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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

[Flow cytometry studies of the DNA content and proliferation kinetics of human tumors]. / Flusszytometrische Untersuchungen des DNA-Gehaltes und der Proliferationskinetik menschlicher Tumoren.

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.

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.

Effects of X-rays on cell membranes. II. Changes of permeability measured by fluorescein efflux.

The effect of irradiation on the permeability of cell membranes of L-929 cells was investigated. Efflux of fluorescein, accumulated by hydrolysis of fluoresceindiacetate in the cells, was measured using flow cytometry. The changes of rate constants for the permeation of florescein through the cell membrane at different temperatures and after various X-ray doses were studied. Decreasing temperatures yielded substantially slower efflux of fluorescein. After irradiation of cells, the rate constant of fluorescein efflux increased linearly with dose; 180 Gy are required to cause an increase by a factor of 2. The results are discussed with respect to radiation damage of active and passive transport mechanisms.

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.

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.

Effects of X-rays on cell membranes. I. Changes of membrane potential of L-cells.

Changes in the membrane potential of cultured L-929lcells were investigated after irradiation with doses ranging from 5-200 Gy. Immediately after irradiation a depolarisation is observed that is followed by a damped oscillation of the membrane potential and finally by a rapprochement to the control value. Whereas the magnitude of depolarisation does not show any dependence on irradiation dose, the time required to reach the control value again increases with increasing dose. Up to 10 Gy, the period of the first half-oscillation rises rapidly to about 12 min, at higher doses a slow linear increase follows reaching a value of 23 min after 200 Gy.

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.