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)

The transcription factor E2F-1 induces cell cycle progression at the G1/S checkpoint, and deregulation of E2F-1 provokes apoptosis in a wide variety of malignant cells. To date only p14(ARF) and p73, a p53 homologue, have been identified as E2F-1-inducible genes capable of mediating an apoptotic response. Here we show that adenovirus-mediated E2F-1 overexpression in cancer cells induces expression and autophosphorylation of the double-stranded RNA-dependent protein kinase PKR leading to phosphorylation of its downstream target, the alpha-subunit of the eukaryotic translation initiation factor 2 (eIF-2alpha) and to apoptotic cell death. This PKR-dependent apoptosis occurs in cell lines with mutated p53 and in cell lines with mutated p53 and p73, and is significantly reduced by the chemical inhibition of PKR activation. Further, PKR(-/-) mouse embryo fibroblasts, but not PKR(+/+) mouse embryo fibroblasts, demonstrate significant resistance to E2F-1-induced apoptosis. We conclude that an important pathway of E2F-1-mediated apoptosis is dependent on PKR activation and does not require p53 or p73.
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PMID:Role for the double-stranded RNA activated protein kinase PKR in E2F-1-induced apoptosis. 1221 68

Using an estrogen-inducible retroviral system, we demonstrate that oncogenic Raf-1 induces growth arrest and morphological changes in finite lifespan human mammary epithelial cells (HMEC). This arrest does not rely on expression of the cyclin-dependent kinase inhibitor (CKI) p16(INK4a), nor on changes in expression of the CKIs p21(Cip1), p14(ARF), p27(Kip1) or p57(Kip2). The Raf-induced arrest is independent of viral oncogene mediated inactivation of p53 and pRB, or c-myc overexpression. Flow cytometric analysis demonstrates that cells arrest in both G1 and G2. The Raf-induced arrest is mitigated or eliminated in some immortally transformed HMEC. Immortal HMEC that have both overcome replicative senescence and undergone the recently described conversion process maintain growth in the presence of transduced oncogenic Raf-1; they also gain EGF-independent growth and a low frequency of anchorage-independent growth. However, HMEC that have overcome replicative senescence but have not undergone conversion and HMEC immortalized by transduction with the catalytic subunit of telomerase, hTERT, remain severely growth arrested. These results indicate that the molecular mechanisms responsible for the Raf-1-induced growth arrest may vary among different finite lifespan cell types, and that in HMEC, this mechanism is altered during the conversion process, rather than as a direct consequence of overcoming senescence or expressing hTERT.
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PMID:Raf-1-induced growth arrest in human mammary epithelial cells is p16-independent and is overcome in immortal cells during conversion. 1221 73

We have analyzed the ability of an adenoviral vector encoding the exon 1beta region of the p14(ARF) tumor suppressor (ARF) to suppress the growth and viability of an array of tumor cell lines of various origins and varying p53 and Rb status, in order to establish the clinical potential of ARF. An important activity of ARF is regulation of p53 stability and function through binding to the mdm2 protein. By sequestering mdm2, ARF may promote growth suppression through the Rb pathway as well because mdm2 can bind to Rb and attenuate its function. Whereas the high frequency of ARF gene deletion in human cancers, accounting for some 40% of cancers overall, suggests that ARF would be a strong candidate for therapeutic application, the possible dependence of ARF activity on p53 and Rb function presents a potential limitation to its application, as these functions are often impaired in cancer. We show here that a replication-defective adenovirus, Ad1beta, encoding the exon 1beta region of ARF is most effective in tumor cells expressing endogenous wild-type p53. Nevertheless, Ad1beta suppresses tumor cell growth and viability in vitro and in vivo, inducing G1 or G2 cell cycle arrest and cell death even in tumor cells lacking both functional Rb and p53 pathways, and independently of induction of the p53 downstream targets, p21, bax, and mdm2. These results point to an activity of ARF in human tumor cells that is independent of Rb or p53, and suggest that therapeutic applications based on ARF would have a broad clinical application in cancer.
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PMID:Growth suppression by a p14(ARF) exon 1beta adenovirus in human tumor cell lines of varying p53 and Rb status. 1222 24

The tumor suppressor p53 is a labile protein whose level is known to be regulated by the Mdm-2-ubiquitin-proteasome degradation pathway. We have found another pathway for p53 proteasomal degradation regulated by NAD(P)H quinone oxidoreductase 1 (NQO1). Inhibition of NQO1 activity by dicoumarol induces p53 and p73 proteasomal degradation. A mutant p53 (p53([22,23])), which is resistant to Mdm-2-mediated degradation, was susceptible to dicoumarol-induced degradation. This finding indicates that the NQO1-regulated proteasomal p53 degradation is Mdm-2-independent. The tumor suppressor p14(ARF) and the viral oncogenes SV40 LT and adenovirus E1A that are known to stabilize p53 inhibited dicoumarol-induced p53 degradation. Unlike Mdm-2-mediated degradation, the NQO1-regulated p53 degradation pathway was not associated with accumulation of ubiquitin-conjugated p53. In vitro studies indicate that dicoumarol-induced p53 degradation was ubiquitin-independent and ATP-dependent. Inhibition of NQO1 activity in cells with a temperature-sensitive E1 ubiquitin-activating enzyme induced p53 degradation and inhibited apoptosis at the restrictive temperature without ubiquitination. Mdm-2 failed to induce p53 degradation under these conditions. Our results establish a Mdm-2- and ubiquitin-independent mechanism for proteasomal degradation of p53 that is regulated by NQO1. The lack of NQO1 activity that stabilizes a tumor suppressor such as p53 can explain why humans carrying a polymorphic inactive NQO1 are more susceptible to tumor development.
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PMID:Mdm-2 and ubiquitin-independent p53 proteasomal degradation regulated by NQO1. 1223 53

The human Ink4a/Arf tumor suppressor locus encodes two distinct products: p16(Ink4a) which prevents phosphorylation and inactivation of the retinoblastoma protein and, p14(Arf), a nucleolar protein which activates the function of the tumor suppressor p53 protein in the nucleoplasm in response to oncogenic stimulation through an as yet ill-defined mechanism. Here we show that the level of endogenous p14(Arf) and its balance between the nucleolus and the nucleoplasm in HeLa cells are exquisitely sensitive to changes in cell morphology and to short-lived perturbations in cell cycle and in nucleolar function such as those induced by the cyclin-dependent kinase inhibitor, roscovitine, and the casein kinase II and RNA synthesis inhibitor, DRB. Most remarkably, whereas p14(Arf) predominantly concentrates in the nucleolus of interphase cells and transiently disappears between metaphase and early G1 under normal growth conditions, it massively and reversibly accumulates in the nucleoplasm of postmitotic and S-phase cells upon short-term treatment with roscovitine and, at a lesser extent, DRB. In line with the fact that the nuclear level of p53 reaches a peak between mid-G1 and the G1/S border in p53-expressor cells which lack Arf expression, these results provide a clue that, in p53+/Arf+ cells, Arf proteins might serve both to speed and to amplify p53-mediated responses in conditions and cell cycle periods in which the mechanisms involved in p53 stabilization and activation are not fully operational. They further suggest that human endogenous p14(Arf) might activate p53 pathways in physiologic situations by acting inside the nucleoplasm, especially when normal cell cycle progression and nucleolar function are compromised.
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PMID:Human p14(Arf): an exquisite sensor of morphological changes and of short-lived perturbations in cell cycle and in nucleolar function. 1236 Apr 4

Carcinoma in situ (CIS) of the urinary bladder is a flat, aggressive lesion and may be the most common precursor of invasive bladder cancer. Although chromosome 9 alterations are among the earliest and most prevalent genetic alterations in bladder cancer, discrepancy exists about the frequency of chromosome 9 losses in CIS. We analyzed 22 patients with CIS of the bladder (15 patients with isolated CIS, 7 patients combined with synchronous pTa or pT1 carcinomas) for gains and losses of chromosome (peri)centromere loci 1q12, 7p11-q11, 9p11-q12, and 9p21 harboring the INK4A/ARF locus (p16(INK4A)/p14(ARF)) and INK4B (p15(INK4B)) by multiple-target fluorescence in situ hybridization, and for p53 protein accumulation by immunohistochemistry. In 15 of 20 (75%) CIS lesions analyzed p53 overexpression was detected, whereas aneusomy for chromosomes 1 and 7 was identified in 20 of 22 (91%) CIS. In 13 of 22 (60%) CIS cases analyzed, 12 of which were not associated with a synchronous pTa or pT1 carcinoma, no numerical losses for chromosome 9 (p11-q12 and 9p21) were detected as compared with chromosomes 1 and 7. Furthermore 6 of 12 (50%) patients showed a metachronous invasive carcinoma within 2 years. In the remaining nine biopsies CIS lesions (40%) were recognized that showed losses of chromosome 9p11-q12 and 9p21, six of these were associated with a synchronous pTa or pT1 carcinoma. Three of these carcinomas were pTa and exhibited loss of 9q12 as well as a homozygous deletion of 9p21. The others were invasive carcinomas in which CIS lesions were also recognized that showed no numerical loss of chromosome 9, but did show an accumulation of p53. In conclusion our data demonstrate that predominantly isolated CIS lesions contained cells with no specific loss of chromosome 9, as opposed to CIS lesions with synchronous carcinomas that showed evidence of chromosome 9 loss. Furthermore our data strengthen the proposition that p53 mutations (p53 overexpression) precede loss of chromosomes 9 and 9p21 in CIS as precursor for invasive bladder cancer, as opposed to noninvasive carcinomas where chromosome 9 (9p11-q12) losses are early and frequently combined with homozygous deletions of 9p21.
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PMID:Identification of chromosome 9 alterations and p53 accumulation in isolated carcinoma in situ of the urinary bladder versus carcinoma in situ associated with carcinoma. 1236 85

Pleomorphic adenomas of the parotid gland are benign tumours composed of epithelial and mesenchymal cells. The INK4a-ARF (CDKN2A) locus on chromosome 9p21 encodes two tumour suppressor proteins, p16(INK4a) and p14(ARF), which act as upstream regulators of the Rb-CDK4 and p53 pathways. To study the contribution of each pathway in pleomorphic adenomas, this study analysed alterations of p14(ARF), p16(INK4a), p53, and pRb in these tumours. After microdissecting the different histological components, 42 pleomorphic adenomas of the parotid gland were analysed for INK4a-ARF inactivation by DNA sequence analysis, methylation-specific PCR (MSP), restriction enzyme-related polymerase chain reaction (RE-PCR), mRNA expression, microsatellite analysis, and immunohistochemistry. In addition, microdeletion of p14(ARF) and p16(INK4a) were assessed by differential PCR. The status of p53 and Rb was examined by direct sequencing and immunohistochemistry. Using microdissection, it was possible to examine the tumour components, i.e. epithelial, mesenchymal, and transitional, separately after immunohistochemical identification. Methylation of p14(ARF) was found in 1/42 cases and alterations of p16(INK4a) occurred in 12/42 of pleomorphic adenomas, which correlated with loss of mRNA transcription. Microdeletions or specific mutations of either exon were not detected. Methylation was detected exclusively in the epithelial and transitional components and not within the mesenchymal part of the tumour. p53 mutations were detected in 4/42 adenomas, also occurring solely in the epithelial components of the tumours. pRb was detected immunohistochemically in 40/42 adenomas. In normal, corresponding parotid tissue, p14(ARF), p16(INK4a), p53, and pRb alterations were not observed. The observation that alterations of p14(ARF) and p16(INK4a), and also p53 mutations, occurred exclusively in the epithelial and transitional components of pleomorphic adenoma supports the theory that these areas are prone to malignant transformation to carcinoma in adenoma.
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PMID:Alterations of the INK4a-ARF gene locus in pleomorphic adenoma of the parotid gland. 1237 65

Abnormal hypermethylation of CpG islands associated with tumor suppressor genes can lead to repression of gene expression and contribute significantly to tumorigenesis. Esophageal squamous cell carcinoma (ESCC) is thought to be developed through a multi-stage process, which involves basal cell hyperplasia (BCH), dysplasia (DYS), carcinoma in situ (CIS) and carcinoma. In the present study, we studied the hypermethylation of 10 selected genes in biopsies from normal individuals and resected tissues from ESCC patients. Tumor and neighboring normal and precancerous tissues including BCH, DYS and CIS were microdissected from the resected tissues by laser capture microdissection. Hypermethylation of CpG islands was examined in these samples for 10 genes: p16(INK4a), p15(INK4b), p14(ARF), human leukocyte antigen (HLA)-A, -B, -C, hMLH1, E-cadherin (E-cad), fragile histidine triad and von Hippel-Lindau (VHL). Methylation of two Alu sequences, which neighbor E-cad and VHL, respectively, was used as control to verify the procedure of DNA extraction and chemical modification. In 48 biopsy samples with BCH or DYS, the most frequent hypermethylated genes were p16(INK4a) (18.8%) and p14(ARF) (14.6%). Seventeen out of these 48 samples (35.4%) contained hypermethylation of at least one gene. In the resected tissues, 52% of the BCH and 81% of the tumors showed hypermethylation of at least one gene. Genes hypermethylated in earlier stage lesions were always found hypermethylated at the later stage lesions in the same patient. All of the genes were methylated at some stages and they were clustered into four groups according to their frequencies. The first group of genes, which consisted of p16(INK4a) and p14(ARF), was most frequently hypermethylated in all stages, and the frequencies increased from normal epithelial (0%) to BCH, to displasia/carcinoma in situ and ESCC. Other genes were hypermethylated less frequently. Our results suggest that hypermethylation of key genes, such as p16(INK4a), p14(ARF) and hMLH1, may be used in combination with other molecular changes, such as p53 mutation, in the development of biomarkers for predicting the risk for ESCC.
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PMID:Detection of multiple gene hypermethylation in the development of esophageal squamous cell carcinoma. 1237 81

We established a new lung cancer cell line, designated Y-ML-1B, from a lung cancer of a 70-year-old Japanese man with leukocytosis and thrombocytosis. Before surgical resection, the white blood cell and platelet counts were elevated to 34,400/mm3 and 668,000/mm3, respectively, and the granulocyte colony-stimulating factor (G-CSF) level in the serum was increased at 141 pg/mL. The primary tumor showed an undifferentiated morphology with large cells and induced extensive thickening of the pleura in the right hemithorax. The Y-ML-1B cells grow as a monolayer, with a doubling time of 19 hours, and are tumorigenic in nude mice, which showed a morphology similar to the primary tumor in xenografts. Analysis of the supernatant of cell culture medium of Y-ML-1B showed elevated levels of G-CSF and other cytokines such as interleukin (IL)-6, IL-8, and granulocyte-macrophage colony-stimulating factor (GM-CSF), consistent with the high levels detected in the patient's serum. Cytogenetic analysis revealed aneuploidy of greater than 56 in metaphases with many structural abnormalities. Mutation analysis of the tumor suppressor genes showed that Y-ML-1B is inactivated in TP53 and RASSF1A, but not in p14(ARF), p16(INK4A), or RB. Neither activating mutations of KRAS or NRAS nor amplification of MYC or MDM2 were detected. Y-ML-1B expressed N-cadherin but not E-cadherin. This newly established cell line might serve as a useful model for studying the molecular pathogenesis for large cell cancers of the lung which express high levels of cytokines.
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PMID:Establishment of a large cell lung cancer cell line (Y-ML-1B) producing granulocyte colony-stimulating factor. 1237 11

The INK4a-ARF locus, located on chromosome 9p21, encodes 2 cell cycle-regulatory proteins, p16(INKa) and p14(ARF), acting through the Rb-CDK4 and p53 pathways. This study was done to investigate the contribution of the INK4a-ARF locus in tumorigenesis of angiosarcoma of the liver. Alterations of p14(ARF), p16(INKa), and p53 in primary liver angiosarcoma from 19 patients were analyzed by methylation-specific polymerase chain reaction (MSP), restriction enzyme-related polymerase chain reaction (RE-PCR), microsatellite analysis, and DNA sequencing. As a control group, 12 angiosarcomas from other organs were analyzed. Promoter methylation of p14(ARF) was found in 5 of 19 cases (26%), and p16(INKa) showed aberrant promoter methylation in 12 of 19 cases (63%). One tumor (5%) had homozygous deletion of the INK4a-ARF locus. Methylation and deletion correlated with loss of mRNA transcription. Methylated p14(ARF) appeared in the context of a methylated p16(INKa) promoter in 3 cases of the 5 angiosarcomas methylated at p14(ARF). p14(ARF) aberrant methylation was not related to the presence of p53 mutations, which was detected in 6 of 19 (32%) cases. Alterations of the INK4a-ARF locus or p53 as were not established independent prognostic factors in these tumors. In conclusion, our data indicate that the INK4a-ARF locus is frequently inactivated in angiosarcoma of the liver and occurs independently of p53 mutations.
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PMID:Abnormalities of the ARF-p53 pathway in primary angiosarcomas of the liver. 1237 12


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