Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0017638 (glioma)
 30,880 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The p16 (MTS1/CDKN2) gene localized at the 9p21 chromosomal region encodes for a cell cycle inhibitor protein and is altered in many human cancers. The frequency of p16 alterations in gliomas exceeds 50%. To restore the missing wild-type p16 gene efficiently in glioma cells an adenovirus vector carrying the full length coding sequence of the wild-type p16 cDNA, Ad5RSV-p16, was constructed. Three human glioma cell lines, U251 MG, U-87 MG and D54 MG, that did not express endogenous p16/CDKN2 gene and were easily infected with adenovirus vectors were selected for these experiments. Introduction of the Ad5RSV-p16 in these malignant glioma cell lines directed the biosynthesis of functional p16 protein in the majority of the exposed cells, significantly inhibited cell growth, influenced cell morphology and modified the transformed phenotype of cells including the ability to form colonies in soft agar. Flow cytometric studies revealed that the majority of the Ad5RSV-p16 infected glioma cells were arrested in the G0-G1 phases of the cell cycle. These results suggest that p16/CDKN2 inactivation is a significant factor in the genesis and progression of gliomas and that the restoration of the wild-type p16 protein could have clinical and therapeutic utility.
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PMID:Adenovirus-mediated p16/CDKN2 gene transfer induces growth arrest and modifies the transformed phenotype of glioma cells. 855 79

Structural alterations in the p16INK4 gene were examined in early passage human glioma cell lines and related to the expression of p16 transcripts and protein. Using the Southern blot approach, we observed both homozygous and hemizygous deletions, as well as rearrangements of the p16 and p15 genes in 5 of the 7 cell lines (71%). Two cell lines, MGR3 and HBT28, revealed hemizygous deletion of the p16 and p15 genes combined with indistinguishable rearrangements of the remaining p15-p16 locus that resulted in loss of exon 2 sequences for p15 and p16, but retention of p16 exon 1; neither of these cell lines expressed p16 mRNA. Data for a third cell line, MGR2, indicated a similar, but unique rearrangement involving the p15 and p16 genes. MGR2, which retained a single wild-type p15-p16 locus, showed expression of p16 transcript, but not of p16 protein as indicated by Western blot analysis. All the glioma cell lines expressed similar levels of the retinoblastoma protein and no amplification of the cyclin-dependent kinase 4 gene. These results demonstrate that human glioma cells contain p16 gene microdeletions and rearrangements that contribute to inactivation of the cell cycle regulatory protein.
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PMID:Deletions and rearrangements inactivate the p16INK4 gene in human glioma cells. 864 64

Malignant gliomas extensively infiltrate the surrounding normal brain, and their diffuse invasion is one of the most important barriers to successful therapy. Recent studies indicate that the progression of gliomas from low-grade to high-grade may depend on the acquisition of a new phenotype and the subsequent addition of genetic defects. One of the most frequent abnormalities in the progression of gliomas is the inactivation of tumor-suppressor gene p16, suggesting that loss of p16 is associated with acquisition of malignant characteristics. Consistent with this hypothesis, our previous studies showed that restoring wild-type p16 activity into p16-null malignant glioma cells modified their phenotype. In order to understand whether the biological consequences of p16 inactivation in high-grade gliomas included facilitating invasiveness, we used a recombinant replication-deficient adenovirus carrying the cDNA of the p16/CDKN2 gene to infect and express high levels of p16 protein in p16-null SNB19 glioma cells. Invasion of SNB19 glioma cells was tested into two models: invasion of glioma cells through Matrigel-coated transwell inserts and invasion of tumor-cell spheroids into fetal rat-brain aggregates in a co-culture system. Matrigel invasion assays showed that the SNB19 cells expressing exogenous p16 exhibited significantly reduced invasion. Similarly, invasion of p16-treated SNB19 cells into fetal rat-brain aggregates was reduced during a 72 h time period compared to invasion of the adenovirus-control and mock-infected cells. Expression of matrix metalloproteinase-2 (MMP-2), an enzyme involved in tumor-cell invasion, in SNB19 cells expressing p16 was significantly reduced compared to that of parental SNB19 and vector-infected cells. Our results show that restoring wild-type p16 activity into p16-null SNB19 glioma cells significantly inhibits tumor-cell invasion, thus suggesting a novel function of the p16 gene.
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PMID:Adenovirus-mediated p16/CDKN2 gene transfer suppresses glioma invasion in vitro. 936 22

Malignant gliomas are highly resistant to chemotherapy, in part because of the blood-brain barrier, which restricts the delivery of chemotherapy to certain areas of tumor and their cellular heterogeneity, which leads to the selection and propagation of resistant clones. However, the molecular basis of the drug resistance is poorly understood. In this study, we examined the effect of the cell cycle-inhibitory protein p16 on the chemosensitivity of human glioma cells. Treatment of the p16-null glioma cells, U-251 MG and D-54 MG, with paclitaxel and topotecan, resulted in cell death within 4 days. However, overexpression of exogenous wild-type p16 protein using an adenovirus vector resulted in G1 arrest of glioma cells and resistance to the anticancer effect of paclitaxel or topotecan. Specifically, the p16-expressing cells showed a 30-fold increase in the ID50 of topotecan and a more than 40-fold increase in the ID50 of paclitaxel. These observations indicate that overexpression of molecules that control cell-cycle progression may be partially responsible for causing the resistance of glioma cells to cytocidal drugs.
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PMID:Adenovirus-mediated p16 transfer to glioma cells induces G1 arrest and protects from paclitaxel and topotecan: implications for therapy. 947 9

Less than 30% of malignant gliomas respond to adjuvant chemotherapy. Here, we asked whether alterations in the p53 and RB pathways and the expression of six BCL-2 family proteins predicted acute cytotoxicity and clonogenic cell death induced by BCNU, vincristine, cytarabine, teniposide, doxorubicin, camptothecin or beta-lapachone in 12 human malignant glioma cell lines. Neither wild-type p53 status, nor p53 protein accumulation, nor p21 or MDM-2 levels, nor differential expression of BCL-2 family proteins predicted drug sensitivity, except for an association of BAX with higher beta-lapachone sensitivity in acute cytotoxicity assays. p16 protein expression was associated with high doubling time and chemoresistance. We conclude that some important molecular changes, which are involved in the development of gliomas and attributed a role in regulating vulnerability to apoptosis, may not determine the response to chemotherapy in these tumors.
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PMID:Predicting chemoresistance in human malignant glioma cells: the role of molecular genetic analyses. 984 75

Interaction between the extracellular matrix and integrin receptors on cell surfaces leads not only to cell adhesion but also to intracellular signaling events that affect cell migration, proliferation, and survival. The vitronectin receptor alpha(v)beta(3) integrin is of key importance in glioma cell biology. The expression of urokinase-type plasminogen activator receptor (uPAR) was recently shown to co-regulate with the expression of alpha(v)beta(3) integrin. Moreover, restoration of the p16 protein in glioma cells inhibits the alpha(v)beta(3) integrin-mediated spreading of those cells on vitronectin. Thus we hypothesized that adenovirus-mediated down-regulation of uPAR and overexpression of p16 might down-regulate the expression of alpha(v)beta(3) integrin and the integrin-mediated signaling in glioma cells, thereby defeating the malignant phenotype. In this study, we used replication-deficient adenovirus vectors that contain either a uPAR antisense expression cassette (Ad-uPAR) or wild-type p16 cDNA (Ad-p16) and a bicistronic adenovirus construct in which both the uPAR antisense and p16 sense expression cassettes (Ad-uPAR/p16) are inserted in the E1-deleted region of the vector. Infecting the malignant glioma cell line SNB19 with Ad-uPAR, Ad-p16, or Ad-uPAR/p16 in the presence of vitronectin resulted in decreased alpha(v)beta(3) integrin expression and integrin-mediated biological effects, including adhesion, migration, proliferation, and survival Our results support the therapeutic potential of simultaneously targeting uPAR and p16 in the treatment of gliomas.
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PMID:Down-regulation of integrin alpha(v)beta(3) expression and integrin-mediated signaling in glioma cells by adenovirus-mediated transfer of antisense urokinase-type plasminogen activator receptor (uPAR) and sense p16 genes. 3291 27

The tumor suppressor p16/CDKN2A/INK4a gene is frequently mutated, mostly by homozygous deletions in high-grade gliomas. Although the p16 protein suppresses cell proliferation primarily through inhibition of cell-cycle progression at the G1 phase, other phenotypic changes in glioma cells associated with p16INK4a alterations have not been fully described. To determine the roles of p16 alterations in glioma formation, we have established ecdysone-driven inducible p16 expression in the human glioblastoma cell line CL-4, which were derived from p16-null U87MG cells. Here we show that exogenous p16 expression in CL-4 cells results in morphological changes, with large and flattened cytoplasm, which are associated with increased formation of cytoplasmic actin-stress fibers and vinculin accumulation in the focal adhesion contacts. Adhesion of CL-4 cells to extracellular matrix proteins, such as laminin, fibronectin, and type IV collagen, significantly increased upon exogenous p16 expression, which correlated with increased expression of integrin alpha5 and alphav. Expression of a small GTP-binding protein, Rac, also decreased. Following epidermal growth factor stimulation, phosphorylation of MAP kinases ERK1 and 2 and induction of an early immediate gene product, c-Fos, were significantly reduced in CL-4 cells with p16 expression. These results suggest that the tumor suppressor p16 may exert its antitumor effects through modulation of multiple aspects of glioblastoma phenotypes, including proliferation, invasiveness, and responsiveness to extracellular growth stimuli.
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PMID:Phenotypic changes associated with exogenous expression of p16INK4a in human glioma cells. 1190 77

The p16 and p53 tumor suppressor proteins, which are frequently altered in malignant gliomas, have been noted as regulators of telomerase activity. However, the link between telomerase regulation and these suppressor proteins has not been adequately clarified. In the present study, we demonstrated that p16, as well as p53, suppress telomerase activity through transcriptional regulation of human telomerase reverse transcriptase (hTERT) in malignant glioma. To examine the effect of p16 and p53 on telomerase activity, we utilized wild-type p16 or p53 expression plasmid and three human glioma cell lines differing in their p53 and p16 status. Restoring p16 significantly reduced the level of telomerase activity of glioma cells. Furthermore, cotransfection of the p16 gene with 5'-deletion constructs of the hTERT promoter carrying Sp1 binding sites, repressed the transcriptional activity of hTERT promoter in p16-deleted cells. In addition, electrophoretic mobility shift assay revealed that p16 expression inhibited the binding of Sp1 to the consensus Sp1 responsive element, indicating that the recruitment of Sp1 to the hTERT proximal core promoter is inhibited by p16 protein. These results were similar to those from a p53 transfection study in p53-mutated cells. These findings implicate p16 in the transcriptional regulation of telomerase activity by inhibiting the function of Sp1 in human malignant gliomas.
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PMID:Introduction of p16INK4a inhibits telomerase activity through transcriptional suppression of human telomerase reverse transcriptase expression in human gliomas. 1506 44

To investigate the effect of P53 protein accumulation and p53 gene mutation in the pathogenesis of glioma and to study the role of MDM2, P53 and P16 protein in glioma formation and progression and their relationship with each other, LSAB immunohistochemical staining method and non-isotopic PCR-SSCP techniques were used to detect the expression of MDM2, P53 and P16 protein and p53 gene mutation in 48 cases of gliomas. The results showed that the positive expression rate of MDM2, P53 and the negative rate of P16 was 22.9%, 41.7% and 60.4%, respectively. The latter two in high grade (grade III, IV) gliomas had a significantly higher rate than in the low grade (grade II) gliomas. Moreover, the co-expression of MDM2 and P53 protein was confirmed in only 1 of 48 cases. No significant difference was found in the rate of the expression of MDM2 between high grade and low grade gliomas (P > 0.1). PCR-SSCP results showed that mutation of 5-8 exons of p53 gene was detected in 17 out of 48 cases (35.42%). Mutation was detected in 16 of 20 cases of positive p53 expression, and another one was detected in 28 cases of negative expression cases. The correlation between p53 mutation and p53 immunopositivity was observed in 89.6% of the cases. P53 gene mutation and the level of MDM2, P53 and P16 protein were not related to age, gender of the patients, tumor location and size. It is concluded that the mutation of p53 and deletion of p16 might play important roles in the tumorigenesis of gliomas and it was significantly associated with the grade of tumor differentiation. P53 protein accumulation can indirectly reflect p53 mutation. MDM2 amplification and overexpression might be an early event in the growth of human gliomas.
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PMID:P53 gene mutation and expression of MDM2, P53, P16 protein and their relationship in human glioma. 1669 7

Swainsonine, an extract from Astragalus membranaceus, is known for its anti-cancer effects and could prevent metastases. In order to investigate the effects and mechanisms of swainsonine in C6 glioma cells, we carry out correlated experiments in vitro and in vivo. After treatment with swainsonine, the effective dose and IC(50) value of swainsonine in the C6 glioma cell were examined using the MTT assay. Cell cycle distribution and apoptotic rates were analyzed using FCM and [Ca(2+)](i) was measured by LSCM. Expressions of p16 and p53 protein were evaluated by immunocytochemical methods. Simultaneously, glioma-bearing rats were administered swainsonine at doses of 2, 4 and 8 mg/kg body wt. The inhibition rate was calculated and pathological sections were observed. The results indicated that the growth of C6 glioma cells is inhibited by swainsonine in vitro, with an IC(50) value within 24h of 0.05 microg/ml. Increases in swainsonine correlate with S phase percentages of 11.3%, 11.6% and 12.4%, respectively. Moreover, the expression of apoptosis inhibiting p53 and p16 protein decreases gradually. Tumor weight in vivo decreased clearly and HE dyeing of tumor tissue showed gray, its texture was soft, with necrosis and hemorrhagic concentrated inward. Swainsonine could inhibit the proliferation of C6 glioma cells in vitro and the growth of C6 glioma in vivo. The mechanisms of swainsonine-induced apoptosis may relate with the expression of apoptosis-related genes and overloading-[Ca(2+)](i)-induced endoplasmic reticulum stress.
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PMID:Suppressive effects of swainsonine on C6 glioma cell in vitro and in vivo. 1942 71


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