Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P43146 (tumour suppressor)
 5,935 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cellular stresses, such as growth factor deprivation, DNA damage or oncogene expression, lead to stabilization and activation of the p53 tumour suppressor protein. Depending on the cellular context, this results in one of two different outcomes: cell cycle arrest or apoptotic cell death. Cell death induced through the p53 pathway is executed by the caspase proteinases, which, by cleaving their substrates, lead to the characteristic apoptotic phenotype. Caspase activation by p53 occurs through the release of apoptogenic factors from the mitochondria, including cytochrome c and Smac/DIABLO. Released cytochrome c allows the formation of a high-molecular weight complex, the apoptosome, which consists of the adapter protein Apaf-1 and caspase 9, which is activated following recruitment into the apoptosome. Active caspase 9 then cleaves and activates the effector caspases, such as caspases-3 and -7, which execute the death program. Released Smac/DIABLO facilitates caspase activation through repression of the IAP caspase inhibitor proteins. The release of mitochondrial apoptogenic factors is regulated by the pro- and anti-apoptotic Bcl-2 family proteins, which either induce or prevent the permeabilization of the outer mitochondrial membrane. The mechanism by which p53 signals to the Bcl-2 family proteins is unclear. It was shown that some of the pro-apoptotic family members, such as Bax, Noxa or PUMA, are transcriptional targets of p53. In addition, transcription-independent, pro-apoptotic activities of p53 have been described. The elucidation of the p53-dependent pathway, resulting in mitochondrial outer membrane permeabilization through the pro-apoptotic Bcl-2 family proteins, is a key to unveiling the mechanism of stress-induced apoptosis.
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PMID:Mechanisms of p53-dependent apoptosis. 1170 54

Malignant melanoma is a life-threatening skin cancer due to its highly metastatic character and resistance to radio- and chemotherapy. It is believed that the ability to evade apoptosis is the key mechanism for the rapid growth of cancer cells. However, the exact mechanism for failure in the apoptotic pathway in melanoma cells is unclear. p53, the most frequently mutated tumour suppressor gene in human cancers, is a key apoptosis inducer. However, p53 mutation is only found in 15-20% of melanoma biopsies. Recently, it was found that Apaf-1, a downstream target of p53, is inactivated in metastatic melanoma. Specifically, loss of heterozygosity (LOH) of the Apaf-1 gene was found in 40% of metastatic melanoma. To determine if loss of Apaf-1 expression is indeed involved in melanoma progression, we employed the tissue microarray technology and examined Apaf-1 expression in 70 human primary malignant melanoma biopsies by immunohistochemistry. Our data showed that Apaf-1 expression is significantly reduced in melanoma cells compared with normal nevi (chi(2)=6.02, P=0.014). Our results also revealed that loss of Apaf-1 was not associated with the tumour thickness, ulceration or subtype, patient's gender, age and 5-year survival. In addition, our in vitro apoptosis assay revealed that overexpression of Apaf-1 can sensitise melanoma cells to anticancer drug treatment. Taken together, our data indicate that Apaf-1 expression is significantly reduced in human melanoma and that Apaf-1 may serve as a therapeutic target in melanoma.
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PMID:Reduced Apaf-1 expression in human cutaneous melanomas. 1530 93

To examine the significance of the methylation level of the p53 target and tumour suppressor genes apoptotic protease activating factor-1 (APAF-1) and death-associated protein kinase-1 (DAPK-1) in 80 microdissected tumour samples from transitional cell carcinoma (TCC) of the bladder and 80 tumour samples from clear-cell renal cell carcinoma (RCC) as well as from non-tumourous bladder and kidney tissue. Growth-inhibitory effects of the demethylating agents 5-Aza-2'-deoxycytidine (5-Aza-CdR) and zebularine were investigated in TCC and RCC cell lines. The methylation frequency of APAF-1 (DAPK-1) was 100% (77%) in TCC and 100% (33%) in RCC. The methylation levels of APAF-1 could differentiate between the individual tumour stages in TCC as well as in RCC. The APAF-1 methylation levels in RCC were significantly higher in tumours larger than 4 cm and in high-grade tumours. The methylation frequencies in normal tissue for APAF-1 (DAPK-1) were 11% (8%) in bladder tissue and 9% (5%) in kidney tissue. The growth-inhibitory effect of the demethylating agents in TCC (RT4, T24) and RCC (A498, ClearCa-5) cell lines resulted in a 17-132% prolongation of the doubling time (DT). In RCC cell lines, zebularine was superior to 5-Aza-CdR in achieving a DT prolongation. Quantitative real time RT-PCR detected a re-expression of mRNA transcripts of APAF-1 or DAPK-1. In conclusion, demethylating agents effectively retard growth of TCC and RCC cell lines. Methylation level analysis of specific genes has the potential for further tumour characterisation in TCC and RCC.
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PMID:Methylation of tumour suppressor genes APAF-1 and DAPK-1 and in vitro effects of demethylating agents in bladder and kidney cancer. 1713 71

The p53 tumour suppressor plays central role in the maintenance of genome integrity. P53 deficient fruit flies are highly sensitive to ionizing radiation (IR) and show genome instability suggesting that the Drosophila melanogaster p53 (Dmp53) is necessary for the proper damage response upon IR. We found that Dmp53 null fruit flies are highly sensitive to ultraviolet radiation (UV) as well. We analyzed the expression levels of apoptotic genes in wild type and Dmp53 null mutant animals after UV or IR using quantitative real-time RT-PCR. Ark (Apaf-1 related killer) was induced in a Dmp53-dependent way upon UV treatment but not by IR, hid (head involution defective/wrinkled) was induced upon both types of DNA damage, while reaper was induced only upon IR but not UV treatment. Using microarray analysis we identified several further genes that are activated upon UV irradiation in the presence of wild type Dmp53 only. Some but not all of these genes show Dmp53-dependent activation upon IR treatment as well. These results suggest that Dmp53 activates distinct cellular pathways through regulation of different target genes after different types of DNA damage.
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PMID:Different sets of genes are activated by p53 upon UV or ionizing radiation in Drosophila melanogaster. 1829 95