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Yeast As a Chassis for Developing Functional Assays to Study Human P53
Published on: August 4, 2019
[Punish or cherish: p53, metabolism and tumor suppression]
1U1016 Inserm-Institut Cochin, groupe hospitalier Cochin-Port-Royal, bâtiment Cassini, 123, boulevard de Port-Royal, 75014 Paris, France.
Abstract:
The p53 gene is essential for tumor suppression, but how it does so remains unclear. Upon genotoxic or oncogenic stresses, increased p53 activity induces transient cell cycle arrest, senescence or apoptosis, the three cornerstones of the so-called triumvirate. Accordingly, it has long been thought that p53 suppresses tumorigenesis by somehow counteracting cell proliferation or survival. However, several recently described genetically modified mice indicate that p53 can suppress tumorigenesis without triggering these three responses. Rather, as an important mechanism for tumor suppression, these mutant mice point to the ability of p53 to prevent the Warburg effect, that is to dampen glycolysis and foster mitochondrial respiration. Interestingly, these metabolic functions of p53 rely, in part, on its "unstressed" (basal) expression, a feature shared by its mechanistically linked anti-oxydant function. Together, these "conservative" activities of p53 may prevent tumor initiation by promoting and maintaining a normal oxidative metabolism and hence underly the "daily" tumor suppression by p53 in most cells. Conversely, destructive activities elicited by high p53 levels and leading to senescence or apoptosis provide a shield against partially or overtly transformed cells. This last situation, although relatively infrequent throughout life, is usual in experimental settings, which could explain the disproportionally high number of data implicating the triumvirate in tumor suppression by p53.
Insights
The p53 gene suppresses tumors by regulating cell metabolism and oxidative respiration, not just by inducing cell cycle arrest or apoptosis. These metabolic functions, reliant on basal p53 expression, prevent tumor initiation and progression.
Area of Science:
- Molecular Biology
- Cancer Research
- Metabolic Regulation
Background:
- The tumor suppressor gene p53 is crucial for preventing cancer, but its precise mechanisms are not fully understood.
- Traditionally, p53's tumor suppression was attributed to inducing cell cycle arrest, senescence, or apoptosis (the triumvirate) in response to stress.
- Recent findings challenge this view, suggesting alternative p53 functions in tumor suppression.
Purpose of the Study:
- To elucidate the multifaceted roles of the p53 gene in tumor suppression.
- To investigate the significance of p53's metabolic regulatory functions in preventing cancer initiation.
- To reconcile the traditional 'triumvirate' model with newer findings on p53's metabolic roles.
Main Methods:
- Analysis of genetically modified mouse models exhibiting altered p53 function.
- Investigation of p53's impact on cellular metabolism, specifically glycolysis and mitochondrial respiration.
- Examination of p53's basal (unstressed) expression and its link to antioxidant functions.
Main Results:
- Genetically modified mice demonstrate p53 can suppress tumors independently of the triumvirate responses.
- A key mechanism involves p53 preventing the Warburg effect by dampening glycolysis and promoting mitochondrial respiration.
- These metabolic functions are partly dependent on basal p53 levels and its antioxidant activity, suggesting a role in daily tumor surveillance.
Conclusions:
- p53 employs both 'conservative' metabolic regulatory functions and 'destructive' stress responses for tumor suppression.
- Basal p53 activity maintains normal oxidative metabolism, preventing early tumor development.
- High p53 levels induce apoptosis or senescence, eliminating established or transformed cells, but this is less frequent than metabolic surveillance.
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