41例人脑胶质瘤组织中p53基因突变的研究

背景与目的:p53抑癌基因在细胞周期的调控、维持细胞基因组的完整性、诱导细胞分化和凋亡中起着重要作用。胶质瘤尤其是星形细胞肿瘤中,经常发生p53基因突变。本研究探讨人脑胶质瘤中p53突变及与胶质瘤发生发展的相关性。方法:应用聚合酶链反应-单链构象多态性分析(polymerase chainreaction-single-strand conformation polymorphism,PCR-SSCP)及DNA测序技术对41例不同类型人脑胶质瘤p53基因突变进行检测。结果:通过PCR-SSCP检测发现在41例人脑胶质瘤组织中有17例(41.5%)呈现p53基因的单链构象多态性改变,均位于5～8外显子,突变例数依次为7(41.2%)、1(5.9%)、4(23.5%)、5(29.4%)。Ⅲ、Ⅳ级胶质瘤中p53基因突变率明显高于Ⅰ、Ⅱ级肿瘤(58.3%vs.17.6%,P<0.01);DNA序列分析显示,17例PCR-SSCP检测阳性的肿瘤p53基因相应外显子均存在基因点突变或缺失,其中错义突变13例,占76.5%;同义突变2例,占11.8%;移码突变2例,占11.8%;碱基突变以G→A或A→G最多,占55.6%。结论:胶质瘤中p53突变多发生于第5、8外显子,基因突变类型以错义突变为主,该基因的突变与胶质瘤的发生及恶性进展过程相关。     

IDH1 mutations are present in the majority of common adult gliomas but rare in primary glioblastomas

We screened exon 4 of the gene isocitrate dehydrogenase 1 (NADP+), soluble (IDH1) for mutations in 596 primary intracranial tumors of all major types. Codon 132 mutation was seen in 54% of astrocytomas and 65% of oligodendroglial tumors but in only 6% of glioblastomas (3% of primary and 50% of secondary glioblastomas). There were no mutations in any other type of tumor studied. While mutations in the tumor protein p53 gene (TP53) and total 1p/19q deletions were mutually exclusive, IDH1 mutations were strongly correlated with these genetic abnormalities. All four types of mutant IDH1 proteins showed decreased enzymatic activity. The data indicate that IDH1 mutation combined with either TP53 mutation or total 1p/19q loss is a frequent and early change in the majority of oligodendroglial tumors, diffuse astrocytomas, anaplastic astrocytomas, and secondary glioblastomas but not in primary glioblastomas.     

Chromosome 10 and 17 deletions and p53 gene mutations in Thai patients with astrocytomas

The tumor suppressor gene locus is known to be partly responsible for the tumorigenesis of sporadic gliomas, but the genetic events that drive the neoplastic process of this tumor remain largely unknown. We correlated the results of loss of heterozygosity (LOH) analysis on chromosomes 10 and 17 and a point mutation analysis of a tumor suppressor gene, p53, in 21 patients with astrocytomas at different stages. LOH was determined in tumor and leukocyte DNAs of primary human central nervous system tumors. The incidence rate of brain tumors corresponded to every p53-coding exon for single-strand conformation polymorphisms (SSCP) and the mutations were confirmed by sequencing. p53 mutations were found in 2 of 10 glioblastomas (20%) and in 1 of 8 low-grade astrocytomas (12.5%). Similarly, LOH on chromosome 10 was also found in 2 of 10 glioblastomas (20%) and 1 of 8 low-grade astocytomas (12.5%). Neither of the p53 mutations nor LOH on chromosome 10 was observed together in the tumor types analyzed. Interestingly, the p53 mutations were found in 29% of patients with LOH on chromosome 17. The fact that p53 mutation and LOH on chromosome 17 were found together only in glioblastomas, suggested that these genetic changes may accumulate during astrocytoma progression.     

Mutational analysis of the PTEN gene in gliomas: molecular and pathological correlations

The PTEN gene, recently identified on chromosome 10q23, has been proposed to be a candidate tumor suppressor gene inactivated in multiple cancers including glial tumors. We investigated 47 glioblastomas (GBM), 14 anaplastic astrocytomas (AA), 6 non-pilocytic low-grade astrocytomas (LGA), 21 low-grade and anaplastic oligodendrogliomas (O) and oligoastrocytomas (OA), and 3 ependymomas (E) for mutation of the PTEN gene using denaturing gradient gel electrophoresis (DGGE) followed by DNA sequencing. These tumors have been previously screened for loss of heterozygosity (LOH) on chromosome 10q, p53 mutations and EGFR amplification. Overall, PTEN mutations, detected in 14 of 91 tumors, were present in 13 of 47 GBM and 1 of 14 AA. In contrast, mutations were absent in other glioma subtypes (0/30). In all informative cases, PTEN mutations occurred in tumors showing LOH on chromosome 10q, confirming the inactivation of this gene by a 2-hit mechanism. No correlation was observed between the presence of PTEN mutation and p53 mutation and EGFR amplification. Our results indicate that biallelic PTEN inactivation plays an important role in the pathogenesis of high-grade astrocytomas as a late event. Moreover, they suggest that PTEN alterations are equally involved in the 2 glioblastoma pathways defined by the presence of EGFR amplification and p53 mutation. Finally, correlation analysis with clinical data did not show that PTEN mutation was linked to survival of the patients.     

Glioblastoma multiforme in four siblings: A cytogenetic and molecular genetic study

Summary The familial occurrence of gliomas, in the absence of well-defined neurological tumor syndromes such as the neurofibromatoses, is uncommon. We present a family of ten children in which the four eldest suffered from gliomas. Three of these siblings had histologically verified glioblastoma multiforme, and one patient also had an intestinal non-Hodgkin's lymphoma, but there were no stigmata or family history of a neurological tumor syndrome. Cytogenetic studies of the proband revealed a normal karyotype. Molecular genetic analysis of the proband's glioblastoma revealed two mutations in the p53 tumor suppressor gene, but these were not present in the germline DNA, mutations were not detected in the MTS1 gene in the tumors or in the germline DNA. These findings suggest that a genetic factor may be responsible for the clustering of glial tumors in this family, but it is unlikely that the genetic alteration is mutation of the p53 gene. The data are discussed in light of the literature on familial brain tumors.     

Influence of p53 mutations on prognosis of patients with glioblastoma

BACKGROUND: The influence of p53 mutations on the biology of astrocytic tumors is controversial. p53 is thought to be inactivated in the early stage of gliomagenesis; however, what role its inactivation plays in the malignancy of gliomas remains unknown. To understand the significance of p53 inactivation, the authors identified the locus of p53 gene mutation in glioma samples at different stages of progression and studied the correlation between the mutation and clinical behavior. METHODS: Samples from newly diagnosed gliomas, including pure and mixed astrocytomas, were analyzed for p53 mutations using a yeast functional assay. To determine the locus of the gene mutations, DNA sequencing was performed. RESULTS: The incidence of p53 mutations was higher in anaplastic astrocytomas (AA, 48%) than glioblastomas (GBM, 31%). There was no significant difference in the average ages of GBM patients with and without p53 mutations (54.9 years +/- 2.3 and 53.2 years +/- 4.6, respectively). In GBM patients, the mutation did not affect progression free survival or overall survival. Astrocytomas and GBM differed in the distribution of p53 mutation loci. CONCLUSIONS: The p53 gene mutation does not markedly affect the survival of GBM patients. The difference in the location of p53 mutations between AA and GBM suggests that in gliomas, the p53 mutation may contribute not only to tumorigenesis (as an early event) but also to progression to malignancy (as a late event).     

Molecular Genetic Changes in a Series of Neuroepithelial Tumors of Childhood

Amplification of the EGFR, mdm2, CDK4 and PDGFR A genes has been widely demonstrated in adult malignant gliomas, almost exclusively glioblastomas. To determine the role of these mutational events in pediatric astrocytic gliomas we investigated the presence of EGFR, mdm2, CDK4 and PDGFR A gene amplification in 38 childhood brain tumor biopsies, including 24 low-grade astrocytomas and 14 malignant tumors. We used differential PCR assay on DNA extracted either from paraffin embedded or frozen tissues. EGFR gene amplification was detected in 4 out of 14 malignant tumors; no low-grade astrocytoma showed amplification. Tumors with EGFR gene amplification were negative for the presence of p53 mutations, as observed in a previous study. One glioblastoma showed PDGFR A amplification, while no amplifications were observed for mdm2 and CDK4 genes.These data are in line with those obtained from studies on gliomas of adults and suggest the existence of two different subsets of malignant gliomas also in pediatric brain tumors: one carrying EGFR gene amplification, the other showing p53 mutations.     

High Incidence of p53 Gene Mutation in Human Ovarian Cancer and Its Association with Nuclear Accumulation of p53 Protein and Tumor DNA Aneuploidy

Using the poylmerase chain reaction and single-strand conformation polymorphism analysis, p53 gene mutations were examined in 24 cases of ovarian tumor including 14 ovarian carcinomas and 2 borderline cases of common epithelial type, 7 germ cell tumors, and one stromal tumor. Abnormal bands indicating mutations were detected in 12 (50%) of the cases examined, being present most frequently in common "epithelial" ovarian carcinoma (71%, 10/14). One case each of squamous cell carcinoma originating in a dermoid cyst and anaplastic dysgerminoma were positive for mutation. Direct sequencing confirmed 12 mutations and revealed G→A and G→C nucleotide changes in 5 and 3 cases (42% and 25%), respectively. The mutation was localized at the CpG site of the gene in 3 cases. Immunohistochemical examination of p53 protein in 21 cases and DNA flow-cytometrical analysis in 17 cases were also performed. Nuclear accumulation of the p53 protein and DNA aneuploidy pattern were detected in 11 (52%) and 9 (53%) cases, respectively. These were significantly correlated with p53 gene mutation ( P <0.01 and P <0.05, respectively; Fisher's exact test). Neither mutation of the p53 gene, nuclear accumulation of p53 protein nor DNA aneuploidy was detected in borderline cases of common "epithelial" type, typical dysgerminoma and immature teratoma. These results suggest that p53 gene mutation, nuclear accumulation of the protein and the DNA aneuploidy pattern are events occurring almost simultaneously in the progression of ovarian tumors, and that p53 abnormalities seem to be correlated with a high grade of malignancy.     

Mutations of the p53 tumor suppressor gene in neoplasms of the human nervous system

A variety of neoplasms of the human nervous system were analyzed for the presence of mutations in the p53 tumor suppressor gene. DNA was extracted from frozen or formalin-fixed, paraffin-embedded material. Single-strand conformation polymorphism (SSCP) analysis for exons 5–8 was followed by direct DNA sequencing. Mutations leading to an amino acid change were found in three of 11 (27%) low-grade (World Health Organization (WHO) Grade II) astrocytomas. They were located in codon 183 (TCA → TGA) of exon 5, codon 237 (ATG → ATA) of exon 7, and codon 273 (CGT → CAT) of exon 8. In one of these cases, the sequence indicated loss of the wild-type allele. Of 12 juvenile pilocytic astrocytomas (WHO Grade I), none contained a p53 mutation, suggesting a different molecular basis for this childhood neoplasm. Except for a mutation in one of seven (14%) meningeal hemangiopericytomas (codon 238; TGT → TTT, Cys → Phe), no mutations were observed in exons 5–8 of the p53 gene in any of the following tumors of the nervous system and its coverings: 13 schwannomas, 12 central neurocytomas, 22 meningiomas, 10 choroid plexus papillomas and carcinomas, and 30 neuroblastomas of the sympathetic nervous system. These and published data support the view that p53 mutations are frequently involved both in low-grade and progressive (anaplastic) astrocytomas, including glioblastomas multiforme. Oligodendrogliomas, medulloblastomas, meningiomas, and hemangiopericytomas rarely (<15%) show p53 mutations in exons 5–8, whereas none of the remaining nervous system neoplasms revealed evidence of an involvement of the p53 gene in their development.     

p53 protein in pediatric malignant astrocytomas: A study of 21 patients

Malignant astrocytomas are uncommon brain tumors in children and it isknown that astrocytic tumors with similar degrees of histologic anaplasia often show different biologic behaviour. Their uncommonoccurrence has resulted in relatively few studies of the molecular biology and genetics of pediatric malignant astrocytomaswith somewhat conflicting results, in contrast with the many studies addressing astrocytomas in adults. p53 immunoreactivity has been usedto screen tissues for the abnormal presence of the p53 protein and abnormal immunoreactivity has been demonstratedin one-half to two-thirds of adult astrocytomas. We studied the frequency of p53 immunoreactivity and gene alteration in 21 childrenwith malignant astrocytomas (anaplastic astrocytomaand glioblastoma multiforme) and analysed the survival of patientswith p53 immunoreactive versus non-reactive tumors. Of the cases examined, 8 were anaplastic astrocytoma (AA) and 13 were glioblastomamultiforme (GM). We found that the overall frequencyof p53 immunoreactivity of 47% in this group of pediatric malignant astrocytomas is similar to that reported for adult astrocytomas. The median survival in both p53-positive and p53-negative groups of pediatric malignant astrocytomas wassimilar; however, the number of deaths in each group and the distributionof p53 scores is not statistically significant. Further studies to precisely identify p53 and other genetic mutations in pediatric gliomas are needed to understand their biology and the rationale for therapeutic options.     

Tumor suppressor gene alterations in malignant gliomas: histopathological associations and prognostic evaluation.

We have examined a series of 135 gliomas for alterations of the p53, CDKN2A (p16) and PTEN tumor suppressor genes (TSGs) in order to evaluate the incidence of their inactivation as a function of tumor malignancy and cellular differentiation, and to examine potential associations with patient outcome. The composition of this series, classified using WHO criteria, is as follows: 27 grade 2 tumors (11 astrocytomas, 12 oligoastrocytomas, 4 oligodendrogliomas), 42 grade 3 tumors (22 astrocytomas, 16 oligoastrocytomas, 4 oligodendrogliomas), and 66 grade 4 tumors (63 astrocytomas and 3 oligoastrocytomas). Similar frequencies of p53 mutation were observed among grade 2 (37.0%), and grade 3 tumors (38.1%), as well as between astrocytomas and mixed tumors. CDKN2A and PTEN mutations were clearly associated with increasing tumor malignancy (occurring in 0% of grade 2 tumors, 14.3% and 4.8% respectively of grade 3 tumors, and 27.3% and 30.3% respectively of grade 4 tumors) and were observed at substantially higher rates among astrocytomas. For the tumor suppressor genes examined, there was no relationship between the occurrence of any two TSG inactivation events. With regard to outcome, the p53 genetic status showed no significant relationship with patient survival. The CDKN2 and PTEN alterations were negative prognostic indicators of survival when evaluated in all 135 gliomas, but failed to predict outcome when evaluated in either of the high grade (3 or 4) tumor groups.     

Detection of p53 Gene Mutations in Aspiration Biopsy Specimens from Suspected Breast Cancers by Polymerase Chain Reaction-Single Strand Conformation Polymorphism Analysis

Genomic DNA was extracted from aspiration biopsy specimens taken from 15 suspected cases of breast cancer, including 7 known cases of breast cancer, and the p53 gene was studied for evidence of mutation by using a polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis. In 5 of the 15'cases (33%), p53 gene mutation was identified and these tumors were subsequently histologically diagnosed as malignant. Further, DNA flow cytometry of the 15 tumors demonstrated that 6 (40%) were aneuploid and malignant, whereas 9 (60%) were diploid and benign. It was also found that the tumor cells in 5 aspirated cases that showed p53 gene mutations were all aneuploid, the p53 protein expression was positive, and the tumors were proved to be histologically malignant. It was thus concluded that the detection of p53 gene mutation by PCR-SSCP analysis of aspirated biopsy specimens from suspected breast cancers is a helpful method for achieving a more accurate diagnosis.     

Association of p53 gene mutation with decreased chemosensitivity in human malignant gliomas

Loss of p53 function is involved in tumorigenesis of various human cancers, but the relation between mutation of the p53 tumor-suppressor gene and the chemo- and radiosensitivity of tumors remains unclear. Mutated p53 gene in malignant glioma is often associated with progression and recurrence of malignancy, and these events are closely linked with increased resistance to both chemotherapy and radiation. We have examined the status of the p53 gene in malignant gliomas obtained from 34 patients (glioblastoma: 29 cases, anaplastic astrocytomas: 5 cases). The chemosensitivities of these specimens using 28 kinds of anti-cancer agents were determined using an in vitro assay system. Overall, 12 mutated cases of p53 gene were found in malignant glioma samples. The mean numbers of effective agents were 0.58 for the tumor samples with p53 mutations and 5.00 for tumors without mutations. Our data indicate that p53 gene mutation predisposes to decreased cell killing via chemotherapy in malignant gliomas. © 1996 Wiley-Liss, Inc.     

Significance of IDH mutations varies with tumor histology, grade, and genetics in Japanese glioma patients

Mutations in isocitrate dehydrogenase 1 (IDH1) and IDH2 are found frequently in malignant gliomas and are likely involved in early gliomagenesis. To understand the prevalence of these mutations and their relationship to other genetic alterations and impact on prognosis for Japanese glioma patients, we analyzed 250 glioma cases. Mutations of IDH1 and IDH2 were found in 73 (29%) and 2 (1%) cases, respectively. All detected mutations were heterozygous, and most mutations were an Arg132His (G395A) substitution. IDH mutations were frequent in oligodendroglial tumors (37/52, 71%) and diffuse astrocytomas (17/29, 59%), and were less frequent in anaplastic astrocytomas (8/29, 28%) and glioblastomas (13/125, 10%). The pilocytic astrocytomas and gangliogliomas did not have either mutation. Notably, 28 of 30 oligodendroglial tumors harboring the 1p/19q co-deletion also had an IDH mutation, and these alterations were significantly correlated (P < 0.001). The association between TP53 and IDH mutation was significant in diffuse astrocytomas (P = 0.0018). MGMT promoter methylation was significantly associated with IDH mutation in grade 2 (P < 0.001) and grade 3 (P = 0.02) gliomas. IDH mutation and 1p/19q co-deletion were independent favorable prognostic factors for patients with grade 3 gliomas. For patients with grade 3 gliomas and without 1p/19q co-deletion, IDH mutation was strongly associated with increased progression-free survival (P < 0.0001) and overall survival (P < 0.0001), but no such marked correlation was observed with grade 2 gliomas or glioblastomas. Therefore, IDH mutation would be most useful when assessing prognosis of patients with grade 3 glioma with intact 1p/19q; anaplastic astrocytomas account for most of these grade 3 gliomas.     

p53 mutation and loss of heterozygosity on chromosomes 17 and 10 during human astrocytoma progression.

The human brain tumor, astrocytoma, typically progresses through three histopathologically defined stages with the passage of time: one premalignant stage, low-grade astrocytoma; and two malignant stages, anaplastic astrocytoma and glioblastoma multiforme. We correlated the results of a sequence analysis of the tumor suppressor gene, p53, and a restriction fragment length polymorphism analysis of chromosomes 17 and 10 in 45 patients with cerebral astrocytomas at different stages. To detect p53 mutations in tumor DNA, we analyzed polymerase chain reaction products corresponding to every p53-coding exon for single-strand conformation polymorphisms and confirmed the mutations by sequencing. Loss of heterozygosity (LOH) was determined by Southern transfer analysis of somatic and tumor DNA from these same patients using polymorphic markers for various loci on chromosomes 10 and 17. p53 mutations were found in 7 of 25 glioblastomas (28%), in 5 of 14 anaplastic astrocytomas (36%) but in 0 of 6 low-grade astrocytomas. p53 mutations were found in 62% of patients with LOH on chromosome 17p. These results indicated that p53 inactivation is a common genetic event in astrocytoma progression that may signal the transition from benign to malignant tumor stages. LOH on chromosome 10 was found in 61% of glioblastomas, in 23% of anaplastic astrocytomas, but in 0% of low-grade astrocytomas. LOH on chromosome 10 and p53 mutation were found together only in patients with glioblastoma multiforme (22%), suggesting that these genetic changes may accumulate during astrocytoma progression.     

Alterations in p53, p21, and MIB-1 Labeling Index in Primary Human Astrocytomas Following Radiation Therapy

Summary Little is known about the cellular and genetic changes that occur in human astrocytomas following radiation therapy (RT). Experimental studies would suggest that early effects include induction of p53 and p21 expression, cell cycle arrest, and selection of tumor cells with molecular changes that correlate with radiation resistance. Unfortunately, tissue sampling of primary human astrocytomas closely following radiation therapy is uncommon, hindering comparative assessment of primary human tumors. Through local databases, we were able to collect eight cases in which tissue was resected within 8 weeks of RT because of bulky residual disease: two patients with grade II diffuse astrocytomas (LGA) and 6 patients with high-grade astrocytomas (HGA; 1 anaplastic astrocytoma, 5 glioblastomas). Routine histopathologic sections, MIB-1 labeling index (LI), p53 and p21 expression, and EGFR expression were compared between the pre- and post-RT samples. Only one tumor (52d post-RT) showed prominent radiation-induced histopathologic changes. p53 expression was detected in two tumors pre-RT and in six tumors post-RT. In the four tumors in which p53 expression was induced, the post-RT LI was lower in each case, and p21 expression had increased in 3/4 of these cases. No change in LI was detected in tumors in which p53 expression was unchanged. EGFR expression was not altered following RT. The results of this unique series document that some primary human astrocytomas increase expression of p53 and p21 and decrease proliferation in response to RT. However, the small size of the series argues for further studies of radiation induced molecular changes in primary human astrocytoma tissue.     

Analysis of mdm2 and p53 Gene Alterations in Glioblastomas and its Correlation with Clinical Factors

Malignant gliomas are the most frequent primary brain tumors. Recent studies defined several genetic markers, which might characterize molecular-biological subsets of glioblastomas with probably prognostic implications. To elucidate the involvement of murine-double-minute (mdm)2 gene amplifications and mutations of the tumor suppressor gene p53 in the tumorigenesis of malignant gliomas we analyzed a series of 75 glioblastomas. The p53 mutations occur in one-third of glioblastomas, mdm2 amplifications were found in 13% of cases. Our analysis revealed a hot spot in the p53 gene locus in codon 156, the same point mutation was detected in 4 tumor samples. None of the mdm2 amplified tumors had p53 mutations, supporting the hypothesis, that mdm2 amplifications are alternative mechanisms for p53 inactivation. Patients with p53 mutated tumors were significantly younger characterized by a mean age of 44 years. Additionally association with longer overall survival could be detected for this subgroup of patients. In our study, survival estimation revealed a significant correlation of mdm2 gene amplification with shorter survival time, and support the hypothesis, that mdm2 oncogene activation appears to occur late in tumor progression and may be characteristic as negative prognostic marker.     

p53 and p16INK4A Mutations during the progression of glomus tumor

Glomus tumors are significantly rare tumors of carotid body. The great majority of these tumors are benign in character. Here we present two brothers with hereditary glomus jugulare tumor who had consanguineous parents. Radiotherapy was applied approximately 8 and 10 years ago for treatment in both cases. Eight years later, one of these cases came to our notice due to relapse. The mutation pattern of p53, p57KIP2, p16INK4A and p15NK4B genes which have roles in the cell cycle, was analyzed in tumor samples obtained from the two affected cases in the initial phase and from one of these cases at relapse. The DNA sample obtained from the case in initial diagnosis phase revealed no p53, p57KIP2, p16INK4A or p15INK4B mutation. He is still in remission phase. Despite the lack of p53, p57KIP2, p16INK4A and p15INK4B mutation at initial diagnosis the tumor DNA of the other case in relapse revealed p53 codon 243 (ATG-->ATC; met-->ile) and p16 codon 97 (GAC-->AAC; asp-->asn) missense point mutations. No loss of heterozygosity in p53 and p16INK4A was observed by microsatellite analysis of tumoral tissues in these cases. P53 and p16INK4A mutations observed in relapse phase were in conserved regions of both genes. No previous reports have been published with these mutations in glomus tumor during progression. The mutation observed in this case may due to radiotherapy. In spite of this possibility, the missense point mutations in conserved region of p53 and p16INK4A genes may indicate the role of p53 and p16INK4A in tumor progression of glomus tumors.