Quantitative detection of p53 mutations in plasma DNA from tobacco smokers

In lung tumors, the p53 tumor suppressor gene is commonly mutated with a characteristic mutation spectrum. The amount of and alterations in plasma DNA, such as mutations in p53, were associated with several cancers. Few studies used quantitative methods of high sensitivity. Previously, we observed p53 mutations in the noncancerous tissue that differed from those in lung tumors using the highly sensitive p53 mutation load assay. Based on our observation of an increased p53 mutation load in nontumorous lung tissue in smokers, we hypothesized that plasma DNA may contain mutant p53 indicative of tobacco smoke exposure and will be an effective biomarker of lung cancer or smoking exposure. We modified the p53 mutation load assay to detect mutations at p53 codons 248 and 249, common mutations in lung cancer, in plasma DNA samples with a sensitivity of 1:5,000. The assay was applied to a set of lung cancer cases (n = 39), hospital controls (n = 21), and population controls (n = 20) from a larger study. Controls were selected to consist of equal numbers of both ever and never smokers. The p53 mutation load (mutated p53 copies per total number of p53 copies) was associated with smoking (P = 0.06), but not with lung cancer (P = 0.59). Most of the individuals with p53 mutations observed in plasma DNA were ever smokers and the p53 mutation load was higher in those who smoked for longer durations (P = 0.04). In summary, we were able to detect p53 mutations in plasma DNA from healthy individuals and our data suggest that p53 mutations in plasma DNA may be a marker of carcinogen exposure from tobacco smoke.     

p53 mutations in benzo(a)pyrene-exposed human p53 knock-in murine fibroblasts correlate with p53 mutations in human lung tumors

Human p53 mutation spectra differ significantly from one cancer type to another. One possible reason is that carcinogenic risk factors differ, and these factors elicit distinct mutation patterns. There has been no mammalian assay, however, with which to generate mutation patterns in human p53 sequences experimentally, hampering interpretation of the human tumor spectra. We have designed a new mammalian cell assay using gene targeting technology that selects and scores human p53 gene sequence mutations in human-p53 knock-in (Hupki) murine embryonic fibroblasts (HUF) that have undergone immortalization. With the Hupki assay we examined here whether benzo(a)pyrene (BaP), a major tobacco smoke carcinogen could elicit p53 mutation patterns characterizing the human lung tumor p53 mutation spectrum. We found that, in contrast to unexposed HUFs or HUFs exposed to other carcinogenic agents, HUFs exposed to BaP acquire mutations that display major features of the human lung tumor p53 mutation spectrum: (a) predominance of G-to-T mutations, (b) unequivocal strand bias of the transversions, and (c) a mutation hotspot at codons 157 to 158. These data are consistent with the hypothesis that BaP has a direct role in causing smokers' lung tumor p53 mutations. The assay can be used to examine various hypotheses on the endogenous or exogenous factors responsible for the p53 mutations in human tumors arising in other tissues.     

p53基因245位点突变对非小细胞肺癌细胞H1299的影响

背景与目的:p53基因突变是肺腺癌发生中的常见的分子生物学事件,第245位点突变为其突变热点之一,因此研究p53基因第245位点突变可能为肺腺痛的诊断、治疗提供一定的理论基础.本研究旨在研究肺癌常见的245位点突变对p53缺失的人肺腺癌细胞系H1299的影响.方法:应用流式细胞术观察脂质体瞬时转染p53基因第245突变体(G245V)对细胞凋亡的影响,同时用稳定转染观察克隆形成率和生长曲线的不同.结果:转染G245V突变体的H1299细胞凋亡平均数低于转染野生型p53基因的细胞,差异有统计学意义(P<0.001);大中克隆形成数量比导入野生型p53基因的细胞大中克隆形成数量明显增多,差异有统计学意义(P<0.05);细胞的生长速度也明显加快.结论:p53基因第245位点发生突变后基本丧失了野生型p53的功能,是肿瘤细胞增殖的原因之一.     

p53 antibodies in the sera of lung cancer patients: Comparison with p53 mutation in the tumour tissue

This study examined the sensitivity and specificity of serum auto-antibodies to p53 protein as a non-invasive marker of p53 genetic alterations or protein accumulation in lung cancer cases. A sensitive ELISA to detect serum p53 antibodies was developed and used to examine sera from 186 patients undergoing pulmonary surgery for a suspected lung cancer. Target antigens in ELISA were wild-type p53 protein and 5 peptides covering the N- and C-terminal parts of the protein. Sixteen sera were positive for serum p53 antibodies in both ELISAs and all were among the 136 patients with confirmed primary lung carcinoma. Of 50 patients with other pulmonary diseases, none had p53 antibodies. In 92 cancer patients exons 5 to 8 of the p53 gene were examined for mutations by denaturing gradient gel electrophoresis and direct sequencing of PCR products. Forty-seven tumours had a p53 mutation and 7 (15.2%) of these were positive for p53 antibodies. Two patients had serum antibodies but no detectable mutation in exons 5 to 8. Frequencies of p53 mutations and serum antibodies were higher in squamous cell carcinoma patients than in adenocarcinoma. Accumulation of p53 protein in tumour tissue was observed in 32 patients, but only 5 were positive for p53 antibodies. In conclusion, serum p53 antibodies were detected only in a proportion of lung cancer cases, but the majority were specifically associated with a detectable p53 mutation in the tumour. © 1995 Wiley-Liss, Inc.     

Alterations of p14ARF, p53, and p73 genes involved in the E2F-1-mediated apoptotic pathways in non-small cell lung carcinoma.

Overexpression of E2F-1 induces apoptosis by both a p14ARF-p53- and a p73-mediated pathway. p14ARF is the alternate tumor suppressor product of the INK4a/ARF locus that is inactivated frequently in lung carcinogenesis. Because p14ARF stabilizes p53, it has been proposed that the loss of p14ARF is functionally equivalent to a p53 mutation. We have tested this hypothesis by examining the genomic status of the unique exon 1beta of p14ARF in 53 human cell lines and 86 primary non-small cell lung carcinomas and correlated this with previously characterized alterations of p53. Homozygous deletions of p14ARF were detected in 12 of 53 (23%) cell lines and 16 of 86 (19%) primary tumors. A single cell line, but no primary tumors, harbored an intragenic mutation. The deletion of p14ARF was inversely correlated with the loss of p53 in the majority of cell lines (P = 0.02), but this relationship was not maintained among primary tumors (P = 0.5). E2F-1 can also induce p73 via a p53-independent apoptotic pathway. Although we did not observe inactivation of p73 by either mutation or DNA methylation, haploinsufficiency of p73 correlated positively with either p14ARF or p53 mutation or both (P = 0.01) in primary non-small cell lung carcinomas. These data are consistent with the current model of p14ARF and p53 interaction as a complex network rather than a simple linear pathway and indicate a possible role for an E2F-1-mediated failsafe, p53-independent, apoptotic pathway involving p73 in human lung carcinogenesis.     

Expression of mutant p53 proteins in lung cancer correlates with the class of p53 gene mutation.

We investigated the immunocytochemical staining and immunoblotting characteristics of 33 different p53 mutant proteins identified in lung cancer cell lines (18 small-cell lung cancer and 15 non-small-cell lung cancer) using monoclonal antibodies pAbs 240, 421 and 1801. The p53 mutants studied were representative of those found in lung cancer and included three deletions, four nonsense, seven splicing and 19 missense lesions. Control cell lines included six B-lymphoblastoid cell lines and two lung cancer cell lines without p53 mutations. Immunocytochemistry demonstrated 16 cell lines (48%) with definite overexpression of p53 protein (the high-expresser group of mutants), while in the remainder of cases either no p53 expression or low levels of p53 protein expression were found (the low-expresser group of mutants). The type of p53 mutation correlated with the expresser group. High expressers all had p53 missense mutations in exons 5-8, and immunocytochemistry identified 16/17 (94%) of these mutants. Several classes of p53 mutations occur in the low-expresser groups: deletions, splicing mutants, nonsense mutants and missense mutations outside of exons 5-8 all resulted in very low or undetectable levels of p53 protein. We conclude that there are low- and high-expression groups of p53 mutants in lung cancer and that the detection of protein expression in tumor cells by immunocytochemistry and immunoblotting is dependent upon the type of mutation of the p53 tumor-suppressor gene.     

肺腺癌p53基因突变与临床病理特征关系的研究

目的探讨p53基因在肺腺癌中突变的频率、位置和在肺腺癌发生发展中的作用及与其临床病理特征的关系。方法聚合酶链式反应一单链构象多态性（PCR－SSCP）检测31例肺腺癌的P53基因第5～8外显子突变。结果14例（45％）出现P53基因5～8外显子突变，其中7、8外显子突变占73％。P53基因突变男性显著高于女性（P—0．003），在肿瘤≤3cm的病例p53基因突变率显著低于肿瘤＞3cm的病例（P=0．005）。p53基因突变与吸烟史、年龄、组织学类型、分化程度、淋巴结状况、国际病理TNM分期及瘤栓无显著性差异（P＞0．05）。结论肺腺癌中P53突变率为45％，主要分布在第7、8外显子，P53基因突变参与肺腺癌癌变的始动和腺癌的进展。     

p53基因缺失和248位密码子点突变与肺癌发生和预后间关系的研究

以野生型p53cDNA片段作探针，采用DNA分子印迹杂交（Southernblot）技术检测20例原发性肺癌和10例肺良性病变p53基因缺失与重排。肺癌组阳性率为30％；肺良性病变组均为阴性。同时采用聚合酶链反应结合限制性片段长度多态性分析（PCR-RFLP）检测20例原发性肺癌，2例肺转移癌以及它们相应的非癌肺组织p53基因248位密码子点突变。结果发现，4例原发性肺癌和2例肺转移癌有p53基因248位密码子点突变，非癌肺组织均为阴性。P53基因缺失和突变与肿瘤大小、分期、非小细胞肺癌病理分型无关（P＞0．05），与肿瘤转移有关（P＜0．05）。提示：p53基因缺失和突变与肺癌的发生和预后密切相关。     

A germ-line p53 mutation accelerates pulmonary tumorigenesis: p53-independent efficacy of chemopreventive agents green tea or dexamethasone/myo-inositol and chemotherapeutic agents taxol or adriamycin

Recent evidence indicates that individuals with a p53 germ-line mutation (Li-Fraumeni syndrome) have a 50% risk of developing lung cancer by age 60. In this study, p53 heterozygous knockout mice and p53 transgenic mice carrying a dominant negative mutant were crossed with the A/J mouse, which is highly susceptible to lung tumor induction, to investigate whether a p53 germ-line mutation is a predisposing gene for carcinogen-induced pulmonary adenomas in mice. The number of lung tumors was not significantly increased in (TSG-p53 x A/J)F1 p53 heterozygous knockout mice as compared with that in (TSG-p53 x A/J)F1 wt mice 16 weeks after exposure to N-nitrosomethylurea (MNU). In contrast, an average of 22 lung tumors were observed in (UL53-3 x A/J)F1 mice carrying a mutant p53 transgene (135Valp53) compared with an average of 7 lung tumors seen in (UL53-3 x A/J)F1 wt mice after treatment with N-nitrosomethylurea. Similar enhancement of lung tumor multiplicity (approximately 3-fold) was seen when mutant versus wt mice were treated with the tobacco-related carcinogens benzo[a]pyrene or 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone. These results suggest that the mutant p53 transgene may have a dominant negative effect on the wt p53. The potential usefulness of this new mouse model in lung cancer chemoprevention and chemotherapy was examined. The chemopreventive efficacy of the green tea or a combination of dietary dexamethasone and myoinositol and the chemotherapeutic efficacy of Taxol or Adriamycin was examined in wt mice or mice with a mutation in the p53 gene. Mice treated with dexamethasone/myo-inositol and green tea displayed an average of 70 and 50% inhibition of lung tumors, respectively, regardless of p53 status. Similarly, when mice bearing established lung adenomas were treated with Taxol or Adriamycin, a decrease in tumor volume of approximately 70% was observed independent of p53 mutation status. Thus, the (UL53-3 x A/J)F1 p53 transgenic mouse seems to be an excellent model for human carriers of p53 germ-line mutations (Li-Fraumeni syndrome). Furthermore, the lung adenomas generated in this model possess mutations in both the K-ras proto-oncogene and the p53 tumor suppressor gene. This model should prove directly useful for chemoprevention and chemotherapy studies.     

Association between Smoking and p53 Mutation in Lung Cancer: A Meta-analysis

AimsTo carry out a meta-analysis on the relationship between smoking and p53 gene mutation in lung cancer patients.Materials and methodsPubMed, Web of Science, ProQest and Medline were searched by using the key words: ‘lung cancer or lung neoplasm or lung carcinoma’, ‘p53 mutation’ and ‘smoking’. According to the selection criteria, 15 articles were identified and methodologically analysed by stata 12.0 software package. Crude odds ratios with 95% confidence intervals calculated using the fixed-effects model were used to assess the strength of association between smoking and p53 mutation in lung cancer.ResultsIn total, 15 articles with 1770 lung cancer patients were identified; 69.6% of the patients were smokers, 30.4% were non-smokers. Overall, smokers with lung cancer had a 2.70-fold (95% confidence interval 2.04–3.59) higher risk for mutation than the non-smokers with lung cancer. In subgroup analyses, the increased risk of p53 mutation in smokers than in non-smokers was found in the non-small cell lung cancer (NSCLC) group (odds ratio = 2.38, 95% confidence interval = 1.71–3.32) and in the NSCLC and SCLC group (odds ratio = 3.82, 95% confidence interval = 2.19–6.69).ConclusionsThis meta-analysis strongly suggests that p53 mutation is associated with smoking-induced lung cancer. Smokers with lung cancer had a higher risk for p53 mutation than non-smokers.     

Detection of p53 mutations in sputum smears precedes diagnosis of non-small cell lung carcinoma

Little progress has been made in reducing lung cancer mortality by applying conventional methods to early diagnosis and screening. Recent advances in molecular oncology, however, have provided tools which may be of use in this area. p53 gene mutation is the most common gene alteration in the development of lung cancer. Conventional cytologic analysis of sputum is an insensitive test for the diagnosis of lung cancer. In this study, we attempted to establish a polymerase chain reaction (PCR)-based assay for assessing the possibility of early detection of p53 mutation in archival Papanicolaou-stained cytologic sputum smears. Ten sputum smear slides were collected prior to clinical diagnosis from 10 lung cancer patients who had been confirmed to have p53 mutations in surgically resected lung tumors. We successfully obtained sufficient amounts of RNA from each sputum smear specimen for amplification of PCR and direct sequencing. Only one patient was found to have p53 mutation at codon 286; the other nine patients had wild type p53 genes. This result supports the possibility that detection of p53 mutations in cytologic sputum smears is an available strategy for the early diagnosis of lung cancer.     

Gene expression in the lung of p53 mutant mice exposed to cigarette smoke

We showed previously that p53 mutations play a role in cigarette smoke-related carcinogenesis not only in humans but also in A/J mice. In fact, (UL53-3 x A/J)F(1) mice, carrying a dominant-negative germ-line p53 mutation, responded to exposure to environmental cigarette smoke more efficiently than their wild-type (wt) littermate controls in terms of molecular alterations, cytogenetic damage, and lung tumor yield. To clarify the mechanisms involved, we analyzed by cDNA array the expression of 1,185 cancer-related genes in the lung of the same mice. Neither environmental cigarette smoke nor the p53 status affected the expression of the p53 gene, but the p53 mutation strikingly increased the basal levels of p53 nuclear protein in the lung. Environmental cigarette smoke increased p53 protein levels in wt mice only. The p53 mutation enhanced the expression of positive cell cycle regulators in sham-exposed mice, which suggests a physiologic protective role of p53. In environmental cigarette smoke-exposed mice, the p53 mutation resulted in a lack of induction of proapoptotic genes and in overexpression of genes involved in cell proliferation, signal transduction, angiogenesis, inflammation, and immune response. Mutant mice and wt mice reacted to environmental cigarette smoke in a similar manner regarding genes involved in metabolism of xenobiotics, multidrug resistance, and protein repair. Irrespective of the p53 status, environmental cigarette smoke poorly affected the expression of oncogenes, tumor suppressor genes, and DNA repair genes. Taken together, these findings may explain the increased susceptibility of p53 mutant mice to smoke-related alterations of intermediate biomarkers and lung carcinogenesis.     

青老年肺癌患者p53基因突变情况的对比研究

目的 分析45例青老年肺癌中p53基因突变,比较青年肺癌与老年肺癌p53基因突变的差异。方法 45例患者均为温州医学院附属第一医院胸外科收治的病例,其中22例为20－45岁肺癌患者,23例为55－80岁肺癌患者。应用PCR－SSCP银染技术检测p53基因的突变情况,并进行PCR产物直接测序。结果 发现青年组和老年组中p53基因突变情况基本相同（50．0％比52．2％）,其中小细胞肺癌突变率分别为70．0％（7／10）和75．0％（6／8）,非小细胞肺癌突变率分别为33．3％（4／12）和40．0％（6／15）,差异均无显著性（P＞0．05）。结论 青年肺癌和老年肺癌p53基因突变并无明显差异,提示p53基因的突变不属“先天”致癌因素。     

p53蛋白表达和基因突变在所谓肺硬化性血管瘤组织中的意义

背景与目的所谓肺硬化性血管瘤（so-called pulmonary sclerosing hemangioma，PSH）是一种至今不能肯定其来源及性质的少见肺肿瘤。虽然目前普遍认为PSH是一种良性肿瘤，但却发现有少数PSH可发生浸润和转移。p53蛋白表达和基因突变是反映肿瘤生物学行为的有用指标。本研究的目的是检测PSH组织中p53基因突变及p53蛋白的表达情况及其意义。方法应用免疫组化S-P法、激光捕获显微切割（laser capture microdissection，LCM）技术、单链构象多态性（single-stranded conformation polymorphism，SSCP）及DNA测序分析方法（5～8外显子）检测19例PSH中多角形细胞和表面立方细胞的p53蛋白表达和基因突变情况。结果19例PSH组织中p53蛋白阳性表达率为21．1％（4／19），SSCP及测序分析检测p53基因突变率分别为26．3％（5／19）和42．1％（8／19）。p53蛋白阳性表达的4例PSH组织，测序分析显示3例标本有突变发生，2例为错义突变，1例同时发生错义突变和移码突变；而p53蛋白阴性表达的15例PSH组织中，5例标本经测序证实亦发生了突变，4例为移码突变，1例为错义突变。在有突变的8例PSH组织中，单一多角形细胞突变5例，单一立方细胞突变2例，多角形细胞和立方细胞同时突变1例。结论PSH组织p53蛋白阳性表达并不能完全反映p53基因突变的真实情况；p53基因突变或蛋白表达异常均可发生在PSH组织中的两种不同的细胞内；p53基因的高突变率提示PSH可能具有潜在的恶性生物学行为。     

nm23和p53基因与肺腺癌生物学特性的关系

目的：检测肺腺癌组织中nm23表达和p53基因外显子突变情况,寻找有助于准确预测局部肿瘤进展、分型和预后情况的临床参照指标。方法：应用PCR技术检测31例肺腺癌术后存档蜡块组织中nm23表达及p53基因外显子突变情况,并与肺腺癌的病理及临床指标进行相关性分析。结果：nm23表达及p53基因突变率分别为38．7％（12／31）及48．4％（15／31）。nm23表达和p53基因突变与临床分期相关,P值分别为0．005、0．037。结论：nm23表达和p53基因突变与肺癌临床分期和生存相关,在判断肺腺癌细胞增殖、分化程度、恶性程度及预后转归方面有一定价值,可作为判断肺腺癌预后的参考指标,指导高危患者的进一步治疗。     

p53突变蛋白在非小细胞肺癌中的表达及与iNOS的关系

目的测定肺癌组织中p53抑癌基因突变蛋白的表达,诱生型一氧化氮合酶(iNOS)的表达及分布.了解肺癌组织中 p53抑癌基因突变蛋白与iNOS的关系.方法按自身配对原则收集人肺癌癌灶组织,癌灶周围组织及远癌组织各40份,分 别进行免疫组化法测定p53抑癌基因突变蛋白的表达,原位杂交法测定iNOSmRNA的表达及分布.结果1、肺癌组织中 p53抑癌基因突变蛋白的表达阳性.与肺癌的临床分期、组织分型、淋巴结转移未见相关,(均为P＞0.05).2、iNOSmRNA 在肺腺癌中的表达高于鳞癌,(均为P＜0.05).3、肺腺癌组织中iNOS在p53抑癌基因突变蛋白表达阳性组高于p53阴性 组,(P＜0.01).结论肺腺癌中p53抑癌基因突变蛋白阳性组iNOS表达高于p53阴性组的表达,提示NO/iNOS途径可诱 使p53抑癌基因突变.     

Patterns of p53 G-->T transversions in lung cancers reflect the primary mutagenic signature of DNA-damage by tobacco smoke

It is unquestionable that the major cause of lung cancer is cigarette smoking. p53 mutations are common in lung cancers from smokers but less common in non-smokers. A large fraction of the p53 mutations in lung cancers are G-->T transversions, a type of mutation that is infrequent in other tumors aside from hepatocellular carcinoma. Previous studies have indicated that there is a good correlation between G-->T transversion hotspots in lung cancers and sites of preferential formation of polycyclic aromatic hydrocarbon (PAH) adducts along the p53 gene. The origin of p53 mutations in lung cancer has been questioned by recent reports suggesting that there are no significant differences in p53 mutation spectra between smokers and non-smokers and between lung cancers and non-lung cancers [S.N.Rodin and A.S.Rodin (2000) Human lung cancer and p53: The interplay between mutagenesis and selection. P:roc. Natl Acad. Sci. USA, 97, 12244-12249]. We have re-assessed these issues by using the latest update of the p53 mutation database of the International Agency for Research on Cancer (14 051 entries) as well as recent data from the primary literature on non-smokers. We come to the conclusion that the p53 mutation spectra are different between smokers and non-smokers and that this difference is highly statistically significant (G-->T transversions are 30 versus 10%; P < 0.0001, chi2 test). A similar difference is seen between lung cancers and non-lung cancers. At a number of mutational hotspots common to all cancers, a large fraction of the mutations are G-->T transversions in lung cancers but are almost exclusively G-->A transitions in non-lung cancers. Our data reinforce the notion that p53 mutations in lung cancers can be attributed to direct DNA damage from cigarette smoke carcinogens rather than to selection of pre-existing endogenous mutations.     

Development of antibodies against p53 in lung cancer patients appears to be dependent on the type of p53 mutation.

Using immunoblotting techniques we studied the sera from small cell lung cancer and non-small cell lung cancer patients for antibodies directed against p53. We have also characterized the majority of these patients' tumors for p53 mutations. In the sera of 13% of the patients (4 of 40 small cell lung cancer and 2 of 6 non-small cell lung cancer) we found antibodies specific for the p53 tumor suppressor gene product. All of the antibody-positive patients tested had p53 missense mutations and expressed detectable p53 antigen in their tumor cell lines. No anti-p53 antibodies were detected in sera from patients whose tumor had p53 stop, splice/stop, splice, or frameshift mutations (n = 10). Thus, while we find that the ability of lung cancer patients to develop anti-p53 antibodies is correlated with the type of p53 mutation, many patients have tumors with missense p53 mutations and did not develop anti-p53 antibodies. The presence of p53 antibodies was not correlated to stage, prior treatment, sex, or survival. None of these lung cancer patient sera had measurable amounts of p53 antigen. By immunoblotting all six anti-p53 antisera we were able to detect a variety of mutant p53 proteins (including those from antibody-negative patients) and detected wild-type p53 protein. The development of anti-p53 antibodies represents an interesting model system for studying immune responses in cancer patients against mutant oncogene products.     

p53基因突变对非小细胞肺癌TSG101/MDM2信号通路的影响

目的探讨p53基因突变在肺癌中对TSG101/MDM2信号通路影响的临床病理学意义。方法采用免疫组织化学方法检测185例肺癌组织标本中TSG101、MDM2及p53的表达,用聚合酶链反应单链构象多态性(Polymerase Chain Reaction ,single-strand conformation polymorphism, PCR-SSCP)分析法检测p53突变情况,以及Western blot检测TSG101在肺癌组织和正常肺组织中的表达。结果（1）肺癌组中p53蛋白的总阳性率为80.54%(149/185),PCR-SSCP检测结果显示总突变率为56.67%（17/30）,p53蛋白表达与病理分期、淋巴结转移有相关性（P<0.05）;TSG101蛋白的低表达率为58.92%(109/185),Western blot结果显示TSG101在癌组织中的表达明显低于对照组（P<0.05）,TSG101蛋白表达与病理分期、分化、淋巴结转移有相关性（P<0.05）;MDM2蛋白的过表达率为77.84%(144/185),MDM2蛋白表达与病理分期、淋巴结转移有相关性（P<0.05）。(2)在p53阳性的149例中TSG101阳性76例,MDM2阳性139例,在p53阴性的36例中TSG101阳性33例,MDM2阳性5例。p53与TSG101两者共表达率为41.08%,一致性为42.70%。p53与MDM2两者共表达率为75.14%,一致性为91.89%。结论（1）p53/MDM2上调与TSG101表达下调肺癌的发生及生物学行为有关。(2)当p53突变时, TSG101与MDM2的表达呈负相关关系。     

In silico p53 mutation hotspots in lung cancer

For cancer one of the primary aims of molecular epidemiology is to identify the endogenous or exogenous cause of mutations within a gene. Regarding exogenous mutagens, many mutation data have become available via in vitro and in vivo mutation assays and become publicly available through mutation databases such as the Mammalian Gene Mutation Database (http://lisntweb.swan.ac.uk/cmgt/index.htm). One particular mutation assay incorporates the bacterial supF tRNA gene which allows selection of mutations at virtually all nucleotides. We have developed an algorithm called LwPy53 that utilizes mutation data from supF that can be used to predict chemically induced hot-spots along the p53 gene. The prediction is based on a number of parameters: the mutability of supF dinucleotides after treatment with a mutagen of interest; DNA curvature along the p53 gene; the selectability of a mutation along the gene; the likelihood of a site being within a nucleosome. We applied LwPy53 to exons 5, 7 and 8 of p53 using benzo[a]pyrene diol epoxide (BPDE)-induced mutation data for supF to obtain a predicted BPDE G-->T transversion spectrum after hypothetical treatment with BPDE. The resulting predicted mutation distribution reveals strong mutation hot-spots at codons 157, 248 and 273 that correlate with known BPDE adduct hot-spots within p53. The predicted BPDE spectrum strongly resembles the G-->T mutation spectrum compiled from known lung cancer mutation data from smokers and further supports evidence that BPDE contributes to the overall smoking-related mutation distribution in lung cancer. The algorithm shows how BPDE target sequence specificity and DNA curvature both shape the overall mutation distribution.