 681 microIU/mg; range, 432-854 microIU/mg) exceeded TKA of normal thyroid tissue (n = 8; median, 356 microIU/mg; range, 194-426 microIU/mg; P = 0.0001) and was 1.1- to 4.2-fold increased compared with TKA activity in the corresponding PNT (median, 430 microIU/mg; range, 162-570 microIU/mg; P = 0.001). In the absence of measurable serum TSH there was a constant increase in the S/G2M fractions and the TKA in AFTA vs. those in PNT. In patients treated with methimazole with serum TSH concentrations of 0.5 mIU/L or more, the S/G2M fraction and TKA in both AFTA and PNT were significantly higher than those in untreated patients with serum TSH concentrations of 0.5 mIU/L or less. In the majority of AFTA, functional autonomy and increased DNA synthesis are concomitant phenomena. Although TSH may stimulate DNA synthesis in both AFTA and PNT, measurable serum TSH concentrations are apparently not essential for DNA synthesis.

Different quiescence states of three culture cell lines detected by acridine orange staining of cellular RNA

Three cell lines (CHO, L-929, and R1H) were investigated for their growth kinetics and the difference of exponential and quiescent state of monolayers in medium with and without serum (L-929). The noncycling populations of L-929 and R1H in medium with serum contained increased G1-phase percentages but also considerable proportions of SQ and G2Q cells. Although about 90% of the cells excluded trypan blue, the viability tested by colony assay was clearly lower than for exponentially growing cultures. CHO cells showed similar fractions of cells in G1-, S-, and G2-Q compartments but in addition considerable cell loss. The RNA content of these cells was reduced in plateau phase by 7-48% depending on cell type and residence time in the noncycling state. The data suggest that the cells suffered from nutrition depletion and were arrested in all phases of the cycle. In contrast, L-929 cells in medium without serum reduced their RNA content down to one-third that of proliferating cells and still retained the full viability as shown by the same plating efficiency in a colony assay. Since about 90% of the cells had G1 DNA content, these cells resemble true G1Q or G0 cells controlled by growth factors rather than nutritional depletion.

Altered growth factor requirements and cell cycle control in rat hepatoma cells versus adult rat hepatocytes in culture

Adult rat hepatocytes multiply in primary cultures when incubated in arginine-free MX-83 medium supplemented with dialyzed fetal calf serum, insulin, glucagon, hydrocortisone, epidermal growth factor, and transferrin. In the absence of mitogens, the fraction of the cells engaged in DNA synthesis dropped sharply. However, cells initiated DNA synthesis in response to the mitogenic mixture indicating that hepatocyte proliferation is controlled by G1----S transition rates. In contrast, rat hepatoma line DTH-3, derived from Morris 7777 "minimal deviation" hepatoma, required only insulin for proliferation in chemically defined MX-83 medium. The lengths of their cell cycle phases varied with the growth rate. The phases of the growth cycle were proportionately shortened (expanded) when the growth rate was increased (decreased). It is concluded that DTH-3 hepatoma cells, which display a decreased growth factor requirement as compared with adult rat hepatocytes differ from normal hepatocytes by fundamental alterations in the mechanisms controlling the progression of the cell cycle.

Prognostic factors in medullary thyroid carcinomas. Survival in relation to age, sex, stage, histology, immunocytochemistry, and DNA content

Patients with medullary thyroid carcinomas (MTC) were analyzed according to age, sex, and tumor stage. In addition, the MTC were screened for the predominant histologic pattern, immunocytochemical spectrum (60 tumors), and DNA content (DNA cytophotometry and DNA flow cytometry, 25 tumors). These findings were correlated with follow-up data available for 45 of these patients. Forty-eight percent of the tumors revealed a polygonal cell pattern, whereas 22% showed spindle-cell predominance. All tumors contained cytokeratin, chromogranin A, and calcitonin (CT). Calcitonin gene-related peptide (CGRP) was present in 92%, carcinoembryonic antigen (CEA) in 77%, neuron-specific enolase (NSE) in 75%, and vimentin in 53% of cases. Positivity for neurotensin, somatostatin, neurofilaments, bombesin, and alpha human chorionic gonadotropin (a-hCG) and serotonin ranged between 3% and 27%. All MTC were negative for substance P, adrenocorticotropic hormone (ACTH), thyroglobulin (TG), or S-100 protein. Local recurrences and regional lymph node metastases revealed identical staining patterns as the primaries. Prognosis of MTC was found not to be related to histologic features (dominant architectural pattern, cellular shape, presence of amyloid deposits) or immunocytochemical pattern. Instead, survival was significantly correlated to age, sex, and stage of disease. The best prognosis was seen in women younger than 40 years and revealing an early stage of disease. DNA measurements added valuable information in assessing the prognosis of MTC.

Evidence for an accessory role of LFA-1 in lymphocyte-high endothelium interaction during homing

In a variety of lymphocyte interactions, lymphocyte function-associated antigen-1 (LFA-1) plays an important role as an accessory mechanism mediating cell adhesion. We tested the possibility that LFA-1 could also be involved in the specific binding of lymphocytes to high endothelial venules (HEV) during homing. Antibodies against LFA-1 but not against various other cell surface molecules (except the putative gp90 homing receptor defined by the MEL-14 antibody) were found to inhibit in vitro adherence of lymphocytes to HEV in frozen sections of lymph nodes. Binding of T cell lines to HEV was also inhibited by anti-LFA-1 antibody. Using sublines selected for differential expression of the MEL-14 antigen, MEL-14 high cells (which bind well to HEV) were less susceptible to inhibition by anti-LFA-1 than poor binders with low levels of the homing receptor, supporting the model of LFA-1 being an accessory mechanism strengthening weak interactions between cells. Parallel results were found in vivo where anti-LFA-1 antibodies reduced the migration of normal lymphocytes into lymph nodes and Peyer's patches by 40 to 60%. Localization in the lung, especially of activated lymphocytes, was also impaired, although to a lesser extent. These findings suggest that LFA-1 plays an accessory role in cellular interactions relevant for lymphocyte migration.

Evidence for an accessory role of LFA-1 in lymphocyte-high endothelium interaction during homing

In a variety of lymphocyte interactions, lymphocyte function-associated antigen-1 (LFA-1) plays an important role as an accessory mechanism mediating cell adhesion. We tested the possibility that LFA-1 could also be involved in the specific binding of lymphocytes to high endothelial venules (HEV) during homing. Antibodies against LFA-1 but not against various other cell surface molecules (except the putative gp90 homing receptor defined by the MEL-14 antibody) were found to inhibit in vitro adherence of lymphocytes to HEV in frozen sections of lymph nodes. Binding of T cell lines to HEV was also inhibited by anti-LFA-1 antibody. Using sublines selected for differential expression of the MEL-14 antigen, MEL-14 high cells (which bind well to HEV) were less susceptible to inhibition by anti-LFA-1 than poor binders with low levels of the homing receptor, supporting the model of LFA-1 being an accessory mechanism strengthening weak interactions between cells. Parallel results were found in vivo where anti-LFA-1 antibodies reduced the migration of normal lymphocytes into lymph nodes and Peyer's patches by 40 to 60%. Localization in the lung, especially of activated lymphocytes, was also impaired, although to a lesser extent. These findings suggest that LFA-1 plays an accessory role in cellular interactions relevant for lymphocyte migration.

Simultaneous staining of exponentially growing versus plateau phase cells with the proliferation-associated antibody Ki-67 and propidium iodide: analysis by flow cytometry

The antibody Ki-67, which detects proliferating cells, was used in combination with propidium iodide, a DNA-specific dye. The double-staining method allowed discrimination of cells in the phases of the cell cycle as well as the recognition of Ki-67 staining characteristics. Suspension cultures of U937 cells were measured in exponential growth and plateau phase in nutritional deprivation. The fraction of Ki-67 positive cells was nearly 100% 2 days after dilution and 46% 7 days after dilution of the cultures. Stathmokinetic measurements with colchicine and flow cytometry measurements with the BrdU-Hoechst technique yielded close to 100% proliferation at day 2 but only 18% and 6%, respectively, at day 7. The discrepancy between Ki-67 results and the results of the two other methods is considered to be a characteristic of nutritionally deprived cells.

[Morphology and prognosis of follicular thyroid cancer--a clinico-pathologic and DNA cytometric study of 95 tumors]

A retrospective study of 95 follicular thyroid carcinomas was conducted to evaluate the prognostic value of different morphological and clinical features. The biological behaviour of these tumours was primarily influenced by presence or absence of a capsule type of confinement: the frequency of lethal outcome among widely invasive carcinomas was six times higher than among encapsulated neoplasms. Furthermore, dismal prognosis could be demonstrated for tumours occurring in older patients (with a sharp break in the prognosis at the age of 52 years) and for those lesions which displayed oxyphilic metaplasia. The same effect was shown for presence of lymph node metastasis, tumour invasion of the cervical soft tissue and, for the case of encapsulated carcinomas, distant haematogenous spread. Conversely, the degree of differentiation and the patients' sex proved to have no significant influence on prognosis. In 22 carcinomas, cytophotometric and flow-cytometric determinations of DNA values were performed. These procedures revealed to have only limited diagnostic value, since for the majority of the tumours, benignancy or malignancy could not be judged from the DNA histograms. However, DNA measurements proved to contribute valuable information for the prognosis in individual cases of widely invasive follicular carcinomas. The discussion focuses on the diagnostic, therapeutic and prognostic relevance of these findings and on their impact on subclassification of follicular thyroid carcinomas.

Long-term serial transplantation of different human bladder carcinomas into NMRI nu/nu mice. Histologic, flow cytometric and growth studies

Sixteen human bladder carcinomas (BCs) were transplanted into NMRI nu/nu mice with an acceptance rate of 62.5%. Six of the 16 (37.5%) BCs were successfully retransplanted up to 14 passages. Histologic grading and traumatization during surgery influenced the acceptance rate. Grade-I tumors were rarely accepted, unless they were obtained during open surgery, rather than by transurethral resection (TUR). Specimens taken by TUR or by electric cut during open surgery were almost never accepted. Identity of the transplanted tumor tissue with the original human BCs could be demonstrated by flow cytometry and by light microscopy through several passages in all accepted tumors. However, although the tumors retained their major structural features, their proliferative activity increased, particularly that of grade-I tumors. The five tumors that were transitional-cell carcinomas and could be subpassed had three characteristics not seen before in transplanted renal cell carcinomas: tumor growth started after a delay which shortened with each further passage; growth rates of tumors only in their first passage correlated with the prognosis of the corresponding patients, and with each further passage, tumor growth accelerated until a doubling time of about 1 week was observed. From then on, tumor growth was almost identical in all five tumors. In contrast to our experience with transplanted renal cell carcinomas, flow cytometric evaluation of the transplanted and further passaged BCs revealed changes in DNA index and an increase in proliferative rate and it seems that BCs were strongly influenced by host factors.

Stability of human renal cell carcinomas during long term serial transplantation into nude mice: histopathology, nuclear grade, mitotic rate, and DNA content in thirty tumors

Thirty human renal cell carcinomas, subpassaged into NMRI-nu/nu mice, were analyzed during long term serial transplantation (range, 10-50 passages) with regard to their histological differentiation, mitotic activity, and DNA content. A quantitative methodology was applied to determine the mitotic rate. The DNA content was measured by flow cytometry. Only five tumors (four primaries and one metastasis) changed their mitotic rate significantly (P less than 0.01). In each case this change was paralleled by a simultaneous alteration of the DNA content. Histological pattern and nuclear grade remained stable in all but one tumor where the change in histological pattern occurred simultaneously with changes in DNA index and mitotic rate. These results indicate that the majority of renal cell carcinomas remain stable during long term serial transplantation, at least with regard to the parameters examined. This is a basic prerequisite for making the grafting of renal cell carcinomas into nude mice a reliable in vivo model for drug sensitivity testing. However, since a few of the transplanted tumors showed instability, continuous monitoring of phenotypic and genotypic tumor features is necessary during long term xenotransplantation.

Xenogenic transplantation of human bladder- and renal-cell carcinoma into NMRI mice treated with cyclosporin A and into NMRI nu/nu mice. Introduction of a new experimental cancer model

128 tumors from three different human renal-cell carcinomas and from one human transitional bladder cancer were transplanted into NMRI mice treated with cyclosporin A at various dosages. Their acceptance rate, proliferation rate, and morphologic and growth characteristics were studied and compared with those of the same human tumors after transplantation into NMRI nu/nu mice. The acceptance rate was 80% in mice treated with cyclosporin A at 100 mg/kg-1 and 150 mg/kg-1/day. The highest acceptance rate was observed after transplantation into nu/nu (thymus-aplastic) mice (100%). Morphologically, the transplanted tumor was similar in the two animal groups and identical with the primary tumors. Metastases were not seen in either animal model. The NMRI mice treated with cyclosporin A had leukocyte infiltration into the transplanted tumor. The growth rate of the human tumors in normal mice depended on the cyclosporin A dosage, and was highest in the nu/nu mice. The proliferation rates of the transplanted human tumors, as judged by flow cytometry, were rather similar in all groups.

Malignancy index based on flow cytometry and histology for renal cell carcinomas and its correlation to prognosis

Fifty-five human renal cell carcinomas, removed by nephrectomy, were classified using flow cytometry and histology. The parameters obtained by flow cytometry were DNA index, fractions of cells in the phases, and fractions of tumor cells versus normal cells. From histology, the routine classification of tumor structure and morphology were obtained, and a nuclear grading according to Arner et al. (Acta Chir Scand [Suppl] 346:1-12, 1965) was determined. All parameters including tumor stage according to Robson et al. (J Urol 101:297-301, 1969) were subjected to discriminant analysis in order to define a malignancy index. The patients were divided into two groups with good and poor prognosis (low and high risk). Those patients who were free of multiple metastases in 2 years and more after nephrectomy were assigned to the group "good prognosis"; those who developed multiple metastases for 2 years represented the "poor prognosis" group. The malignancy index determined by discriminant analysis yielded 91% correct predictions of prognosis.

Long-term serial transplantation of 30 different human renal cell carcinomas into NMRI (nu/nu) mice: flow cytometric, histologic, and growth studies

Thirty human renal cell carcinomas were transplanted into NMRI (nu/nu) mice. The take rate from surgical specimens was 100%, and all tumors were established as permanent transplantable tumor lines. The xenotransplants were followed up to around passages 10-50. In addition to histology and volume growth the DNA indices (DI), proportion of tumor cells, and fractions of cells in the phases of the cycle were measured by flow cytometry. All 30 tumors retained their primary histologic structure and cellular morphology throughout all passages. The DI, as ascertained by the DNA content per cell of G1-phase tumor cells divided by the DNA content per cell of normal diploid G1-phase cells, remained the same as those in the original tumors in 21 of 27 xenotransplants. Three original lymph nodes or metastases were not available for flow cytometry. During passage, 4 of 30 tumors changed their DI. In 2 of these cases the tumor doubling time (td), the proportion of tumor cells versus the proportion of host cells, and the fractions of cells in the cell cycle phases changed simultaneously. All other tumor lines were stable in td, DI, proportion of tumor cells, and fractions of cells in the phases during serial transplantation. However, the measure of parameters varied considerably between individual tumors of every passage. Tumor growth rate was generally related to the prognosis of the patients from whom the tumor was derived.

Prognosis of renal cell carcinoma related to nuclear grade, DNA content and Robson stage

In 135 renal cell carcinomas (RCCs), nuclear grade, Robson stage and DNA content, determined by flow cytometry, were related to the 3-year survival rates of the respective patients. All three parameters showed prognostic value, nuclear grading being most effective. Combined evaluation of the parameters showed that staging and also DNA determination add supplementary prognostic information. As the four nuclear grades clearly uncover the biological potential of RCC, they are regarded as the most significant criteria for the prognostic assessment of RCC.

Transplantation of human renal cell carcinoma into NMRI nu/nu mice. III. Effect of irradiation on tumor acceptance and tumor growth

Irradiation of human renal cell carcinoma before radical tumor nephrectomy resulted in a significantly lower acceptance rate (1 of 7) in nude mice than for nonirradiated tumors (all of 13). The tumor tissue was transplanted into NMRI nu/nu mice immediately after nephrectomy. In this experimental system we demonstrated the reduced vitality of human tumor cells after irradiation. In a second series of experiments, 3 morphologically different human renal cell carcinomas were irradiated at various doses after establishment in nude mice. The irradiated tumor tissue was transplanted to the next passage. The morphology, proliferation rate and growth of these tumors were compared with those of nonirradiated controls. Radiation effect was dose dependent in the responding tumor types. The characteristics correlated with radiosensitivity were high proliferation rate (measured by flow cytometry), low cytologic grading and fast growth rate in the nude mice.

Cell cycle analysis of a cell proliferation-associated human nuclear antigen defined by the monoclonal antibody Ki-67

The monoclonal antibody Ki-67 detects a nuclear antigen that is present only in proliferating cells. The aim of the present investigation was to clarify whether the Ki-67 nuclear antigen is restricted in its expression to certain phases of the cell cycle. All experiments consistently showed that the Ki-67 nuclear antigen is present in S, G2, and M phase, but is absent in G0. However, the results concerning Ki-67 antigen expression in G1 phase varied: cells passing the early events of mitogen triggered transition from G0 to G1, i.e., G1T and first G1A, lacked the Ki-67 nuclear antigen, whereas G1 cells after mitosis were constantly Ki-67-positive. This result suggests that after mitosis cells might not follow the same metabolic pathways as G0 cells do when entering G1 for the first time. Therefore, we suggest that the early stages of mitogen stimulation represent initial sequences of proliferation and not parts of the cell cycle. Because our data show that the Ki-67 nuclear antigen is present throughout the cell cycle, immunostaining with monoclonal antibody Ki-67 provides a reliable means of rapidly evaluating the growth fraction of normal and neoplastic human cell populations.

Cell cycle analysis of a cell proliferation-associated human nuclear antigen defined by the monoclonal antibody Ki-67

The monoclonal antibody Ki-67 detects a nuclear antigen that is present only in proliferating cells. The aim of the present investigation was to clarify whether the Ki-67 nuclear antigen is restricted in its expression to certain phases of the cell cycle. All experiments consistently showed that the Ki-67 nuclear antigen is present in S, G2, and M phase, but is absent in G0. However, the results concerning Ki-67 antigen expression in G1 phase varied: cells passing the early events of mitogen triggered transition from G0 to G1, i.e., G1T and first G1A, lacked the Ki-67 nuclear antigen, whereas G1 cells after mitosis were constantly Ki-67-positive. This result suggests that after mitosis cells might not follow the same metabolic pathways as G0 cells do when entering G1 for the first time. Therefore, we suggest that the early stages of mitogen stimulation represent initial sequences of proliferation and not parts of the cell cycle. Because our data show that the Ki-67 nuclear antigen is present throughout the cell cycle, immunostaining with monoclonal antibody Ki-67 provides a reliable means of rapidly evaluating the growth fraction of normal and neoplastic human cell populations.

Tumor cell deoxyribonucleic acid content and prognosis in human renal cell carcinoma

Flow cytometry was used to study tumor tissue from 68 patients with stages I to III renal cell carcinoma who were followed for 1 to 4 years. Results of flow cytometry correlated extremely well with the clinical course of the patients: 21 per cent of those with diploid tumor cells had metastases during the interval of observation, compared to 89 per cent of those with aneuploid tumor cells. We concluded that flow cytometry helps to identify at the time of radical nephrectomy patients who are most likely to suffer recurrent tumor and, therefore, are candidates for early chemotherapy. If nuclear grading is applied in addition to flow cytometry the rates of false positive and false negative results in respect to prediction of prognosis are reduced to 3 and 14 per cent, respectively.

[Flow cytometry studies of the DNA content and proliferation kinetics of human tumors]

The authors investigate if cytometric parameters can be used for discerning malignant and benign tumors as well as for the prognostic classification of malignant tumors. Measures on leukemias, brain and prostate tumors, colorectal carcinomas, and renal carcinomas taken by some study groups of the Institute of Biophysics and Radiobiology are cited and discussed with respect to the above mentioned aspects. The analysis showed that fractions of cells in phases of the cellular cycle as indicators of the proliferation rate are only of little diagnostic value because of the too great zone of dispersion. Especially the differentiation between benign and malignant tumors is not clear enough. In case of renal carcinomas, however, there is a marked correlation between prognosis and aneuploidy measured by cytometry. Thus the DNA index as a quantitative parameter of aneuploidy seems to be also of clinical interest for the determination of malignancy.

Transplantation of human renal cell carcinoma into NMRI nu/nu mice. II. Evaluation of response to vinblastine sulfate monotherapy

Four different renal cell carcinomas, successfully transplanted into nude mice, were treated with different dosages of vinblastine sulfate. Decrease of tumor growth was observed in 3 out of 4 of the tumors; the response was dose-dependent. The histologic appearance, cytologic grading, proliferation rate (judged by flow cytometry), and growth characteristics in the nude mouse model were correlated with the response to vinblastine therapy. Good response was seen in tumors with low cellular differentiation, progressive tumor growth, and high proliferation rate.

Transplantation of human renal cell carcinoma into NMRI nu/nu mice. I. Reliability of an experimental tumor model

Human renal cell carcinomas of 20 consecutive patients were obtained by radical nephrectomy and were transplanted into nu/nu mice (NMRI). All tumors that were not pretreated were accepted without selection and were identical with the original tumor in morphology and chromosomal modes and usually in DNA content per cell. The growth rate of these tumors after transplantation correlated well with the clinical course of the corresponding patients and was strongly influenced by pretreatment with radiation therapy. This proves the reliability of such an experimental tumor model to study adjuvant therapy in renal cell carcinoma.

DNA content of human kidney carcinoma cells in relation to histological grading

Ploidy and cell-cycle stage were determined by flow cytometry (FCM) in 46 human renal carcinomas. Cell populations with aneuploid DNA were detected in 46% of these. In the investigated samples, the fraction of cells with abnormal DNA content varied from 8 to 100%. The proliferative activity was generally low as indicated by the small fractions of cells in S and (G2 + M) phases. This was confirmed by the labelling indices on autoradiographic slides. The fraction of cells in phases S and (G2 + M) for tumours that were pre-irradiated with 15 or 25 Gy before nephrectomy was only slightly less than in unirradiated tumours. Comparison of the FCM ploidy with the results of histological grading showed that all cases classified as the most malignant grades IV or IIIB (according to the nuclear and to the combined grading system of Syrjänen and Hjelt (1978) were hyperdiploid. On the other hand, 45% of the hyperdiploid and 89% of the diploid tumours were of the low grades I and II. After a follow-up for 6 months to 2 years, 8/17 patients with hyperdiploid and only 1/14 patients with diploid tumours have died or relapsed with multiple metastases. The results indicate that the aneuploidy of tumours, measured by FCM, might provide useful additional information for prognosis.

A comparison of mathematical methods for the analysis of DNA histograms obtained by flow cytometry

Twelve methods for analysing FCM-histograms were compared using the same set of data. Some of the histograms that were analysed were simulated by computer and some were taken from experiments. Simulated data were generated assuming synchronously growing cell populations and (i) measurement coefficients of variation (CV) from 2 to 16%; (ii) constant measurement CV or VC's increasing from G1 to G2 phase, and (iii) varying fractions of cells in each phase. Simulated data were also generated assuming synchronous cell populations in which a block in early S phase was applied and released. DNA histograms were measured for L-929 cells at various times after mitotic selection. Labelling indices were also measured for these cells at the same time. The fractions of cells in the G1, S, and (G2 + M) phases were calculated by each analytical method and compared with the actual fractions used for simulation, or in case of experimental data, with autoradiographic results. Generally, all methods yielded reasonably accurate fractions of cells in each phase with relative errors in the range of 10-20%. However, most methods tended to overestimate G1 fractions and underestimate S fractions. In addition, variations in the shape of the S phase distribution often caused considerable errors. Phase fractions were also calculated for histograms of kinetically perturbed populations, simulated as well as experimental. The errors were only slightly larger than for histograms from asynchronously growing cell populations.

Prescreening of cervical smears using two-parameter flow cytometry. Cytologic identification of artifacts

Individual properties of gynecologic specimens can produce artifacts in flow cytometric (FMC) measurements, possibly leading to false interpretations. An identification of such artifacts was undertaken by parallel FCM and microscopic investigations. One hundred fifty unselected cervical smears were measured by FCM using the fluorochromes 4'-6-diamidino-2-phenylindole (DAPI) for DNA and sulforhodamine (SR 101) for protein. Microscopic specimens were stained by the Papanicolaou technique, and a detailed cytogram was prepared from each smear. FCM discrimination of fluorochrome-stained superficial and intermediate cells was very difficult. On the other hand, a correlation could be established between the fraction of cells from the deeper epithelial layers in the microscopic cytogram and the mean protein content in the FCM histogram. Furthermore, the role of microorganism could be elucidated. Some microorganisms may produce a reduction of the protein content by cytolytic changes. Other microorganisms adhere to the cell surface, resulting in a misleading increase of the DNA fluorescence. Implications for the problem of false alarms are discussed.

[Age dependency of normal and modified nucleobases in urine in correlation to growth velocity (author's transl)]

Up to now no age-correlated normal values of normal and modified nucleobases in urine have been published. In this paper such normal values are presented, obtained from 116 healthy subjects from 0 to 16 years by high performance liquid chromatography of creatinine-correlated single urine specimens. A narrow correlation between the excretion of nucleobases and growth velocity was found. A polynomial function including the puberal growth spurt could be fitted to the analytical data. It is felt that this method should be suitable to assess growth processes of different kinds, e.g. effects of nutrition or drugs and hormones on growth velocity, furthermore intrauterine and malignant growth.

DNA synthesis and cell cycle progression of synchronized L-cells after irradiation in various phases of the cell cycle

The varying sensitivity to radiation in the different phases of the cell cycle was investigated using L-929 cells of the mouse. The cells were synchronized by mechanical selection of mitotic cells. The synchronous populations were X-irradiated with a single dose of 10 Gy in the middle of the G1-phase, at the G1/S-transition or in the middle of the S-phase, respectively. The radiation effect was determined in 2 h intervals a) by 14C-TdR incorporation (IT) into the DNA, b) by autoradiography (AR), c) by flow cytometry (FCM). The incorporation rate decreased in all three cases, but the reasons appeared to be different, as can be derived from FCM and AR data: After irradiation in G1, a fraction of cells was prevented from entering S-phase, after irradiation at G1/S a proportion of cells was blocked in the S-phase, and after irradiation in S, DNA synthesis rate was reduced. As a consequence of these effects, the mean transition time through S-phase increased. The G2 blocks, obtained after irradiation at the three stages of the cycle were also different: Cells irradiated in G1 are partly released from the block after 10 h. Irradiation at G1/S caused a persisting accumulation of 50% of the cells in G2, and for irradiation in S more than 80% of the cells were arrested in G2.

Analysis of flow cytometric data of irradiated cell populations

Flow cytometry (FCM) and autoradiography have been applied to determine changes in the cell kinetics of irradiated cells. Synchronized L-929 cells were irradiated with 10 Gy of X-rays when progressing from B1- to S-phase of the cell cycle. In this study three methods to analyse DNA histograms were tested for applicability on FCM data obtained from cell populations blocked or retarded in the cycle: A) the Gaussian integral method, B) the peak-half-reflection method, and C) the rectangle method. Since histograms from synchronized cells are heavily distorted as compared to those obtained from exponentially growing cells and are quite similar to histograms from irradiated cells, they were used to test the suitability of the evaluation methods. Comparing the evaluated FCM data with the autoradiographic results from the same experimental series, the Gaussian integral method proved to be superior to the two other relatively simple approximation methods. The FCM histograms of irradiated cells were therefore analyzed only by the Gaussian integral method. It was shown that a considerable fraction of cells is still in the S-phase 25 h post irradiation, the DNA synthesis of which had ceased, as shown by autoradiography. This indicated that parallel measurements using FCM and autoradiography yield additional information on cell kinetic changes that cannot be obtained from applying one of the two methods used.

[Normal and modified nucleobases excreted in urine of patients with chronic nyeloproliferative disorders (author's transl)]

The qualitative and quantitative analysis by high performance liquid chromatography of the normal and modiefied nucleobases excreted in urine represents a new and versatile tool, especially in oncology. The excretion of 2 normal (adenine, guanine) and 4 modified nucleobases (methylated guanine derivatives) in urine was measured by cation exchange LC. All chronic myeloproliferative syndromes showed highly elevated total excretion values of all determined nucleobases, the "pattern" being characteristic with N2, N2-dimethylguanine most prominent (up to 29.8 S.D. above the pertinent normal value). A follow-up study of a case of CML with two episodes of extreme leukocytosis showed a correlation of the nucleobases excretion with the number of leukocytes. Thus, a method has been established which permits the assessment of myeloproliferation and probably therapy effects.

[Analysis of normal and methylated urinary nucleobases: a new criterion for diagnosis and follow-up of malignancies (author's transl)]

The qualitative and quantitative analysis by high performance liquid chromatography of the normal and modified nucleobases excreted in urine represents a new and versatile tool. Its use for the diagnosis of malignancies, deliminating infectious diseases, and for the follow-up of the effects of a cytostatic therapy is shown. This method offers a chance to introduce the analysis of a series of fragments of primary gene products into the routine of clinical biochemistry.

Flow cytometric prescreening of cervical smears

One-parameter (nuclear DNA) and two-parameter (nuclear DNA and protein or cellular light scatter) measurements of cervical smears were performed using an ICP 11 and a cytofluorograf 4800 respectively. A total of about 1000 cases was analyzed. For the estimation of nuclear DNA alone two fluorochromes were tested (ethidium bromide (EB) and mithramycin (MMC)) combined with three different methods of cell preparation. For the two-parameter measurements cells were double stained with EB and fluorescein isothiocyanate (FITC). Red fluorescence (EB) versus green fluorescence (FITC) or red fluorescence versus scatter were recorded. A computer analysis of the one-parameter histograms was performed using discriminant analysis and the results were compared with the cytodiagnosis of microscopic specimens stained with the Papanicolaou technique. The error rates of the flow cytometric (FCM) data were as follows: (a) standard EB staining, 11% false negative, 26% false positive, 6% unsatisfactory results; (b) pepsination of vital cells and EB staining, 12% false negative, 14% false positive and 4% unsatisfactory results; (c) MMC staining, 10% false negative, 65% false positive and 5% unsatisfactory results. Our two-parameter measurements prove that, as confirmed by cell sorting, red fluorescence versus scatter allows separation of at least three subpopulations in most analyzed samples: (a) anucleated cells; (b) leukocytes; and (c) intermediate and superficial cells.