p53 mutations in colorectal cancer.

Immunohistological staining of primary colorectal carcinomas with antibodies specific to p53 demonstrated gross overexpression of the protein in approximately 50% of the malignant tumors examined. Benign adenomas were all negative for p53 overexpression. To determine the molecular basis for this overexpression we examined p53 protein expression in 10 colorectal cancer cell lines. Six of the cell lines expressed high levels of p53 in ELISA, cell-staining, and immunoprecipitation studies. Direct sequencing and chemical-mismatch-cleavage analysis of p53 cDNA by using the polymerase chain reaction in these cell lines showed that all cell lines that expressed high levels of p53 were synthesizing mRNAs that encoded mutant p53 proteins. In two of those four cell lines where p53 expression was lower, point mutations were still detected. Thus, we conclude that overexpression of p53 is synonymous with mutation, but some mutations would not be detected by a simple immunohistochemical analysis. Mutation of the p53 gene is one of the commonest genetic changes in the development of human colorectal cancer.     

Over-expression of p53 protein in esophageal squamous cell carcinoma of women

BACKGROUND/AIMS: Most physicians naturally accept the etiological aspect that the incidence of esophageal squamous cell carcinoma (ESCC) is excessively more frequent in men than that in women. However, a definitely scientific confirmation to explain it has not been found. In the current study, we investigated the relationship between gender and p53 over-expression, which might resolve the difference between the genders in the mechanism for carcinogenesis in ESCC. METHODOLOGY: Immunohistochemical expression of p53 was examined for 134 ESCCs, and the correlation of the gender with the clinicopathologic features and over-expression of p53 was compared. RESULTS: The proportion of p53 over-expression in women was 23.8% (5 out of 21) and this incidence proportion was significantly lower than that in men (48.7%, 55 out of 113; p=0.031). CONCLUSIONS: This biological modulation might be correlated with the lower incidence of ESCC in women.     

Specific intronic p53 mutation in esophageal squamous cell carcinoma in Southern Thailand

AIM:To investigate p53 mutations in esophageal cancer in a high-risk population,and correlate them with smoking,alcohol consumption and betel chewing.METHODS:One hundred and sixty-five tumor samples of esophageal squamous cell carcinoma(ESCC) obtained from a university hospital in Songkhla province,Southern Thailand were investigated for p53 mutations in exons 5-8,using polymerase chain reaction-single strand conformation polymorphism analysis,followed by direct sequencing.A polymerase chain reactionrestric...     

Mutation hotspots due to sunlight in the p53 gene of nonmelanoma skin cancers.

To identify the sites in the p53 tumor suppressor gene most susceptible to carcinogenic mutation by sunlight, the entire coding region of 27 basal cell carcinomas (BCCs) of the skin was sequenced. Fifty-six percent of tumors contained mutations, and these were UV-like: primarily CC-->TT or C-->T changes at dipyrimidine sites. Such mutations can alter more than half of the 393 amino acids in p53, but two-thirds occurred at nine sites at which mutations were seen more than once in BCC or in 27 previously studied squamous cell carcinomas of the skin. Seven of these mutation hotspots were specific to skin cancers. Internal-cancer hotspots not located at dipyrimidine sites were not mutated in skin cancers; moreover, UV photoproducts were absent at these nucleotides. The existence of hotspots altered the process of inactivating p53 in BCC compared to other cancers: allelic loss was rare, but 45% of the point mutations were accompanied by a second point mutation on the other allele. At least one of each pair was located at a hotspot. Sunlight, acting at mutation hotspots, appears to cause mutations so frequently that it is often responsible for two genetic events in BCC development.     

p53蛋白在口腔鳞癌中的表达

目的 通过对突变型p53蛋白在口腔鳞癌组织中表达的观察,分析p53与口腔鳞癌临床病理特征之间的关系,探讨p53在口腔鳞癌发生中的作用机制。方法 利用免疫组化(P-V法)检测116例患者口腔鳞癌组织及10例正常人口腔黏膜组织中突变型p53蛋白的表达情况。结果 p53蛋白在正常人口腔黏膜和口腔鳞癌组织中的表达率分别为20％、63.8％,二者比较差异有统计学意义(X2=5.660 4,P<0.05);口腔鳞癌在不同病理分级时,p53蛋白表达差异有统计学意义(X2=7.536 2,P<0.05);p53蛋白表达与年龄、性别、发生部位及有无淋巴结转移无相关性。结论 突变型p53蛋白表达与口腔鳞癌的发生有关。不同病理分级,p53蛋白表达也不同。     

Defining the origins of Ras/p53-mediated squamous cell carcinoma

The precise identity of cancer cells of origin and the molecular events of tumor initiation in epidermal squamous cell carcinoma (SCC) are unknown. Here we show that malignancy potential is related to the developmental capacity of the initiating cancer cell in a genetically defined, intact, and inducible in vivo model. Specifically, these data demonstrate that SCCs can originate from inside the hair follicle stem cell (SC) niche or from immediate progenitors, whereas more developmentally restricted progeny, the transit amplifying (TA) cells, are unable to generate even benign tumors in the same genetic context. Using a temporal model of tumorigenesis in situ, we highlight the phenotypes of cancer progression from the hair follicle SC niche, including hyperplasia, epithelial to mesenchymal transition, and SCC formation. Furthermore, we provide insights into the inability of hair follicle TA cells to respond to tumorigenic stimuli.     

Clinical implication of screening p53 gene mutations in head and neck squamous cell carcinomas

The role of the tumour-suppressor gene p53 in the tumorigenesis of head and neck cancer has been well established, but the clinical significance of p53 alteration is still unclear. A group of 50 patients with head and neck squamous cell carcinoma (HNSCC) were investigated for p53 alterations. DNA was extracted from fresh tumour samples and polymerase chain reaction/single-strand conformation polymorphism analysis was used to detect p53 gene mutations in the region from exon 5 to exon 9. In addition, p53 protein overexpression was assessed by immunohistochemistry using the monoclonal antibody DO-7 on paraffin-embedded tissue sections. p53 gene mutations were found in 45% and p53 protein expression was detected in 61.2% of tumour samples. While p53 protein expression was not correlated with any clinical factors, p53 gene mutations indicated local regional recurrences of HNSCC. The risk of locoregional recurrence was significantly greater in patients with a p53 gene mutation than in patients with the wild-type p53 gene (P = 0.001). Multivariate analysis confirmed p53 gene mutation to be an independently predictive factor for the tumour recurrence (P = 0.0064). When we analysed p53 gene mutation in 12 patients with primary and recurrent tumours, we found that 4 patients (33.3%) had a different p53 gene mutation in the recurrent tumour from that in the original primary tumour. The results indicate that p53 gene mutations and not protein overexpression are valuable predictors for tumour recurrences and for differential diagnosis of a second primary HNSCC. Received: 20 January 1998 / Accepted: 20 March 1998     

原发性胃癌p53基因突变

目的 p53基因是当前抑癌基因研究中的热点之一。迄今,有关 p53基因异常与胃癌临床病理学参数如大体类型、临床分期、组织分化程度,浸润深度及淋巴结转移之间的关系尚无定论。Tumura 报告p53基因改变主要发生于异倍体瘤,国内尚无报道。本实验目的主要是分析中国人原发性胃癌 p53基因突变与这些病理参数,包括 DNA 倍体之间的关系。方法用聚合酶链式反应—单构象多态分析(PCR—SSCP)技术对20例原发性胃癌 p53基因外显子5—8突变进行检测。结果 8例(40%)发生了突变,其中2例发生在外显子7,4例发生在外显子8。0至Ⅲ期均有突变存在。66.7%(6/9)的异倍体瘤检测到了p53突变,而二倍体瘤中只有18.2%(2/11)发生了 p53突变。结论 p53基因突变与胃癌临床病理参数如大体类型、分期、组织分化程度、浸润深度及淋巴结转移之间无明显关系,而与胃癌 DNA 倍体改变有关。     

p53在人和小鼠口腔鳞状细胞癌组织中表达的比较

目的比较p53在人和小鼠正常口腔黏膜、口腔异常增生组织、口腔鳞状细胞癌(简称鳞癌)组织中的表达及意义。方法采用免疫组织化学方法分别检测人和小鼠各8例口腔正常黏膜,各8例口腔异常增生组织,各8例口腔鳞癌组织中p53的表达情况。结果人口腔正常黏膜p53表达率为0.0%(0/8),口腔异常增生组织p53表达率37.5%(3/8)、口腔鳞癌p53表达率62.5%(5/8);小鼠正常口腔黏膜p53表达率为0(0/6),口腔异常增生组织p53表达率为50.0%(4/8),口腔鳞癌p53表达率为75.0%(6/8)。结论 p53蛋白阳性表达在人和小鼠保持一致性,均随病理恶性程度升高而增加。小鼠口腔鳞癌模型与人类口腔鳞癌的发生发展具有相似性。     

Five-year postsurgical monitoring of serum p53 antibody for locally advanced esophageal squamous cell carcinoma

Serum p53 antibody (s-p53-Ab) titers were postoperatively monitored for over 5 years in a 67-year-old man with locally advanced esophageal squamous cell carcinoma. The tumor stage was classified as clinical stage II (cT3N0M0). Serum SCC antigen (s-SCC-Ag; 6.2 ng/mL) and s-p53-Ab (3.83 U/mL) were noted to be positive before surgery. Radical esophagectomy with three-field lymph node dissection was performed without neoadjuvant therapy. Pathological findings of the surgically resected specimens revealed a stage II tumor (pT3N0M0). Postoperatively, the patients did not receive any adjuvant therapy. Although the s-SCC-Ag was found to be negative at 2 months postoperatively, s-SCC-Ag was found to be six times positive despite no signs of recurrence. The s-p53-Ab titers constantly decreased to less than the cutoff value at 6 months postoperatively and continuously decreased over 5 years postoperatively. Finally, s-p53-Ab titers became less than the detection limit value at 60 months postoperatively. No recurrence was observed throughout the postoperative course. This case report is the first to describe the five-year monitoring of postoperative changes in s-p53-Ab titers in a patient with locally advanced esophageal squamous cell carcinoma without recurrence. s-p53-Ab titers seemed to be more useful than s-SCC-Ag for disease monitoring in this case.     

曲古抑菌素A对甲状腺鳞癌SW579细胞株p53和p21表达的影响

目的观察曲古抑菌素A(TSA)对甲状腺鳞癌SW579细胞株生长增殖及p53和p21表达的影响,进而探讨TSA抗甲状腺癌的作用机制。方法体外培养SW579细胞,实验分为DMSO组、TSA组(终浓度为50、100、200、400 nmol/L),采用MTT比色法测定细胞增殖活性;用RT-PCR方法检测SW579细胞p53及p21的mRNA表达;用Western blot方法检测SW579细胞p53及p21的蛋白表达。结果 MTT结果显示,TSA可明显抑制SW579的增殖,并呈剂量依赖性。RT-PCR与Western blot检测结果表明,与未加TSA组比较,TSA组随着浓度的逐渐加大,p21 mRNA和蛋白表达水平明显升高;p53 mRNA表达不变,而p53蛋白表达水平上调。结论 TSA在一定浓度范围内对甲状腺鳞癌细胞株SW579有剂量依赖性地增殖抑制作用,其机制可能与TSA提高SW579细胞p53的表达,进而再上调p21的表达有关。     

p53 mutations in british patients with hepatocellular carcinoma: clustering in genetic hemochromatosis.

BACKGROUND & AIMS: Environmental factors are important in the etiology of hepatocellular carcinoma (HCC). Aflatoxin B1 causes a specific point mutation in the p53 tumor-suppressor gene in exposed individuals. In Western populations, mutations of this gene seem to be less frequent. We have investigated the role of p53 mutations in tumorigenesis in British patients with HCC. The aim of this study was to determine the frequency and mutational spectrum of the p53 gene in HCCs from British patients. METHODS: DNA from 170 HCCs, of well-defined etiology, in British patients was analyzed by single-stranded conformational polymorphism using the polymerase chain reaction technique. Mutations were then characterized by direct sequencing. RESULTS: Twenty-nine percent of tumors had p53 mutations. Ten of 14 (71%) hemochromatotic cancers had mutations within the p53 gene, and clustering of these mutations at codon 220 (A-G) was found in 5 cases; 3 others had T-A mutations. No clustering was found in HCCs with other etiologies. CONCLUSIONS: p53 mutations are more common than was thought in Northern European HCCs. This is the first demonstration of p53 mutational clustering in HCCs from hemochromatotic subjects.     

Changes of serum p53 antibodies and clinical significance of radiotherapy for esophageal squamous cell carcinoma

AIM： To explore the relationship between serum p53 antibodies （p53-Abs） and clinicopathological characteristics and therapeutic effect in patients with esophageal carcinoma （EC）, and to investigate sequential changing regularity of serum pS3-Abs after radiotherapy.
METHODS： The serum pS3-Ab levels were detected in 46 EC patients and 30 healthy adults by enzyme linked immunosorbent assay （ELISA）. The blood samples were collected on the day before radiotherapy and on the administration of an irradiation dose of 20 Gy/10 f/12 d, 40 Gy/20 f/24 d and 60 Gy/30 f/36 d after radiotherapy.
RESULTS： The level and positive rate of serum pS3-Abs in EC patients were significantly higher than those in normal individuals （P 〈 0.05）. Serum anti-p53 antibodies were positive in 18 of 46 EC patients （39.1%）. The positive rate of pS3-Abs in EC was related to histological grade, disease stage and lymph node metastasis （P 〈 0.05）, but it was not significantly related to sex, age and to the size and site of tumor. The level and positive rate of p53-Abs had significant differences between before radiotherapy and after administration of an irradiation dose of 40 Gy/20 f/24 d and 60 Gy/30 f/36 d （P 〈 0.05 orP 〈 0.01）. The positive rate of p53-Abs in EC patients with effect was significantly lower than that in those without effect after radiotherapy （P 〈 0.0001）.
CONCLUSION： Detection of serum p53-Abs is helpful to the diagnosis of esophageal carcinoma. Monitoring for sequential change of serum p53-Abs before and after radiotherapy in patients with esophageal carcinoma is also useful to evaluate the response to the treatment and prognosis of the patients.     

p53 gene mutations and protein accumulation in human ovarian cancer.

Mutations of the p53 gene on chromosome 17p are a common genetic change in the malignant progression of many cancers. We have analyzed 38 malignant tumors of ovarian or peritoneal müllerian type for evidence of p53 variations at either the DNA or protein levels. Genetic studies were based on single-strand conformation polymorphism analysis and DNA sequencing of exons 2 through 11 of the p53 gene; mutations were detected in 79% of the tumors. These data show a statistically significant association between mutations at C.G pairs and a history of estrogen therapy. Two of 20 patients whose normal tissue could be studied carried germ-line mutations of p53. Immunohistochemical analysis of the p53 protein was carried out using monoclonal antibody PAb1801. Ninety-six percent of the missense mutations were associated with abnormal accumulation of p53 protein, but nonsense mutations, a splicing mutation, and most deletions did not result in p53 protein accumulation. A statistically significant association between p53 protein accumulation in poorly differentiated stage III serous carcinomas and small primary tumor size at diagnosis was found, perhaps suggesting that p53 protein accumulation accelerates the metastatic spread from a primary tumor. Overall, our findings indicate that alterations of p53 play a major role in ovarian cancer, including predisposition to the disease in some patients, and suggest a possible mechanism for somatic mutations leading to this cancer.     

Dominant-negative p53 mutations selected in yeast hit cancer hot spots.

Clinically important mutant p53 proteins may be tumorigenic through a dominant-negative mechanism or due to a gain-of-function. Examples for both hypotheses have been described; however, it remains unclear to what extent they apply to TP53 mutations in general. Here it is shown that the mutational spectrum of dominant-negative p53 mutants selected in a novel yeast assay correlates tightly with p53 mutations in cancer. Two classes of dominant-negative mutations are described; the more dominant one affects codons that are essential for the stabilization of the DNA-binding surface of the p53 core domain and for the direct interaction of p53 with its DNA binding sites. These results predict that the vast majority of TP53 mutations leading to cancer do so in a dominant-negative fashion.     

The clinicopathological significance of p21 and p53 expression in esophageal squamous cell carcinoma: an analysis of 153 patients

OBJECTIVE: The p21 gene is thought to play a central role in tumor suppression. The aim of this study was to examine the clinicopathological role of p21 and p53 in esophageal squamous cell carcinomas. METHODS: The expression of p21 and p53 proteins in 153 Chinese patients (131 men, 22 women) with resected esophageal squamous cell carcinomas was investigated by the immunohistochemical method. Correlation between p21 and p53 expression and clinicopathological features was examined. RESULTS: The expression of p21 and p53 was detected in 70% and 64% of the tumors, respectively. The staining of p21 and p53 was also found in squamous carcinoma in situ, dysplasia, and nontumor epithelium. p21 expression was often weak in the suprabasal cells and found in better differentiated tumors. There was no significant correlation between the expression of p21 and the abnormal accumulation of p53. The prognosis of the patients depended on the size, stage, and p21 expression of the lesion. In stage III lesions with tumor diameter < or = 7.5 cm (n = 93), patients with loss of p21 expression had better survival. The survival rates of patients were worse if they had expression of both p21 and p53. CONCLUSIONS: Thus, p21 and p53 had prognostic value for esophageal squamous cell carcinomas. Loss of p21 expression was shown without p53 alternations, indicating that other mechanisms are also involved in turning off the gene. The pattern of p21 and p53 expression predicts an aggressive clinical course of esophageal squamous cell carcinomas.     

Prognostic significance of high serum p53 antibody titers in patients with esophageal squamous cell carcinoma

Background

The p53 protein overexpression that usually results from genetic alterations reportedly induces serum antibodies against p53. However, little information is available about the prognostic significance of perioperative serum p53 antibody (s-p53-Abs) titers in patients with esophageal squamous cell carcinoma.

Methods

In this study, we retrospectively evaluated the clinical significance of perioperative s-p53-Abs in 135 patients with esophageal squamous cell carcinoma. Of these, 58 patients received neoadjuvant chemotherapy comprising 5-FU and CDDP. While the cutoff level at 1.3 U/ml indicated seropositive patients, level of 13.4 U/ml was used to identify high-titer patients. We monitored serum titers seropositive patients after surgery and evaluated the prognostic significance by the univariate and multivariate analyses.

Results

In this study, 29 patients (21.5%) were positive for s-p53-Abs before treatment. The frequency of both seropositive patients and high-titer patients (>?13.4 U/ml) was not significantly associated with tumor progression. While seropositive patients did not demonstrate significant poor overall survival, high-titer patients demonstrated significant poor overall survival based on the multivariate analysis (P?<?0.001). Moreover, the s-p53-Abs titer did not correlate with the response to neoadjuvant chemotherapy. Among seropositive patients, the negative conversion of s-p53-Abs more likely led to be long-term survival.

Conclusions

This study determined that the high-titer of s-p53-Abs was an independent risk factor to reduce the overall survival of patients with esophageal cancer patients. The negative conversion of s-p53-Abs could be a good indicator of favorable prognosis.

     

Germ-line mutations of the p53 tumor suppressor gene in patients with high risk for cancer inactivate the p53 protein.

Germ-line mutations in the p53 tumor suppressor gene have been observed in patients with Li-Fraumeni syndrome, brain tumors, second malignancies, and breast cancers. It is unclear whether all of these mutations have inactivated p53 and thereby provide an increased risk for cancer. Therefore, it is necessary to establish the biological significance of these germ-line mutations by the functional and structural analysis of the resulting mutant p53 proteins. We analyzed the ability of seven germ-line mutant proteins observed in patients with Li-Fraumeni syndrome, second primary neoplasms, or familial breast cancer to block the growth of malignant cells and compared the structural properties of the mutant proteins to that of the wild-type protein. Six of seven missense mutations disrupted the growth inhibitory properties and structure of the wild-type protein. One germ-line mutation retained the features of the wild-type p53. Genetic analysis of the breast cancer family in which this mutation was observed indicated that this germ-line mutation was not associated with the development of cancer. These results demonstrate that germ-line p53 mutations observed in patients with Li-Fraumeni syndrome and with second malignancies have inactivated the p53 tumor suppressor gene. The inability of the germ-line p53 mutants to block the growth of malignant cells can explain why patients with these germ-line mutations have an increased risk for cancer. The observation of a functionally silent germ-line mutation indicates that, before associating a germ-line tumor suppressor gene mutation with cancer risk, it is prudent to consider its functional significance.