Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P10415 (Bcl-2)
 33,771 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have cloned cDNA encoding hamster Bcl-2 protein from total RNA of CHO-9 cells by RT-PCR using oligonucleotide primers sharing homology with the sequence of mouse and rat bcl-2. The fragments spanning the total coding region were cloned into pCR4-TOPO and sequenced for verification. The hamster bcl-2 cDNA has a size of 711 nucleotides and encodes a polypeptide of 236 amino acids. Hamster Bcl-2 shares 95.8 and 88.6% similarity with mouse and human Bcl-2, respectively. Northern blot analysis revealed a single 7.5 kb bcl-2 transcript in hamster (CHO-9), mouse (BK4), and rat (H5) cells and a 8.5 kb bcl-2 mRNA in human (HeLa MR) cells. The bcl-2 cDNA (771 bp) was recloned into pcDNA3 and the recombinant construct was transiently transfected into MGMT-deficient HeLa MR cells. Expression of hamster Bcl-2 rendered the cells more resistant to MNNG-induced cytotoxicity, which is consistent with the anti-apoptotic function of Bcl-2.
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PMID:Cloning and functional analysis of cDNA encoding the hamster Bcl-2 protein. 1097 19

In the therapy of various kinds of tumors, methylating agents generating O6-methylguanine (O6MeG) in DNA are used. We studied the molecular mechanism of cell death induced by these agents by comparing isogenic cell lines proficient (MGMT+) and deficient (MGMT-) for the DNA repair protein alkyltransferase and exhibiting the tolerance phenotype. Hypersensitivity to methylation-induced cell killing of MGMT- cells is attributable to the potent induction of apoptosis. We show that apoptosis is a late event occurring >48 h after methylation. It was preceded by decrease in Bcl-2 protein level and accompanied by activation of caspase-9 and caspase-3. We also observed cytochrome c release and hypophosphorylation of Bad. Other members of the Bcl-2 family (Bag-1, Bak, Bax, and Bcl-xL) were not altered in expression. Transfection of MGMT- cells with bcl-2 protected against methylation-induced apoptosis, indicating that Bcl-2 plays a key role in the response. Induction of apoptosis in MGMT- cells was not triggered by Fas and Fas ligand (CD95, Apo-1) because both proteins remained unaltered in expression and receptor-proximal caspase-8 was not activated after methylation. Also, inhibition of caspase-8 was ineffective in modifying the apoptotic response, whereas inhibition of caspase-3 and caspase-9 blocked apoptosis. Tolerant cells that are unable to repair O6MeG and are impaired in mismatch repair were less sensitive regarding the induction of apoptosis and Bcl-2 decline, supporting the view that O6MeG-induced apoptosis requires mismatch repair. The ultimate O6MeG-derived lesions triggering the apoptotic pathway are likely to be DNA double-strand breaks, which were significantly formed in MGMT- but not in MGMT+ and tolerant cells and which preceded apoptosis. Overall, the data indicate that O6MeG induces apoptosis via secondary lesions that trigger Bcl-2 decline, cytochrome c release, and caspase-9 and caspase-3 activation independently of Fas/Fas ligand and p53, for which the cells are mutated.
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PMID:Apoptosis induced by DNA damage O6-methylguanine is Bcl-2 and caspase-9/3 regulated and Fas/caspase-8 independent. 1105 78

Early detection of lung cancer requires none or few invasive techniques. Distal lung cancer (40% of the cases in most European countries) can be sensitively detected by spiral computed tomography. Theoretically, in 60% of cases, the proximal lesions (main to segmental bronchi, accessible by bronchoscopy) should be able to be detected by sputum cytology. Unfortunately, this very specific technique has a low sensitivity and is time consuming. Fluorescent bronchoscopy increases the detection rate of early or micro-invasive lesions and may be proposed in highly selected populations, but not as a screening test. Biomarkers in blood and sputum have not yet been clinically validated. However, the amount of data generated from studies first on resected tumours, then on early bronchial lesions and more recently on blood and sputum offer a wide field for investigation. Lung carcinogenesis is a multistep process characterised by the accumulation of successive molecular genetic and epigenetic abnormalities, resulting in selection of clonal cells with uncontrolled growth capacities throughout the whole respiratory tract (field cancerisation). Molecular lesions far precede morphological transformation of preneoplastic bronchial lesions (dysplasia) or alveolar lesions (atypical alveolar hyperplasia). Genetic and epigenetic abnormalities in the genes involved in cell cycle, senescence, apoptosis, repair, differentiation and cell migration control may be detected on bronchial biopsies, on respiratory cells from the sputum and even in the circulating deoxyribonucleic acid (DNA). The key genes involved include those in the P53-retinoblastoma (Rb) pathways. The balance between cyclin-dependent kinases and their inhibitors regulates the level of Rb phosphorylation and its function at G1-S transition; P53 plays at least two functions (cell cycle and apoptosis control). The balance of bax-bcl2 is important in the control of apoptosis as well as loss of fragile histidine triad expression. O(6)-methylguanine-DNA methyltransferase seems to be important in DNA repair control, the RARbeta receptor in differentiation, and cadherin H and E and different metalloproteases genes in cell migration. The demonstration of hyperexpression or silencing of these genes needs different validated techniques: immunohistochemistry on biopsies or cytological preparations, molecular biology techniques for mutations, loss of heterozygosity and aberrant methylation abnormalities. Automation and miniaturisation of these techniques will allow early detection and may be widely applied once clinically validated.
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PMID:Early detection of lung cancer: role of biomarkers. 1257

Various tumor-therapeutic drugs and environmental carcinogens alkylate DNA inducing O(6)-methylguanine (O(6)MeG) that provokes cell death by apoptosis. In rodent fibroblasts, apoptosis triggered by O(6)MeG is executed via the mitochondrial damage pathway. Conversion of O(6)MeG into critical downstream lesions requires mismatch repair (MMR). This is thought to signal apoptosis upon binding to O(6)MeG lesions mispaired with thymine. Alternatively, O(6)MeG lesions might be processed by MMR giving rise to DNA double-strand breaks (DSBs) during replication that finally provoke apoptosis. To test this, we examined apoptosis triggered by O(6)MeG in human peripheral lymphocytes in which O(6)-methylguanine-DNA methyltransferase (MGMT) had been inactivated by O(6)-benzylguanine (O(6)BG) and which were not proliferating or proliferating upon CD3/CD28 stimulation. Treatment with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or the anticancer drug temozolomide induced apoptosis only in proliferating, but not resting cells. With exceptional high alkylation doses (>/=15 microM of MNNG), apoptosis was also observed in resting lymphocytes, albeit at a lower level than in proliferating cells. This response was not affected by O(6)BG, suggesting that replication-independent apoptosis at high dose levels is caused by lesions other than O(6)MeG. O(6)MeG-triggered apoptosis in proliferating lymphocytes was preceded by a wave of DSBs, which coincided with p53 and Fas receptor upregulation, while Fas ligand, Bax and Bcl-2 expression was not altered. Treatment with anti-Fas neutralizing antibody attenuated MNNG-induced apoptosis in MGMT-depleted proliferating lymphocytes. The data suggest that O(6)MeG is converted by MMR and DNA replication into DSBs that trigger apoptosis by p53 stabilization and Fas/CD95/Apo-1 upregulation. This is supported by the finding that ionizing radiation, inducing DSBs on its own, provokes apoptosis in lymphocytes in a replication-independent way. The strict proliferation dependence of apoptosis triggered by O(6)MeG may explain the specific killing response of MGMT-deficient proliferating cells, including tumors, to O(6)MeG generating anticancer drugs and suggests that tumor proliferation rate, Fas responsiveness, MGMT and MMR status are important prognosis parameters.
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PMID:Apoptosis triggered by DNA damage O6-methylguanine in human lymphocytes requires DNA replication and is mediated by p53 and Fas/CD95/Apo-1. 1472 64

Temozolomide is an alkylating agent that mediates its cytotoxic effects via O(6)-methylguanine (O(6)-meG) adducts in DNA. O(6)-alkylguanine-DNA-alkyltransferase (MGMT) can repair such adducts and therefore constitutes a major resistance mechanism to the drug. MGMT activity can be attenuated in vitro and in vivo by the pseudosubstrate O(6)-(4-bromothenyl)guanine (PaTrin-2, Patrin, Lomeguatrib), which in clinical trials is in combination with temozolomide. Resistance to cytotoxic agents can also be mediated by the Bcl-2 protein, which inhibits apoptosis and is frequently up-regulated in tumor cells. Attenuation of Bcl-2 expression can be affected by treatment of cells with the antisense oligonucleotide, oblimersen sodium (Genasense), currently in phase III clinical trials in combination with the methylating agent dacarbazine. Using a human ovarian cancer cell line (A2780) that expresses both Bcl-2 and MGMT, we show that cells treated with active dose levels of either oblimersen (but not control reverse sequence or mismatch oligonucleotides) or PaTrin-2 are substantially sensitized to temozolomide. Furthermore, the exposure of oblimersen-pretreated cells to PaTrin-2 leads to an even greater sensitization of these cells to temozolomide. Thus, growth of cells treated only with temozolomide (5 microg/mL) was 91% of control growth, whereas additional exposure to PaTrin-2 alone (10 micromol/L) or oblimersen alone (33 nmol/L) reduced this to 81% and 66%, respectively, and the combination of PaTrin-2 (10 micromol/L) and oblimersen (33 nmol/L) reduced growth to 25% of control. These results suggest that targeting both Bcl-2 with oblimersen and MGMT with PaTrin-2 would markedly enhance the antitumor activity of temozolomide and merits testing in clinical trials.
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PMID:Sensitization of a human ovarian cancer cell line to temozolomide by simultaneous attenuation of the Bcl-2 antiapoptotic protein and DNA repair by O6-alkylguanine-DNA alkyltransferase. 1548 88

Methylating drugs such as temozolomide (TMZ) are widely used in the treatment of brain tumours (malignant gliomas). The mechanism of TMZ-induced glioma cell death is unknown. Here, we show that malignant glioma cells undergo apoptosis following treatment with the methylating agents N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and TMZ. Cell death determined by colony formation and apoptosis following methylation is greatly stimulated by p53. Transfection experiments with O(6)-methylguanine-DNA methyltransferase (MGMT) and depletion of MGMT by O(6)-benzylguanine showed that, in gliomas, the apoptotic signal originates from O(6)-methylguanine (O(6)MeG) and that repair of O(6)MeG by MGMT prevents apoptosis. We further demonstrate that O(6)MeG-triggered apoptosis requires Fas/CD95/Apo-1 receptor activation in p53 non-mutated glioma cells, whereas in p53 mutated gliomas the same DNA lesion triggers the mitochondrial apoptotic pathway. This occurs less effectively via Bcl-2 degradation and caspase-9, -2, -7 and -3 activation. O(6)MeG-triggered apoptosis in gliomas is a late response (occurring >120 h after treatment) that requires extensive cell proliferation. Stimulation of cell cycle progression by the Pasteurella multocida toxin promoted apoptosis whereas serum starvation attenuated it. O(6)MeG-induced apoptosis in glioma cells was preceded by the formation of DNA double-strand breaks (DSBs), as measured by gammaH2AX formation. Glioma cells mutated in DNA-PK(cs), which is involved in non-homologous end-joining, were more sensitive to TMZ-induced apoptosis, supporting the involvement of DSBs as a downstream apoptosis triggering lesion. Overall, the data demonstrate that cell death induced by TMZ in gliomas is due to apoptosis and that determinants of sensitivity of gliomas to TMZ are MGMT, p53, proliferation rate and DSB repair.
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PMID:Apoptosis in malignant glioma cells triggered by the temozolomide-induced DNA lesion O6-methylguanine. 1681 6

Drug selection, the key for chemotherapy, is one of the most difficult decision-making in clinic for the treatment of malignant tumors. How to choose is undetermined. Here a new strategy--predictive molecule-targeted chemotherapy (PMTC)--is put forward to choose relatively sensitive chemotherapeutic drugs and to avoid relatively resistant traditional drugs according to the expression of predictive molecules in individual tumor tissue. For example, paclitaxel is regarded as a relatively sensitive drug and may be chosen for the tumors with high expression of p53, while it is predicted as relatively resistant drug and should be avoided for the tumors with high expression of P-glycoprotein (P-gp). Here, we reviewed the predictive values of a variety of molecules, such as p53, P-gp, topoisomerase-1, topoisomerase-2, MSI, BRCA-1, ERCC1, FANC, hMHL1/2, XPD, Bcl-2, ErbB-2, MGMT, dihydropyridine dehydrogenase (DPD), thymidylate synthetase (TS), deoxycytidine kinase (dCK), Ras, Bax, Cyclin A, tubulin proteins, and so on, for the efficacy of some traditional chemotherapeutic drugs, such as platinum, oxaliplatin, cyclophosphamide, ifosfamide, dacarbazine, methotrexate, 5-flurouracil, gemcitabine, vincristine, vinorelbine, paclitaxel, etoposide, irinotecan, topotecan, and so on.
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PMID:[Routine chemotherapeutic drug treatment effectiveness predictive molecules and chemotherapeutic drug selection]. 1716 91

1,3,8-Trihydroxy-6-methylanthaquinone (emodin) is recognized as an antiproliferative compound. In the present study, however, we show that emodin has both toxic and survival effects in glioma cells and that the survival effects involve Mdr1a. Emodin inhibited the proliferation and induced apoptosis of C6 cells in a 12-h treatment, but C6 cells survived a 72-h drug treatment, indicating resistance to emodin. Emodin-induced apoptosis was reduced by inhibition of the expression and activation of apoptosis-associated proteins including p53, Bax, Bcl-2, Fas, and caspase-3. C6 cells could express antioxidant proteins (superoxide dismutase and catalase) to decrease reactive oxygen species-induced cytotoxicity of emodin and overexpress multidrug resistance genes (Mdr1a, MRP2, MRP3, and MRP6) to decrease the intracellular accumulation of emodin. Electrophoretic mobility shift analysis showed that emodin decreased nuclear factor kappaB (NF-kappaB) expression in 24 h of treatment, but in 48 h, emodin increased NF-kappaB activity. A confocal microscope showed that emodin induced NF-kappaB translocation from cytoplasm to nuclei. C6 cells would activate the mitogen-activated protein kinase survival pathway and express the DNA repair gene (MGMT) and associated proteins (PARP and XRCC1) to recover the cell activity. C6 cells also expressed GRP78 to decrease emodin-induced endoplasmic reticulum (ER) stress that would cause apoptosis in C6 cells, and GRP78 inhibited the expression of GADD153 to enhance the expression of Bcl-2 that could balance the ER- and mitochondria-induced apoptosis of C6 cells.
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PMID:Emodin has cytotoxic and protective effects in rat C6 glioma cells: roles of Mdr1a and nuclear factor kappaB in cell survival. 1954 30

Although chemotherapy plays an important role in combined treatment of human gliomas, it fails to bring about satisfactory outcomes in a number of patients. One of the major obstacles in this treatment is the development of multidrug resistance (MDR) during treatment. Regulation of MDR in the context of gliomas is poorly understood, and clinical efforts to inhibit it have not been fruitful. Activation of the Hedgehog (HH) pathway has been shown to contribute to the growth, maintenance and relapse of various cancers. As data were not available on the role of Gli1 expression in glioma progression, we analyzed the correlation between Gli1 expression and tumor recurrence after chemotherapy in 60 glioma samples. The effects of inhibiting or activating the HH pathway on sensitizing or rendering glioma cell lines resistant to VCR, VP16, CDDP and ACNU, which are widely used in clinical chemotherapy, were determined. Additionally, the impact of the HH pathway on the expressions of MDR1, MRP1, MVP, MGMT, Bcl-2 and Survivin genes was determined. Our results indicate that overexpression of Gli1 is correlated with glioma recurrence after chemotherapy. We further show that the HH pathway activity can promote clonogenic survival of glioma cell lines in chemotherapy. Additionally, we found that blocking the HH pathway enhanced cytotoxicity of chemotherapeutic agents in glioma cells, through down-regulating the expressions of MDR1, MRP1, MVP, MGMT, Bcl-2 and Survivin genes. Taken together, these results suggest that Gli1 plays a dominant role in chemoresistance of glioma cells, and that suppression of Gli1 expression might be a valid therapeutic option for overcoming MDR and for increasing the success of chemotherapy.
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PMID:Gli1 is a potential target for alleviating multidrug resistance of gliomas. 1981 66

Antiapoptotic Bcl-2 family members suppress both apoptosis and autophagy and are of major importance for therapy resistance of malignant gliomas. To target these molecules, we used BH3 mimetics and analyzed the molecular mechanisms of cell death induced thereby. Glioma cells displayed only limited sensitivity to single-agent treatment with the BH3 mimetics HA14-1, BH3I-2', and ABT-737, whereas the pan-Bcl-2 inhibitor (-)-gossypol efficiently induced cell death. Furthermore, (-)-gossypol potentiated cell death induced by temozolomide (TMZ) in MGMT (O(6)-methylguanine-DNA methyltransferase)-negative U343 cells and, to a lesser extent, in MGMT-expressing U87 cells. (-)-Gossypol triggered translocation of light chain 3 to autophagosomes and lysosomes and cytochrome c release, but cell death occurred in the absence of lysosomal damage and effector caspase activation. Lentiviral knockdown of Beclin1 and Atg5 in U87, U343, and MZ-54 cells strongly diminished the extent of cell death induced by (-)-gossypol and combined treatment with TMZ, indicating that autophagy contributed to this type of cell death. In contrast, stable knockdown of the endogenous autophagy inhibitor mammalian target of rapamycin increased autophagic cell death. Our data suggest that pan-Bcl-2 inhibitors are promising drugs that induce caspase-independent, autophagic cell death in apoptosis-resistant malignant glioma cells and augment the action of TMZ. Furthermore, they indicate that efficient killing of glioma cells requires neutralization of Mcl-1.
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PMID:The pan-Bcl-2 inhibitor (-)-gossypol triggers autophagic cell death in malignant glioma. 2058 33


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