Analysis of the Ha-ras oncogene in C3H/He mouse liver tumours derived spontaneously or induced with diethylnitrosamine or phenobarbitone.

In a study of the mechanisms involved in the induction of tumours by chemicals, the Ha-ras oncogene was analysed in liver tumours induced by the genotoxic carcinogen diethylnitrosamine (DEN), or the non-genotoxic agent phenobarbitone (PB) in C3H/He mice. Mutations were detected using the polymerase chain reaction and oligonucleotide hybridization. Codon 61 mutations were detected in 41% of DEN-induced tumours (19/46), either in the first base (CG----AT, 12/19), a transversion, or the second base (AT----GC, 7/19), a transition. Codon 61 mutations were also found in 29% of spontaneous tumours (all CG----AT, 6/21) but none were detected in PB-induced tumours (0/15) or in normal liver tissue of untreated mice (0/30). No mutations were detected at codon 12. Low and variable expression of the Ha-ras gene was detected in all liver tissues with moderately raised levels (175-200%) in spontaneous, DEN and PB-induced tumours as compared to normal liver tissue. The H-ras gene was methylated to some extent in all liver tissues, with no discernible difference between the treatments. The frequency of the Ha-ras mutation at codon 61 in DEN-induced tumours is greater than in spontaneously arising tumours. This increase is not accompanied by any specific alteration in the expression or methylation of the gene. Since PB-induced tumours do not possess mutations in the Ha-ras gene at codons 12 or 61, the data suggest that the non-genotoxic agent PB induces tumours in the C3H/He mouse liver with a mechanism distinct from that of spontaneous tumours or those that result from treatment with a potent genotoxic carcinogen such as DEN.     

p53 mutations are absent from carcinogen-induced mouse liver tumors but occur in cell lines established from these tumors.

Mutations in the p53 gene are frequent genetic alterations in human hepatocellular carcinomas. We have examined, by single-strand conformation polymorphism analysis of polymerase chain reaction products, a total of 93 carcinogen-induced liver tumors from mice of three different strains (C3H/He, C57BL/6J, and B6C3F1) for the presence of p53 aberrations. Hepatoma lines, established from 12 liver tumors, were also included in the analysis. While structural aberrations of the p53 gene were not detected in any of the primary mouse liver tumors analyzed, single-base substitutions occurred at different locations within the p53 gene in three of the cell lines during in vitro propagation. One hepatoma line carried two point mutations on separate alleles. All four mutations were either G:C----C:G or C:G----G:C transversions. Mutations at codon 61 of the c-Ha-ras gene, which were frequent in primary liver tumors from C3H/He and B6C3F1 mice, were not detected in the hepatoma lines. Our data indicate (i) that c-Ha-ras but not p53 mutations play an important role during the early stages of mouse hepatocarcinogenesis and (ii) that p53 mutations confer a selective growth advantage to the mutated hepatoma cells in vitro.     

Alterations in the structural gene and the expression of p53 in rat liver tumors induced by aflatoxin B1.

Rat hepatocellular carcinomas (HCCs) induced by aflatoxin B1 (AFB) treatment were examined for changes in the p53 tumor suppressor gene and in p53 suppressor gene expression. A high proportion of HCCs (nine of 11 tumors in six of eight animals) exhibited new p53 restriction fragments, indicating genomic alterations of one of the p53 alleles. Each tumor with an altered p53 restriction-fragment pattern exhibited a new fragment in one of two size classes (3 kb or 7 kb with EcoRI digestion) that were missing portions of the 3' end of the p53 gene. These findings indicate that apparently similar genomic rearrangements or deletions occurred independently in AFB-induced tumors. When compared with nontumor liver tissue from the same animal, the tumors with p53 gene alterations showed dramatically reduced levels of p53 mRNA and protein and greatly increased levels of histone H2B and retinoblastoma tumor suppressor (Rb) mRNA. In two HCCs showing no evidence of p53 restriction-fragment alterations, mutant p53 protein was detected. Mutant protein was also detected in two liver samples containing an adenoma and altered foci. These data suggest that alterations of the p53 tumor suppressor gene are involved in the induction of rat HCC by AFB.     

TACC3和p53蛋白在原发性肝癌组织中的表达及其临床意义

目的 探讨TACC3蛋白和p53蛋白在原发性肝癌组织中的表达及其临床意义。方法 本院原发性肝癌患者138例,酶联免疫吸附法及免疫组化法测定癌旁组织、原发性肝癌组织中TACC3、p53蛋白的表达水平,分析其与临床病理参数和预后的关系。结果 原发性肝癌组TACC3蛋白、p53蛋白表达水平高于癌旁组(P＜0.05);原发性肝癌组TACC3、p53阳性率高于癌旁组(P＜0.05);TACC3、p53蛋白表达与年龄无关(P＞0.05);与TMN分期、病理学分级、复发、浸润深度、淋巴血管间隙浸润、肿瘤最大径、淋巴结转移有关,且TNM分期越高、病理学分期越高、有复发、浸润深度越深、有淋巴血管间隙浸润、肿瘤最大径≥5 cm、有淋巴结转移,TACC3、p53蛋白阳性表达率越高(P＜0.05);TACC3、p53阴性组3年生存率均明显高于TACC3、p53阳性组(P＜0.01)。结论 原发性肝癌组织中TACC3、p53蛋白表达量增加,其与原发性肝癌的进展呈正相关;TACC3、p53蛋白低表达能提高原发性肝癌患者预后。     

Infrequent p53 mutations in 7,12-dimethylbenz[a]anthracene–induced mammary tumors in BALB/c and p53 hemizygous mice

We conducted experiments to determine if p53 alterations, which are frequent in human breast cancers, were also common in murine mammary tumors. In 13 mammary tumors from 7,12-dimethylbenz[a]anthracene (DMBA)-treated BALB/c mice were immunohistochemically analyzed for overexpression of p53; p53 protein was not detectable. Three of the tumors were established as cell lines in vitro. p53 protein was rarely detected at passage 4 in these lines but was overexpressed by passage 8 in two of them. The p53 nucleotide sequence was shown to be wild type in one primary mammary tumor and in the two p53-overexpressing cell lines. One cell line that overexpressed p53 in vitro was implanted into BALB/c mice. The resulting tumors retained the wild-type p53 nucleotide sequence but no longer expressed detectable levels of p53 protein, suggesting that the overexpression of wild-type p53 was related to in vitro culture conditions. The effect of DMBA on mammary-tumor development was also tested in mice rendered hemizygous for p53. These mice and wild-type littermate controls had no differences in susceptibility to induction of mammary tumors by oral administration of DMBA. Furthermore, Southern blot hybridizations detected no gross alterations in the wild-type p53 allele in mammary tumors from the p53-deficient mice. Point mutation of the wild-type p53 allele was also infrequent in the DMBA-induced mammary tumors from hemizygous p53 mice; it occured in only one of seven tumors. Thus, the p53 gene is apparently not a primary target for genetic alterations in DMBA-induced mammary tumors. Next, we examined mammary tumors derived from D1 and D2 transplantable hyperplastic alveolar nodule (HAN) outgrowths, which rapidly form tumors containing Ha-ras mutations after DMBA treatment. As ras and p53 mutants can cooperate in transformation, we examined whether D1 and D2 HAN outgrowths have p53 mutations. Unlike in the DMBA-induced primary mammary tumors, nuclear p53 accumulation was observed frequently (10 of 14) in tumors that arose from D1 and D2 HAN outgrowths. Direct sequencing of the entire coding region of the p53 cDNA from six D1 and D2 tumors confirmed that the sequence was wild type. Although wild-type p53 was retained in both DMBA-induced mammary tumors and mammary tumors derived from D1 and D2 preneoplastic outgrowths, wild-type p53 overexpression was detected only in D1 and D2 tumors. Therefore, D1 and D2 tumors appear to arise by a pathway in which p53 expression is altered, whereas DMBA induction affects a different pathway that does not require such alteration. © 1994 Wiley-Liss, Inc.     

Aflatoxin-B exposure does not lead to p53 mutations but results in enhanced liver cancer of Hupki (human p53 knock-in) mice

Hepatocellular carcinoma (HCC) is a common human malignancy that is often associated with risk factors such as aflatoxin-B1 (AFB1) exposure and Hepatitis-B virus infection in developing countries. There is a strong correlation between these risk factors and mutation of the tumor-suppressor gene p53 at codon 249. In vitro experiments have also shown that treatment of human liver cells with AFB1 results in p53 mutations. A tumor-promoting role for mutant p53 was demonstrated using transgenic mice models, in which HCC development was accelerated upon AFB1-exposure. However, wild-type mice in which AFB1 alone was used to induce liver cancers have failed to recapitulate p53 mutations, raising the possibility that mouse DNA context may not be appropriate for the generation of AFB1-induced p53 mutations. We have now tested this hypothesis using the Hupki mice (human p53 knock-in) in which the mouse DNA-binding domain has been replaced by the homologous human p53 segment. Mice were followed for 80 weeks after AFB1 injection for survival and HCC formation. Hupki mice were found to be more susceptible to AFB1 than wild-type mice. Moreover, only 19% of wild-type mice developed HCCs compared to 44% in Hupki mice. However, none of the liver tumors and normal tissues from Hupki mice contained any mutations in the DNA-binding domain of p53. These findings suggest that the human DNA context of the p53 gene alone may not be the sole determinant of AFB1-induced mutagenesis. Furthermore, humanized p53 appears not to be as effective as murine p53 in the mouse cellular environment in preventing malignant transformation.     

突变型p53基因与肝细胞癌组织学分级、转移、肿块大小和包膜形成的相关性研究

目的：探讨突变型p53基因与肝细胞癌组织学分级、转移、肿块大小和包膜形成的相关性。方法：随机选择41例肝细胞肝癌患者的癌和癌旁肝组织标本，SP法检测其p53蛋白表达，分析突变型p53基因与肝细胞癌组织学分级、转移、肿块大小和包膜形成的相关性。结果．p53在癌和癌旁肝组织中阳性表达率分别为43．9％和6．67％，两者比较，差异显著（P〈0．01）；p53蛋白阳性表达率，Ⅲ-Ⅳ级肝癌明显高于Ⅰ～Ⅱ级肝癌，发生转移（血道或淋巴道转移）肝癌明显高于未发生转移（血道或淋巴道转移）肝癌，两者之间比较，差异有显著性意义（P〈0．05）；但p53蛋白阳性表达率与肝癌组织大小和其是否有包膜无关（P〉0．05）。结论：突变型p53基因与肝细胞癌组织学分级、转移密切相关，但与肝癌组织大小和包膜形成无关。     

Lack of concordant p53 mutations in some paired primary and metastatic mouse squamous cell carcinomas induced by chemical carcinogenesis

We studied the frequency and pattern of p53 mutations in 16 mouse skin primary squamous carcinomas induced by chemical carcinogens and their 19 matched metastases. The molecular changes were analyzed by polymerase chain reaction-single-strand conformation polymorphism and subsequent direct sequencing analysis. Eleven mutations of the p53 gene were detected in a total of eight primary tumors, and 10 mutations were detected in nine metastases. Only four pairs had identical mutations in primary and paired metastatic tumors. Eight mutations in six pairs were detected in primary tumors but not in their metastases, and four mutations from three matched pairs were detected in metastases but not in primary tumors. The four pairs that contained the same mutations in both the primary and secondary tumors had lymph-node metastases, and all mutations occurred in exon 8. Conversely, five of six pairs with p53 mutations only in primary tumors had lung metastases and only one of the mutations occurred in exon 8. None of the mutations found only in metastases were located in exon 8. These data indicate that p53 mutations are prevalent in lymph-node metastases and infrequent in lung metastases of mouse skin tumors and that primary tumors with exon 8 mutations may be more likely to metastasize to the lymph nodes. © 1995 Wiley-Liss Inc.     

A novel clonality assay for the mouse: Application to hepatocellular carcinomas induced with diethylnitrosamine

A polymerase chain reaction-based clonality assay was developed for mouse tumors and cellular proliferations of the mouse. This assay was based on a polymorphism of the phosphoglucokinase-1 (Pgk-1) gene on the X chromosome between two different mouse subspecies and the different methylation patterns of active and inactive X chromosomes. All 15 tumor cell lines examined showed one of the two allelic bands on gel electrophoresis, which is consistent with the theory that tumor cell lines are monoclonally derived. This suggests that the Pgk-1 system is useful for clonality studies that will give insight into cancer development. With this method, nine hepatocellular carcinomas were examined, and eight showed monoallelic patterns. The remaining tumor exhibited a biallelic pattern, which is suggestive of polyclonal origin; however, other possibilities are discussed. © 1996 Wiley-Liss, Inc.     

p53 gene mutational spectra in hepatocellular carcinomas induced by 2-acetylaminofluorene and N-nitroso-2-acetylaminofluorene in rats

In this study, the mutation frequencies of the p53 gene in rat hepatocellular carcinomas (HCCs) induced by N-nitroso-2-acetylaminofluorene (NO-AAF) and 2-acetylaminofluorene (AAF) were 19.23% (20 of 104) and 31.1% (33 of 106), respectively. Four noteworthy features of the mutation spectrums of the p53 gene in HCCs induced by both NO-AAF and AAF were observed: (i) There was preferential clustering of mutations at exons 5–8 in both the NO-AAF or AAF groups, (ii) Nearly all the mutations (98%) induced by NO-AAF and AAF were point mutations, (iii) A high frequency of the p53 mutations were transition mutations, and the ratios of transition to transversion in the NO-AAF and the AAF group were 13:6 and 21:12, respectively. Almost all the mutations were G→A transitions and guanosine was the major target base. (iv) The frequency and base location of p53 mutations were significantly associated with cancer cell differentiation. In poorly differentiated HCCs (58 individual tumor samples), mutations were detected in 24 of 58 samples (41.1%) and clustered mostly in exons 7 and 8 (19 of 24 samples), whereas in well-differentiated HCCs (105 individual tumor samples), the incidence of mutations was low (one of 10 in the AAF group, 17 of 95 in the NO-AAF group), and the mutations were located in exon 5 (11 of 18). The biological significance of these different mutational spectra among p53 genes deserves further investigation. © 1995 Wiley-Liss, Inc.     

p53 status in spontaneous and dimethylnitrosamine—induced renal cell tumors from rats

Rats carrying the Eker tumor–susceptibility mutation (Eker rats) are predisposed to developing renal cell carcinoma. Rats heterozygous for the Eker mutation develop spontaneous multiple bilateral renal cell tumors by the age of 1 yr. In a previous study, Eker-mutation carrier and noncarrier rats were exposed to the renal carcinogen dimethylnitrosamine (DMN), and male rats carrying the Eker mutation exhibited a 70-fold increase in the induction of renal adenomas and carcinomas when compared with noncarrier rats. In this study, spontaneous and DMN-induced rat renal cell tumors (adenomas and carcinomas) were analyzed for mutations of the p53 gene by direct sequencing of cDNA polymerase chain reaction products. There were no mutations in p53 cDNA derived from renal tumors from six untreated rats. Mutations were found in one of 15 of the DMN-induced tumors: a transition at codon 140, CCT → CTT, in a renal adenoma. Additionally, seven cell lines derived from spontaneous renal cell tumors did not contain mutations in p53. The low frequency of p53 mutations (one of 21 renal cell tumors and none of seven cell lines derived from renal cell tumors) indicates that the development of both spontaneous and carcinogen-induced renal tumors involved a non–p53-dependent pathway. As p53 is infrequently mutated in human renal cell carcinomas and in rat renal mesenchymal tumors, it is likely that a tumor suppressor gene or genes other than p53 are involved in the development of renal cancer. © 1995 Wiley-Liss Inc.     

肿瘤相关粘蛋白 MUC1 和抑癌基因 p53 在原发性肝癌中的表达

目的：通过测定MUC1和p53在肝脏不同组织中的表达差异，探讨MUC1和p53在肿瘤诊断和免疫治疗中的意义。方法：采用免疫组化方法检测35例肝癌（28例肝细胞癌，7例胆管细胞癌），8例肝硬化，8例肝血管瘤和10例正常肝组织中MUC1和p53的表达。结果：MUC1和p53基因均阳性表达于肝癌组织，它们在肝癌组织中的阳性表达率明显高于其它肝脏组织（P〈0．01），MUC1主要表达于细胞膜，其表达与肝癌的病理分型和组织学分化无相关性（P〉0．05），但肝癌伴有门静脉癌栓组与不伴有门静脉癌栓组之间MUC1表达率具有显著差异性（P〈0．05）；p53表达于细胞核，在Ⅰ、Ⅱ、Ⅲ级肝癌组织中的表达呈现递增趋势。结论：p53与肝癌的发生发展密切相关，MUC1在肝癌组织中的表达与分布特点可以作为肝癌诊断、判断预后的指标，同时，MUC1作为一种靶抗原，为今后的肝癌免疫治疗提供新的线索。     

大肠癌原发灶和肝转移灶p53变异及蛋白表达

目的 了解Ｐ５３及其蛋白在大肠癌发生、转移过程中的动态变化。方法Ｐ５３基因外显子５－９以ＤＧＧＥ及自动ＤＮＡ序列分析来检测,Ｐ５３蛋白表达以免疫组化方法检测。结果 ３４例中２１例呈Ｐ５３变异,占６１．８％,其中５例仅在肝转移灶发现Ｐ５３变异,其余均为原发灶、转移灶生的变异。另有２例原发灶即有Ｐ５３变异者,在转移灶出现了新增加的变异。在３７处变异中,２７和为错义突变占７３．０％;６处为无义突变占１６     

启东肝癌组织p53过表达的免疫组化检测

目的　了解p5 3突变在启东地区的肝癌发生中所起的作用。方法　应用免疫组化 (IHC)的方法对 90例肝癌和 75例癌旁组织切片进行p5 3蛋白检测。结果　在 90例肝癌中 ,有 4 0例 (44 .4 % )在核中表达为强阳性 ,2 5例 (2 7.8% )在核中表达为弱阳性 ;在 75例癌旁中 ,没有细胞核强阳性表达 ,仅 1例 (1.3% )有核弱阳性表达 ;肝癌的p5 3核表达显著高于癌旁 (P =0 .0 0 0 )。另外 ,在肝癌中有 9例 (10 % )为细胞质p5 3表达阳性 ,在癌旁中有 17例 (2 2 .7% )为细胞质表达阳性 ,肝癌的胞质p5 3表达显著低于癌旁 (P =0 .0 2 6 )。结论　p5 3基因突变和p5 3的功能失活在启东的肝癌发展中有着重要意义。     

p53 gene mutations in primary lung tumors are conserved in brain metastases

The p53 product is frequently mutated in human tumors. Both acquired and inherited mutations have been described. These mutations transform p53 from a growth suppressor gene to a transforming oncogene. We examined tissue from 6 patients with primary lung carcinoma and the corresponding brain metastases for the presence of p53 mutations by immunohistochemistry. We then confirmed and characterized the mutations by single strand conformation analysis and by direct sequence analysis. All 6 patients had primary and metastatic tumor expressing a mutant p53. The mutations were all G-T transversions and mapped to exons 5, 6, 7, and 8. The mutations in the primary tumors were precisely conserved in the brain metastases.     

Identification of RB and p53 mutations in mouse lymphoma cell lines

We analyzed the genomic structure and mRNA of the RB and p53 genes in four mouse lymphoid leukemia cell lines (DL-1, DL-5, DL-8, and DL-12). Although no gross structural alteration of the RB gene was observed in any cell line, abnormalities of RB mRNA were detected in at least two cell lines. RB mRNA expression was greatly reduced in DL-12. In addition, cloning and sequencing analysis of the RB cDNA revealed that the RB mRNA in DL-8 had a 276-nucleotide deletion presumably consisting of exons 10, 11, and 12, suggesting that altered splicing resulted in the loss of these exons. Analysis of the p53 gene indicated that DL-5 had a deletion in both alleles and expressed a smaller mRNA. These results suggest that mutations of the RB or p53 genes, or both, are associated with lymphoid leukemogenesis in mice.     

Pokemon和p53蛋白在肝细胞癌组织中的表达及临床意义

目的：探讨Pokemon和p53蛋白在人肝细胞癌组织中的表达,分析其与肝细胞癌转移复发的关系。方法：应用免疫组织化学法检测60例肝细胞癌组织和癌旁组织中Pokemon和p53蛋白的表达情况。结果：60例肝细胞癌组织中Pokemon和p53表达率显著高于癌旁组织（P〈0.05）。Pokemon的表达与临床分期、肿瘤直径、肿瘤分化程度密切相关（P〈0.05）;p53的表达与脉管癌栓、术后复发、肝外转移及肿瘤分化程度密切相关（P〈0.05）。Pokemon和p53的表达呈显著正相关（γ=-0.275,P=0.033）。结论：Pokemon和p53蛋白的高表达可能在肝细胞癌的发生及进展中起着重要作用。     

肿瘤相关粘蛋白MUC1和抑癌基因p53在原发性肝癌中的表达

目的：通过测定MUC1和p53在肝脏不同组织中的表达差异，探讨MUC1和p53在肿瘤诊断和免疫治疗中的意义。方法：采用免疫组化方法检测35例肝癌（28例肝细胞癌，7例胆管细胞癌），8例肝硬化，8例肝血管瘤和10例正常肝组织中MUC1和p53的表达。结果：MUC1和p53基因均阳性表达于肝癌组织，它们在肝癌组织中的阳性表达率明显高于其它肝脏组织（P〈0．01），MUC1主要表达于细胞膜，其表达与肝癌的病理分型和组织学分化无相关性（P〉0．05），但肝癌伴有门静脉癌栓组与不伴有门静脉癌栓组之间MUC1表达率具有显著差异性（P〈0．05）；p53表达于细胞核，在Ⅰ、Ⅱ、Ⅲ级肝癌组织中的表达呈现递增趋势。结论：p53与肝癌的发生发展密切相关，MUC1在肝癌组织中的表达与分布特点可以作为肝癌诊断、判断预后的指标，同时，MUC1作为一种靶抗原，为今后的肝癌免疫治疗提供新的线索。     

非放射性PCR-LIS-SSCP技术快速分析肝癌患者p53基因249位密码子的突变

目的应用非放射性PCR-LIS-SSCP方法快速分析肝癌患者p53基因第249位密码子突变.方法采用PCR-LIS-SSCP方法,研究了16例来自中国广西、江苏启东和上海地区肝癌患者p53基因第249位密码子的突变情况,并用限制性内切酶和DNA测序对PCR-LIS-SSCP方法所获得的结果进行了验证.结果从16例肝癌病人中检出3例在该位点具有突变.其中广西地区的4例肝癌病人有1例发生突变,江苏启东地区的4例肝癌病人有1例发生突变,上海地区的8例肝癌病人有1例发生突变. 结论用该方法检测肝癌病人p53基因第249位密码子突变频率为18.8%(3/16),为该方法应用于候选新基因的未知突变研究奠定了基础.