Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Epigenetic alterations of DNA methylation play an important role in the regulation of gene expression associated with chemosensitivity of gastric carcinomas. With the aim of improving the chemotherapeutic efficacy of gastric carcinoma, the effect of DNA methyltransferase inhibitor, 5-aza-CdR, on the chemosensitivity of five anticancer drugs was investigated. Human gastric cancer cell lines, OCUM-2M and MKN-74, and five anticancer drugs, 5-FU, PTX, OXA, SN38, and GEM, were used. In both gastric cancer cell lines, a synergistic antiproliferative effect by a combination of 5-aza-CdR at 5 microM was found in SN38 and GEM. 5-Aza-CdR at 5 microM increased apoptosis induced by SN38 and GEM in both cell lines. 5-Aza-CdR increases the expression of DAPK-2 and DAPK-3, RASSF1, and THBS1 genes in both OCUM-2M and MKN-74 cells, but not that of hMLH1, p16, MGMT, E-cadherin, and p53 genes. These findings suggest that 5-aza-CdR is a promising chemotherapeutical agent for gastric carcinomas, in combination with the anticancer drugs SN38 and GEM, in apoptosis signaling. The upregulation of DAPK-2 and DAPK-3, RASSF1, and THBS1 genes by 5-aza-CdR might be associated with the synergistic effect.
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PMID:Synergic antiproliferative effect of DNA methyltransferase inhibitor in combination with anticancer drugs in gastric carcinoma. 1680 21

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

Epigenetic mechanisms in carcinogenesis may have a significant role in the development of colorectal cancer. To investigate this phenomenon in early-stage disease, promoter methylation status in the tumour suppressor genes APC, MGMT, hMLH1, P14/P14ARF, and CDKN2A/P16 was investigated in 78 colorectal adenomas. These had previously been characterized for mutations of APC, KRAS, and TP53 genes and for chromosomal abnormality by comparative genomic hybridization (CGH). APC hypermethylation was seen in 52 tumours (66.7%). APC showed either methylation or mutation in 66 lesions (84.6%), but these events were not statistically associated. MGMT methylation was detected in 39 cases (50%). Adenomas with this abnormality showed a significantly lower number of chromosomal changes by CGH (p < 0.02), confirming that DNA repair defect of this type is associated with a lower level of chromosomal instability. An hMLH1 methylation defect was seen in only one adenoma (1.3%), from a patient who had a synchronous cancer showing the same defect. Methylation of P14 (P14ARF) was seen in 31 adenomas (39.7%) and CDKN2A (P16) abnormality in 25 (32.1%). DNA methylation at two or more loci was seen in 46 tumours (59%), while 11 lesions (14.1%) showed no evidence of hypermethylation at any of the loci studied. Methylation at any or all of MGMT, P14 or P16 was significantly associated with APC methylation (p = 0.01). Those neoplasms with more than two methylated genes showed significantly fewer chromosomal abnormalities than adenomas with one or no methylated loci (p < 0.001). There was no association between specific individual chromosomal abnormalities, APC, KRAS or TP53 mutations and any pattern of methylation abnormality. We conclude that methylation abnormality is very common in pre-invasive colorectal neoplasia, and that high level methylation is associated with low level chromosomal instability.
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PMID:Relationship between point gene mutation, chromosomal abnormality, and tumour suppressor gene methylation status in colorectal adenomas. 1690 13

Methionine deprivation stress (MDS) eliminates mitotic activity in melanoma cells regardless of stage, grade, or TP53 status, whereas it has a negligible effect on normal skin fibroblasts. In most cases, apoptosis accounts for the elimination of up to 90% of tumor cells from the culture within 72 hours after MDS, leaving a scattered population of multinucleated resistant cells. Loss of mitosis in tumor cells is associated with marked reduction of cyclin-dependent kinase (CDK) 1 transcription and/or loss of its active form (CDK1-P-Thr(161)), which is coincident with up-regulation of CDKN1A, CDKN1B, and CDKN1C (p21, p27, and p57). Expression of the proapoptotic LITAF, IFNGR, EREG, TNFSF/TNFRSF10 and TNFRSF12, FAS, and RNASEL is primarily up-regulated/induced in cells destined to undergo apoptosis. Loss of Aurora kinase B and BIRC5, which are required for histone H3 phosphorylation, is associated with the accumulation of surviving multinucleated cells. Nevertheless, noncycling survivors of MDS are sensitized to temozolomide, carmustin, and cisplatin to a much greater extent than normal skin fibroblasts possibly because of the suppression of MGMT/TOP1/POLB, MGMT/RAD52/RAD54, and cMET/RADD52, respectively. Sensitivity to these and additional genotoxic agents and radiation may also be acquired due to loss of cMET/OGG1, reduced glutathione reductase levels, and a G(2)-phase block that is a crucial step in the damage response associated with enhancement of drug toxicity. Although the genes controlling mitotic arrest and/or apoptosis in response to low extracellular methionine levels are unknown, it is likely that such control is exerted via the induction/up-regulation of tumor suppressors/growth inhibitor genes, such as TGFB, PTEN, GAS1, EGR3, BTG3, MDA7, and the proteoglycans (LUM, BGN, and DCN), as well as the down-regulation/loss of function of prosurvival genes, such as NFkappaB, MYC, and ERBB2. Although MDS targets several common genes in tumors, mutational variability among melanomas may decide which metabolic and signal transduction pathways will be activated or shutdown.
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PMID:Mitotic arrest, apoptosis, and sensitization to chemotherapy of melanomas by methionine deprivation stress. 1690 95

Microsatellite instability (MSI) has been associated with colitic cancer. However, reported frequency of MSI was varied and the association of MSI with mismatch repair (MMR) deficiency was unclear. In addition, the occurrence of genetic alterations in stromal cells within ulcerative colitis (UC) is still controversial. We therefore sampled 164 microareas in various pathological lesions of UC with or without colitic cancer and studied the MSI status in relation to the DNA repair protein expressions. A total of 129 microfoci from colorectal tissue of 5 colitic cancer patients and 35 microfoci of 7 UC patients (without neoplasm) were carefully sampled by laser-capture microdissection. MSI was analyzed in each microsamples. The protein expression of MMR genes (MLH1, MSH2, MSH6), O(6)-methylguanine-DNA methyltransferase and p53 were assessed by immunohistochemical analysis. Variety of di-nulcleotide microsatellite markers was altered in individual microfoci from different morphological epithelial lesions, in full range of nonneoplastic epithelium to colitic cancer. Interestingly, MSI was not observed in stromal cells at any sites, including those within colitic cancer/dysplasia lesions. Expression of the MMR proteins was not lost in any of the lesions examined. Microsatellite alterations rather seem to be related to the initiation than to the progression of colitic cancer.
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PMID:Heterogeneous microsatellite instability observed within epithelium of ulcerative colitis. 1692 96

Early colorectal carcinomas (submucosal invasive adenocarcinomas) can be classified into polypoid growth carcinoma (PG-Ca) and non-polypoid growth carcinoma (NPG-Ca) types, the latter transforming more rapidly to advanced carcinoma. Previously, we indicated that stromal genetic instability might contribute to tumorigenesis of both sporadic and ulcerative colitis-associated colorectal adenocarcinomas. In the present study, we analyzed genetic instability of both epithelial and surrounding stromal components in PG-Ca and NPG-Ca. In 99 colorectal submucosal invasive adenocarcinomas, epithelial and stromal genetic instability was analyzed with National Cancer Institute standard microsatellite markers, chromosome 17 (Chr.17) markers and tumor suppressor gene-related markers, using a combination of the laser-captured microdissection and GeneScan approaches. Immunohistochemical analysis was carried out for hMLH1, hMSH2, MGMT and p53. In addition, we investigated methylation of the hMLH1 and MGMT promoters. The frequencies of epithelial microsatellite instability (MSI) with Chr.17 markers were significantly higher in NPG-Ca (33.3%) compared to PG-Ca (10.4%), particularly with D17S579 and D17S796. For loss of heterozygosity, only D17S786 showed a significant difference. The frequencies of stromal MSI with all markers were 31.7% and 25.9% in NPG-Ca and PG-Ca, respectively, but D17S579 and TP53 showed higher MSI in NPG-Ca than PG-Ca. Immunohistochemically, p53 protein expression in PG-Ca was significantly higher in loss of heterozygosity-positive cases with altered Chr.17 markers overall, especially the D17S796 marker, compared to cases without genetic instability. These results suggest that epithelial and stromal MSI of Chr.17 markers contributes more to carcinogenesis in NPG-Ca, whereas stromal genetic instability might be necessary for the development of both types of colorectal carcinoma.
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PMID:Genetic instability on chromosome 17 in the epithelium of non-polypoid colorectal carcinomas compared to polypoid lesions. 1703 12

The gene for the DNA-repair enzyme O6-methylguanine-DNA methyltransferase (MGMT), which is closely related with cellular sensitivity to alkylating agents, is inactivated by promoter hypermethylation in several human cancers, including malignant lymphoma. Promoter hypermethylation of the MGMT gene is a favorable prognostic factor in diffuse large B-cell lymphoma (DLBCL). Although inactivation of the MGMT gene is closely related to p53 gene mutations in several cancers, the relationship between p53 gene mutation and MGMT inactivation in malignant lymphoma has not been thoroughly examined. We studied the correlation between MGMT hypermethylation and p53 mutation in DLBCL and their impacts on patient prognosis. In a retrospective cohort study, we used a methylation-specific polymerase chain reaction technique to analyze the methylation status of the promoter region of the MGMT gene in 116 DLBCL patients who received cyclophosphamide as part of multidrug combination chemotherapies. Denaturing high-performance liquid chromatography and direct sequencing were used to search for p53 gene mutations in exons 5 through 9 in 96 of the 116 samples. Disease-free survival and overall survival were estimated by the Kaplan-Meier method. Multivariate survival analyses were performed with the Cox proportional hazards model. Forty-five (38.8%) of 116 DLBCL patients showed MGMT promoter hypermethylation. The presence of MGMT hypermethylation was associated with better overall survival (P = .036). MGMT promoter hypermethylation was a prognostic factor that was independent of established prognostic factors, such as age, disease stage, serum lactic dehydrogenase level, and the number of extranodal disease sites (hazard ratio, 2.43; 95% confidence interval, 1.28-4.61; P = .007). p53 mutations were detected in 19 (19.8%) of 96 patients and were identified as a risk factor in the complete remission rate and overall survival (P = .0040, and P = .027, respectively). A correlation between MGMT hypermethylation and p53 mutation or p53 G:C-to-A:T mutation was not observed (P = .88, and P = .31, respectively). MGMT promoter hypermethylation and p53 mutation are useful prognostic markers in DLBCL. The impact of MGMT inactivation on p53 mutation in DLBCL is unclear.
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PMID:Promoter hypermethylation of the DNA-repair gene O6-methylguanine-DNA methyltransferase and p53 mutation in diffuse large B-cell lymphoma. 1705 Feb

O6-methylguanine, a methylated damage lesion in DNA, correlates with spontaneous G:C --> A:T transition mutations and leads to activation of oncogene K-ras or dysfunction of the tumor suppressor gene p53. O6-methylguanine-DNA methyltransferase (MGMT) is critical for repairing damage to the O6-position of guanine. Therefore, we tested our hypothesis that genetic variants of MGMT are associated with increased lung cancer risk in a Caucasian population of 1,121 lung cancer patients and 1,163 matched cancer-free controls. We genotyped four potentially functional single nucleotide polymorphisms (SNPs) of MGMT: exon 3 codon 84C --> T (L84F), exon 5 codon 143A --> G (I143V), and two promoter SNPs 135G --> T and 485C --> A. The allele frequency distributions of the SNPs of codon 84C --> T and the promoter 135G --> T in the cases were borderline different from that in the controls. After defining the minor allele (T for codon 84C --> T and G for codon 143A --> G) as the variant allele, we categorized the MGMT genotypes as either 0 variants (84CC-143AA) or 1-4 variants. Compared with 0 variants, those with 1-4 variants showed a statistically significantly increased risk of lung cancer (P = 0.040). Further stratification analysis showed that this increased risk was more pronounced in women, current smokers, and non-small cell lung cancer. We did not find any association between the MGMT promoter SNPs and lung cancer risk. Our findings suggest that non-synonymous SNPs in MGMT are associated with modestly increased risk of lung cancer in Caucasians and need to be further investigated.
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PMID:Association of genetic variants of O6-methylguanine-DNA methyltransferase with risk of lung cancer in non-Hispanic Whites. 1716 58

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

MGMT promoter methylation, which has been correlated with the response to alkylating agents, was investigated in a retrospective series of 219 glioblastomas (GBMs) treated with various modalities. MGMT methylation had no impact on survival for the whole group, but showed a significant advantage (17.1 months vs. 13.1) for patients treated with RT+ adjuvant chemotherapy (relative risk of death (RR) = 0.53; P = 0.041), particularly when patients received CT during the course of RT (MS = 19.9 months vs. 12.5 months; RR = 0.227, P = 0.001). This suggests that the prognostic impact of MGMT methylation is dependent on therapeutic modalities and schedules. MGMT methylation was not correlated with the main molecular alterations, such as 10q loss and p53 expression.
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PMID:MGMT prognostic impact on glioblastoma is dependent on therapeutic modalities. 1721 56


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