Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0596263 (carcinogenesis)
 64,820 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pre-neoplastic lesions in rodent liver often express high levels of MDM2 and lack a p53 response to DNA damage. The question we posed was whether there is a liver-specific regulation of the p53/MDM2 feedback loop and if it can be related to the development of pre-neoplastic lesions, referred to as enzyme altered foci (EAF) in rats. Acute responses of p53 and MDM2 to diethylnitrosamine (DEN) were characterized by employing immunohistochemistry, western blotting, RT-PCR and in situ hybridization. A single dose of DEN induced a centrilobular p53 response that peaked at 24 h. It was associated with transcriptional activation of MDM2 and signs of apoptosis. However, in midzonal hepatocytes, which constitutively expressed high levels of cytoplasmic MDM2, there was a rapid-onset but transient p53 response. It was terminated at 24 h and there were no signs of apoptosis. The rapidly declining p53 levels in midzonal areas was preceded by a transient peak in MDM2 mRNA levels at 6 h. Rats pre-treated with repeated low or high weekly doses of DEN exhibited EAF and these lesions expressed high levels of cytoplasmic MDM2. Using MDM2 as a marker for EAF gave similar results as using glutathione transferase-P (GST-P) as a marker. Furthermore, small EAF, elicited by low doses of DEN, were preferentially localized to midzonal areas. It is concluded that in centrilobular areas DEN-induced alterations in p53/MDM2 levels are compatible with a previously described feedback loop. An attenuated p53 response in midzonal hepatocytes can be related to a high constitutive expression of MDM2 in these cells. The localization of small EAF to midzonal areas, and the fact that EAF cells expressed high levels of MDM2, indicates that MDM2 expression is a factor governing initiation and early development of EAF. The data support the hypothesis that EAF hepatocytes are initiated via epigenetic mechanisms.
Carcinogenesis 2004 Jan
PMID:Characterizing the role of MDM2 in diethylnitrosamine induced acute liver damage and development of pre-neoplastic lesions. 1455 11

To identify a set of genes involved in the development of radiation-induced tumorigenesis, we used DNA microarrays consisting of 1176 mouse genes and compared expression profiles of radioresistant cells, designated NIH3T3-R1 and NIH3T3-R4. These cells were tumorigenic in a nude mouse grafting system, as compared with the parental NIH3T3 cells. Expression of MDM2, CDK6 and CDC25B was found to increase more than 3-fold. Entactin protein levels were down-regulated in NIH3T3-R1 and NIH3T3-R4 cells. Changes in gene expression were confirmed by reverse transcription-PCR or western blotting. When these genes were transfected into NIH3T3 cells, CDC25B and MDM2 overexpressing NIH3T3 cells showed radioresistance, while CDK6 overexpressing cells did not. In the case of entactin, overexpressing NIH3T3-R1 and NIH3T3-R4 cells were still radioresistant. Furthermore, CDC25B and MDM2 overexpressing cells grafted into nude mice were tumorigenic. NIH3T3-R1 and NIH3T3-R4 cells showed increased radiation-induced apoptosis accompanied by a faster growth rate, rather than an earlier radiation-induced G2/M phase arrest, suggesting that the radioresistance of NIH3T3-R1 and NIH3T3-R4 cells was due to a faster growth rate rather than induction of apoptosis. In the case of MDM2 and CDC25B overexpressing cells, similar phenomena, such as increased apoptosis and a faster growth rate, were shown. The above results, therefore, demonstrate involvement of CDC25B and MDM2 overexpression in radiation-induced tumorigenesis and provide novel targets for detection of radiation-induced carcinogenesis.
Carcinogenesis 2004 Jan
PMID:Alteration of gene expression during radiation-induced resistance and tumorigenesis in NIH3T3 cells revealed by cDNA microarrays: involvement of MDM2 and CDC25B. 1455 13

Transitional cell carcinomas (TCC) of the urinary bladder develop by a multistep process characterized by various stages of transformation differing in their grade of malignancy and biological behaviour. Since the prospective clinical outcome cannot be reliably predicted on histopathological grounds, we analysed the mRNA expression of the MDM2-p73-P14ARF tumour surveillance pathway in an attempt to detect alterations of gene activity, allowing a better understanding of the mechanisms responsible for conversion of low to high malignant TCC. Expression of the mRNA was determined in 71 TCC of various grades and stages using the real-time quantitative reverse transcription-polymerase chain reaction. The MDM2-p73-P14ARF pathway was dominated by the MDM2 gene, the mRNA expression of which proved to be significantly (5-fold) lower in advanced high-grade, high-stage than in superficial low-grade, low-stage TCC. Conversely, the expression of p73 mRNA increased with increasing tumour grades and stages, while the activity of the P14ARF gene was not substantially altered during early and late phases of urothelial carcinogenesis. Analysing the expression of spliced variants of MDM2 mRNA, we found a heterogeneous pattern including a novel splicing transcript coding for an abnormal protein. Promoter hypermethylation of P14ARF occurred in 10% of the TCC with an under-expression of mRNA. An analysis of the effects of lifestyle and occupational bladder cancer risk factors revealed that TCC of smokers showed a 2-fold elevated expression of MDM2 mRNA and an approximately 2-fold lower expression of P14ARF mRNA, whereas the activity of the p73 gene was unchanged. Heavy coffee consumption was associated with a 2-fold decreased expression level of P14ARF mRNA. Exposure to certain occupational hazards (plastic products, paints and lacquer, polycyclic hydrocarbons, chemical solvents) was observed to modulate the activity of the genes analysed. Our findings suggest that an alteration in the MDM2-p73-P14ARF pathway is involved in the progression of bladder cancer to a more malignant and aggressive form.
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PMID:Alteration of the MDM2-p73-P14ARF pathway related to tumour progression during urinary bladder carcinogenesis. 1549 52

The tumor suppressor p53 gene is mutated in minimally half of all cancers. It is therefore reasonable to assume that naturally occurring polymorphic genetic variants in the p53 stress response pathway might determine an individual's susceptibility to cancer. A central node in the p53 pathway is the MDM2 protein, a direct negative regulator of p53. In this report, a single nucleotide polymorphism (SNP309) is found in the MDM2 promoter and is shown to increase the affinity of the transcriptional activator Sp1, resulting in higher levels of MDM2 RNA and protein and the subsequent attenuation of the p53 pathway. In humans, SNP309 is shown to associate with accelerated tumor formation in both hereditary and sporadic cancers. A model is proposed whereby SNP309 serves as a rate-limiting event in carcinogenesis.
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PMID:A single nucleotide polymorphism in the MDM2 promoter attenuates the p53 tumor suppressor pathway and accelerates tumor formation in humans. 1555 Feb 42

As combinations of genetic and/or epigenetic alterations occurring during salivary gland carcinogenesis are largely unknown, we here analyzed 36 salivary gland carcinomas (SGCs) for changes in INK4a/ARF, RB1, p21, p27, PTEN, p53, MDM2 and O6-MGMT genes using methylation specific PCR (MSP), loss of heterozygosity (LOH) assays and mutational analysis with immunohistochemistry (IHC), as well as histone H3 and H4 acetylation status. The RB1 gene was found to be the most frequently methylated (41.7% of cases), while methylation of p27(Kip1) and O6-MGMT were less frequent 8.3% and 5.6%, respectively). Two other genes, p21(Waf1) and PTEN, were unmethylated in the SGCs examined. RB1 methylation significantly correlated with loss of expression as determined by IHC (P=0.03), and also a poor prognosis (P=0.02). p53 mutations were found in 8 cases (22.2%), coupled with p14ARF hypermethylation in two cases. LOH in INK4a/ARF and the RB1 locus was observed in 33.3% and 28.6% of the lesions, respectively. There was no correlation between 9p21 LOH and methylation of the INK4a/ARF gene. Promoter hypermethylation of RB1 coupled with LOH was evident in three samples immuno-negative for RB1. Acetylation of histone H3 and H4 was detected in 6 and 5 cases, respectively. These findings indicate that epigenetic silencing of tumour suppressor genes via promoter hypermethylation might be crucial for salivary gland carcinogenesis, particularly in the RB1 gene. Thus epigenetic events including methylation and acetylation as well as genetic alterations may have important contributions.
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PMID:Genetic and epigenetic alteration profiles for multiple genes in salivary gland carcinomas. 1569 18

The tumor suppressor P53 pathway plays a crucial role in preventing carcinogenesis and genetic variations of this pathway may be associated with cancer susceptibility. We tested this hypothesis by examining the contribution of functional polymorphisms in P53 and MDM2 to risk of esophageal squamous cell carcinoma (ESCC). DNA from 758 ESCC patients and 1,420 controls were genotyped for P53 codon 72Arg>Pro and MDM2 309T>G polymorphisms. Odds ratios (OR) and 95% confidence intervals (CI) of ESCC were estimated by logistic regression. We observed an increased risk of ESCC associated with the P53 Pro/Pro (OR, 1.83; 95% CI, 1.43-2.35; P < 0.001) or MDM2 GG (OR, 1.49; 95% CI, 1.16-1.91; P = 0.002) genotype, compared with the P53 Arg/Arg or MDM2 TT genotype, respectively. Interaction between these P53 and MDM2 polymorphisms increased risk of ESCC in a multiplicative manner, with the OR being 3.10 (95% CI, 2.07-4.69) for subjects carrying both P53 Pro/Pro and MDM2 GG genotypes. Significant interactions were observed between these polymorphisms and smoking, with risk being the highest (OR, 5.29; 95% CI, 2.91-9.61) in smokers having both P53 Pro/Pro and MDM2 GG genotypes. The MDM2 GG genotype was also associated with risk of developing poorly differentiated and advanced ESCC compared with the GT or TT genotype (OR for high-grade and stages III-IV versus low-grade and stages I-II = 1.60; 95% CI, 1.00-2.64; P = 0.049). The P53 and MDM2 polymorphisms may be genetic determinants for the development of ESCC.
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PMID:The role of P53 and MDM2 polymorphisms in the risk of esophageal squamous cell carcinoma. 1623 Apr 24

Carcinoma of the uterine cervix is one of the most common malignancies among women worldwide. Human papillomaviruses (HPV) have been identified as the major etiological factor in cervical carcinogenesis. However, the time lag between HPV infection and the diagnosis of cancer indicates that multiple steps, as well as multiple factors, may be necessary for the development of cervical cancer. The development and progression of cervical carcinoma have been shown to be dependent on various genetic and epigenetic events, especially alterations in the cell cycle checkpoint machinery. In mammalian cells, control of the cell cycle is regulated by the activity of cyclin-dependent kinases (CDKs) and their essential activating coenzymes, the cyclins. Generally, CDKs, cyclins, and CDK inhibitors function within several pathways, including the p16(INK4A)-cyclin D1-CDK4/6-pRb-E2F, p21(WAF1)- p27(KIP1)-cyclinE-CDK2, and p14(ARF)-MDM2-p53 pathways. The results from several studies showed aberrant regulation of several cell cycle proteins, such as cyclin D, cyclin E, p16(INK4A), p21(WAF1), and p27(KIP1), as characteristic features of HPV- infected and HPV E6/E7 oncogene-expressing cervical carcinomas and their precursors. These data suggested further that interactions of viral proteins with host cellular proteins, particularly cell cycle proteins, are involved in the activation or repression of cell cycle progression in cervical carcinogenesis.
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PMID:Aberrant cell cycle regulation in cervical carcinoma. 1625 56

The tumor suppressor TP53 pathway plays a crucial role in preventing carcinogenesis through its ability to impose cell cycle arrest and apoptosis following DNA damage and oncogene activation. MDM2 is a key negative regulator of the TP53 pathway and is overexpressed in many cancers as oncoprotein. We investigated the association between genetic variation in the promoter region of MDM2 (c.-5+309G>T, rs2279744:g.G>T) and the coding region of TP53 (c.215G>C, rs1042522:g.G>C, designated Arg72Pro) and the risk of developing lung cancer. The genotypes of 1,106 patients and 1,420 controls were determined by tetra-primer amplification refractory mutation system (ARMS)-PCR or PCR-based restriction fragment length polymorphism (RFLP). Associations with risk of lung cancer were estimated by logistic regression. We observed an increased lung cancer risk associated with the MDM2 GG (odds ratio [OR] = 1.83, 95% confidence interval [CI] = 1.45-2.32) and TG (OR = 1.33, 95% CI = 1.09-1.63) genotypes. An increased risk was also associated with the TP53 Pro/Pro genotype (OR = 1.47, 95% CI = 1.17-1.85, P = 0.003) compared to the Arg/Arg genotype. The gene-gene interaction of MDM2 and TP53 polymorphisms increased lung cancer risk in a supermultiplicative manner (OR for the presence of both MDM2 GG and TP53 Pro/Pro genotypes = 4.56, 95% CI = 2.76-7.54). Significant interactions were observed between these polymorphisms (respectively and jointly) and smoking (OR = 10.41, 95% CI = 5.26-20.58) for smokers with both the MDM2 GG and TP53 Pro/Pro genotypes. In conclusion, genetic polymorphisms in cell cycle regulatory genes MDM2 and TP53 contribute to the risk of developing lung cancer.
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PMID:Genetic polymorphisms in cell cycle regulatory genes MDM2 and TP53 are associated with susceptibility to lung cancer. 1628 56

The MDM2 oncogene has an important role in human carcinogenesis and has been suggested as a novel target for cancer therapy. Many published in vitro and in vivo investigations have demonstrated that various MDM2 inhibitors including antisense oligonucleotides, siRNA, and small molecule MDM2 inhibitors have antitumor activity in in vitro and in vivo human cancer models, used alone or in combination with cancer chemotherapeutics and radiation therapy. For example, the mixed backbone antisense oligonucleotide developed in our laboratory specifically inhibited MDM2 expression in a dose- and time-dependent manner, resulting in significant antitumor activity in vitro and in vivo. Interestingly, the antisense MDM2 inhibitors have a broad spectrum of antitumor activities in human cancers, regardless of p53 status. These results prompted new investigations into the p53-independent functions of MDM2. This article summarizes the biochemical and molecular studies of the role of MDM2 in the regulation of p21 and E2F1 expression, stability and function, providing evidence for the utility of RNA-silencing technologies, including antisense oligonucleotides and siRNAs.
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PMID:Novel MDM2 p53-independent functions identified through RNA silencing technologies. 1639 38

Monochloramine (NH2Cl) is one of the inflammation-derived oxidants, and has various effects on cell cycle, apoptosis and signal transduction. We studied the effects of NH2Cl on DNA repair response induced by ultraviolet B (UVB) irradiation in normal human diploid fibroblasts, TIG-1. TIG-1 irradiated with 20 mJ/cm2 UVB showed marked increase in thymine dimer, which decreased by about 50% after 24 h. This decrease in thymine dimer was significantly attenuated (P < 0.05) by the pretreatment of NH2Cl (200 microM), which indicated DNA repair inhibition. UVB induced p53 phosphorylation at Ser15, Ser20 and Ser37, and p53 accumulation, and NH2Cl also inhibited these changes. Consequently, UVB-induced increase in the downstream effectors of p53, namely p21Cip1 and Gadd45a, were almost completely inhibited by NH2Cl. Immunoprecipitation study indicated that the association of p53 and MDM2, an E3 ubiquitin ligase for p53, did not change substantially by NH2Cl and/or UVB. The phosphorylation of p53 (Ser15 and Ser37) by UVB is catalyzed by ATR (ataxia telangiectasia mutated and Rad3 related kinase), which works as DNA damage sensor, and ATR also phosphorylates checkpoint kinase 1(Chk1) at Ser345. NH2Cl also inhibited the phosphorylation of Chk1 (Ser345). As UVB-induced DNA damage is repaired by nucleotide excision repair (NER) in human cells, these findings indicated that NH2Cl inhibited NER through the inhibition of p53 phosphorylation and accumulation, and NH2Cl probably impaired DNA damage recognition and/or ATR activation. NH2Cl may facilitate carcinogenesis through the inhibition of NER that repairs DNA damages from various carcinogens.
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PMID:Monochloramine inhibits ultraviolet B-induced p53 activation and DNA repair response in human fibroblasts. 1641 31


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