P53 and disease: When the guardian angel fails
ABSTRACT The p53 tumor suppressor gene (TP53) is mutated more often in human cancers than any other gene yet reported. Of importance, it is mutated frequently in the common human malignancies of the breast and colorectum and also, but less frequently, in other significant human cancers such as glioblastomas. There is also one inherited cancer predisposing syndrome called Li-Fraumeni that is caused by TP53 mutations. In this review, we discuss the significance of p53 mutations in some of the above tumors with a view to outlining how p53 contributes to malignant progression. We also discuss the usefulness of TP53 status as a prognostic marker and its role as a predictor of response to therapy. Finally, we outline some evidence that abnormalities in p53 function contribute to the etiology of other non-neoplastic diseases.
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- "At normal circumstances, P 53 expression is low because of its limited needs which result in its speed inactivation but it has an ability to be more stable, active and accumulative in response to activator signals such as DNA destruction, then its transcriptive and expression level increase leading to disturbance in the cell cycle which revealed the apoptotic features (Naderi et al., 2009). P 53 prevents tumor evolution and progression and activates death of cells subjected to anti-tumor therapy which made P 53 as ''guardian angel'' as described by Royds and Iacopetta, 2006. In addition to P 53 , caspases in general are important mediators in apoptosis, executive cas- pase-3 is the most involved pathway which should be generated from its inactive protein (procaspase-3), caspase 3 is required for some apoptosis features (chromatin condensation, DNA damage and apoptotic body formation) and its role may take place before cell viability suppression starts (Porter and Ja¨nicke (1999). "
ABSTRACT: Apoptosis is a significant physiological function in the cell. P53 is known as tumor suppressor cellular factor, executive caspases are also the most involved pathway for apoptosis. Menadione (VK3) has apoptotic action on many harmful cells, but the molecular role of adipokines is not enough studied in this regard, so the ability of menadione to modify the adipokine (leptin hormone), caspase-3 and P53 signals to induce its apoptotic action on HepG2 cells was studied. The study revealed that menadione has anti-viability and apoptotic effect at sub-G1 phase of HepG2 cell cycle. Its cytotoxic effect is mediated by molecular mechanisms included: inhibiting leptin expression and level, activating caspase-3 pathway and up-regulating the expression of P53. Menadione exerts its apoptotic mechanisms in a concentration and time dependent way through ROS generation. In addition to the known apoptotic pathways, the results indicates that suppressing leptin pathway is a significant mechanism for menadione apoptotic effect which made it as potential therapeutic vitamin in preventing hepatocytes survival and proliferation.Saudi Journal of Biological Sciences 03/2014; 21(6). DOI:10.1016/j.sjbs.2014.03.002 · 0.74 Impact Factor
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- "The complex repertoire of p53- regulated genes further highlights the imperative need to understand how p53 selects its key target genes. Mutation of p53 is a common occurrence in many cancers and is associated with tumor progression, resistance to chemotherapy, and poor prognosis . A study of breast cancers found that p53 mutation frequency was not related to nodal involvement or tumor size , although another study found a marginally increased frequency in recurrent tumors . "
ABSTRACT: In breast carcinoma, disruption of the p53 pathway is one of the most common genetic alterations. The observation that the p53 can express multiple protein isoforms adds a novel level of complexity to the outcome of p53 mutations. p53 expression was analysed by Western immunoblotting and immunohistochemistry using monoclonal antibodies DO-7, Pab240, and polyclonal antiserum CM-1. The more frequently p53-positive nuclear staining has been found in the invasive breast tumors. One of the most intriguing findings is that mutant p53 appears as discrete dot-shaped regions within the nucleus of breast cancer cells. In many malignant cells, the nucleolar sequestration of p53 is evident. These observations support the view that the nucleolus is involved directly in the mediation of p53 function or indirectly by the control of the localization of p53 interplayers. p53 expressed in the nuclear fraction of breast cancer cells revealed a wide spectrum of isoforms. p53 isoforms ΔNp53 (47 kDa) and Δ133p53 β (35 kDa), known as dominant-negative repressors of p53 function, were detected as the most predominant variants in nuclei of invasive breast carcinoma cells. The isoforms expressed also varied between individual tumors, indicating potential roles of these p53 variants in human breast cancer.The Scientific World Journal 01/2014; 2014(22):618698. DOI:10.1155/2014/618698 · 1.73 Impact Factor
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- "Tumor suppressor protein p53 when stimulated regulates the cellular localization and activity of key effectors involved in the apoptotic process (Lahiry et al., 2008). However, in order to overcome the threats posed by a functional p53- network, tumor cells either activate an anti-p53 network to hamper p53 functions or else directly acquire p53 mutations, (Royds and Iacopetta 2006; Meulmeester and Jochemsen, 2008) thereby predicting a substantially worsened prognosis and treatment. The best example can be that of virally infected cervical cancers where despite the presence of wild-type p53 gene, a number of mechanisms co-operate to suppress the functional execution of a pro-p53-network (Kastan, 2007). "
ABSTRACT: Abrogation of functional p53 is responsible for malignant cell transformation and maintenance of human papilloma virus (HPV)-infected cancer cells. Restoration of p53 has, therefore, been regarded as an important strategy for molecular intervention of HPV-associated malignancies. Here we report that differential regulation of pro- and anti-p53 setups not only upregulates p53 transcription but also stabilizes and activates p53 protein to ensure p53-induced apoptosis in HPV-18-infected cervical cancer. Functional restoration of p53 can be achieved by non-steroidal anti-inflammatory drug celecoxib via multiple molecular mechanisms: (i) inhibition of p53 degradation by suppressing viral oncoprotein E6 expression, (ii) promoting p53 transcription by downmodulating cycloxygenase-2 (Cox-2) and simultaneously retrieving p53 from Cox-2 association and (iii) activation of p53 via ataxia telangiectasia mutated-/p38 mitogen-activated protein kinase-mediated phosphorylations at serine-15/-46 residues. That restored p53 is functional has been confirmed by its ability of transactivating Bax and p53-upregulated modulator of apoptosis, which in turn switch on the apoptotic machinery in these cells. Studies undertaken in biopsy samples of cervical carcinoma further validated celecoxib effect. Our approaches involving gene manipulation and pharmacological interference finally highlight that celecoxib alters pro- and anti-p53 networks, not in isolation but in concert, to rejuvenate p53-dependent apoptotic program in HPV-infected cervical cancer cells.Oncogene 07/2011; 31(2):173-86. DOI:10.1038/onc.2011.234 · 8.56 Impact Factor