scholarly journals Mutant p53 tumor suppressor alleles release ras-induced cell cycle growth arrest.

1991 ◽  
Vol 11 (3) ◽  
pp. 1344-1352 ◽  
Author(s):  
G G Hicks ◽  
S E Egan ◽  
A H Greenberg ◽  
M Mowat
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Growth Regulation ◽  
Growth Arrest ◽  
Mutant P53 ◽  
Wild Type ◽  
Type Activity ◽  
Wild Type P53 ◽  
Negative Growth ◽  
P53 Genes

Overexpression of an activated ras gene in the rat embryo fibroblast line REF52 results in growth arrest at either the G1/S or G2/M boundary of the cell cycle. Both the DNA tumor virus proteins simian virus 40 large T antigen and adenovirus 5 E1a are able to rescue ras induced lethality and cooperate with ras to fully transform REF52 cells. In this report, we present evidence that the wild-type activity of the tumor suppressor gene p53 is involved in the negative growth regulation of this model system. p53 genes encoding either a p53Val-135 or p53Pro-193 mutation express a highly stable p53 protein with a conformation-dependent loss of wild-type activity and the ability to eliminate any endogenous wild-type p53 activity in a dominant negative manner. In cotransfection assays, these mutant p53 genes are able to rescue REF52 cells from ras-induced growth arrest, resulting in established cell lines which express elevated levels of the ras oncoprotein and show morphological transformation. Full transformation, as assayed by tumor formation in nude mice, is found only in the p53Pro-193-plus-ras transfectants. These cells express higher levels of the ras protein than do the p53Val-135-plus-ras-transfected cells. Transfection of REF52 cells with ras alone or a full-length genomic wild-type p53 plus ras results in growth arrest and lethality. Therefore, the selective event for p53 inactivation or loss during tumor progression may be to overcome a cell cycle restriction induced by oncogene overexpression (ras). These results suggest that a normal function of p53 may be to mediate negative growth regulation in response to ras or other proliferative inducing signals.

Mutant p53 tumor suppressor alleles release ras-induced cell cycle growth arrest

1991 ◽  
Vol 11 (3) ◽  
pp. 1344-1352
Author(s):  
G G Hicks ◽  
S E Egan ◽  
A H Greenberg ◽  
M Mowat
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Growth Regulation ◽  
Growth Arrest ◽  
Mutant P53 ◽  
Wild Type ◽  
Type Activity ◽  
Wild Type P53 ◽  
Negative Growth ◽  
P53 Genes

Overexpression of an activated ras gene in the rat embryo fibroblast line REF52 results in growth arrest at either the G1/S or G2/M boundary of the cell cycle. Both the DNA tumor virus proteins simian virus 40 large T antigen and adenovirus 5 E1a are able to rescue ras induced lethality and cooperate with ras to fully transform REF52 cells. In this report, we present evidence that the wild-type activity of the tumor suppressor gene p53 is involved in the negative growth regulation of this model system. p53 genes encoding either a p53Val-135 or p53Pro-193 mutation express a highly stable p53 protein with a conformation-dependent loss of wild-type activity and the ability to eliminate any endogenous wild-type p53 activity in a dominant negative manner. In cotransfection assays, these mutant p53 genes are able to rescue REF52 cells from ras-induced growth arrest, resulting in established cell lines which express elevated levels of the ras oncoprotein and show morphological transformation. Full transformation, as assayed by tumor formation in nude mice, is found only in the p53Pro-193-plus-ras transfectants. These cells express higher levels of the ras protein than do the p53Val-135-plus-ras-transfected cells. Transfection of REF52 cells with ras alone or a full-length genomic wild-type p53 plus ras results in growth arrest and lethality. Therefore, the selective event for p53 inactivation or loss during tumor progression may be to overcome a cell cycle restriction induced by oncogene overexpression (ras). These results suggest that a normal function of p53 may be to mediate negative growth regulation in response to ras or other proliferative inducing signals.

Human p53 and CDC2Hs genes combine to inhibit the proliferation of Saccharomyces cerevisiae

1992 ◽  
Vol 12 (3) ◽  
pp. 1357-1365
Author(s):  
J M Nigro ◽  
R Sikorski ◽  
S I Reed ◽  
B Vogelstein
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Growth Inhibition ◽  
Mammalian Cells ◽  
P53 Protein ◽  
Inducible Promoter ◽  
Mutant P53 ◽  
Wild Type ◽  
Growth Inhibitory Activity ◽  
Wild Type P53 ◽  
P53 Genes

Human wild-type and mutant p53 genes were expressed under the control of a galactose-inducible promoter in Saccharomyces cerevisiae. The growth rate of the yeast was reduced in cells expressing wild-type p53, whereas cells transformed with mutant p53 genes derived from human tumors were less affected. Coexpression of the normal p53 protein with the human cell cycle-regulated protein kinase CDC2Hs resulted in much more pronounced growth inhibition that for p53 alone. Cells expressing p53 and CDC2Hs were partially arrested in G1, as determined by morphological analysis and flow cytometry. p53 was phosphorylated when expressed in the yeast, but differences in phosphorylation did not explain the growth inhibition attributable to coexpression of p53 and CDC2Hs. These results suggest that wild-type p53 has a growth-inhibitory activity in S. cerevisiae similar to that observed in mammalian cells and suggests that this yeast may provide a useful model for defining the pathways through which p53 acts.

scholarly journals The mdm-2 oncogene can overcome wild-type p53 suppression of transformed cell growth

1993 ◽  
Vol 13 (1) ◽  
pp. 301-306 ◽  
Author(s):  
C A Finlay
Keyword(s):  
P53 Protein ◽  
Mutant P53 ◽  
Wild Type ◽  
Rat Embryo ◽  
Ras Gene ◽  
Double Minute ◽  
Murine Double Minute ◽  
Low Levels ◽  
Wild Type P53 ◽  
P53 Genes

Expression of a p53-associated protein, Mdm-2 (murine double minute-2), can inhibit p53-mediated transactivation. In this study, overexpression of the Mdm-2 protein was found to result in the immortalization of primary rat embryo fibroblasts (REFs) and, in conjunction with an activated ras gene, in the transformation of REFs. The effect of wild-type p53 on the transforming properties of mdm-2 was determined by transfecting REFs with ras, mdm-2, and normal p53 genes. Transfection with ras plus mdm-2 plus wild-type p53 resulted in a 50% reduction in the number of transformed foci (relative to the level for ras plus mdm-2); however, more than half (9 of 17) of the cell lines derived from these foci expressed low levels of a murine p53 protein with the characteristics of a wild-type p53. These results are in contrast to previous studies which demonstrated that even minimal levels of wild-type p53 are not tolerated in cells transformed by ras plus myc, E1A, or mutant p53. The mdm-2 oncogene can overcome the previously demonstrated growth-suppressive properties of p53.

An accelerated senescence response to radiation in wild-type p53 glioblastoma multiforme cells

2006 ◽  
Vol 105 (1) ◽  
pp. 111-118 ◽  
Author(s):  
Quincy A. Quick ◽  
David A. Gewirtz
Keyword(s):  
Glioblastoma Multiforme ◽  
Growth Arrest ◽  
Terminal Deoxynucleotidyl Transferase ◽  
Viable Cell Number ◽  
Mutant P53 ◽  
Wild Type ◽  
Fractionated Radiotherapy ◽  
Accelerated Senescence ◽  
Wild Type P53 ◽  
U87 Cells

Object Radiotherapy is one of the few treatment options available for glioblastoma multiforme (GBM); however, the basis for its overall ineffectiveness in GBM is not fully understood. The present study was designed to explore the nature of the response to ionizing radiation in GBM cells to gain insight into the basis for the general failure of radiotherapy in the treatment of this disease. Methods The response to fractionated radiotherapy was examined in GBM cell lines with differing p53 status. A viable cell number was determined during an 8-day period; accelerated senescence was based on β-galactosidase staining and cell morphology; apoptosis was evaluated by the terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick-end labeling assay and fluorescence-activated cell-sorter analysis, whereas the expression of cell-cycle regulatory proteins was monitored by Western blot analysis. Based on clonogenic survival, the wild-type p53 U87 cells and mutant p53 T98 cells demonstrated essentially identical sensitivity to fractionated radiotherapy; however, neither cell line underwent apoptosis, and the primary response to irradiation was growth arrest. The wild-type p53 GBM cells showed clear evidence of accelerated senescence in response to irradiation. In contrast, senescence was not evident in mutant p53 GBM cells or GBM cells in which p53 function was abrogated by the viral E6 protein. The T98 (mutant p53) cells demonstrated a relatively robust proliferative recovery whereas both the rate and extent of recovery were attenuated in the wild-type p53 U87 cells. Conclusions Both accelerated senescence and conventional growth arrest are likely to represent alternative responses to apoptosis in irradiated GBM cells.

scholarly journals Inhibition of p53-mediated growth arrest by overexpression of cyclin-dependent kinases.

1996 ◽  
Vol 16 (8) ◽  
pp. 4445-4455 ◽  
Author(s):  
K M Latham ◽  
S W Eastman ◽  
A Wong ◽  
P W Hinds
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Growth Arrest ◽  
Temperature Sensitive ◽  
Wild Type ◽  
Aberrant Expression ◽  
Cycle Progression ◽  
Cyclin Dependent Kinases ◽  
Rat Fibroblasts ◽  
Wild Type P53

Rat fibroblasts transformed by a temperature-sensitive mutant of murine p53 undergo a reversible growth arrest in G1 at 32.5 degrees C, the temperature at which p53 adopts a wild-type conformation. The arrested cells contain inactive cyclin-dependent kinase 2 (cdk2) despite the presence of high levels of cyclin E and cdk-activating kinase activity. This is due in part to p53-dependent expression of the p2l cdk inhibitor. Upon shift to 39 degrees C, wild-type p53 is lost and cdk2 activation and pRb phosphorylation occur concomitantly with loss of p2l. This p53-mediated growth arrest can be abrogated by overexpression of cdk4 and cdk6 but not cdk2 or cyclins, leading to continuous proliferation of transfected cells in the presence of wild-type p53 and p2l. Kinase-inactive counterparts of cdk4 and cdk6 also rescue these cells from growth arrest, implicating a noncatalytic role for cdk4 and cdk6 in this resistance to p53-mediated growth arrest. Aberrant expression of these cell cycle kinases may thus result in an oncogenic interference with inhibitors of cell cycle progression.

scholarly journals The USP7 Inhibitor P5091 Induces Cell Death in Ovarian Cancers with Different P53 Status

2017 ◽  
Vol 43 (5) ◽  
pp. 1755-1766 ◽  
Author(s):  
Mengying Wang ◽  
Yayun Zhang ◽  
Taishu Wang ◽  
Jinrui Zhang ◽  
Zhu Zhou ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Ovarian Cancer ◽  
Cell Death ◽  
Cancer Cells ◽  
Pharmacological Intervention ◽  
Ovarian Cancer Cells ◽  
Mutant P53 ◽  
Wild Type ◽  
Ovarian Cancers ◽  
Wild Type P53

Background/Aims: Ovarian cancer is often diagnosed at later stages with poor prognosis. Recent studies have associated the expression of deubiquitylase USP7 with the survival of ovarian cancers. Being a cysteine protease, USP7 could become a target for pharmacological intervention. Therefore, in this study, we assessed the influence of its inhibitor P5091 on ovarian cancer cells. Methods: Ovarian cancer cells were treated with P5091, and cell proliferation was measured with MTT assay; cell morphology was inspected under a phase-contrast microscope; cell cycle and cell death were examined by flow cytometry. To gain mechanistic insights into its effects, immunoblotting was performed to detect USP7, HDM2, p53, p21, apoptosis and autophagy related proteins. Results: P5091 effectively suppressed the growth of ovarian cancer cells, caused cell cycle blockage, and induced necrosis and apoptosis with more severe phenotypes observed in HeyA8 cells with wild-type p53 than in OVCAR-8 cells with mutant p53. P5091 also prompted autophagy, with more efficient p62 degradation in HeyA8. Conclusion: P5091 shows efficacy in suppressing ovarian cancers harbouring wild-type and mutant p53. Its effects seemed to be enhanced by wild-type p53. The potency of this USP7 inhibitor also correlated with autophagy to some extent. Therefore, the pharmacological targeting of USP7 may serve as a potential therapeutic strategy and warrants further investigation.

scholarly journals Mutant p53 elicits context-dependent pro-tumorigenic phenotypes

Oncogene ◽  
2021 ◽  
Author(s):  
Jennifer J. McCann ◽  
Irina A. Vasilevskaya ◽  
Christopher McNair ◽  
Peter Gallagher ◽  
Neermala Poudel Neupane ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Tumor Suppressor ◽  
Dna Binding ◽  
Mutant P53 ◽  
Wild Type ◽  
P53 Expression ◽  
Transcriptional Profiles ◽  
Cancer Types ◽  
Context Dependent ◽  
Wild Type P53

AbstractThe tumor suppressor gene TP53 is the most frequently mutated gene in numerous cancer types, including prostate cancer (PCa). Specifically, missense mutations in TP53 are selectively enriched in PCa, and cluster to particular “hot spots” in the p53 DNA binding domain with mutation at the R273 residue occurring most frequently. While this residue is similarly mutated to R273C-p53 or R273H-p53 in all cancer types examined, in PCa selective enrichment of R273C-p53 is observed. Importantly, examination of clinical datasets indicated that TP53 heterozygosity can either be maintained or loss of heterozygosity (LOH) occurs. Thus, to mimic tumor-associated mutant p53, R273C-p53 and R273H-p53 isogenic PCa models were developed in the presence or absence of wild-type p53. In the absence of wild-type p53, both R273C-p53 and R273H-p53 exhibited similar loss of DNA binding, transcriptional profiles, and loss of canonical tumor suppressor functions associated with wild-type p53. In the presence of wild-type p53 expression, both R273C-p53 and R273H-p53 supported canonical p53 target gene expression yet elicited distinct cistromic and transcriptional profiles when compared to each other. Moreover, heterozygous modeling of R273C-p53 or R273H-p53 expression resulted in distinct phenotypic outcomes in vitro and in vivo. Thus, mutant p53 acts in a context-dependent manner to elicit pro-tumorigenic transcriptional profiles, providing critical insight into mutant p53-mediated prostate cancer progression.

scholarly journals The mdm-2 oncogene can overcome wild-type p53 suppression of transformed cell growth.

1993 ◽  
Vol 13 (1) ◽  
pp. 301-306 ◽  
Author(s):  
C A Finlay
Keyword(s):  
P53 Protein ◽  
Mutant P53 ◽  
Wild Type ◽  
Rat Embryo ◽  
Ras Gene ◽  
Double Minute ◽  
Murine Double Minute ◽  
Low Levels ◽  
Wild Type P53 ◽  
P53 Genes

Expression of a p53-associated protein, Mdm-2 (murine double minute-2), can inhibit p53-mediated transactivation. In this study, overexpression of the Mdm-2 protein was found to result in the immortalization of primary rat embryo fibroblasts (REFs) and, in conjunction with an activated ras gene, in the transformation of REFs. The effect of wild-type p53 on the transforming properties of mdm-2 was determined by transfecting REFs with ras, mdm-2, and normal p53 genes. Transfection with ras plus mdm-2 plus wild-type p53 resulted in a 50% reduction in the number of transformed foci (relative to the level for ras plus mdm-2); however, more than half (9 of 17) of the cell lines derived from these foci expressed low levels of a murine p53 protein with the characteristics of a wild-type p53. These results are in contrast to previous studies which demonstrated that even minimal levels of wild-type p53 are not tolerated in cells transformed by ras plus myc, E1A, or mutant p53. The mdm-2 oncogene can overcome the previously demonstrated growth-suppressive properties of p53.

scholarly journals Human p53 and CDC2Hs genes combine to inhibit the proliferation of Saccharomyces cerevisiae.

1992 ◽  
Vol 12 (3) ◽  
pp. 1357-1365 ◽  
Author(s):  
J M Nigro ◽  
R Sikorski ◽  
S I Reed ◽  
B Vogelstein
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Growth Inhibition ◽  
Mammalian Cells ◽  
P53 Protein ◽  
Inducible Promoter ◽  
Mutant P53 ◽  
Wild Type ◽  
Growth Inhibitory Activity ◽  
Wild Type P53 ◽  
P53 Genes

Human wild-type and mutant p53 genes were expressed under the control of a galactose-inducible promoter in Saccharomyces cerevisiae. The growth rate of the yeast was reduced in cells expressing wild-type p53, whereas cells transformed with mutant p53 genes derived from human tumors were less affected. Coexpression of the normal p53 protein with the human cell cycle-regulated protein kinase CDC2Hs resulted in much more pronounced growth inhibition that for p53 alone. Cells expressing p53 and CDC2Hs were partially arrested in G1, as determined by morphological analysis and flow cytometry. p53 was phosphorylated when expressed in the yeast, but differences in phosphorylation did not explain the growth inhibition attributable to coexpression of p53 and CDC2Hs. These results suggest that wild-type p53 has a growth-inhibitory activity in S. cerevisiae similar to that observed in mammalian cells and suggests that this yeast may provide a useful model for defining the pathways through which p53 acts.

scholarly journals Activated H-ras rescues E1A-induced apoptosis and cooperates with E1A to overcome p53-dependent growth arrest.

1995 ◽  
Vol 15 (8) ◽  
pp. 4536-4544 ◽  
Author(s):  
H J Lin ◽  
V Eviner ◽  
G C Prendergast ◽  
E White
Keyword(s):  
Cell Proliferation ◽  
Cell Death ◽  
Dna Synthesis ◽  
Growth Arrest ◽  
Mutant P53 ◽  
Permissive Temperature ◽  
Wild Type ◽  
Wild Type P53 ◽  
Dependent Growth ◽  
Induced Apoptosis

The adenovirus E1A oncogene products stimulate DNA synthesis and cell proliferation but fail to transform primary baby rat kidney (BRK) cells because of the induction of p53-mediated programmed cell death (apoptosis). Overexpression of dominant mutant p53 (to abrogate wild-type p53 function) or introduction of apoptosis inhibitors, such as adenovirus E1B 19K or Bcl-2 oncoproteins, prevents E1A-induced apoptosis and permits transformation of BRK cells. The ability of activated Harvey-ras (H-ras) to cooperate with E1A to transform BRK cells suggests that H-ras is capable of overcoming the E1A-induced, p53-dependent apoptosis. We demonstrate here that activated H-ras was capable of suppressing apoptosis induced by E1A and wild-type p53. However, unlike Bcl-2 and the E1B 19K proteins, which completely block apoptosis but not p53-dependent growth arrest, H-ras expression permitted DNA synthesis and cell proliferation in the presence of high levels of wild-type p53. The mechanism by which H-ras regulates apoptosis and cell cycle progression is thereby strikingly different from that of the E1B 19K and Bcl-2 proteins. BRK cells transformed with H-ras and the temperature sensitive murine mutant p53(val 135), which lack E1A, underwent growth arrest at the permissive temperature for wild-type p53. p53-dependent growth arrest, however, could be relieved by E1A expression. Thus, H-ras alone was insufficient and cooperation of H-ras and E1A was required to override growth suppression by p53. Our data further suggest that two complementary growth signals from E1A plus H-ras can rescue cell death and thus permit transformation.

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