Lack of expression of tumor-suppressor genes in human malignant glioma cell lines.

Human malignant gliomas (glioblastomas and anaplastic astrocytomas) are the most frequent brain tumors and are associated with a variety of genetic alterations including retinoblastoma (RB) and p53 gene mutations, loss of interferon alpha and beta (IFNA, IFNB) genes and lack of O6-methylguanine-DNA methyltransferase (MGMT) expression. Yet, in the studies performed to date, the relationship between these alterations has not been addressed. In this report, we have studied gene expression in 29 malignant glioma cell lines and have determined that, although loss of the interferon genes and loss of RB, p53 and MGMT mRNAs are frequent events, combinations of genetic alterations involving these four proven or putative tumor-suppressor genes are relatively infrequent. The exception was loss of RB mRNA, which may be associated with lack of MGMT mRNA.     

Etoposide sensitivity of radioresistant human glioma cell lines

Purpose: Malignant gliomas display aggressive local behavior and are not cured by existing therapy. Etoposide, a topoisomerase-II-inhibitor agent, is one of the most active and useful antineoplastic agents. However, etoposide is not usually used on these tumors. We undertook an in vitro study to prove that etoposide is a useful drug for malignant gliomas. Methods: Five human glioma cell lines were the basis for this study. Following exposure to various concentrations of etoposide, the glioma cell lines were found to be sensitive; the median concentration inhibiting the number of cells by 50% (IC₅₀) was 8.76 μg/ml (range 8–15.8 μg/ml). Since topoisomerase II is the critical target for etoposide, it was of interest to determine the topoisomerase II activity (decatenation of kinetoplast DNA isolated from Cryphtidia fasciculata) and the etoposide-induced inhibition of topoisomerase II activity. Results: The topoisomerase II activity was homogeneous in glioma cell lines (average of 50% decatenation with 7,000 cells), and topoisomerase II was the target of the etoposide. Conclusions: Our results suggest that topoiomerase II-reactive agents may prove to be clinically useful drugs for patients with malignant gliomas. Received: 4 March 1997 / Accepted: 1 June 1997     

Sensitivities of human glioma cell lines to interferons and double-stranded RNAs individually and in synergistic combinations

Summary The antiproliferative effects of human interferons (IFNs) and double-stranded RNAs (dsRNAs) were studied in five human glioma cell lines. Dose response curves were generated over a 72 hour treatment period. The concentration of interferon or double-stranded RNA necessary to produce a 50% antiproliferative response (GI₅₀) was calculated by linear regression analysis. Two cell lines were more sensitive to IFN- than to IFN-, one cell line was more sensitive to IFN- than to IFN- and two cell lines had approximately equal sensitivities to both interferons. All cell lines showed some sensitivity to either IFN- or IFN-. IFN- had no antiproliferative effect on any of the cell lines. In addition, only one of the cell lines displayed sensitivity to dsRNA, in which the response to poly(I) · poly(C) was greater than that to a mismatched analogue of poly(I) · poly(C), r(I)n · r(C₁₂,U)_n (Ampligen). There was no correlation between the sensitivities to type I IFNs ( and ), type II IFN () or the dsRNAs. The antiproliferative effect of combinations of IFNs, or IFNs and Ampligen, was studied in one of the cell lines. A significant synergistic antitumor effect was seen with all of the IFN/Ampligen combinations (p < 0.02), including IFN-/Ampligen, even though these cells were resistant to IFN- alone. Synergy was also seen in the IFN-/IFN- (p < 0.02) and IFN-/IFN- (p < 0.05) combinations. The IFN-/IFN- combination gave an additive antitumor effect. These results indicate that IFN- and IFN- alone or combinations of type I IFNs, type II IFNs and Ampligen can be effective in inhibiting the growth of glioma cells.     

Chromosomal imbalances associated with response to chemotherapy and cytotoxic cytokines in human malignant glioma cell lines

The median survival for human malignant glioma patients treated with neurosurgery and postoperative radiotherapy does not exceed one year. Only a minority of patients benefit from adjuvant chemotherapy. It was the aim of our study to determine which genomic alterations in malignant gliomas modulate the sensitivity to chemotherapy or cytotoxic cytokines such as CD95 ligand (CD95L) or Apo2L/tumor necrosis factor-related apoptosis-inducing ligand (Apo2L/TRAIL). Therefore, we analyzed 12 human malignant glioma cell lines for chromosomal gains and losses by comparative genomic hybridization (CGH). The gains most commonly identified were on chromosomes 7q, 19, 1, and 20q, whereas the most frequent losses were on 13q, 11q, 18q, and 4q. By comparison with previously published data on this panel of glioma cell lines1112, we defined candidate regions which may carry genes responsible for sensitivity to chemotherapy or cytotoxic cytokines. All but one of the chromosomal regions associated with response to chemotherapy, i.e. 1p12, 3p21, 11p11.2-p13, 12q23, 17p11. 2-p13, were different from those associated with response to cytotoxic cytokines, i.e. lp12, 1q22, 12q12-q21. Genomic regions known to harbor major candidate genes, including genes encoding death ligands, death receptors, caspases and BCL-2 family proteins, were not found to be imbalanced. In addition, we identified 5q13-q14, 5q34, 10p11.2, 9q21-q34 as genomic regions associated with the proliferative activity of malignant glioma cell lines. Cell lines with gain on proximal 5q, where CCNB1 and CCNH reside, showed an increased growth rate, suggesting that cyclins activating cdc2, the dominant G2/M phase kinase, may play a role in glioma tumorigenes.     

Sensitivity to etoposide of human malignant glioma cell lines. Mechanisms of action]

AIM OF THE STUDY: Etoposide, a Topoisomerase II inhibitor agent, is currently being explored as a therapeutic agent for brain tumors. The aim of this experimental study was to compare the in vitro etoposide sensitivity of human glioma cells vs human squamous cell carcinoma (SCC) cells. MATERIAL AND METHODS: Twelve human cell lines (six malignant glioma cell lines and six head and neck SCC cell lines) were used for this comparative study. A standard colony formation assay was used to assess cell survival. Since Topoisomerase II is the critical target for etoposide, it was of interest to determine Topoisomerase II activity and etoposide induced inhibition of Topoisomerase II activity for the glioma cells vs the SCC cells. RESULTS: Except for etoposide-induced inhibition of Topoisomerase II activity, no difference was found for etoposide sensitivity and Topoisomerase II activity between the both type of cells. CONCLUSION: These results suggested that the Topoisomerase II reactive agents may prove to be clinically a useful drug for patients presenting with malignant gliomas.     

A comparison of heat and radiation sensitivity of three human glioma cell lines

Three human glioma cell lines were tested for radiation and hyperthermia sensitivity and compared to the responses of a normal human fibroblast cell line. The radiation response of the glioma cell lines exhibited a large shoulder on the radiation survival curve indicating radioresistance when compared to the more radiosensitive fibroblast cell line. The hyperthermia response for the glioma cell lines was qualitatively similar to responses reported for other cell lines. When compared to normal human fibroblasts the glioma cells were found to be more sensitive to hyperthermia than the normal fibroblasts indicating hyperthermia may be a promising method or adjunct to radiotherapy in the treatment of resistant glioma cells or tumors. The results also show that both the radiation and thermal response is influenced by cell culture conditions and growth status. Two of the cell lines grown to confluency and treated in confluency showed an increased radiation resistance at low doses and the cell lines showed decreased resistance at high doses compared to cells plated to confluency (see Methods and Materials). An increased thermal resistance, especially at the lower heating temperatures, was also observed for cells grown to confluency. Measurements of residual glucose in the culture medium at the time of irradiation was about the same for the two culture methods (55%-65%). Cell cycle analysis showed that the differences were not related to changes in cell cycle distribution.     

Anti-tumor activity of human recombinant TNF against human malignant glioma cell lines and combined effect with Hu INF-beta

Human TNF was detected fairly recently and at present the anti-tumor activity of human recombinant TNF is being examined against various malignant tumors of human origin. In the present study, we report the anti-tumor activity of recombinant human TNF against human malignant glioma cell lines in vitro and in vivo, in addition to its combined effects with HuIFN-beta. The in vitro study was conducted as follows. Thirteen human glioma cell lines were exposed to 100 U/ml TNF, 1,000 IU/ml HuIFN-beta, or both, and the suppression rate was calculated on days 3, 5 and 7. In the in vivo study, nude mice carrying a human glioma cell line, KMS II, in the subcutaneous tissues were divided into groups and drugs were administered intratumorally as described below. 1) control, 2) TNF 5,000 U single administration, 3) TNF 5,000 U, intermittently administered (once/week for two weeks), 4) TNF 5,000 U, continuously administered (3/week for two weeks), 5) HuIFN-beta 50 X 10(4) IU (3/week for two weeks), and 6) combination of 4) with 5). Results of the in vitro study revealed some suppressive effects on proliferation of tumor cells on day 7 in all 13 glioma cell lines examined with 100 U/ml TNF. And also, especially in 8 of 13 cell lines, the suppression rate was more than 30%. The suppressive effects of TNF were augmented by combined use of HuIFN-beta in all cell lines, giving a range of suppression of 67.8 to 99.3%. The in vivo study revealed that the mean tumor weight ratios (control = 100%) on day 19 (the end of the experiment) were as follows; single administration of TNF: 41.3%, intermittent: 46.7%, continuous: 26.7%, HuIFN-beta: 65.9%, combination: 18.5%. Statistical analysis disclosed significant suppressive effects on tumor proliferation between the control group and 3 TNF-administered groups (single, intermittent, and continuous) and that suppression in the continuously administered group was more severe in comparison with the group given single administration. Moreover, it was suggested that combination therapy with TNF and Hu IFN-beta was more effective than a single therapy with TNF only or HuIFN-beta only. From the results described above, it was found that human recombinant TNF had some cytotoxic effects against human malignant gliomas in vitro and in vivo, although the degree of cytotoxicity was not always higher in comparison with the effects of TNF.     

Correlation between DNA topoisomerase II alpha expression and sensitivity to etoposide in human glioma cell lines

The expression of topoisomerase II alpha (Topo II alpha) was investigated in six human glioma cell lines as a function of doubling time, cell cycle distribution, and sensitivity to an antineoplastic agent, etoposide (ETP). The Topo II alpha level was determined by immunohistochemical and flow cytometric studies using monoclonal antibody, 8D2, specific for Topo II alpha. In all cell lines, the Topo II alpha level correlated directly with sensitivity to ETP, but not with doubling time or percentage of cells in any phase of the cell cycle. These findings suggest that the cytocidal activity of ETP may be mediated by qualitative and quantitative changes in Topo II alpha in human glioma cells. We speculate that better knowledge of Topo II alpha expression in surgical specimens may lead to more individualized use of ETP in patients with malignant glioma.     

Human malignant glioma cell lines are sensitive to low radiation doses

Malignant gliomas display aggressive local behavior and are not cured by existing therapy. Some cell lines that are considered radioresistant respond to low radiation doses (<1 Gy) with increased cell killing (low-dose hypersensitivity). In our study, 4 of 5 human glioma cell lines exhibited significant X-ray sensitivity at doses below 1 Gy. The surviving fractions (SFs) obtained at 0.7 and/or 0.8 Gy were comparable to those at 1.5 Gy. Low-dose hypersensitivity was evident when irradiation was combined with etoposide treatment. Repeated irradiation with low doses was markedly more effective than irradiation with single, biologically equivalent doses in decreasing SFs, inhibiting xenograft tumor growth in mice. All experiments were conducted with an accelerator used in clinics, establishing that low-dose hypersensitivity was present following megavoltage X-irradiation. Thus, repeated low-dose irradiation (ultrafractionation) could greatly improve the effectiveness of radiotherapy of gliomas and could allow safe treatment of patients with cumulative doses greater than 60 Gy.     

Retention of cellular radiation sensitivity in cell and xenograft lines established from human melanoma surgical specimens.

Six human melanoma xenograft lines have been established in athymic mice from metastatic lesions in six different patients. Permanent cell lines in monolayer culture have been established from four of the xenograft lines. The cellular radiation sensitivity of the donor patients' tumors, the xenograft lines, and the cell lines were measured in vitro. The Courtenay soft agar colony assay was used for the donor patients' tumors, and a conventional plastic surface colony assay was used for the cell lines, whereas both assays were used for the xenograft lines. The cell survival data were analyzed using the multitarget single-hit as well as the linear-quadratic model. The donor patients' tumors differed considerably in cellular radiation sensitivity (the D0 ranged from 0.85 +/- 0.08 to 1.17 +/- 0.09 Gy, the alpha from 0.25 +/- 0.06 to 0.87 +/- 0.14 Gy-1, and the surviving fraction at 2.0 Gy from 0.15 +/- 0.04 to 0.50 +/- 0.06). The xenograft lines showed similar survival curves in soft agar and on the plastic surface, and the survival curves of a xenograft line and the corresponding cell line were not significantly different. These survival curves were not significantly different from those of the donor patients' tumors, regardless of which survival curve parameter was considered, i.e., the cellular radiation sensitivity of the donor patients' tumors was retained in the cell and xenograft lines. Moreover, the cell and xenograft lines have growth properties in vitro and in vivo that render a wide variety of experiments possible. Consequently, they show great promise for future studies of human tumor radiation biology.     

Photodynamic therapy of malignant glioma with hypericin: comprehensive in vitro study in human glioblastoma cell lines

The poor prognosis of patients suffering from malignant glioma requires further efforts. Photodynamic therapy (PDT) might be a therapeutic option to increase surgical radicality. Hypericin (HY) exhibit high phototoxicity to malignant cells and accumulates to a higher extent in glioblastoma cells as compared to neurons. Therefore, the impact of various experimental parameters on cytotoxicity, intracellular accumulation and phototoxicity of HY was quantitatively assessed in the three human glioblastoma cell lines U373 MG, LN229 and T98G. Additionally, intracellular location of HY was studied with fluorescence microscopic techniques. For all three cell lines, no cytotoxicity was found for incubation concentrations up to 5 microM. For short-time incubation (2 h), maximum HY fluorescence was achieved at an incubation concentration of about 5 microM. However, uptake kinetics of HY was dependent on its incubation concentration. Moreover, increase in HY fluorescence was negligible at 4 degrees C, which strongly indicates that the compound is taken up by an energy-dependent process. HY exhibited high phototoxicity (at 595 nm) in all three cell lines with ID50-values ranging from 0.15 J/cm(2) to 0.22 J/cm(2), but sensitivity decreased in the order U373 MG > LN229 > T98G. However, assessment of phototoxicity at different wavelengths revealed that highest cell inactivation was achieved at 600 nm. Fluorescence microscopy showed that HY fluorescence arose predominantly from the perinuclear region and the nuclear membrane. Fluorescence pattern of HY was significantly different from those observed for organelle markers staining lysosomes or mitochondria. Location of HY in the plasma membrane was proven by total internal reflection fluorescence microscopy. Thus, the present study demonstrates that glioblastoma cells can be effectively inactivated by HY-PDT after short-time incubation and exposure to low light doses. These results obtained in cell culture are encouraging and justify further evaluation HY-PDT for the treatment of malignant glioma in animal experiments.     

Doxorubicin sensitivity pattern in a panel of small-cell lung-cancer cell lines: correlation to etoposide and vincristine sensitivity and inverse correlation to carmustine sensitivity

Summary The aim of our investigations is to evaluate whether the sensitivity patterns of small-cell lung-cancer (SCLC) cell lines in vitro can be used in evaluating new drugs and in selecting drugs for the optimization of combination therapy. In our attempts to obtain a panel of cell lines demonstrating differential patterns in sensitivity, we have developed three SCLC lines exhibiting different types of multidrug resistance (MDR). In the present investigations we compared the sensitivity patterns shown by five wild-type SCLC lines and three MDR lines in response to six different types of drugs: doxorubicin, cytarabine, carmustine, cisplatin, vincristine, and etoposide. In the wild-type SCLC cell lines, the range of variation in sensitivity to all drugs was within a factor of 10. Cell lines showing low sensitivity to doxorubicin also exhibited low sensitivity to etoposide and vincristine, and vice versa. In contrast, the pattern of sensitivity to carmustine was almost the opposite of that to doxorubicin. A tendency to an inverse relationship between doxorubicin and carmustine sensitivity was also observed when doxorubicin sensitivity was reduced in near stationary cells and in cells exposed to the metabolic inhibitor 2-deoxy-d-glucose. In agreement with the pattern observed for the wild-type lines, all of the MDR sublines demonstrated collateral sensitivity to carmustine. As to cytarabine, the wild-type lines expressed a sensitivity pattern similar to that shown in response to doxorubicin. Interestingly, the opposite pattern was found in the MDR lines, as all three demonstrated cytarabine hypersensitivity. The combination of alkylating agents and MDR drugs are of proven clinical benefit in the treatment of solid tumors, as is the combination of anthracycline and cytarabine in acute myeloid leukemia. The experimentally derived sensitivity data on cytarabine, alkylating agents, and MDR drugs (i.e., etoposide, doxorubicin, vincristine) thus resemble the clinical experience with these drugs, and we conclude that the use of a clonogenic asay on the described panel of SCLC cell lines can give valuable information for the selection of agents for combination therapy.This work was supported by grants from the Danish Cancer Society, the Danish Medical Research Council, and the Lundbeck Foundation     

Comparison of cellular basis of drug sensitivity of human colon,pancreatic, and renal carcinoma cell lines with that of leukemia cell lines

Summary In an attempt to find how much the low therapeutic effectiveness of antitumor drugs against so-called chemotherapy-refractory tumors such as colon carcinoma depends on drug sensitivity at the cellular level, sensitivity of five carcinoma cell lines (three colorectal, one pancreatic, and one renal) to nine typical anticancer agents was compared in vitro with that of four generally chemotherapysusceptible leukemia cell lines. Sensitivity was assesed in terms of the percentage cell growth in control cultures, which was determined by exposing exponentially growing cells for 48 h to the following antitumor drugs: 1-(4-amino-2-methylpyridine-5-yl)-methyl-3-(2-chloroethyl)3-nitrosourea hydrochloride (ACNU), adriamycin (ADM), bleomycin (BLM), cisplatin (DDP), etoposide (VP-16), 5-fluorouracil (5FU), mitomycin C (MMC), methotrexate (MTX), and vinblastine (VLB). As expected, 10-fold or greater differences in sensitivity were scarcely ever observed between the two kinds of cell lines. Thus, we recorded a result of more (or less) sensitivity when there was a difference of 3-fold or more; and compared the drug sensitivity in every pair of carcinoma and leukemia cell lines (20 pairs for each drug). We found that carcinoma cell lines were less sensitive to VP-16, ADM, DDP, and MTX than leukemia cell lines in 18, 15, 12, and 10 of 20 pairs, respectively; only one opposite case was observed, with DDP. On the other hand, no such tendency between the two groups was observed with BLM, 5FU, or MMC. Overall, significantly different sensitivities were observed between them in 91 out of 180 pairs (i.e., 9 antitumor drugsx5 carcinomasx4 leukemias), and carcinoma cell lines were less sensitive than leukemia cell lines in 79 of these 91 pairs. These results suggest that the refractoriness of colon carcinoma, etc. to chemotherapy is, at least in part, due to low drug sensitivity of the tumor cell itself.This study was supported in part by Grants-in-Aid for Cancer Research from the Ministry of Education, Science and Culture, Japan     

Mutational analysis of 9 different tumour-associated genes in human malignant mesothelioma cell lines

Seven tumour suppressor genes (Chk1, Chk2, Apaf1, Rb1, p53, p16(INK4a) and p14(ARF)) and two oncogenes (N-ras and BRAF) were screened in nine human malignant melanoma (HMM) cell lines for point mutations or small deletions/insertions by DGGE, TGGE and SCCP analysis. For the first time in human mesothelioma, Chk1 gene mutations were detected in two of the nine investigated HMM cell lines. P53 gene mutations were found in three cell lines and p16(INK4a) mutations in 5. Mutation of the Chk1 gene implies a novel disruption mechanism of the p53 pathway in HMM, without affecting p53 itself. According to our knowledge, this is the first mutation screening of Chk1, Chk2, Apaf1 and Rb1 in human malignant mesothelioma.     

CPT-11 in human colon-cancer cell lines and xenografts: Characterization of cellular sensitivity determinants

CPT-11, a new semisynthetic derivative of camptothecin, is active in a number of tumor types in the clinic, including colon cancer. CPT-11 is a drug that is converted into the active metabolite SN-38 by a carboxylesterase. Experiments were performed to obtain more insight in the cellular characteristics in 5 unselected human colon-cancer cell lines that account for the differential sensitivity to CPT-11 and SN-38. In vitro, the sensitivity to CPT-11 and SN-38 was highest in LS174T and COLO 320 cells, intermediate in SW1398 cells and lowest in COLO 205 and WiDr cells. SN-38 was 130 to 570 times more active than CPT-11. CPT-11 induced complete remissions in 6 out of 12 COLO 320 tumors grown as subcutaneous xenografts, but was not effective in WiDr tumors. The cellular carboxylesterase activity did not relate to the sensitivity to CPT-11. The enzyme activity was higher in normal mouse tissues, i.e., serum and liver, than in COLO 320 or WiDr xenografts, indicating that tumor carboxylesterase is of minor importance for CPT-11 efficacy. The topoisomerase-l mRNA expression in tumor cells was not predictive of the antiproliferative effects of CPT-11 or SN-38. We observed a positive relationship between the DNA topoisomerase-1 activity and the cellular sensitivity to carboxylesterase-activated CPT-11 (r = 0.75, p < 0.1) as well as to SN-38 (r = 0.89, p < 0.05). The higher topoisomerase-1 activity in COLO 320 cells and tumors when compared with that in WiDr cells and tumors reflected the differences in sensitivity to the drug(s). In conclusion, the DNA topoisomerase-1 activity was the best determinant for CPT-11/SN-38 sensitivity in this panel of unselected human colon-cancer cell lines. Int. J. Cancer, 70:335–340, 1997. © 1997 Wiley-Liss, Inc.     

Radiation-induced apoptosis in human sarcoma and glioma cell lines

Six human soft-tissue sarcoma and 14 glioma cell lines, exhibiting considerable differences in radioresponsiveness and histological grade of differentiation of the parental tumour, were examined with respect to apoptosis development after irradiation with ⁶⁰Co γ-rays. After test doses of 6 and 25 Gy, significant changes characteristic of apoptosis occurring within 6 to 30 hr were exhibited by only 2 differentiated sarcoma cell lines, EL7 and ESS2. The characteristic intemucleosomal fragmentation of DNA was detected as early as 6 hr after exposure of subconfluent monolayer cultures to 6 Gy. It was limited to cells that had detached from the culture plate, whereas adherent cells showed random degradation of DNA, namely after higher doses (25Gy) or longer incubation times (30 hr). As assessed by fluorescence microscopy of unfixed cultures stained with Hoechst 33342 and propidium iodide, the proportion of cells showing apoptotic bodies in non-irradiated controls was < 0.l% and 0.3% for EL7 and ESS2, respectively. The doseresponse relationship for apoptosis was determined at 9 hr post-irradiation. After 2 Gy, the percentage of apoptotic cells was elevated to 3.4% in EL7 and 4.5% in ESS2 cultures. Saturation was obtained above 6 Gy, with 8.4% apoptosis in EL7 and 15% in ESS2 after 25 Gy. Taken together, rapid ionizing-radiation-induced apoptosis seems to be limited to a subgroup of sarcomas and is unlikely to occur in gliomas. © 1995 Wiley-Liss Inc.     

Mitoxantrone sensitivity of human hematopoietic cell lines

A panel of 18 human hematopoietic cell lines was tested for sensitivity to mitoxantrone, an anthracenedione derivative with antitumor activity in vitro and in vivo. Cells in logarithmic growth phase were tested for mitoxantrone at concentrations of 0.1-1000 ng/ml for 1-3 days. Cell growth inhibition was profound for all lines at a mitoxantrone concentration of 10 ng/ml, whereas a variable response was seen at a concentration of 1 ng/ml. Inhibition of cell proliferation was mainly depending on arrest at the G2 phase of the cell cycle (or S + G2 at higher mitoxantrone concentrations), together with a cytotoxic effect. The cell cycle block was found in all lines tested, whereas the cytotoxic activity varied much between different cell lines.