人类恶性肿瘤中染色体17p13.3区带的杂合性丢失

人类恶性肿瘤中经常发生染色体染合性丢失,从而丢失抑癌基因的某一个等基因。人类１７号染色本特别是该色体的１７ｐ１３．３区带,在多种肿瘤中都存在着染色的体杂支失。     

大肠癌中p53基因突变的研究

应用聚合酶链反应(PCR)──单链构型多态性(SSCP)结合银染法对14例大肠癌p53基因的第4、第5─6和第7外显子进行了点突变的研究,结果共检测出6例点突变,而且发现各外显子的突变频率存在差异。另外,利用购自ATCC的两个探针 (p53cDNA探针和pYNZ22探针)对大肠癌中p53基因的杂合性失去进行了研究,在14例大肠癌中共检出6例杂合性丢失。将点突变检测结果同杂合性丢失结果进行比较分析, 并着重探讨了大肠癌中p53基因失活导致肿瘤的作用方式。 Abstract:The exons 4-7 of p53 gene were examined in 14 colorectal Cancer patients by using PCR-SSCP-silver staining method.The results showed 6 cases of point mutation and the mutation frequencies of exons were different from each other.p53 cDNA and pYNZ22 VNTR were used as probes to examine LOH(Loss of heterozygosity)of 14 colorectal cancers.6 cases with LOH were found.The results of present research suggest that mutation and LOH of p53 gene are critical events in the progress and development of Cancer.There were different kinds of inactivation model of p53 gene in the process of development of cancer and transformation of cells.     

贲门癌中染色体8p21-p23杂合性丢失的研究

目的 研究贲门癌中染色体8p21-p23杂合性丢失的情况。方法 采用激光捕获显微切割技术获得均质的肿瘤细胞及正常的胃粘膜细胞,多重置换扩增技术扩增捕获细胞的基因组DNA。PCR结合硝酸银染色方法分析19例贲门癌染色体8p21-p23的杂合性丢失。结果 在贲门癌中染色体8p21-p23的缺失频率非常高（63.2%）,我们确定了一个最小丢失区域. 结论 进一步明确此最小丢失区域内的抑癌基因将有助于贲门癌发生机制的阐明。     

脑星形胶质瘤基因表达及其与临床病理的关系

采用原癌基因Ｂｃｌ－２、Ｐ２１及抑癌基因Ｐ５３、Ｒｂ蛋白４种抗体,用ＡＢＣ免疫组织化学方法对４０例脑星形胶质瘤组织作免疫组化染色．结果发现：Ｂｃｌ－２及Ｐ５３基因表达在Ⅰ～Ⅳ级胶质瘤中阳性率有显著性差异,而且染色强度也有明显差异．Ｐ２１、Ｒｂ基因表达在Ⅰ～Ⅳ级胶质瘤中呈上升趋势,但仅在Ⅰ～Ⅲ级、Ⅰ～Ⅳ级之间有明显差异．可以认为：Ｂｃｌ－２、Ｐ５３、Ｐ２１、Ｒｂ在胶质瘤的发生中发挥一定的作用,尤其是Ｂｃｌ－２、Ｐ５３基因,这些基因蛋白的表达与胶质瘤恶性程度有关．测定胶质瘤中的Ｂｃｌ－２、Ｐ５３、Ｐ２１、Ｒｂ蛋白对于胶质瘤的诊断、鉴别诊断以及判断肿瘤的恶性程度与预后均有一定意义．     

脑胶质瘤组织中p16基因启动子区CpG岛甲基化检测及其临床意义研究

目的：研究脑胶质瘤中p16基因启动子区甲基化情况及其临床意义。方法：用甲基化特异性PCR技术检测42例脑胶质瘤组织和癌旁正常脑组织中p16基因启动子甲基化,并分析该基因启动子甲基化与临床病理特征之间的关系。结果：脑胶质瘤组织中p16基因异常甲基化率（38.27%）显著高于癌旁正常脑组织中p16基因的异常甲基化率（8.8%,P=0.000）。发生甲基化的肿瘤组织或者正常脑组织中p16基因mRNA和蛋白表达显著降低。此外,p16基因异常甲基化和肿瘤病理分级有相关性（P=0.007）,而与患者性别、年龄及肿瘤类型等临床特征无关（P=0.669,0.869和0.944）。结论：p16基因启动子区CpG岛高甲基化与p16表达下调相关,推测p16启动子区CpG岛高甲基化是导致p16基因在脑胶质瘤中表达下调的重要因素,有望成为脑胶质瘤早期辅助诊断的分子标志物之一。     

胃粘膜损伤中EB病毒感染与P53抑癌基因突变的研究

为了探讨EB病毒（EBV）感染与胃癌发生的关系,应用PCR技术对166例胃粘膜损伤标本的EBVDNA进行检测．其中66例应用银染PCR－SSCP分析技术检测了p53exon5～8突变情况,10例应用直接法原位PCR技术检测了EBV在组织中的感染情况。结果166例标本中EBV感染率为30．1％;EBV在细胞中感染大体是弥散型,主要存在于细胞核。66例标本中p53基因突变率为54．5％。对比分析,EBV阳性标本中p53基因突变率为75％（21／28）,EBV阴性标本中p53基因突变率为39．5％（15／38）。结果表明,EBV对胃粘膜组织细胞具有易感性,p53基因突变在胃粘膜病变中是一个常发事件,EBV感染与p53基因突变之间存在着高度相关性．对癌症的发生具有重要作用。     

胃粘膜损伤中EB病毒感染与P53抑癌基因突变的研究

为了探讨EB病毒(EBV)感染与胃癌发生的关系,应用PCR技术对166例胃粘膜损伤标本的EBV DNA进行检测,其中66例应用银染PCR-SSCP分析技术检测了p53 exon5～8突变情况,10例应用直接法原位PCR技术检测了EBV在组织中的感染情况.结果166例标本中EBV感染率为30.1%;EBV在细胞中感染大体呈弥散型,主要存在于细胞核.66例标本中p53基因突变率为54.5%.对比分析,EBV阳性标本中p53基因突变率为75%(21/28),EBV阴性标本中p53基因突变率为39.5%(15/38).结果表明,EBV对胃粘膜组织细胞具有易感性,p53基因突变在胃粘膜病变中是一个常发事件,EBV感染与p53基因突变之间存在着高度相关性,对癌症的发生具有重要作用.     

人脑星形细胞瘤中p53，Fas/FasL 的表达及其与凋亡关系的研究

目的:探讨细胞凋亡在星形细胞瘤中的作用及其与p53、Fas和Fas配体(Fas ligand,FasL)的关系。方法:对43例星形细胞瘤的标本分别进行HE染色,TUNEL及免疫组化分别标记p53,Fas和FasL。结果:高级别肿瘤和低级别肿瘤间的凋亡无显著差异(P>0.05)。高级别星形细胞瘤的p53,Fas和FasL的表达均显著高于低级别肿瘤(P均<0.05)。结论:突变型p53可作为评价星形细胞瘤生物学行为的参考指标。与低级别星形细胞瘤相比,高级别肿瘤中的细胞凋亡受到了抑制,且Fas与FasL的过表达对细胞凋亡可产生明显影响。     

Household Income Is Associated with the p53 Mutation Frequency in Human Breast Tumors

Background

A study from Scotland reported that the p53 mutation frequency in breast tumors is associated with socio-economic deprivation.

Methods

We analyzed the association of the tumor p53 mutational status with tumor characteristics, education, and self-reported annual household income (HI) among 173 breast cancer patients from the greater Baltimore area, United States.

Results

p53 mutational frequency was significantly associated with HI. Patients with < $15,000 HI had the highest p53 mutation frequency (21%), followed by the income group between $15,000 and $60,000 (18%), while those above $60,000 HI had the fewest mutations (5%). When dichotomized at $60,000, 26 out of 135 patients in the low income category had acquired a p53 mutation, while only 2 out of 38 with a high income carried a mutation (P < 0.05). In the adjusted logistic regression analysis with 3 income categories (trend test), the association between HI and p53 mutational status was independent of tumor characteristics, age, race/ethnicity, tobacco smoking and body mass. Further analyses revealed that HI may impact the p53 mutational frequency preferentially in patients who develop an estrogen receptor (ER)-negative disease. Within this group, 42% of the low income patients (< $15,000 HI) carried a mutation, followed by the middle income group (21%), while those above $60,000 HI did not carry mutations (P _trend < 0.05).

Conclusions:

HI is associated with the p53 mutational frequency in patients who develop an ER-negative disease. Furthermore, high income patients may acquire fewer p53 mutations than other patients, suggesting that lifetime exposures associated with socio-economic status may impact breast cancer biology.     

Variable Spontaneous Mutation and Loss of Heterozygosity among Heterozygous Genomes in Yeast

Mutation and recombination are the primary sources of genetic variation. To better understand the evolution of genetic variation, it is crucial to comprehensively investigate the processes involving mutation accumulation and recombination. In this study, we performed mutation accumulation experiments on four heterozygous diploid yeast species in the Saccharomycodaceae family to determine spontaneous mutation rates, mutation spectra, and losses of heterozygosity (LOH). We observed substantial variation in mutation rates and mutation spectra. We also observed high LOH rates (1.65–11.07×10⁻⁶ events per heterozygous site per cell division). Biases in spontaneous mutation and LOH together with selection ultimately shape the variable genome-wide nucleotide landscape in yeast species.     

Protein Tyrosine Kinases in Human Brain and Gliomas

Tyrosine kinase activity was determined in neonatal and adult human brain, oligodendrogliomas, and astrocytomas. The astrocytomas were divided into low- (grade I and grade II) and high-grade (grade III and grade IV) tumors. We measured the tyrosine kinase activity in the cytosolic and membrane fraction using poly(glutamic acid:tyrosine, 4:1) as an artificial substrate. The cytosolic activity in oligodendrogliomas (n = 7), low-grade astrocytomas (n = 7), and neonatal brain (n = 1) was increased, on average, two- to fourfold compared with that in normal adult brain (n = 14). The cytosolic activities of high-grade astrocytomas (n = 11) were in approximately the same range as found in normal adult brain. The absence of an increase in cytosolic activity in high-grade astrocytomas compared with adult brain is likely due to the occurrence of necrosis in these tumors. In contrast to the cytosolic activity, no differences were found in the membrane-bound activity. By fast protein liquid chromatography, at least three forms of cytosolic protein tyrosine kinase could be separated, which eluted at 0, 115, and 210 mM NaCl. In most cases the highest amount of activity eluted at 210 mM NaCl. However, in oligodendrogliomas, high-grade astrocytomas, and neonatal brain, more activity eluted at 115 mM NaCl than in normal adult brain (p = 0.043). Nevertheless, protein tyrosine kinases from all three peaks contributed to the elevated levels of total cytosolic activity of oligodendrogliomas and low-grade astrocytomas.     

Loss of Heterozygosity in DNA Mismatch Repair Genes in Human Atherosclerotic Plaques

To detect the incidence of loss of heterozygosity (LOH) in DNA mismatch repair genes (MMR) occurring in atherosclerosis, fifty human autopsy cases of atherosclerosis were examined for LOH using 19 microsatellite markers, in three single and four tetraplex microsatellite assays. The markers used are located on or close to MMR genes. Fourteen specimens (28%) showed allelic imbalance in at least one locus. Loci hMSH2 (2p22.3–p16.1), hPMS1 (2q24.1–q32.1), and hMLH1 (3p21.32–p21.1) exhibited LOH (10, 10, and 12% respectively). We found that loss of heterozygosity on hMSH2, hPMS1, and hMLH1, occurs in atherosclerosis. The occurrence of such genomic alterations may represent important events in the development of atherosclerosis.     

Localization of Human Cadherin Genes to Chromosome Regions Exhibiting Cancer-Related Loss of Heterozygosity

This report presents the chromosomal localization of cadherin genes. Cadherins are cellular adhesion molecules. Since disturbance of intracellular adhesion is important for invasion and metastasis of tumor cells, cadherins are considered prime candidates for tumor suppressor genes. A variety of solid tumors show loss of heterozygosity of the long arm of chromosome 16, which is indicative of the potential location of tumor suppressor genes. Refined and new localizations of six cadherin genes (CDH3, 5, 8, 11, 13, and 15) to the long arm of chromosome 16 are shown. CDH15 was localized to 16q24.3, in a region that exhibits loss of heterozygosity in a number of sporadic breast cancer tumors. Previous localization of CDH13 (H-cadherin) to 16q24 suggested this gene as a tumor suppressor candidate in the 16q24.3 loss of heterozygosity region; however, refined mapping presented in this report localizes CDH13 proximal to this region. A human EST homologous to the chicken cadherin-7 was partially sequenced and found to represent a new human cadherin. This cadherin mapped to chromosome 18q22–q23, a region that exhibits loss of heterozygosity in head and neck squamous cell carcinomas. CDH16 was localized to 8q22.1, a region exhibiting loss of heterozygosity in adult acute myeloid leukemia.     

Mutation Load in Sunflower Inversions Is Negatively Correlated with Inversion Heterozygosity

Recombination is critical both for accelerating adaptation and purging deleterious mutations. Chromosomal inversions can act as recombination modifiers that suppress local recombination in heterozygotes and thus, under some conditions, are predicted to accumulate such mutations. In this study, we investigated patterns of recombination, transposable element abundance, and coding sequence evolution across the genomes of 1,445 individuals from three sunflower species, as well as within nine inversions segregating within species. We also analyzed the effects of inversion genotypes on 87 phenotypic traits to test for overdominance. We found significant negative correlations of long terminal repeat retrotransposon abundance and deleterious mutations with recombination rates across the genome in all three species. However, we failed to detect an increase in these features in the inversions, except for a modest increase in the proportion of stop codon mutations in several very large or rare inversions. Consistent with this finding, there was little evidence of overdominance of inversions in phenotypes that may relate to fitness. On the other hand, significantly greater load was observed for inversions in populations polymorphic for a given inversion compared to populations monomorphic for one of the arrangements, suggesting that the local state of inversion polymorphism affects deleterious load. These seemingly contradictory results can be explained by the low frequency of inversion heterozygotes in wild sunflower populations, apparently due to divergent selection and associated geographic structure. Inversions contributing to local adaptation represent ideal recombination modifiers, acting to facilitate adaptive divergence with gene flow, while largely escaping the accumulation of deleterious mutations.     

P53 Mutation and c-fos Overexpression Are Associated With Detection of the Antigen VLA-2 in Human Melanoma Cell Lines

In this study, we examined the expression of c-fos, c-myc, mutant c-Ha-ras and mutant p53 proteins in three normal human melanocyte cell lines and the following 12 melanoma cell lines: M5, Mewo, A375, Bro, Mel 2a, O-Mel II, IgR 39, SkMel-13, -19, -28 Mel-57 and NKI-4, using an immunohistochemical assay (APAAP). An effort was made to correlate oncogene expression with growth parameters, differentiation antigens (HMB-45, vla-2, k.1.2.58, HLA-DR, HLA-I), and pigmentation. All melanocyte cell lines were negative for the oncogenes examined, whereas six of the melanoma cell lines were found also positive (three for c-fos, two for c-myc, one for c-Ha-ras, and four for p53). Three melanoma cell lines expressed one oncogene and three the combination c-fos/p53. These three melanoma cell lines were positive for the “late” tumor progression marker A. 1. 43 (vla-2 adhesion molecule) and negative for the differentiation marker k. 1. 2. 58. Positivity for A. 1. 43 combined with negative staining for k. 1. 2. 58 was found in six out of the 12 cell lines. The observed oncogene expression correlated neither with growth parameters nor melanin content. The present findings revealed a coexpression of mutant p53 and c-fos proteins being associated with a highly malignant phenotype in melanoma cell lines. Further studies are necessary to clarify the significance of the above findings     

Frequency Specificity of Regional Homogeneity in the Resting-State Human Brain

Resting state-fMRI studies have found that the inter-areal correlations in cortical networks concentrate within ultra-low frequencies (0.01–0.04 Hz) while long-distance connections within subcortical networks distribute over a wider frequency range (0.01–0.14 Hz). However, the frequency characteristics of regional homogeneity (ReHo) in different areas are still unclear. To examine the ReHo properties in different frequency bands, a data-driven method, Empirical Mode Decomposition (EMD), was adopted to decompose the time series of each voxel into several components with distinct frequency bands. ReHo values in each of the components were then calculated. Our results showed that ReHo in cortical areas were higher and more frequency-dependent than those in the subcortical regions. BOLD oscillations of 0.02–0.04 Hz mainly contributed to the cortical ReHo, whereas the ReHo in limbic areas involved a wider frequency range and were dominated by higher-frequency BOLD oscillations (>0.08 Hz). The frequency characteristics of ReHo are distinct between different parts of the striatum, with the frequency band of 0.04–0.1 Hz contributing the most to ReHo in caudate nucleus, and oscillations lower than 0.02 Hz contributing more to ReHo in putamen. The distinct frequency-specific ReHo properties of different brain areas may arise from the assorted cytoarchitecture or synaptic types in these areas. Our work may advance the understanding of the neural-physiological basis of local BOLD activities and the functional specificity of different brain regions.     

Different Mode of Afferents Determines the Frequency Range of High Frequency Activities in the Human Brain: Direct Electrocorticographic Comparison between Peripheral Nerve and Direct Cortical Stimulation

Physiological high frequency activities (HFA) are related to various brain functions. Factors, however, regulating its frequency have not been well elucidated in humans. To validate the hypothesis that different propagation modes (thalamo-cortical vs. cortico-coritcal projections), or different terminal layers (layer IV vs. layer II/III) affect its frequency, we, in the primary somatosensory cortex (SI), compared HFAs induced by median nerve stimulation with those induced by electrical stimulation of the cortex connecting to SI. We employed 6 patients who underwent chronic subdural electrode implantation for presurgical evaluation. We evaluated the HFA power values in reference to the baseline overriding N20 (earliest cortical response) and N80 (late response) of somatosensory evoked potentials (HFA_SEP(N20) and HFA_SEP(N80)) and compared those overriding N1 and N2 (first and second responses) of cortico-cortical evoked potentials (HFA_CCEP(N1) and HFA_CCEP(N2)). HFA_SEP(N20) showed the power peak in the frequency above 200 Hz, while HFA_CCEP(N1) had its power peak in the frequency below 200 Hz. Different propagation modes and/or different terminal layers seemed to determine HFA frequency. Since HFA_CCEP(N1) and HFA induced during various brain functions share a similar broadband profile of the power spectrum, cortico-coritcal horizontal propagation seems to represent common mode of neural transmission for processing these functions.