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Tumor suppression in the absence of p53-mediated cell-cycle arrest, apoptosis, and senescence
Tongyuan Li1, Ning Kon, Le Jiang
1Institute for Cancer Genetics, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
Abstract:
Cell-cycle arrest, apoptosis, and senescence are widely accepted as the major mechanisms by which p53 inhibits tumor formation. Nevertheless, it remains unclear whether they are the rate-limiting steps in tumor suppression. Here, we have generated mice bearing lysine to arginine mutations at one (p53(K117R)) or three (p53(3KR); K117R+K161R+K162R) of p53 acetylation sites. Although p53(K117R/K117R) cells are competent for p53-mediated cell-cycle arrest and senescence, but not apoptosis, all three of these processes are ablated in p53(3KR/3KR) cells. Surprisingly, unlike p53 null mice, which rapidly succumb to spontaneous thymic lymphomas, early-onset tumor formation does not occur in either p53(K117R/K117R) or p53(3KR/3KR) animals. Notably, p53(3KR) retains the ability to regulate energy metabolism and reactive oxygen species production. These findings underscore the crucial role of acetylation in differentially modulating p53 responses and suggest that unconventional activities of p53, such as metabolic regulation and antioxidant function, are critical for suppression of early-onset spontaneous tumorigenesis.
Insights
The tumor suppressor protein p53 normally halts tumor formation through cell-cycle arrest, apoptosis, and senescence. However, this study reveals that p53
Area of Science:
- Molecular Biology
- Cancer Research
- Tumorigenesis
Background:
- The tumor suppressor protein p53 is crucial for preventing cancer.
- Canonical functions of p53 include cell-cycle arrest, apoptosis, and senescence.
- The role of p53 acetylation in these tumor suppression mechanisms is not fully understood.
Purpose of the Study:
- To investigate the role of p53 acetylation in tumor suppression.
- To determine if canonical p53 functions are rate-limiting for tumor suppression.
- To explore alternative p53 functions in preventing spontaneous tumorigenesis.
Main Methods:
- Generated mice with specific mutations in p53 acetylation sites (p53(K117R) and p53(3KR)).
- Assessed p53-mediated cell-cycle arrest, apoptosis, and senescence in mutant cells.
- Monitored tumor formation and survival in mutant mice.
- Evaluated p53's regulation of energy metabolism and reactive oxygen species (ROS).
Main Results:
- p53(K117R/K117R) cells retained cell-cycle arrest and senescence but lost apoptosis.
- p53(3KR/3KR) cells lost all three canonical p53 functions (arrest, apoptosis, senescence).
- Neither p53(K117R/K117R) nor p53(3KR/3KR) mice developed early-onset tumors.
- p53(3KR) retained metabolic regulation and ROS scavenging functions.
Conclusions:
- p53 acetylation differentially modulates its functions.
- Canonical p53 functions are not rate-limiting for spontaneous tumor suppression.
- Non-canonical p53 activities, like metabolic regulation and antioxidant function, are critical for preventing early-onset tumors.
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