S-phase fraction of human brain tumors in situ measured by uptake of bromodeoxyuridine

Tumour cell repopulation during fractionated radiotherapy: correlation between flow cytometric and radiobiological data in three murine tumours

This study tested whether the potential doubling time of tumour cells measured before or during treatment could predict the repopulation rate of surviving clonogens during fractionated radiotherapy. Tumours used for the study were a fibrosarcoma (SSK 2), an adenocarcinoma (AT 7) and a squamous cell carcinoma (AT 478), all grown subcutaneously in the C3H mouse. Potential doubling times (Tpot) were measured using the thymidine nanalogue iododexyuridine (IUdR) and flow cytometry. Results were compared with previous radiobiological studies on these tumours in which repopulation rates during radiotherapy were estimated using the tumour growth delay and tumour cure assays. Fractionated treatments consisted of daily doses of 4 or 8 Gy to clamped (hypoxic) tumours, 6 days per week for 1-3 weeks. Tpot values increased markedly during therapy for two of the tumours (SSK 2 and AT 478), by a factor of more than 10 for AT 478 in the third treatment week. Tpot remained approximately constant for the third tumour (AT 7). In no case was there evidence from the labelling studies of a shortening of Tpot which would suggest accelerated repopulation. From the radiobiological data, effective clonogen doubling times during radiotherapy were calculated from the doses required to produce a given effect in short and long treatment schedules. In the second week of treatment, effective clonogen doubling times in two tumours were approximately equal to the pretreatment Tpot, and shorter than the pretreatment Tpot in the third tumour. At some time during treatment, the surviving clonogens in these tumours therefore proliferated at the same rate or faster than before treatment. The difference between the labelling and radiobiological measurements was ascribed to the fact that, shortly after the start of a fractionated treatment, the IUdR labelling technique measures primarily doomed cells. These results show that kinetic measurements using DNA labelling techniques made during fractionated radiotherapy in most cases do not reflect the proliferation status of the surviving cells which are responsible for treatment outcome. Pretreatment Tpot measurements give a much better indication of the proliferation rate of surviving cells but in some cases may underestimate repopulation during radiotherapy.

Low-dose craniospinal radiation therapy for medulloblastoma

At the University of California, San Francisco, 65 children with medulloblastoma of the posterior fossa were treated postoperatively with craniospinal irradiation; the dose to the posterior fossa was 54 Gy. The 26 children initially treated had only radiation therapy, receiving 30 to 40 Gy to the spine and 40 to 50 Gy to the brain. Subsequently, 39 children were treated with low-dose craniospinal irradiation and chemotherapy; 24 to 30 Gy was directed to the whole brain and 24 to 26 Gy to the spinal axis. Chemotherapy generally consisted of procarbazine just before, and hydroxyurea during, radiation therapy. Poor-risk and good-risk patients (defined by tumor resection less than 75% or greater than 75%, positive or negative myelogram, positive or negative cerebrospinal fluid analysis, age less than or greater than 2 years, respectively) were evenly distributed between the low-dose and high-dose craniospinal radiation therapy groups. Median follow-up was 51 months (range, 24 to 228 months). Kaplan-Meier actuarial survival for all patients was 73% at 5 years, 70% at 10 years. Freedom from disease progression was 68% at 5 years, 65% at 10 years. Whereas poor-risk patients treated with low-dose craniospinal irradiation and chemotherapy had a 5-year survival of 58% and a 5-year freedom from disease progression of 39%, those figures in the comparable good-risk patients were 83% and 77%, respectively. For both good-risk and poor-risk patients, the posterior fossa was the primary site of recurrence. Tumors recurred in the frontal region, probably under blocks, in three patients receiving low-dose irradiation and in two receiving the higher dose. Reducing the dose of whole-brain and spinal irradiation and giving chemotherapy did not result in a higher rate of recurrence in the brain or spinal cord. Intellectual and social function appeared better in patients receiving the lower dose. We did not study whether chemotherapy benefitted good-risk patients. Craniospinal axis irradiation at a lower dose than conventionally used does not compromise local control or survival in patients with medulloblastoma, and may reduce toxicity.

Cell proliferation in human tumour xenografts: measurement using antibody labelling against bromodeoxyuridine and Ki-67

Cell proliferation was investigated in human tumour xenografts using bromodeoxyuridine (BrdUrd) labelling, evaluated either by flow cytometry or in tissue sections, and also using the proliferation marker Ki-67. BrdUrd labelling was found to increase when cryostat tumour sections were digested with an enzymic solution. This yielded a labelling index up to four times higher than that obtained using the flow cytometer. Ki-67 indices were found to be higher than those reported for human tumour biopsies, as may be expected due to the enhanced growth rate of the xenografts. Significant heterogeneity was observed in the results for cervix, breast and bladder tumours, and the results of the three methods were poorly correlated. However, three of the four tumour types showed that the tumour with the lowest Ki-67 index also had the longest potential doubling time. Since the measurement of Ki-67 index was found technically easier to perform, and also adequately reflects relative tumour cell proliferation, it is preferred over the other techniques.

Determination of proliferative activities in human brain tumor specimens: a comparison of three methods

Proliferative activities were determined in 72 human brain tumors, including 20 metastatic carcinomas, 41 gliomas, 8 meningiomas and 3 hematological tumors. Immunocytochemical techniques included labeling with monoclonal antibody (mAb) to bromodeoxyuridine (BrdU) which identifies S phase cells after previous in vitro BrdU incubation and paraffin embedding of fixed tissue specimens, and with mAb Ki-67 which reacts, in frozen sections, with a nuclear antigen expressed by all proliferating cells. BrdU labeling index (LI), Ki-67 LI and mitotic index (MI) correlated well with histological malignancy. Among the three proliferation indices, Ki-67 LI and BrdU LI were highly significantly correlated. With the exception of hematological malignancies, hyperbaric oxygenation of in vitro BrdU labeling did not significantly increase BrdU LI or depth of BrdU penetration into tissue. This study indicates that in vitro BrdU labeling is a useful alternative to Ki-67 immunolabeling of human brain tumor specimens. By such determination of tumor proliferation, it might be possible to design a more adequate postoperative therapy tailored to patients individually.

An indirect immunofluorescence double staining procedure for the simultaneous flow cytometric measurement of iodo- and chlorodeoxyuridine incorporated into DNA

In this paper we describe an indirect fluorescence double staining procedure for the simultaneous detection of IdUrd and CldUrd in the same cell nucleus. Two commercially available antibodies were selected for this purpose. A rat anti-BrdUrd monoclonal antibody from Sera-lab was found to bind specifically to CldUrd and BrdUrd. A mouse monoclonal anti-BrdUrd antibody from Becton Dickinson used in a 1:2 dilution binds to all halogenated deoxyuridines but, when the cells were extensively washed with Tris buffer with a high salt concentration, almost no binding to CldUrd was observed. An immunofluorescence procedure was developed, based on these primary antibodies, raised in different species (rat and mouse), in combination with highly purified second antibodies: FITC conjugated goat antirat and Texas-Red conjugated goat antimouse.

The predictive value of cell kinetic measurements in a European trial of accelerated fractionation in advanced head and neck tumors: an interim report

The value of cell kinetic measurements in head and neck tumors in predicting which patients will benefit from accelerated fractionation radiotherapy regimens is being tested in a multicenter European trial (EORTC trial 22851). This paper reports on the first analysis of the correlation of kinetics with outcome in this trial. A proportion of patients in both the accelerated arm (72 Gy in 5 weeks, 1.6Gy per fraction, 45 fractions) and the conventional arm (70-72 Gy in 7-8 weeks, 1.8-2.0 Gy per fraction, 35-40 fractions) were given an i.v. injection of 100 mg/m2 IUdR (iododeoxyuridine) before treatment, and a tumor biopsy was taken several hours later. The potential doubling time of the tumor (Tpot) was obtained from a flow cytometric analysis of tumor cell nuclei using an anti-IUdR antibody. From a total of 260 patients entered in the trial, 53 have undergone kinetic analysis. Adequate IUdR labeling was seen in 47 patients (88.7%), from which the mean value for Tpot was found to be 4.5 +/- 2.5 days (+/- S.D.). Of the IUdR labeled patients, 30 have now been followed up for at least 1 year, 17 with conventional and 13 with accelerated radiotherapy. These patients were split into those with fast and those with slowly growing tumors, the dividing line being the median Tpot value of 4.6 days. After conventional 7-week radiotherapy, 2 of 6 patients with "fast" growing tumors obtained local control compared with 8 of 11 with "slow" growing tumors. A small difference in local control was seen been fast and slow tumors in the accelerated arm (5/9 vs. 3/4). These preliminary data support the hypothesis that patients with fast growing tumors do poorly with conventional radiotherapy and that pretreatment kinetic measurements can select patients at risk. The predictive power of the method must await the final analysis of trial results.

Mutagenic effects of brief exposure to bromodeoxyuridine on mouse FM3A cells

The time- and dose-dependency of the mutagenic effects of bromodeoxyuridine (BrdU), a thymidine analogue used for cell kinetics studies in vivo and in vitro, were investigated in FM3A cells. Cells incubated with 50-1000 microM BrdU for 72 h showed some inhibition of growth. Cells cultured in BrdU-free medium for 3 d after a 30 min or 2 h exposure to BrdU showed no growth inhibition, while those previously exposed for 24 h to BrdU showed retarded growth. After a 30 min exposure, 60% of cells were labelled with BrdU; after 2 h 70%; and after 24 h almost 100%. After incubation in BrdU-free medium for 3 d (the time required for this cell line to express mutation), cells previously treated for 30 min or 2 h showed reduced BrdU positivity, whereas almost 100% of those treated for 24 h remained BrdU positive. The mutation rate, determined by the number of colonies resistant to ouabain (2 mM) and 6-thioguanine (10 microM) 3 d after exposure to BrdU, was not affected by a 30 min treatment with up to 1000 microM BrdU. Cells treated for 1 or 2 h showed increased resistance to ouabain after exposure to BrdU at concentrations above 100 microM; cells treated for 12 or 24 h showed an increased mutation rate at BrdU concentrations above 50 microM. The number of colonies resistant to 6-thioguanine did not increase in cells treated with BrdU at concentrations up to 1000 microM for 1, 12 or 24 h. We cannot conclude with certainty that brief exposure to BrdU does not modulate DNA to the point of mutation. This study may serve as a guideline for limiting the dose and time of exposure to BrdU for cell kinetics studies in vivo and in vitro.

Cell kinetics of rat 9L brain tumors determined by double labeling with iodo- and bromodeoxyuridine

Rats with 9L brain tumors received intraperitoneal injections of iododeoxyuridine (IUdR) and bromodeoxyuridine (BUdR) to estimate the duration of the deoxyribonucleic acid (DNA) synthesis phase (Ts) and the potential doubling time (Tp) of individual tumors. Different sequences and intervals (2 or 3 hours) of IUdR and BUdR administration were evaluated. After denaturation, tumor sections were reacted with Br-3, a monoclonal antibody that identifies only BUdR, and then were stained immunohistochemically by the avidinbiotin complex method. An antibody that recognizes both IUdR and BUdR, IU-4, was applied to the sections and identified by the alkaline phosphatase-antialkaline phosphatase method. Nuclei labeled only with IUdR stained blue, while those labeled with BUdR or with BUdR and IUdR stained brown. The fraction of cells that either left or entered the S-phase during the time between administration of IUdR and BUdR was measured to calculate Ts and Tp, assuming that the labeled cohort completed the DNA synthesis at a constant rate. The Ts was 8.8 hours (coefficient of variation (cv) = 0.05) and the Tp was 64.2 hours (cv = 0.08). The sequence and interval of administration of IUdR and BUdR had a minimal effect on Ts and Tp. In studies of 9L cells in monolayer culture, the Ts was 9.6 hours (cv = 0.08) and the TP was 30.6 hours (cv = 0.06). Double labeling with BUdR and IUdR allows the duration of the S-phase and potential doubling time of individual brain tumors to be estimated in situ from a single biopsy specimen.

S-phase fraction of human prostate adenocarcinoma studied with in vivo bromodeoxyuridine labeling

Forty-six patients with adenocarcinoma of the prostate were given an intravenous infusion of the thymidine analogue, bromodeoxyuridine (BrdU), 200 mg/m2, at the time of needle biopsy or transurethral resection to label tumor cells in the DNA synthesis phase. The tumor specimens were stained by an indirect immunoperoxidase method with anti-BrdU monoclonal antibody. The BrdU labeling index, S-phase fraction, was determined by counting the number of BrdU-labeled cells in the tissue sections. S-phase fraction correlates with the results of histologic tumor grade, Gleason score, and growth patterns. The higher S-phase fraction may indicate biologic malignancy. Moreover, the degree of heterogeneity concerning S-phase fraction distribution within prostate cancer tissue could be evaluated and the findings compared with the morphologic appearance. The authors results suggest that the measurement of BrdU labeling index in prostate cancer may prove to be a new objective and quantitative assay for biologic potential of individual tumors.

Bromodeoxyuridine labeling study of intracranial meningiomas: proliferative potential and recurrence

Ninety-six patients with intracranial meningiomas and two with hemangiopericytic variants received a 30-min intravenous infusion of bromodeoxyuridine (BrdUrd), 200 mg/m2, before tumor removal. Excised tumor specimens were stained by the indirect immunoperoxidase method to determine the BrdUrd labeling index (LI), or percentage of cells in DNA synthesis. The BrdUrd LI was less than 1% in 63 (86.3%) of 73 nonmalignant meningiomas and less than 1% in 20 (87%) of 23 malignant meningiomas. Of 23 malignant meningiomas 11 were recurrent tumors; 8 patients had recurrence 3 to 33 months after the study. The recurrence rate was 100% (five of five) in patients whose tumors had a BrdUrd LI greater than 5%, 44% (11 of 25) in those with a BrdUrd LI 1% to 5%, and 6.1% (4 of 66) in those with an LI less than 1%. Thus, meningiomas with a BrdUrd LI greater than 1% may grow faster and recur more frequently. Among patients with malignant meningiomas, the mean time to recurrence after the study was 7.5 months in those with a BrdUrd LI greater than 5% and 20.2 months for those with an LI 1% to 5%. The mean time to recurrence was 97.8 months in patients with nonmalignant meningiomas. Both hemangiopericytic variants were recurrent and showed LIs of 0.5% and 4.1%; the former tumor recurred 8 years after complete resection, while the latter recurred three times in 3.5 years. Thus, the proliferative potential of intracranial meningiomas as reflected by the BrdUrd LI appears to be a prognostic variable that can help to elucidate the biological behavior of individual meningiomas.

Metastatic intracranial carcinoid with immunohistochemical observation. Case report

A case of metastatic carcinoid tumor in the right occipital lobe originating from a primary tumor in the right colon is reported in a 68-year-old man. The tumor had a high bromodeoxyuridine labeling index. Although immunohistochemical studies of the tumor specimen showed positive reactivity for serotonin and somatostatin, blood levels of serotonin and urinary 5-hydroxyindoleacetic acid content were normal. This suggests that coexistence of somatostatin with serotonin in the tumor tissue might lead to inhibition of serotonin release by "autocrine regulation." The neurological complications of carcinoid tumors, including intracranial metastasis, are discussed briefly.

Immunocytochemical determination of ploidy class-dependent bromodeoxyuridine incorporation in rat liver parenchymal cells after partial hepatectomy

Immunocytochemistry of bromodeoxyuridine (BrdU) incorporated in DNA was performed on cryostat sections of rat liver and on isolated hepatocytes after partial hepatectomy using a two-step labeling technique. The method enabled the detection of S-phase nuclei in both tissue preparations. Quantification of the number of labeled nuclei in sections showed that the number of nuclei in S-phase increased from 0.3% in control liver to about 36% at 24 h after partial hepatectomy. The detection of BrdU in isolated hepatocytes showed the same labeling index of binuclear diploid, mononuclear tetraploid and binuclear tetraploid cells. A special role for mononuclear diploid cells in proliferation did not seem to occur.

Radiotherapy for high grade gliomas

This presentation will review recent data on the treatment of high grade gliomas. It deals primarily with results of radiotherapy even though several of the clinical trials to be considered also included chemotherapy. Present emphasis will be on, but not limited to, the larger prospective randomized trials conducted by various cooperative clinical groups in the United States, the United Kingdom and on the continent.

The proliferative activity of neurilemomas

Twenty-one patients with neurilemomas (15 intracranial and 6 intraspinal) received a 1-hour intravenous infusion of 5-bromodeoxyuridine (BrdU), 200 mg/m2 before tumor removal, to label S-phase tumor cells. Excised tumor specimens were stained by the indirect immunoperoxidase method with anti-BrdU monoclonal antibodies to determine the BrdU labeling index, or percentage of S-phase cells. The BrdU labeling index ranged from 0.1% to 3.1% (mean, 0.9%). The BrdU labeling index was greater than 1.5% in four of the 21 tumors (three trigeminal and one spinal). One acoustic tumor in a patient with neurofibromatosis type 1 had a labeling index of 1.3%, which was the highest among the acoustic tumors. The BrdU labeling indices did not correlate with the patient's age, tumor size, or the duration of signs and symptoms. There was no significant difference between the BrdU labeling indices of Antoni type A and Antoni type B tissue. The low BrdU labeling index of most of the intracranial neurilemomas coincides well with the slow growth of these tumors. As the BrdU labeling index may reflect growth potential of individual tumors, it could be used to guide the follow-up patients with incompletely resected tumor.

A cell kinetic study of pulmonary adenocarcinoma by an immunoperoxidase procedure after bromodeoxyuridine labeling

By in vitro labeling with bromodeoxyuridine (BrdU) and immunohistochemical staining with anti-BrdU monoclonal antibody, the tumor cell kinetics were investigated in 52 resected pulmonary adenocarcinomas. The values of the BrdU labeling index (LI) varied widely among cases of adenocarcinoma in comparison with four cases of small cell carcinoma and ten cases of squamous cell carcinoma examined as controls. The LI was below 3.0 in 60% of the adenocarcinomas. When the LI was analyzed according to the cytologic subtypes of adenocarcinoma, the values were low for goblet cell type and type II alveolar cell type, whereas the values for the bronchial surface epithelial cell type varied widely (average, 5.2) and those for the Clara cell type were intermediate (average, 1.8). A comparison of the LI with TNM classification, histologic differentiation, degree of nuclear atypia, and mitotic cell count showed a correlation between the LI and each of these prognostic factors. Thus, the possibility of the BrdU LI being a useful new prognostic factor of pulmonary adenocarcinomas was suggested.

Radiobiology and clinical application of halogenated pyrimidine radiosensitizers

Halogenated pyrimidines (HP) represent a unique class of non-hypoxic cell radiosensitizers currently under clinical re-investigation. In order for halogenated pyrimidines to sensitize cells to radiation, they must be incorporated into cellular DNA. In the case of human tumors, which have in general rather long cell cycle times, this may require many days of continuous drug infusion to achieve adequate replacement of the DNA base thymidine with HP. In vitro studies support the relationship between the extent of radiosensitization and the percentage of thymidine replacement. Recent clinical studies evaluating the role of iododeoxyuridine (IdUrd) as a radiation sensitizer in large unresectable sarcomas have been extremely encouraging. To support and expand upon these positive clinical findings more information and research is needed regarding: (1) the mechanism of HP-induced radiosensitization; (2) the percentage of HP thymidine replacement in human tumors achievable and how it relates to treatment outcome; (3) the means of increasing HP incorporation in tumor and minimizing incorporation in normal tissues; (4) a better understanding of optimal timing between HP administration and radiation treatment; and (5) methods to evaluate which tumors are appropriate candidates for HP therapy. While presently limited to use in conventional high dose-rate X-ray therapy, laboratory studies suggest that HP might also be effective in low dose-rate brachytherapy and for selected high LET clinical beams. HPs probably will not be 'general' non-hypoxic cell radiosensitizers for all tumor types, but with appropriate tumor-type/anatomical site selection and refinement in their administration, HPs may prove beneficial in cancer treatment.

Prognostic implications of the bromodeoxyuridine labeling index of human gliomas

This study includes 182 patients with intracranial gliomas who received bromodeoxyuridine (BUdR), 200 mg/sq m intravenously, at the time of craniotomy but before tumor biopsy. The tumor specimens were stained for BUdR using the immunoperoxidase method; the BUdR labeling index (LI), or S-phase fraction, was calculated as the percentage of BUdR-positive cells. The median BUdR LI's for 127 primary moderately anaplastic astrocytomas, highly anaplastic astrocytomas, and glioblastomas (less than 1%, 2.7%, and 7.3%, respectively; range 0% to 38.1%) were not significantly different from those of 55 similar recurrent tumors (less than 1%, 4.3%, and 7.4%, respectively; range 0% to 30.5%). The mean LI was significantly higher in tumors from patients over 50 years of age than in tumors from younger patients (p less than 0.001). The age-related difference in LI's was found in both groups of patients with astrocytomas but not in those with glioblastomas. Kaplan-Meier survival curves showed a significantly greater probability of survival among patients whose tumors had LI's of less than 1% than among those with LI's greater than 5%; survival probability of patients with tumor LI's of 1% to 5% was intermediate between the two extremes. Thus, the BUdR LI appears to reflect the proliferative potential more accurately than the histopathological diagnosis and should therefore be considered an important factor in determining the prognosis of individual patients with intracranial gliomas and in selecting their treatment.

In situ demonstration of tissue proliferative activity using anti-bromo-deoxyuridine monoclonal antibody

Immunohistochemical staining with anti-bromo-deoxyuridine (BrdU) monoclonal antibody was performed on a variety of human tissues following in vitro incubation with BrdU. The effect of different fixatives and DNA denaturation techniques on the reactivity with anti-BrdU was investigated. Optimal preservation of the antigenicity of BrdU incorporated into the DNA of proliferating cells was seen in tissues fixed in Bouin's fluid, while samples which had been fixed with cross-linking reagents, such as formalin, were usually unreactive. Positivity for BrdU was restored in formalin fixed tissues after digestion with pepsin, but this was usually associated with loss of morphological details. Acid and thermal DNA denaturation techniques gave similar results. It is concluded that Bouin fixation followed by acid or thermal denaturation of DNA is the method of choice for the in situ detection of cells in S-phase using anti-BrdU monoclonal antibody.

Variability in the proliferative potential of human gliomas

One hundred forty-three patients with gliomas of astrocytic origin (61 with glioblastomas multiforme (GM) and 82 with astrocytomas) received an intravenous infusion of bromodeoxyuridine (BUdR), 150-200 mg/m2 at the time of surgery, to label tumor cells undergoing DNA synthesis. BUdR-labeled cells were identified by the indirect immunoperoxidase method using anti-BUdR monoclonal antibodies. The percentage of BUdR-labeled cells, or BUdR labeling index (LI), was calculated by microscopic examination of selected viable areas of the tissue sections. The GMs had a median LI of 7.5%, and three quarters of these tumors had LIs greater than 5%. Highly anaplastic astrocytomas (HAAs) and moderately anaplastic astrocytomas (MoAAs) had median LIs of 2.3% and less than 1%, respectively. Among the HAAs, the LI was 1% to 5% in 56% of tumors, greater than 5% in 26%, and less than 1% in 18%. More than 60% of MoAAs had LIs less than 1%, which agrees with the slow clinical progression of this type of tumor, and the remainder had LIs of 1.4% to 9.3%. These results show that histopathologically similar tumors may have different proliferative potentials. Measuring the proliferative potential of individual gliomas is therefore crucial for predicting the prognosis more accurately and for devising more tumor-specific treatment regimens for individual patients.

Cell kinetics in leukaemia and solid tumours studied with in vivo bromodeoxyuridine and flow cytometry

During a 15-month period, we used in vivo bromodeoxyuridine (BUDR) infusion to study cell kinetics in 112 consecutive patients with various types of malignant tumours: acute leukaemia (50 patients), gastric cancer (42) and brain gliomas (20). The in vivo BUDR method requires that a single tumour sample be taken 4-6 h after infusion and that bivariate flow cytometry (FCM) be employed to measure simultaneously the percentage of BUDR-labelled cells (which are identified with a green fluorescent anti-BUDR monoclonal antibody) and their mean DNA content (following propidium iodide staining). This technique rapidly furnishes the labelling index (LI) and the DNA synthesis time (TS), from which the tumour potential doubling time (Tpot) and production rate (fractional turnover rate, FTR) are calculated. The procedure took 6-9 h to complete and there was no immediate toxicity from BUDR administration. Successful LI and TS determinations were obtained in 89 (80%) and 80 (72%) of the 112 patients, respectively. Correlations were sought between kinetic parameters and a number of pathological and clinical ones. In 34 patients with acute non-lymphoblastic leukaemias who were uniformly treated for remission (CR) induction and maintenance, proliferative activity, as measured by Tpot and FTR, was greater in responsive than in non-responsive patients, and in those who experienced CR for over 8 months than in those who had a shorter CR. Proliferative activity was also greater in patients with advanced gastric cancers than in those with more limited disease. No correlations between kinetic and clinical and pathological parameters were found in gliomas. These data indicate the in vivo BUDR infusion coupled with FCM measurements can be performed in clinical settings to obtain kinetic data rapidly in quite large patient series. This will probably allow the inclusion of kinetic data in clinical trials aimed at evaluating the prognostic relevance of these data.

Determination of the proliferative potential of human brain tumors using the monoclonal antibody Ki-67

The proliferative activity of 133 human tumors of the nervous system was investigated by means of immunohistochemistry using the monoclonal antibody Ki-67 in order to evaluate the usefulness of this method for histopathological tumor grading. Ki-67 recognizes a proliferation-associated nuclear antigen present in human cells during all active phases of the cell cycle but absent in the G0 phase [Gerdes J, Schwab U, Lemke H, Stein H (1983) Int J Cancer 31:13-20]. In 28 WHO grade I and II gliomas of all major types Ki-67 indices were generally low with mean values ranging from less than 1% in pilocytic astrocytomas to 4.2% in grade II oligodendrogliomas. Individual cases of grade II astrocytomas and oligodendrogliomas had, however, values up to 8.5%. In 13 primary anaplastic gliomas of WHO grade III consistently higher statistical means were obtained with values ranging from 8.6% for anaplastic astrocytomas to 14.2% for anaplastic mixed gliomas. Interestingly, 18 WHO grade IV glioblastomas demonstrated a mean value of only 7%, which is probably due to the pronounced phenothypic heterogeneity in this tumor group. This heterogeneity results in enormous intra- and intertumor variability in Ki-67 indices (range less than 1%-22.1%). Investigation of 17 recurrent gliomas revealed mean values for Ki-67 ranging from 1.7% for three WHO grade II astrocytomas up to 48.5% obtained in two highly anaplastic recurrent astrocytomas corresponding to WHO grade IV. Other tumors of the nervous system evaluated included 9 medulloblastomas (mean 17.9%, range 5.0%-42.0%), 17 benign meningiomas (mean 1.1%, range 0%-5%), 15 metastatic carcinomas (mean 16.5%, range less than 1%-46.0%), and individual tumors of various types. Our results indicate that Ki-67 immunohistochemistry can add useful additional information for histopathological grading which, by supplementing and refining the traditional WHO grading system, might lead to a better assessment of the biological behaviour of human tumors of the nervous system.

Response of human HT-29 colorectal tumor cells to extended exposure to bromodeoxyuridine

Effects of the extended exposure of a human colorectal tumor-cell line (HT-29) to bromodeoxyuridine (BrdUrd) were studied in anticipation of the clinical use of that agent to treat colorectal cancer, particularly as a regionally delivered radiosensitizer. We found that 72-h exposure to a concentration of BrdUrd that is estimated to be locally maintained in the liver (100 microM) was significantly cytotoxic with a 3-log reduction in survival. As measured by GC/MS-SIM method, incorporation of BrdUrd into DNA followed an unexpected time course in that continuous exposure to 10 microM BrdUrd resulted in maximal incorporation at 3 days, after which the extent of incorporated analog fell significantly (despite daily changes of the medium). This finding was apparently due to a greater rate of loss of BrdUrd from the medium at later time points. Flow cytometric analysis using an anti-BrdUrd antibody (IU-4) revealed that antibody binding also peaked and fell off with time. However, at exposure times of greater than 24 h, the timing and extent of this decline were significantly different than had been indicated by the GC/MS method. These results indicate that the quantitative relationship between antibody staining and BrdUrd incorporation changes as drug-exposure time increases and that quantitative studies of anti-BrdUrd antibody binding must be interpreted with caution, especially when extended drug-treatment protocols have been used.

Correlation of DNA ploidy and proliferative activity in human gastric cancer

Analysis of DNA ploidy patterns was performed on 129 cases of primary gastric cancer and the results were correlated with histologic findings and in vivo bromodeoxyuridine (BrdU) labeling. Forty-nine cases were diploid (38%) and 80 cases were aneuploid (62%). There was no correlation between DNA ploidy and histologic type. In aneuploid tumors, incidence of lymphatic invasion, lymph node metastasis, and rate of advanced cases were significantly higher than those in diploid tumors. During the follow-up period of 5 to 10 years, 23 of 40 patients (55%) with aneuploid tumors died of disease within 3 to 120 months. Only 13 of 36 patients (36%) with diploid tumors died of disease. The BrdU labeling indices (BrdU LI) ranged from 2.8% to 26.7%, with a mean of 10.4%. There was no correlation between BrdU LI and histologic type or stage. The mean BrdU LI of early cancers was 8.1%. The mean BrdU LI of advanced cancers was 11.9%. The BrdU LI of cancers with lymphatic invasion or lymph node metastasis was higher than those without them. The mean BrdU LI of diploid cancers was 6.0%. The mean BrdU LI of aneuploid cancers was 11.9%. There was a good correlation between BrdU LI and DNA ploidy patterns. These results indicate that DNA ploidy patterns and BrdU LI may possibly be useful prognostic markers for gastric cancers.

Flow cytometric determination of modal DNA population in relation to proliferative potential of human intracranial neoplasms

Paraffin-embedded specimens of brain tumors from 256 patients who had received an intravenous infusion of bromodeoxyuridine (BUdR) at the time of craniotomy were analyzed retrospectively by flow cytometry to determine the modal deoxyribonucleic acid (DNA) population. A single G1 peak was considered to represent a unimodal DNA population; two or more G1 peaks indicated a multimodal population. Most of the pituitary tumors and moderately anaplastic astrocytomas had unimodal DNA populations, whereas a higher percentage of other slow-growing tumors, such as meningiomas, ependymomas, and neurilemmomas, had multimodal populations (46.2%, 50.0%, and 60.0%, respectively). A relatively high percentage of the rapidly growing or highly malignant brain tumors, including highly anaplastic astrocytomas, glioblastomas multiforme, metastatic tumors, and medulloblastomas, also had multimodal populations (52.9%, 48.7%, 57.1%, and 66.7%, respectively). In most tumor groups, however, the percentage of tumors with a multimodal DNA population did not correlate with the BUdR labeling index or with the percentage of BUdR-labeled S-phase cells. Thus, modal DNA analysis by flow cytometry may provide information about the degree of heterogeneity and the biological behavior of individual brain tumors, but the results do not necessarily correlate with the rate of tumor growth or the prognosis in individual patients.

Proliferative characteristics of intracranial and spinal tumors of developmental origin

The proliferative potential of 17 intracranial and spinal tumors (six craniopharyngiomas, four chordomas, three mature teratomas, one immature teratoma, one embryonal carcinoma, one choriocarcinoma, and one dermoid tumor) was assessed. The patients received a 30-minute to 60-minute infusion of bromodeoxyuridine (BUdR) (200 mg/m2 intravenously [IV]) at the time of surgery but before a biopsy of the tumor was performed, to label cells in the DNA synthesis phase. The labeling index (LI) was calculated by determining the percentage of BUdR-labeled cells. The mean LI of the squamous epithelial elements of mature teratomas, craniopharyngiomas, and the dermoid tumor were 3.1 +/- 1.2%, 1.9 +/- 0.9%, and 2.9 +/- 1.9%, respectively. As in normal epithelium, the labeled cells were located in the basal layer. These results and the clinical findings suggest that the proliferation kinetics of these tumors are similar to those of normal skin and differ from those of rapidly growing malignant neoplasms. The other tissue elements (i.e., respiratory epithelium and cartilage) also demonstrated "organized" proliferation patterns similar to those of the corresponding normal tissues. An immature teratoma, an embryonal carcinoma, and a choriocarcinoma each had a high LI (24.6 +/- 5.3%, 32.3 +/- 3.8%, and 17.0 +/- 4.6%, respectively), and no organized pattern of proliferation was observed. In contrast, the mean LI of the four chordomas varied from 1.5% to 5.8%, and there was an even larger variation in the LI of different areas in individual tumors (from less than 1% to 7.5%). This finding suggests that even "slow-growing" chordomas sometimes can be locally aggressive and show a high incidence of recurrence, regardless of morphologic similarities.

Proliferative potential of brain metastases

Thirteen patients with metastatic brain tumors received an intravenous infusion of bromodeoxyuridine (BUdR) 200 mg/m2 at craniotomy) to label S-phase tumor cells. Excised tumors were stained immunohistochemically for BUdR. The percentage of BUdR-positive cells was calculated to determine the BUdR labeling index (LI) (or fraction of S-phase cells), which provides an estimate of the proliferative potential. Histologically, 11 patients had adenocarcinoma (four well-differentiated, three moderately differentiated, and four poorly differentiated), one had a large cell carcinoma, and one had a small cell carcinoma. All tumors had a BUdR LI greater than 5% (mean, 13.3 +/- 7% standard deviation). Moderately and poorly differentiated adenocarcinomas had a higher LI than well-differentiated adenocarcinomas (median, 15.3% versus 8.2%). These LI values are considerably higher than those reported for primary tumors with comparable histologic features. Thus, metastatic tumors in the brain may grow faster than the primary tumors from which they originate.

The proliferative potential of human ependymomas measured by in situ bromodeoxyuridine labeling

Twelve patients with ependymomas received a 30- to 60-minute intravenous infusion of bromodeoxyuridine (BrdU), 150 to 200 mg/m2 at surgery, to label tumor cells in the DNA synthesis phase. Labeled cells were detected in excised tumor specimens by indirect immunoperoxidase staining using anti-BrdU monoclonal antibody as the first antibody. The BrdU labeling index (LI, defined as the percentage of labeled cells in relation to the total number of cells scored) was calculated for each specimen. All four spinal cord ependymomas had a BrdU LI of less than 1%, which is consistent with our clinical experience that most such tumors grow slowly and have an excellent prognosis. Five of the eight intracranial ependymomas also had a low BrdU LI of approximately 1% or less, and three had a BrdU LI of 3.2%, 3.4%, and 4.8%. The latter three tumors, only one of which was diagnosed as a malignant ependymoma at the time of study, were either recurrent or recurred within 2 years after gross or subtotal removal. Cytologic analysis of cerebrospinal fluid (CSF) was performed in five cases; CSF seeding of tumor cells was found in only one patient, who had a malignant ependymoma. A high BrdU LI did not always correlate with CSF seeding. Measurement of the LI using BrdU and anti-BrdU monoclonal antibodies can provide more accurate information on the proliferative potential of individual tumors and may lead to a more rational grading system of ependymomas. The results of such studies do not always predict the potential for CSF seeding.

Cell kinetics of human brain tumors: in vivo study with bromodeoxyuridine and flow cytometry

Bromodeoxyuridine (BUDR) is a thymidine analog which is incorporated into the DNA of proliferating cells. Since the dose of BUDR needed to label cells is not toxic, cell labelling can be accomplished in vivo, by infusing the substance in patients. A monoclonal antibody against BUDR is then used to identify BUDR-labelled cells. The same cell population can also be stained for DNA content with propidium iodide (PI). Using bivariate flow cytometry (FCM) for measurements, both the percentage of BUDR-labelled cells and their total DNA content can be evaluated. This technique allows one to obtain the labelling index (LI) and the DNA synthesis time (TS). The potential doubling time (Tpot) and the fractional turnover rate (FTR) can be mathematically derived, so that a complete picture of tumor growth can be obtained. Our aim was to ascertain whether this method is clinically applicable and whether the kinetic values obtained are reliable. We studied 22 patients with benign and malignant brain tumors, and observed no immediate toxicity from BUDR administration. The BUDRLI obtained ranged from 0.9% to 3.9% (median: 2.0%) in meningiomas and from 3.8% to 7.6% (median: 6.3%) in malignant gliomas (P less than 0.01). The fraction of S-phase cells determined with the BUDR FCM technique was statistically similar to that found by single DNA flow cytometric analysis performed on duplicate samples of both benign and malignant brain tumors. The TS obtained in malignant gliomas ranged from 10.5 to 227 h (median: 12.8). The calculated Tpot ranged from 7.6 to 26.8 days (median: 11.6), and the calculated FTR ranged from 3.7 to 13.1 cells/100 cells/day (median: 8.8). These data suggest that in vivo BUDR infusion coupled with FCM can be performed in clinical settings, and it is reliable and can easily be used for kinetic studies in clinical trials aimed at evaluating the prognostic relevance of proliferative parameters and in planning tumor treatment.

Primary cerebral angiosarcoma. Case report

A 65-year-old man with a history of exposure to industrial solvents developed a primary cerebral angiosarcoma in the left posterior parieto-occipital lobe. The tumor had features typical of angiosarcoma on light and electron microscopy, immunohistochemical evidence of factor VIII-related antigen produced in tumor cells, and a high labeling index with bromodeoxyuridine. The relationship of angiosarcoma to toxins and viruses is discussed.

Comparison of bromodeoxyuridine labeling indices obtained from tissue sections and flow cytometry of brain tumors

Sixteen patients with brain tumors were given a 30- to 60-minute intravenous infusion of bromodeoxyuridine (BUdR), 200 mg/sq m. Grossly viable fragments were taken from the biopsied tumor specimens and divided into two portions. One portion was dissociated into single cells, stained both with fluorescein isothiocyanate (FITC) using anti-BUdR monoclonal antibody as the first antibody and with propidium iodide (for deoxyribonucleic acid), and analyzed by flow cytometry (FCM). The labeling index (LI) was calculated as the number of FITC-labeled cells expressed as a percentage of the total number of cells analyzed. The other portion was fixed in 70% ethanol, embedded in paraffin, sectioned, and stained with immunoperoxidase using anti-BUdR monoclonal antibody as the first antibody. The LI of these tissue sections was calculated in two ways: from selected areas in which the labeled cells were evenly distributed and from the entire tissue section. The LI's obtained by FCM correlated closely with those from the entire tissue sections (r = 0.99, p less than 0.000001) and were usually lower than LI's from selected areas of tissue sections. The LI's determined by FCM also correlated well with the LI's from selected areas of tissue sections (r = 0.82, p less than 0.00012), despite the difference in values between them. Thus, the FCM-derived LI and the tissue LI can both provide useful information for predicting the biological malignancy of individual tumors and for designing treatment regimens for individual patients with brain tumors; however, different standards should be used to interpret the LI's obtained by these two methods.

Treatment of medulloblastoma with procarbazine, hydroxyurea, and reduced radiation doses to whole brain and spine

Forty-seven patients with medulloblastoma were treated postoperatively with procarbazine, followed by craniospinal radiation therapy in combination with hydroxyurea. The radiation dose to the posterior fossa was 55 Gy; the spinal cord received 25 Gy and the whole brain 25 to 35 Gy (mean 33 Gy). Seventeen tumors recurred. Only one initial recurrence was in the spinal subarachnoid space; 10 (59%) were in the posterior fossa, and four (24%) were supratentorial. The estimated 5-year disease-free survival probability was 55%; the 5-year overall survival rate was 66%. Myelotoxicity occurred in 38% of patients, but in only one case was it severe enough to warrant reducing the total dose of radiation. It was concluded that good-risk medulloblastoma patients may be treated with radiation dosages as low as 25 Gy to the spinal axis and to the whole brain without increasing the risk of recurrence outside the posterior fossa. Chemotherapy with procarbazine followed by radiation therapy and hydroxyurea during radiation therapy was well tolerated and may play a role in reducing radiation dosages outside the posterior fossa.

Comparative analysis of different approaches to investigate cell kinetics

The potential of different methods to investigate proliferative activity of cell populations was analysed for non-Hodgkin's lymphomas. Cells in S phase and all cycling cells were determined on cell suspensions obtained from fresh lymph node material by [3H]-thymidine autoradiography [( 3H]TdR LI), a monoclonal antibody to bromodeoxyuridine (BrdU LI), and the monoclonal antibody Ki67. A good correlation was observed between the values of [3H]TdR LI and BrdU LI (rs = 0.90; P less than 0.01), [3H]TdR LI and S phase (rs = 0.62; P less than 0.01) and [3H]TdR LI and Ki67 (rs = 0.64; P less than 0.01) in individual lymphomas. Using the median values obtained from the different approaches as cut-off points to define slowly and rapidly proliferating tumours, the best agreement was observed between [3H]TdR LI and BrdU LI (91%) and poorer agreements, even though statistically significant, were observed between [3H]TdR LI and S phase (73%) or Ki67 (76%). In conclusion, the kinetic information derived from different approaches was more or less concordant and newly proposed approaches should be directly and carefully verified for their prognostic relevance before using them as alternatives to conventional methods.

In vivo bromodeoxyuridine incorporation in human gastric cancer: a study on formalin-fixed and paraffin-embedded sections

Bromodeoxyuridine (BUDR) is a non-radioactive thymidine analogue which is incorporated into the DNA of proliferating cells. This allows evaluation of the size of the S-phase as the BUDR labelling index (BUDR-LI) not only in vitro but also in vivo, since BUDR is not toxic at the doses needed to label cells. To ascertain whether in vivo BUDR incorporation can be detected on routine histological material we tested several different procedures prior to immunoperoxidase staining, on formalin-fixed, paraffin-embedded sections from five patients with gastric cancer, who received BUDR (250 mg m-2, intravenous) 4 h before surgery. To determine the optimal conditions for detecting BUDR in formalin-fixed tissues, immunohistochemical testing for BUDR was performed simultaneously on duplicate sections fixed with 70% ethanol. It was found that hydrolysis with 3N HCl at 37 degrees C for 30 min and digestion with 0.5% in at 37 degrees C for 30 min were sufficient to detect BUDR immunoreactivity in formalin-fixed sections. The method presented extends the range of applications of the in vivo BUDR technique for cell kinetics studies in human neoplasms because it can be used on routinely fixed archival material, with the advantage of correlating the kinetic data with histopathological characters.

Ki-67 immunoperoxidase stain as marker for the histological grading of nervous system tumours

The monoclonal antibody Ki-67 recognizes a nuclear antigen which is expressed during the G1, S, G2 and M phases of the cell cycle. Immunostaining of frozen biopsy material thus presents a convenient and rapid method for the estimation of the growth fraction in human neoplasia. This report summarizes the results obtained in 178 neurosurgical biopsies. The highest incidence of Ki-67 positive nuclei was observed in 8 metastatic carcinomas (mean: 20%) and in 53 cases of glioblastoma multiforme (10%). Glioblastomas showed considerable variation, the fraction of stained nuclei ranging from 1 to 28%. For astrocytomas and oligodendrogliomas we found a close correlation between the Ki-67 index and the histological grade in agreement with known biological behaviour. In anaplastic gliomas (WHO grade III) the upper limit was 11%, in grade II gliomas, 6%. Juvenile pilocytic astrocytomas and pituitary adenomas showed mean staining indices of approximately 1%. In 13 meningiomas the mean Ki-67 index was 1% but rose to 5% in recurrent and anaplastic meningiomas. Assessment of the growth fraction in human brain tumours by immunostaining with Ki-67 could become an important tool in the prediction of the biological behaviour of nervous system neoplasms and the planning of adjuvant therapy.

Kinetics of the human medulloblastoma cell line, D283 Med, maintained in an organ culture system. Autoradiographic study after cumulative labelling in vitro: similarities to the kinetics of human medulloblastoma in situ

Cells of the human D283 Med medulloblastoma cell line were collected by gravity sedimentation and maintained in vitro in an organ culture system. The explants grew as clusters of small cells with scanty cytoplasm; some cells were arranged in solid trabeculae, sometimes forming rows and columns, and occasionally rosettes. The kinetic parameters were estimated after 6 days in vitro by cumulative labelling of the cultures with tritiated thymidine in three different experiments. The length of G2 phase (TG2) was obtained from an analysis of the fractions of continuously labelled mitoses (FCLM), the length of S phase (TS) from the median values of grains over mitotic figures (grain index, GI), and the other parameters from mathematical models that related growth fraction (GF), TG2, total cell cycle time (TC) and labelling index (LI) as a function of time. Mean GF, TC, TG1, TS and TG2 were estimated respectively to be 0.35, 30 h, 13 h, 10 h, and 7 h. These estimates correspond to those reported for human medulloblastomas in situ and confirm previous in vitro experiments which suggest that the organ culture technique is a suitable system for the study of cell kinetics in human malignant gliomas and for an analysis of the in vitro effects of chemotherapeutic agents.

Cytotoxic effect and induction of sister chromatid exchange in exponentially growing rat 9L gliosarcoma cells after brief exposure to BrdU

The magnitude of DNA modulation in rat 9L gliosarcoma cells after a brief exposure to bromodeoxyuridine (BrdU) was studied by assaying colony-forming efficiency (CFE) and the number of sister chromatid exchanges (SCEs) per metaphase. The CFE assay showed that a 1-hr exposure to BrdU, at concentrations ranging from 10 to 1000 microM, produced a maximum cell kill of 5%. After a 2-hr exposure to 20 microM BrdU, the surviving fraction was 0.99, and even at a BrdU concentration of 1000 microM, 77% of the 9L cells survived. Compared with control cultures, the relative number of SCEs per metaphase in treated cultures was increased after a 1-hr exposure to BrdU at concentrations of 100 microM or more and after a 2-hr exposure to concentrations of 20 microM or more; no increase was observed in cells treated for 30 min with BrdU at concentrations up to 1000 microM. When the treated cells were allowed to grow in BrdU-free growth medium, the number of SCEs per metaphase returned to the control level within 24 hr, even after exposure to BrdU at concentrations as high as 1000 microM. These results demonstrate that exposure to BrdU at concentrations of up to 1000 microM for 30 min, 100 microM for 1 hr, and 20 microM for 2 hr causes little modulation of DNA.