Drug cytotoxicity at elevated temperature

1987 ◽  
Vol 67 (6) ◽  
pp. 885-888 ◽  
Author(s):  
Vasco F. Da Silva ◽  
Gjisbert P. Raaphorst ◽  
Ravi Goyal ◽  
Mark Feeley
Keyword(s):  
Elevated Temperature ◽  
Glioma Cell ◽  
Malignant Gliomas ◽  
Drug Dose ◽  
Glioma Cell Line ◽  
Colony Formation Assay ◽  
Therapeutic Application ◽  
Content Type ◽  
Higher Temperature ◽  
Fine Print

✓ The malignant glioma cell line U-87MG was used for 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), aziridinylbenzoquinone (AZQ), cis-diaminodichloroplatinum (II) (cis-DDP), and spirohydantoin mustard (SHM) treatments at 37° and 42°C. With the exception of SHM, all drugs killed a greater proportion of cells at the higher temperature, as assessed by the colony-formation assay. Drug-dose enhancement ratios were 1.6, 2.8, 2, and 1:1 for BCNU, AZQ, cis-DDP, and SHM, respectively. Because methods to heat discrete volumes of brain are now available, we conclude that hyperthermic increase of BCNU, AZQ, and cis-DDP cytotoxicity might have therapeutic application for malignant gliomas.

Enhancement of radiosensitivity of wild-type p53 human glioma cells by adenovirus-mediated delivery of the p53 gene

1998 ◽  
Vol 89 (1) ◽  
pp. 125-132 ◽  
Author(s):  
Frederick F. Lang ◽  
W. K. Alfred Yung ◽  
Uma Raju ◽  
Floralyn Libunao ◽  
Nicholas H. A. Terry ◽  
...  
Keyword(s):  
Cell Line ◽  
Glioma Cell ◽  
Radiation Treatment ◽  
P53 Protein ◽  
Glioma Cells ◽  
Glioma Cell Line ◽  
Wild Type ◽  
Content Type ◽  
Infected Cells ◽  
Fine Print

Object. The authors sought to determine whether combining p53 gene transfer with radiation therapy would enhance the therapeutic killing of p53 wild-type glioma cells. It has been shown in several reports that adenovirus-mediated delivery of the p53 gene into p53 mutant gliomas results in dramatic apoptosis, but has little effect on gliomas containing wild-type p53 alleles. Therefore, p53 gene therapy alone may not be a clinically effective treatment for gliomas because most gliomas are composed of both p53 mutant and wild-type cell populations. One potential approach to overcome this problem is to exploit the role p53 plays as an important determinant in the cellular response to ionizing radiation. Methods. In vitro experiments were performed using the glioma cell line U87MG, which contains wild-type p53. Comparisons were made to the glioma cell line U251MG, which contains a mutant p53 allele. Monolayer cultures were infected with an adenovirus containing wild-type p53 (Ad5CMV-p53), a control vector (dl312), or Dulbecco's modified Eagle's medium (DMEM). Two days later, cultures were irradiated and colony-forming efficiency was determined. Transfection with p53 had only a minor effect on the plating efficiency of nonirradiated U87MG cells, reducing the plating efficiency from 0.23 ± 0.01 in DMEM to 0.22 ± 0.04 after addition of Ad5CMV-p53. However, p53 transfection significantly enhanced the radiosensitivity of these cells. The dose enhancement factor at a surviving fraction of 0.10 was 1.5, and the surviving fraction at 2 Gy was reduced from 0.61 in untransfected controls to 0.38 in p53-transfected cells. Transfection of the viral vector control (dl312) had no effect on U87MG radiosensitivity. In comparison, transfection of Ad5CMV-p53 into the p53 mutant cell line U251MG resulted in a significant decrease in the surviving fraction of these cells compared with controls, and no radiosensitization was detected. To determine whether Ad5CMV-p53—mediated radiosensitization of U87MG cells involved an increase in the propensity of these cells to undergo apoptosis, flow cytometric analysis of terminal deoxynucleotidyl transferase-mediated biotinylated-deoxyuridinetriphosphate nick-end labeling—stained cells was performed. Whereas the amount of radiation-induced apoptosis in uninfected and dl312-infected control cells was relatively small (2.1 ± 0.05% and 3.7 ± 0.5%, respectively), the combination of Ad5CMV-p53 infection and radiation treatment significantly increased the apoptotic frequency (18.6 ± 1.4%). To determine whether infection with Ad5CMV-p53 resulted in increased expression of functional exogenous p53 protein, Western blot analysis of p53 was performed on U87MG cells that were exposed to 9 Gy of radiation 2 days after exposure to Ad5CMV-p53, dl312, or DMEM. Infection with Ad5CMV-p53 alone increased p53 levels compared with DMEM- or dl312-treated cells. Irradiation of Ad5CMV-p53—infected cells resulted in a further increase in p53 that reached a maximum at 2 hours postirradiation. To determine whether exogenous p53 provided by Ad5CMV-p53 had transactivating activity, U87MG cells were treated as described earlier and p21 messenger RNA levels were determined. Infection of U87MG cells with Ad5CMV-p53 only resulted in an increase in p21 compared with DMEM- and dl312-treated cells. Irradiation of Ad5CMV-p53—infected cells resulted in an additional time-dependent increase in p21 expression. Conclusions. These data indicate that adenovirus-mediated delivery of p53 may enhance the radioresponse of brain tumor cells containing wild-type p53 and that this radiosensitization may involve converting from a clonogenic to the more sensitive apoptotic form of cell death. Although the mechanism underlying this enhanced apoptotic susceptibility is unknown, the Ad5CMV-p53—infected cells have a higher level of p53 protein, which increases further after irradiation, and this exogenous p53 is transcriptionally active. Thus, it is possible that the combination of Ad5CMV-p53 infection and radiation treatment increases p53 protein to a level that is sufficient to overcome at least partially the block in apoptosis existing in U87MG cells.

Radiosensitization of C6 glioma by thymidine and 41.8°C hyperthermia

1990 ◽  
Vol 72 (5) ◽  
pp. 782-785 ◽  
Author(s):  
Justin D. Cohen ◽  
H. Ian Robins ◽  
Manucher J. Javid
Keyword(s):  
Cell Survival ◽  
Cell Line ◽  
Untreated Control ◽  
Glioma Cell ◽  
Glioma Cell Line ◽  
C6 Glioma ◽  
Content Type ◽  
C6 Glioma Cell ◽  
Fine Print

✓ The cytotoxic, antiproliferative, and radiosensitizing effects of thymidine (a nucleoside metabolite) were studied using the C6 glioma cell line in vitro. Radiosensitization by a combination of thymidine and 41.8°C hyperthermia was also evaluated. Thymidine concentrations above 100 µg/ml completely inhibited C6 proliferation while concentrations of 100 to 1000 µg/ml (for up to 24 hours) decreased C6 cell survival to as little as 7.4% compared to untreated control cells. Radiosensitivity was enhanced by the administration of thymidine alone (400 µg/ml × 24 hours before irradiation); sensitization by 41.8°C hyperthermia alone (1 hour ending immediately before irradiation) was less pronounced. Thymidine and hyperthermia together produced greater radiosensitization than did heat alone or thymidine alone. These data support the further investigation of thymidine as a neuro-oncology radiosensitizer.

Interaction between p53 and p16 expressed by adenoviral vectors in human malignant glioma cell lines

2002 ◽  
Vol 97 (1) ◽  
pp. 143-150 ◽  
Author(s):  
Seung-Ki Kim ◽  
Kyu-Chang Wang ◽  
Byung-Kyu Cho ◽  
Hyun-Tai Chung ◽  
Young-Yim Kim ◽  
...  
Keyword(s):  
Cell Lines ◽  
Western Blotting ◽  
Glioma Cell ◽  
Malignant Gliomas ◽  
G1 Arrest ◽  
Moderate Degree ◽  
Wild Type ◽  
Content Type ◽  
Glioma Cell Lines ◽  
Fine Print

Object. Multiple gene replacements have been examined as a potential treatment modality for malignant gliomas. Nevertheless, no reports are available that detail the synergy, additivity, or antagonism of multiple genes. The aim of this study was to assess the interaction between p53 and p16 genes in the growth of glioma cell lines. Methods. The human glioma cell lines U87MG and U373MG were transduced using an adenoviral vector with Ad-p53, Ad-p16, or both. Western blotting was performed to determine the expression of the protein products of the transduced p53 and p16 genes. To establish whether the combination of Ad-p53 and Ad-p16 would be beneficial, the effects of gene combinations at the median inhibitory concentration level were analyzed using the isobologram method. Annexin assays and cell cycle analyses were performed on the transduced cells. Western blotting demonstrated the expression of p53 and p16 in transduced cells. Simultaneous exposure to Ad-p53 and Ad-p16 produced additive effects in both glioma cell lines. Experimental data points in U373MG lay near the Mode I line, indicating that the vectors had a different mode of action. The restoration of normal p53-encoded protein in the mutant cell lines induced apoptosis, whereas in the wild-type p53 cell lines, the overexpression of wild-type p53 resulted in a moderate degree of apoptosis and G1 arrest. Furthermore, Ad-p16 induced more marked G1 arrest than Ad-p53 in cells with wild-type p53. Conclusions. The results show that interaction between Ad-p53 and Ad-p16 is additive, regardless of p53 gene status.

Characterization of neuroectodermal antigen by a monoclonal antibody and its application in CSF diagnosis of human glioma

1988 ◽  
Vol 68 (3) ◽  
pp. 449-455 ◽  
Author(s):  
Toshihiko Wakabayashi ◽  
Jun Yoshida ◽  
Hisao Seo ◽  
Kyoto Kazo ◽  
Yoshiharu Murata ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Monoclonal Antibody ◽  
Brain Tumors ◽  
Cell Lines ◽  
Glioma Cell ◽  
Glioma Cell Line ◽  
Human Glioma ◽  
Content Type ◽  
Sds Page ◽  
Fine Print

✓ Monoclonal antibodies were produced by immunization of the human glioma cell line SK-MG-4. One of the antibodies, designated G-22, reacted with 18 of 20 glioma cell lines, two melanoma cell lines, and three lung cancer cell lines, but not with 39 cell lines derived from sarcoma, carcinoma, or hematopoietic tumors. The antigen was expressed in the brain of human fetuses in early gestation (9 weeks) but not in late gestation (8 months) or in normal adult brain, suggesting that the antibody recognizes neural differentiation antigens expressed by neuroectodermal origin. A high incidence of positive antigens has been observed in gliomas but not in the other neural tumors, such as ependymomas, meningiomas, and neuroblastomas. Thus, the antigen defined by the G-22 monoclonal antibody could be defined as glioma-associated antigen. Pulse-labeling with tritiated leucine and subsequent immunoprecipitation of the solubilized cell membrane revealed that the antigen recognized by this antibody had a molecular weight of 67 kD on sodium dodecyl sulfate-poly-acrylamide gel electrophoresis (SDS-PAGE). It was shown by dot-blot enzyme-linked immunospecific assay (ELISA) that the antigen could be detected in the cerebrospinal fluid (CSF) from patients with gliomas. From analysis of affinity chromatography and SDS-PAGE, the antigen present in the CSF had a molecular weight similar to that of a 1% Nonidet P-40 (NP-40) extract from a glioma cell line. When the antigen in CSF was quantitatively assayed by ELISA, the mean antigen level (expressed as optical density at 450 nm) in the CSF of seven patients was 0.8 ± 0.28 (mean ± standard deviation), which was significantly higher than the 0.38 ± 0.14 level observed in the CSF of 15 patients with nonglioma brain tumors and the 0.23 ± 0.09 level in the CSF of four patients without brain tumors. These results indicate that the monoclonal antibody G-22 is useful for the diagnosis of glioma.

Camptothecin analogs in malignant gliomas: comparative analysis and characterization

2003 ◽  
Vol 98 (3) ◽  
pp. 570-577 ◽  
Author(s):  
Prakash Sampath ◽  
Eric Amundson ◽  
Monroe E. Wall ◽  
Betty M. Tyler ◽  
Mansukh C. Wani ◽  
...  
Keyword(s):  
Brain Tumors ◽  
Cell Lines ◽  
Topoisomerase I ◽  
Glioma Cell ◽  
Malignant Gliomas ◽  
Sodium Dodecyl ◽  
Local Therapy ◽  
Content Type ◽  
Glioma Cell Lines ◽  
Fine Print

Object. The authors compared and characterized several new classes of camptothecin (CPT) analogs (a total of 22 drugs) directed against human and murine glioma cell lines in vitro, trying to identify CPT analogs that can be used for local therapy in future clinical trials. Camptothecin is a naturally occurring alkaloid that inhibits the DNA-replicating enzyme topoisomerase I. Moreover, CPT and its analogs have shown promising antitumor activity against both systemic and intracranial neoplasms. Because the CPTs have poor bioavailability and are unable to cross the blood—brain barrier, they may best be delivered to the central nervous system by polymers. The authors have previously shown that local delivery of Na-CPT by implantable polymers prolongs survival in a rat intracranial glioma model. In recent years, a number of newly synthesized CPT analogs have been developed that exhibit more potency and stability than Na-CPT. Methods. Cytotoxicities of the drugs were tested using modified clonogenic and monotetrazolium assays in three glioma cell lines. A potassium chloride—sodium dodecyl sulfate coprecipitation assay was used to determine the frequency of drug-stabilized cleavable complexes. Of the CPT analogs analyzed, the 10,11-methylenedioxy (MD) class consistently demonstrated the greatest cytotoxicity. Three of these analogs, 10,11-MD-20(RS)-CPT, 10,11-MD-20(S)-CPT-glycinate ester (Gly).HCl, and 9-amino-10,11-MD-20(S)-CPT-Gly, exhibit significantly greater antiproliferative activities than CPT, Na-CPT, or 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) against all three glioma cell lines. In addition, the 10,11-MD20(RS)-CPT analog induces more cleavable complexes than Na-CPT at every concentration. Conclusions. The increased potency and greater stability of CPT analogs hold promise for more effective local antitumor treatments against malignant intracranial brain tumors. The greater cytotoxicity of 10,11-MD CPTs in comparison with other CPT analogs as well as CPT, BCNU, or Na-CPT, may present an ideal candidate drug class for development against both primary and metastatic brain tumors.

Administration of interleukin-12 and -18 enhancing the antitumor immunity of genetically modified dendritic cells that had been pulsed with Semliki Forest virus—mediated tumor complementary DNA

2002 ◽  
Vol 97 (5) ◽  
pp. 1184-1190 ◽  
Author(s):  
Ryuya Yamanaka ◽  
Naoki Yajima ◽  
Naoto Tsuchiya ◽  
Junpei Honma ◽  
Ryuichi Tanaka ◽  
...  
Keyword(s):  
Dendritic Cells ◽  
Antitumor Immunity ◽  
Semliki Forest Virus ◽  
Malignant Gliomas ◽  
Glioma Cells ◽  
Antitumor Effects ◽  
Content Type ◽  
Immunogene Therapy ◽  
Fine Print

Object. Immunogene therapy for malignant gliomas was further investigated in this study to improve its therapeutic efficacy. Methods. Dendritic cells (DCs) were isolated from bone marrow and pulsed with phosphate-buffered saline or Semliki Forest virus (SFV)—mediated 203 glioma complementary (c)DNA with or without systemic administration of interleukin (IL)-12 and IL-18 to treat mice bearing the 203 glioma. To study the immune mechanisms involved in tumor regression, the authors investigated tumor growth of an implanted 203 glioma model in T cell subset—depleted mice and in interferon (IFN) γ—neutralized mice. To examine the protective immunity produced by tumor inoculation, a repeated challenge of 203 glioma cells was given by injecting the cells into the left thighs of surviving mice and the growth of these cells was monitored. The authors demonstrated that the combined administration of SFV-cDNA, IL-12, and IL-18 produced significant antitumor effects against the growth of murine glioma cells in vivo and also can induce specific antitumor immunity. The synergic effects of the combination of SFV-cDNA, IL-12, and IL-18 in vivo were also observed to coincide with markedly augmented IFNγ production. The antitumor effects of this combined therapy are mediated by CD4+ and CD8+ T cells and by NK cells. These results indicate that the use of IL-18 and IL-12 in DC-based immunotherapy for malignant glioma is beneficial. Conclusions. Immunogene therapy combined with DC therapy, IL-12, and IL-18 may be an excellent candidate in the development of a new treatment protocol. The self-replicating SFV system may therefore provide a novel approach for the treatment of malignant gliomas.

Thymidine kinase activation of ganciclovir in recurrent malignant gliomas: a gene-marking and neuropathological study

2000 ◽  
Vol 92 (5) ◽  
pp. 804-811 ◽  
Author(s):  
Griffith R. Harsh ◽  
Thomas S. Deisboeck ◽  
David N. Louis ◽  
John Hilton ◽  
Michael Colvin ◽  
...  
Keyword(s):  
Gene Expression ◽  
Enzymatic Activity ◽  
Thymidine Kinase ◽  
Tumor Cells ◽  
Malignant Gliomas ◽  
Retroviral Vectors ◽  
Content Type ◽  
Tumor Bed ◽  
Immunohistochemical Evidence ◽  
Fine Print

Object. The gene therapy paradigm of intratumoral activation of ganciclovir (GCV) following transduction of tumor cells by retroviral vectors bearing the thymidine kinase (tk) gene has produced dramatic remissions of malignant gliomas in animal models. In human trials, although the technique has been deemed safe, little antitumor effect has been demonstrated. To evaluate the basis of this inefficacy in human gliomas, the authors conducted a gene-marking trial involving neuropathological and biochemical studies of treated tumor specimens.Methods. Five patients with malignant recurrent gliomas underwent stereotactic biopsy sampling and intratumoral implantation procedures with three aliquots of 106 vector-producing cells (VPCs) in columns. After 5 days, the tumor was resected and the tumor bed reimplanted with VPCs, and a course of GCV was given. Patients received clinical and radiological follow up for 6 months. Tumor specimens were analyzed neuropathologically and for tk gene expression by anti-TK immunohistochemistry and TK enzymatic activity.Four patients tolerated the treatment well but experienced tumor progression. The other developed an abscess after the second operation and died. Increased TK enzymatic activity was demonstrated in the one tumor specimen analyzed. Immunohistochemical evidence of tk gene expression was limited to VPCs. Transduction of tumor cells was not seen. Viable tumor cells were seen near VPCs containing TK. The lymphocytic immune response was mild.Conclusions. Except for the risk of infection inherent in reoperation, this tk—GCV paradigm was both feasible and safe. Pathological studies indicated that limited dissemination of VPCs and vector from the infusion site and failure to transduce tumor cells with the tk gene are major barriers to efficacy.

Induction of reactive oxygen intermediates—dependent programmed cell death in human malignant ex vivo glioma cells and inhibition of the vascular endothelial growth factor production by taurolidine

2005 ◽  
Vol 102 (6) ◽  
pp. 1055-1068 ◽  
Author(s):  
Roksana Rodak ◽  
Hisashi Kubota ◽  
Hideyuki Ishihara ◽  
Hans-Pietro Eugster ◽  
Dilek Könü ◽  
...  
Keyword(s):  
Vascular Endothelial Growth Factor ◽  
Cell Death ◽  
Cell Lines ◽  
Glioma Cell ◽  
Ex Vivo ◽  
Vascular Endothelial ◽  
Content Type ◽  
Glioma Cell Lines ◽  
Endothelial Growth Factor ◽  
Fine Print

Object. Taurolidine, a derivative of the amino acid taurin, was recently found to display a potent antineoplastic effect both in vitro and in vivo. The authors therefore initiated studies to assess the potential antineoplastic activity of taurolidine in human glioma cell lines and in ex vivo malignant cell cultures. They also studied the mechanisms that induce cell death and the impact of taurolidine on tumor-derived vascular endothelial growth factor (VEGF) production. Methods. Cytotoxicity and clonogenic assays were performed using crystal violet staining. In the cytotoxicity assay 100% of glioma cell lines (eight of eight) and 74% of ex vivo glioma cultures (14 of 19) demonstrated sensitivity to taurolidine, with a mean median effective concentration (EC50) of 51 ± 28 µg/ml and 56 ± 23 µg/ml, respectively. Colony formation was inhibited by taurolidine, with a mean EC50 of 7 ± 3 µg/ml for the cell lines and a mean EC50 of 3.5 ± 1.7 µg/ml for the ex vivo glioma cultures. On observing this high activity of taurolidine in both assays, the authors decided to evaluate its cell death mechanisms. Fragmentation of DNA, externalization of phosphatidylserine, activation of poly(adenosine diphosphate—ribose) polymerase, loss of the mitochondrial membrane potential followed by a release of apoptosis-inducing factor, and typical apoptotic features were found after taurolidine treatment. Cell death was preceded by the generation of reactive O2 intermediates, which was abrogated by N-acetylcysteine but not by benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone. Moreover, taurolidine also induced suppression of VEGF production on the protein and messenger RNA level, as shown by an enzyme-linked immunosorbent assay and by reverse transcription—polymerase chain reaction. Conclusions. Given all these findings, taurolidine may be a promising new agent in the treatment of malignant gliomas; it displays a combination of antineoplastic and antiangiogenic activities, inducing tumor cell apoptosis and inhibiting tumor-derived VEGF production.

Immunobiology of primary intracranial tumors

1983 ◽  
Vol 59 (2) ◽  
pp. 208-216 ◽  
Author(s):  
M. Stephen Mahaley ◽  
G. Yancey Gillespie ◽  
Ritchie P. Gillespie ◽  
Pamela J. Watkins ◽  
Darell D. Bigner ◽  
...  
Keyword(s):  
Tissue Culture ◽  
Cell Line ◽  
Glioma Cell ◽  
Malignant Gliomas ◽  
Osteogenic Sarcoma ◽  
Culture Cell ◽  
Glioma Cell Line ◽  
Tissue Culture Cell ◽  
Serological Studies ◽  
Line Following

✓ Serial serological studies were carried out on 19 of 20 patients with malignant gliomas who were actively immunized with one of two human glioma tissue culture cell lines (D-54MG or U-251MG). Most patients mounted a significant serum reaction to histocompatibility antigens (HLA's), as well as an antibody response to fetal bovine serum (FBS) which was added to the glioma-cell inoculum. These two sources of antibody accounted for greater than 90% of the antibody induced by these inoculations. Two patients continued to have significant amounts of binding antibody to the original immunizing cell line following exhaustive absorptions of FBS and HLA antibodies. One of these two had all remaining significant antibody removed by further absorption of the serum against the 2-T osteogenic sarcoma tissue culture cell line known to possess antigens cross-reactive with human gliomas. One single patient continued to show significant antibody binding to the original glioma cell line following absorption against FBS, human platelets, and the 2-T cell line, and therefore seems to have produced glioma-distinctive antibodies in response to immunization. The antibody preparation from this patient was also cytotoxic against the original glioma cell line, as well as another recently cultured human glioblastoma cell line. The significance of these serological studies is discussed as it relates to immunological responses patients with gliomas may make to active immunization.

Resistance to growth inhibition by transforming growth factor—β in malignant glioma cells with functional receptors

1998 ◽  
Vol 88 (3) ◽  
pp. 529-534 ◽  
Author(s):  
Shiro Isoe ◽  
Hirofumi Naganuma ◽  
Shin Nakano ◽  
Atsushi Sasaki ◽  
Eiji Satoh ◽  
...  
Keyword(s):  
Growth Inhibition ◽  
Malignant Glioma ◽  
Cell Lines ◽  
Glioma Cell ◽  
Glioma Cells ◽  
Content Type ◽  
Glioma Cell Lines ◽  
Malignant Glioma Cells ◽  
Tgf Β1 ◽  
Fine Print

Object. The aim of this study was to investigate the mechanism by which malignant glioma cells escape from growth inhibition mediated by transforming growth factor-β (TGF-β), a ubiquitous cytokine that inhibits cell proliferation by causing growth arrest in the G1 phase of the cell cycle. Methods. The authors measured the response of eight malignant glioma cell lines to the growth-inhibiting activity of TGF-β in vitro and the expression of TGF-β Types I and II receptors in malignant glioma cells. The effect of TGF-β on the expression of a p27Kip1 cyclin-dependent kinase inhibitor was also investigated to assess the downstream signal transmission from TGF-β receptors. All malignant glioma cell lines were insensitive to growth inhibition by TGF-β1 and TGF-β2. Analyses of TGF-β receptors by means of affinity labeling in which 125I-TGF-β1 was used showed that six glioma lines had both TGF-β Types I and II receptors on their cell surfaces, whereas two lines had very small amounts of TGF-β Type I and/or Type II receptors. Northern blot analysis showed that all tumor lines expressed variable levels of messenger RNAs for both TGF-β Types I and II receptors. Flow cytometric analyses revealed that treatment of malignant glioma cells with TGF-β1 significantly downregulated the expression of p27Kip1 protein in all malignant glioma cell lines except one. Conclusions. The authors suggest that most malignant glioma cells express TGF-β Types I and II receptors, which can transmit some signals downstream and that the loss of response to TGF-β growth inhibition may not be caused by an abnormality of the TGF-β receptors.

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