The Role of the Tumor Suppressor Gene p53 in Cardiomyocyte Apoptosis

The possibility that a significant fraction of cardiac myocyte loss in various disease states occurs through apoptosis has elicited considerable attention in recent years. Evidence from human studies as well as in vitro and animal models of disease has shown that cardiac myocyte apoptosis can be induced by a variety of stimuli and in a number of disease states, including hypoxia, ischemia–reperfusion, myocardial infarction, mechanical stretch, aortic constriction, and heart failure. Because adult cardiac myocytes are terminally differentiated cells, the effects of such loss can never be fully compensated. Interest in cardiomyocyte apoptosis has been fueled by the possibility that once the proximal and distal signals were defined that initiate this pathway of cell removal, it would be possible to develop stategies to selectively interfere with such signaling and prevent the loss of cardiac function. This article examines the evidence for possible proximal stimuli of apoptosis in the heart, including ligand-dependent activation of the membrane receptors for Fas ligand and tumor necrosis factor-, and, in particular, activation of the tumor suppressor gene p53. It relates what is known about the mechanism by which these stimuli in other cells induce apoptosis and discusses possible strategies for inhibiting apoptosis in the heart.     

p53 expression in K562 cells is associated with caspase-mediated cleavage of c-ABL and BCR-ABL protein kinases

The chimaeric BCR-ABL oncoprotein is the molecular hallmark of chronic myeloid leukaemia (CML). Expression of Bcr-Abl has been associated with arrested differentiation as well as resistance to apoptosis. The downstream pathway involved in apoptosis resistance has been extensively studied, whereas the role of Bcr-Abl in cell differentiation is largely unclear. A recent report has shown that Bcr-Abl expression alone is sufficient to increase the number of multipotent and myeloid lineage-committed progenitors in a dose-dependent manner while suppressing the development of committed erythroid progenitors. In accordance with this model, downregulation of c-Abl and Bcr-Abl has been observed during differentiation in different systems, although the mechanism is still largely unknown. To investigate the relationship between erythroid differentiation and c-Abl and Bcr-Abl levels, we induced differentiation in K562 cells using a temperature-inducible p53 mutant (p53Val1335). It was found that p53-induced erythroid differentiation in K562 cells required caspase activity. During this process, caspase-dependent cleavage of c-Abl and Bcr-Abl tyrosine kinases was observed, suggesting a new mechanism for the downregulation of the kinases during erythroid differentiation.     

Aberrant nuclear p53 protein expression detected by immunohistochemistry is associated with hemizygous P53 deletion and poor survival for multiple myeloma

Hemizygous TP53 deletion is an adverse risk factor in multiple myeloma (MM) but its relationship with p53 protein expression is unclear. We investigated 105 newly diagnosed myeloma patients and correlated nuclear p53 protein immunoreactivity with TP53 deletion status, myeloma-associated genetic risk factors and survival. Fluorescence in situ hybridisation (FISH) detected hemizygous TP53 deletions in 13 (12%) patients while immunohistochemistry detected nuclear p53 protein expression in 12 (11%). Ten (77%) of the 13 del(TP53) cases expressed nuclear p53 protein while 10 (83%) of the 12 nuclear p53 immunoreactive cases had hemizygous TP53 deletions. Hemizygous TP53 deletion and p53 protein expression were strongly correlated (P < 0.001). The overall survival of patients with p53 protein expression was significantly shorter than that of patients without p53 expression (P < 0.001). A multivariate analysis including other myeloma-associated genetic risk factors confirmed p53 expression as an independent risk factor for survival. Our data indicate that nuclear p53 protein expression, detected by a widely available immunohistochemical method, is strongly associated with TP53 deletion and an adverse clinical outcome for MM.     

肝胆管癌丙型肝炎病毒感染与p53和p21WAFD/CIP1异常表达的关系

为探讨丙型肝炎病毒（ＨＣＶ）感染与Ｐ５３和Ｐ２１ＴＷＡＦ－／ＣＩＰ１基因的关系。采用 化技术对２９例原发性肝胆管癌中ＨＣＶ抗原（ＮＳ５－Ａｇ）、ｐ５３和ｐ２１＾ＷＡＦＩ＝／ＣＩＰ１蛋白表达进行研究。结果：２９例胆管癌中ＮＳ５－Ａｇ、ｐ５３及Ｐ２１ＴＷＡＦＩ／ＣＩＰＩ蛋白表达进行研究。结果：２９例胆管癌中ＮＳ５－Ａｇ、Ｐ５３display structure     

Aberrant p53 protein expression and function in a panel of hematopoietic cell lines with different p53 mutations

The p53 gene is one of the most important genes involved in carcinogenesis and its role in part has been clarified by research using cell lines. To know the comprehensive characteristics of 22 hematopoietic cell lines (T, 13 and non‐T, nine lines), the relationship between p53 mutational status, its altered functioning, and its mRNA and protein levels were examined. p53 mutations were less frequent in T‐cell lines (38% vs. 78%) with mainly single nucleotide substitutions generating missense codons. Of 22 different p53 mutations, 12 (54.5%) resulted in mutated proteins, with the mutations clustering mainly in the sequence‐specific DNA‐binding site region located from amino acid residues 102 to 292. p53 mRNA and protein assays determined that wild‐type cell lines expressed constant levels of both mRNA and protein, but mutated cell lines demonstrated two expression patterns: protein over‐expression with reduced mRNA levels, because of missense mutations; and protein under‐expression with little mRNA expression, because of other mutations. The resistance to Nutlin (MDM2 inhibitor)‐induced apoptosis was associated with p53 mutations independently of MDM2 expression levels. This clarification of the unique associations in cell lines useful for bio‐medical studies will contribute to a better understanding of p53‐associated carcinogenesis.     

p53, Mdm2, and c-Myc overexpression is associated with a poor prognosis in aggressive non-Hodgkin's lymphomas

The expression of p53, p21/WAF-1, Mdm2, c-Myc, and proliferating cell nuclear antigen (PCNA) proteins was examined by the immunohistochemistry of paraffin-embedded tissues of 62 patients with aggressive non-Hodgkin's lymphomas (NHL) and correlated to clinical data. Expression of p53, p21/WAF-1, Mdm2, and c-Myc protein was observed in 17 out of 62 cases (30%), 25 out of 60 (42%), 13 out of 44 (30%), and 39 out of 51 (76.5%), respectively. The p53+/p21WAF-1 phenotype, which is more frequently found in p53 mutations, was associated with a worse overall survival (P = 0.04) and with a lower rate of complete response (CR) (PF = 0.01). p53 and c-Myc negative expression was related to a better response to chemotherapy (PF = 0.005 and 0.035, respectively). The expression of p53, c-Myc, and Mdm2 was related to a shortened overall survival (P < 0.001, 0.05, and 0.037, respectively), suggesting that the expression of these proteins could be associated with a poor outcome in these patients.     

Association of p53/p21 expression with cigarette smoking and prognosis in esophageal squamous cell carcinoma patients

factors,such as cigarette smoking,in esophageal squamous cell carcinoma(ESCC)in northeastern Iran,a region with a high incidence of ESCC.METHODS:The expression of p53 and p21 proteins was investigated immunohistochemically in tumor tissue from 80 ESCC patients and in 60 available paraffinembedded blocks of adjacent normal specimens from the cases,along with normal esophageal tissue from 80 healthy subjects.RESULTS:Positive expression of p53 protein was detected in 56.2%(45/80)of ESCC cases,and in none of the normal esophageal tissue of the control group(P<0.001).Furthermore,73.8%(59/80)of ESCC cases and 43.8%(35/80)of controls had positive expression of p21 protein(P<0.001).Cigarette smoking was significantly associated with p53 over-expression in ESCC cases(P=0.010,OR=3.64;95%CI:1.32-10.02).p21 over-expression was associated with poorer clinical outcome among the ESCC patients(P=0.009).CONCLUSION:Over-expression of p53 in association with cigarette smoking may play a critical role in ESCC carcinogenesis among this high-risk population of northeastern Iran.Furthermore,p21 over-expression was found to be associated with poor prognosis,specifically in the operable ESCC patients.     

Expression of cyclooxygenase-2 is associated with p53 accumulation in premalignant and malignant gallbladder lesions

AIM: To examine the relationship between cyclooxygenase-2 (COX-2) overexpression and p53 accumulation in gallbladder carcinoma and its precursor lesions. METHODS: Sixty-eight gallbladder tissue samples comprising 14 cases of normal gallblader epithelium, 27 cases of dysplasia (11 low-grade dyplasia and 16 high-grade dysplasia) and 27 adenocarcinomas were evaluated by immunohistochemistry for COX-2 expression and p53 accumulation. The relationship among COX-2 expression, p53 accumulation and clinicopathological characteristics was analysed. RESULTS: COX-2 was expressed in 14.3% of normal gallbladder epithelium, 70.3% of dysplastic epite hlium, and 59.2% of adenocarcinomas. When divided into low- and high-grade dysplasia, COX-2 was positive in 5 (45.4%) cases of low-grade and 14 (87.5%) of high-grade dysplasia (P = 0.019). Accumulation of p53 was detected in 5 (31.2%) cases of high-grade dysplasia and in 13 (48.1%) of carcinomas. No p53 accumulation was found in normal epithelium or low-grade dysplasia. COX-2 overexpression was observed in 17 of 18 (94.4%) cases with p53-accumulation in comparison with 20 (40.0%) out of 50 cases without p53 accumulation (P < 0.001). CONCLUSION: The significant differences in COX-2 expression among normal epithelium, low-grade dysplasia and high-grade dysplasia suggest that overexpression of COX-2 enzyme is an early event in gallbladder carcinogenensis. Furthermore, since accumulation of p53 correlates with COX-2 expression, COX-2 overexpression observed in gallbladder high-grade dysplasia and carcinoma might be partly due to the dysfunction of p53.     

p53 abnormalities in CLL are associated with excess of prolymphocytes and poor prognosis

To determine the role of the p53 gene in chronic lymphocytic leukaemia (CLL) and its possible involvement in the pathogenesis of a progressive form of CLL characterized by > 10% prolymphocytes (CLL/PL), we selected 32 cases, 17 with typical morphology and 15 CLL/PL. The extent of inactivation of p53 was examined by assessing loss of heterozygosity (LOH) at 17p13.3, by sequencing the highly conserved region (exons 5–9) of the p53 gene and by analysing p53 protein expression. LOH was detected in 8/28 (29%) cases, p53 mutations in 5/32 (16%) cases and p53 expression in 5/27 (19%) cases. Overall 11 cases (30%) had p53 abnormalities of which eight cases had CLL/PL. There was a significant association between CLL/PL and p53 abnormalities ( P  = 0.05); 75% of cases with LOH, 80% of p53 mutations and 80% of cases positive for p53 protein had CLL/PL. Thus, p53 inactivation is the first gene abnormality identified so far to be involved in the development of CLL/PL. All the cases with typical CLL and p53 abnormalities had only one allele affected whereas 4/6 CLL/PL had both alleles inactivated. This difference in the extent of p53 inactivation suggests that accumulation of p53 abnormalities may be associated with progression of CLL to CLL/PL.
CLL cases with p53 abnormalities were characterized by a higher incidence of stage C ( P  < 0.025), a higher proliferative rate ( P  = 0.05), short survival ( P  < 0.005) and resistance to first-line therapy ( P  < 0.02) but not to nucleoside analogues. Analysis of the correlation between p53 status and incidence of trisomy 12 by fluorescence in situ hybridization (FISH) showed that trisomy 12 was more frequent in cases without p53 abnormalities, suggesting that trisomy 12 and p53 may represent different pathways of transformation in CLL.     

胃癌p53基因表达与转移及预后的研究

目的观察胃癌组织ｐ５３基因的超表达及其与预后的关系。方法用抗人Ｐ５３基因蛋白单克隆抗体Ｓ＿Ｐ免疫组织化学方法，观察１２８例胃癌组织ｐ５３表达状况，并对ｐ５３表达与胃癌淋巴结转移状态和术后５年生存率进行比较分析。结果胃癌组织１２８例的ｐ５３表达阳性率为４３８％（５６／１２８）；ｐ５３表达阳性和阴性组的胃癌局部和远处淋巴结转移率分别为６７９％（３８／５６）和５１４％（３７／７２），两者经统计学处理无显著性差异（Ｐ＞００５）。获得随访９８例，胃癌术后５年生存率的随访结果显示，ｐ５３阳性和阴性组分别为３８１％（１６／４２）和３０１％（１７／５６），两组间无统计学意义（Ｐ＞００５）。结论胃癌的发生与ｐ５３基因突变关系密切，并可用免疫组化检测，但Ｐ５３基因蛋白在胃癌组织中的超表达，似不能作为判断胃癌预后的参考指标，应进一步探讨     

Coexpression of HER-2/neu and p53 is associated with a shorter disease-free survival in node-positive breast cancer patients

Breast cancer tissue was examined for overexpression of HER-2/neu and p53 oncogene proteins. Samples from 105 breast cancer patients were investigated by Western-blot analysis and their relationship to other established markers and clinical outcome was examined. In 21.0% of the cases HER-2/neu was overexpressed, and in 46.7% the p53 protein level was increased. Expression of these two oncogene products was closely correlated. Overexpression of both oncogenes was associated with larger tumour size and negative hormone receptor. The percentage of HER-2/neu and p53 overexpression was higher in node-positive patients, although statistical evaluation was not significant. While overexpression of HER-2/neu as well as p53 in node-positive patients was associated insignificantly with shorter disease-free survival, a significant difference could be documented when the disease-free survival of patients with overexpression of both oncogene proteins was compared to that of patients with no overexpression.     

Long non-coding RNA GAS5 inhibits migration and invasion in gastric cancer via interacting with p53 protein

BackgroundThe rapid progress of gastric cancer (GC) is mainly due to metastasis. Long non-coding RNA (lncRNA) GAS5 has been identified as a tumor suppressor in numerous cancers, and its downregulation in GC has already been reported.AimsIn this study, we planned to investigate the role of GAS5 in GC metastasis.MethodsGene expressions were detected by qRT-PCR. ISH staining was applied to assess GAS5 level in clinical tissues. Gain-of-function assays were conducted to evaluate the function of GAS5 in GC metastasis. RNA pull down, RIP and cycloheximide assays were performed to confirm the relationship between GAS5 and p53 protein.ResultsGAS5 expression was markedly decreased in GC tissues and cell lines, and its low expression was strongly related to GC metastasis and unsatisfactory prognosis. GAS5 overexpression repressed GC cell migration and invasion by targeting p53. Intriguingly, GAS5 relied on the exon 12 to interact with and stabilize p53 protein.ConclusionOur data implied that GAS5 is a suppressor in GC metastasis via modulating p53 signaling, suggesting GAS5 as a potential therapeutic target for GC, especially for patients with metastasis.     

Aging is associated with decreased pancreatic acinar cell regeneration and phosphatidylinositol 3-kinase/Akt activation

BACKGROUND & AIMS: The effects of aging on pancreatic acinar cell proliferation have not been clearly defined. Phosphatidylinositol 3-kinase (PI3K)-mediated phosphorylation of Akt is a critical step for proliferation of various cell types and insulin secretion from pancreatic endocrine cells; however, its role in acinar cell proliferation is not known. The purpose of this study was to (1) delineate the effects of aging on pancreatic regeneration after partial pancreatectomy (Px) and (2) define the involvement of the PI3K/Akt pathway in pancreatic regeneration. METHODS: Following partial Px, pancreatic regeneration and activation of the PI3K pathway were compared in young and aged mice. Activation of the PI3K/Akt pathway was evaluated by Akt phosphorylation (pAkt). The role of the PI3K pathway in pancreatic regeneration after partial Px was assessed by effects of a pharmacologic PI3K inhibitor wortmannin or small interfering RNA (siRNA) to the p85alpha regulatory subunit. To confirm further the critical role of the PI3K/Akt pathway in pancreatic acinar cell proliferation, IGF-1-mediated cell proliferation was determined in cultured acinar cells pretreated with wortmannin or p85alpha siRNA. RESULTS: Pancreatic regeneration and pAkt expression after partial Px were significantly decreased with aging. Treatment with wortmannin or p85alpha siRNA reduced pancreatic regeneration after partial Px. The IGF-1-mediated cell proliferation in vitro was completely blocked by wortmannin or p85alpha siRNA but not by the MEK/ERK inhibitor PD98059. CONCLUSIONS: PI3K/Akt activation plays a critical role in the regeneration of pancreatic acini after resection. Furthermore, pancreatic regeneration is markedly attenuated in the aged pancreas most likely because of decreased PI3K/Akt activation.     

CHFR和mp53基因编码蛋白在胃癌组织中的表达及临床病理学意义

目的:观察CHFR和P53蛋白的表达与胃癌临床病理学特征的关系,探讨其在胃癌发生发展过程中的作用及相关的分子机制.方法:利用组织芯片制作仪(美国),构建成5个包括151例胃癌及101例与其配对的正常胃黏膜、肠化生或不典型增生的组织芯片蜡块.采用Envision免疫组化二步法检测151例胃癌及101例配对癌旁胃黏膜组织中CHFR蛋白和P53蛋白的表达.结果:CHFR蛋白在非癌胃黏膜组织中阳性表达率为85.25%(52/61),在胃癌组织中阳性表达率显著降低(49.67%,75/151,P<0.05);CHFR表达下调或缺失与胃癌患者的性别显著相关,女性患者胃癌组织中CHFR表达缺失率显著高于男性患者(64% vs 43.56%,P<0.05).BorrmanⅢ Ⅳ型胃癌组织中CHFR表达缺失率显著高于BorrmanⅠ Ⅱ型胃癌(57.14% vs 34.78%,P<0.05).虽然不同组织学类型胃癌之间CHFR的表达无统计学差异,但本研究发现胃印戒细胞癌组CHFR表达缺失率最高(71.43%).胃癌组织中CHFR蛋白的表达缺失与肿瘤浸润深度、淋巴结转移以及mP53蛋白表达未见显著相关性(P>0.05).结论:有丝分裂前期检查点CHFR基因表达下调或缺失在胃癌中是频发事件.可能参与胃癌的发生,其与女性、弥漫浸润型胃癌发生发展的关系可能更为密切.     

Expression of p53 and p21WAF1/CIP1 Proteins in Gastric and Esophageal Cancers (Comparison with Mutations of the p53 Gene)

The p53 gene has been shown to be commonlymutated in various human cancers, and mutant p53 can actas a dominant oncogene. The intact p53 protein is alsoknown to induce the cyclin-dependent kinase inhibitor p21^WAF1/CIP1 and is implicated incell cycle arrest. We investigated p53 gene alterationsin gastric adenocarcinoma and esophageal squamous cellcarcinoma to elucidate the association of the nuclearaccumulation of the p53 protein and/orp21^WAF1/CIP1 protein. Abnormalities of thetumor suppressor gene p53 protein and the expression ofp21^WAF1/CIP1 protein were analyzed byimmunohistochemical techniques in 32 cases of gastric adenocarcinoma and 15 cases ofesophageal squamous cell carcinoma. Twenty cases ofgastric cancer and five cases of esophageal cancer werealso analyzed for p53 gene mutation by polymerase chain reaction and direct nucleotide sequencing.Overexpression of p53 protein was found in 13/32 (41%)of gastric cancers and 5/15 (33%) of esophageal cancers.We found immunodetectable p53 in 10/14 cases with mutations and in none of 11 cases withoutmutations in gastric and esophageal cancers. Hence,immunohistochemical and genetic analyses gave concordantresults in 84% of 25 cases, revealing a good correlation between immunostaining of p53 and missensemutation of the p53 gene. p53 immunostaining was notobserved in cases with frameshift or splicing mutation.The expression of p21^WAF1/CIP1 protein wasfound in 9/32 (29%) of gastric cancers and 4/15 (27%) ofesophageal cancers and in 2/14 (14%) cases withalteration of the p53 gene and in 5/11 (45%) without.These results suggest that abnormalities of p53 may be closely associated with the pathogenesisof gastric adenocarcinoma and esophageal squamous cellcarcinoma and that the immunoreactivity of p53 proteinis a general indicator of the tumors with altered p53 function. The expression ofp21^WAF1/CIP1 protein was suppressed in theneoplastic tissues with and without p53 genealteration.     

Cystic medial degeneration of the aorta is associated with p53 accumulation, Bax upregulation, apoptotic cell death, and cell proliferation

OBJECTIVE—To address a potential role for p53, Bcl2 associated protein X (Bax), and apoptosis in the processes associated with cell turnover during cystic medial degeneration (CMD) of the aorta.
METHODS—Histochemical, immunohistochemical, biochemical, and morphometric methods were used to assess the presence and distribution of p53 immunoreactivity (p53-IR) and Bax immunoreactivity (Bax-IR), as well as the presence of apoptosis and tissue repair processes.
RESULTS—Immunohistochemical staining disclosed evidence for p53-IR in all specimens in 26.1 (11.5)% of vascular smooth muscle cells (VSMCs) (controls 0.8 (1.3)%; p < 0.001). Bax-IR was present in all specimens in 10 (5.4)% of medial cells (controls 0.3 (0.5)%; p < 0.001). Medial VSMCs (α-actin positive) with cytoplasmic staining for an apoptosis specific protein (c-jun/ASP) were present in 20/20 specimens (0.7 (0.6)% of VSMCs, controls 0%, p < 0.001), whereas terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling (TUNEL) positive VSMCs were present in 17/20 specimens (1 (1.5)% of VSMCs, controls 0%, p < 0.001). The presence of apoptosis was confirmed by electron microscopy and the demonstration of oligonucleosomal DNA fragments after agarose gel electrophoresis. As shown by double labeling and investigation of serial sections, p53-IR, Bax-IR, c-jun/ASP-IR, and positive TUNEL labeling localised to the same compartments of the aortic media, raising a possible role for p53 and Bax in the triggering of apoptosis of VSMC during CMD. MIB1/Ki-67 positive medial VSMCs (α-actin positive) and mesenchymal cells (vimentin positive) were present in all specimens (2.5 (2.8)% of medial cells; controls 0.3 (0.9)%, p < 0.001) mainly in the region around the vasa vasorum, indicating that cell regeneration during CMD may originate mainly from the mesenchyme surrounding the vasa vasorum.
CONCLUSION—This study shows that the formal pathogenesis of CMD is characterised by p53 accumulation, Bax upregulation, cell death by apoptosis, and cell regeneration. Nevertheless, the precise stimuli of p53 activation and Bax upregulation as well as the role of p53 and apoptosis in the dissection process itself remain elusive.


Keywords: mucoid cystic medial degeneration of the aorta; p53 accumulation; apoptosis; cell proliferation     

Expression of p53 and Ki-67 antigen in bone marrow giant proerythroblasts associated with human parvovirus B19 infection

Giant proerythroblasts are hallmarks of human parvovirus B19 infection. We attempted to characterize these cells in 5 patients with parvovirus B19-induced pure red cell aplasia using immunostaining of paraffin-embedded bone marrow sections with antibodies against erythroid-lineage-specific proteins, viral capsid antigen VP-1, and apoptosis- and cell-cycle-related proteins. Giant proerythroblasts are immunohistochemically consistent with early erythroid precursors of cells in the differentiation stage of CD34-, cytoplasmic spectrin+, glycophorin A-, and band-3-. VP-1 was expressed in the nucleus and cytoplasm of small- to medium-sized spectrin+ erythroid cells but not in giant proerythroblasts. The giant proerythroblasts displayed nuclear staining for p53 (41%+/-16%) and Ki-67 antigen (100%+/-0%) and cytoplasmic staining for Bax (65%+/-11%) and procaspase-3 (78%+/-10%), whereas they were not stained for p21Wafl/Cip1, active form of caspase-3, or terminal deoxynucleotidyltransferase-mediated deoxyuridine nick-end labeling (TUNEL). Antiapoptotic proteins, Bcl-2 and Mcl-1, were not expressed in the giant cells, and Bcl-x was infrequently expressed in these cells (11%+/-4%). These immunohistochemical findings suggest that giant proerythroblasts are proliferating erythroid precursors with accumulation of nonfunctional p53.