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Biomedical subjects

P Kleihues

Publications and source records attributed to P Kleihues.

At least 19 recordsLinked to original sources
PubMed2001

Smoking cessation in cancer prevention.

Tobacco smoking is the largest preventable risk factor for morbidity and mortality in industrialized countries. WHO estimates that tobacco will become the largest single health problem by 2020, causing an estimated 8.4 million deaths annually. Tobacco has central importance in the etiology of cancers of the lung, head and neck, urinary tract, and pancreas. Reducing the number of young people who take up smoking and helping those who have started to smoke to quit the habit are the key ways of preventing these cancers. Tobacco- or nicotine-dependence is a common, chronic, relapsing medical condition. Studies of twins have implicated genetic factors in most of the differences in vulnerability to tobacco smoke and in the persistence of the smoking phenotype. The available interventions for reducing tobacco use and treatment for nicotine dependence offer public health officials and clinicians the greatest single opportunity for disease prevention. Five medications -- nicotine chewing gum, nicotine patches, nicotine inhalers, nicotine nasal sprays and bupropion -- and behavioural therapy appear to be both effective and safe: they double the quitting rates and are associated with a dropout rate due to adverse events of less than 5%.

Antidepressive Agents, Second-Generation↗
PubMed2001

Germline SDHD mutation in paraganglioma of the spinal cord.

Hereditary paraganglioma of the head and neck is associated with germline mutations in the SDHD gene, which encodes a mitochondrial respiratory chain protein. Paragangliomas of the central nervous system are very rare, occur almost exclusively in the cauda equina of the spinal cord and are considered non-familial. In the present study, we screened 22 apparently sporadic paragangliomas of the cauda equina for SDHD mutations. One spinal paraganglioma and similar cerebellar tumours that developed 22 years later in the same patient contained a missense mutation at codon 12 (GGT-->AGT, Gly-->Ser) and a silent mutation at codon 68 (AGC-->AGT, Ser-->Ser). There was no family history of paragangliomas but DNA from white blood cells of this patient showed the same sequence alterations, indicating the presence of a germline mutation. All other cases of spinal paraganglioma had the wild-type SDHD sequence, except one case with a silent mutation at codon 68 (AGC-->AGT, Ser-->Ser). This is the first observation indicating that inherited SDHD mutations may occasionally cause the development of paragangliomas in the central nervous system.

Cauda Equina↗
PubMed2001

Soluble decoy receptor 3 is expressed by malignant gliomas and suppresses CD95 ligand-induced apoptosis and chemotaxis.

Decoy receptor 3 (DcR3) is a newly identified soluble protein that binds to CD95 ligand (CD95L) and inhibits its proapoptotic activity. Here we report that DcR3 is expressed by the majority of long-term and ex vivo malignant glioma cell lines as well as in human glioblastoma in vivo. Expression of DcR3 correlates with the grade of malignancy: 15 of 18 (83%) glioblastomas (WHO grade IV) but none of 11 diffuse astrocytomas (WHO grade II) exhibited DcR3 immunoreactivity. We also demonstrate that human malignant glioma cells engineered to release high amounts of DcR3 into the cell culture supernatant are protected from CD95L-induced apoptotic cell death. In contrast, DcR3 does not confer protection from the death ligand Apo2 ligand (TRAIL). Importantly, ectopic expression of DcR3 resulted in substantial differences in immune cell infiltration in the 9L rat gliosarcoma model. Thus, the infiltration of CD4+ and CD8+ T cells as well as microglia/macrophages into glioma was substantially decreased in DcR3-producing tumors compared with control tumors. Chemotaxis assays revealed that DcR3 counteracts the chemotactic activity of CD95L against microglial cells in vitro. These findings suggest that DcR3 may be involved in the progression and immune evasion of malignant gliomas.

Animals↗
PubMed2001

Reduced expression of the Aalpha subunit of protein phosphatase 2A in human gliomas in the absence of mutations in the Aalpha and Abeta subunit genes.

Protein phosphatase 2A (PP2A) consists of 3 subunits: the catalytic subunit, C, and the regulatory subunits, A and B. The A and C subunits both exist as 2 isoforms (alpha and beta) and the B subunit as multiple forms subdivided into 3 families, B, B' and B". It has been reported that the genes encoding the Aalpha and Abeta subunits are mutated in various human cancers, suggesting that they may function as tumor suppressors. We investigated whether Aalpha and Abeta mutations occur in human gliomas. Using single strand conformational polymorphism analysis and DNA sequencing, 58 brain tumors were investigated, including 23 glioblastomas, 19 oligodendrogliomas and 16 anaplastic oligodendrogliomas. Only silent mutations were detected in the Aalpha gene and no mutations in the Abeta gene. However, in 43% of the tumors, the level of Aalpha was reduced at least 10-fold. By comparison, the levels of the Balpha and Calpha subunits were mostly normal. Our data indicate that these tumors contain very low levels of core and holoenzyme and high amounts of unregulated catalytic C subunit.

Alleles↗
PubMed2001

Promoter hypermethylation and homozygous deletion of the p14ARF and p16INK4a genes in oligodendrogliomas.

The INK4a/ARF locus on chromosome 9p21 encodes two gene products that are involved in cell cycle regulation through inhibition of CDK4-mediated RB phosphorylation (p16INK4a) and binding to MDM2 leading to p53 stabilization (p14ARF). The locus is deleted in up to 25% of oligodendrogliomas and 50% of anaplastic oligodendrogliomas, but little is known on the frequency of gene silencing by DNA methylation. We assessed promoter hypermethylation of p14ARF and p16INK4a using methylation-specific PCR, and homozygous deletion of the p14ARF and p16INK4a genes by differential PCR in 29 oligodendrogliomas (WHO grade II) and 20 anaplastic oligodendrogliomas (WHO grade III). Promoter hypermethylation of the p14ARF gene was detected in 6/29 (21%) oligodendrogliomas and 3/20 (15%) anaplastic oligodendrogliomas. None of the oligodendrogliomas and only 1 out of 20 anaplastic oligodendrogliomas showed hypermethylation of p16INK4a. Homozygous deletion was not detected in any of the WHO grade II oligodendrogliomas but was present in 5/20 (25%) anaplastic oligodendrogliomas and always affected both genes. In one tumor containing distinct areas with and without anaplasia, p14ARF hypermethylation was detected in the WHO grade II area, while homozygous co-deletion of p14ARF and p16INK4a was found in the region with anaplastic features (grade III). These data suggest that aberrant p14ARF expression due to hypermethylation is the earliest INK4a/ARF change in the evolution of oligodendrogliomas, while the presence of p14ARF and p16INK4a deletions indicates progression to anaplastic oligodendroglioma.

Adolescent↗
PubMed2001

Mutation analysis of hBUB1, hBUBR1 and hBUB3 genes in glioblastomas.

Glioblastomas, the most malignant human brain tumors, are characterized by marked aneuploidy, suggesting chromosomal instability which may be caused by a defective mitotic spindle checkpoint. We screened 22 glioblastomas for mutations in the mitotic spindle check-point genes hBUB1, hBUBR1 and hBUB3. DNA sequencing revealed a silent mutation at codon 144 of hBUB1 (CAG-->CAA, Gln-->Gln) in one glioblastoma, a silent mutation at codon 952 of hBUBR1 (GAC-->GAT, Asp-->Asp) in another glioblastoma, and a silent mutation at codon 388 of the hBUBR1 gene (GCG-->GCA, Ala-->Ala) in 8 glioblastomas. We also observed a known polymorphism at hBUBR1 codon 349 (CAA/CGA, Gln/Arg), with an allelic frequency of 0.75 for Gln and 0.25 for Arg, which is similar to that among healthy Caucasian individuals (0.73 vs 0.27). The coding sequence of the hBUB3 gene did not contain any mutation, but in 4 glioblastomas (18%), a C-->T point mutation was detected at position -6 (6 nucleotides upstream of the ATG initiator codon). Analysis of blood DNA of these patients showed identical sequence alterations, indicating that this is a polymorphism. Again, the frequency in glioblastomas was similar to that in healthy Caucasians (15%). We further screened hBUB1 in 18 cases of giant cell glioblastoma, a variant characterized by a predominance of bizarre, multinucleated giant cells. There were no changes, except for a silent mutation at codon 144 in two cases. These results suggest that mutations in these mitotic spindle checkpoint genes do not play a significant role in the causation of chromosomal instability in glioblastomas.

Adult↗
PubMed2001

Genetic evidence of the neoplastic nature of gemistocytes in astrocytomas.

Gemistocytic astrocytoma is characterized by a predominance of large astrocytes with plump processes and massive accumulation of glial fibrillary acidic protein (gemistocytes). This histological variant of low-grade diffuse astrocytoma (WHO grade II) is prone to more rapid progression to anaplastic astrocytoma and glioblastoma than the ordinary fibrillary astrocytoma. The biological basis of this unfavorable prognosis is unclear, since gemistocytes themselves have low proliferative activity, even if present in anaplastic astrocytomas or glioblastomas. This has raised the question of whether gemistocytes are neoplastic cells or dysplastic reactive astrocytes. In this study, gemistocytes and non-gemistocytic neoplastic cells were separated by laser-assisted microdissection from six gemistocytic astrocytomas carrying TP53 mutations. In all cases, identical TP53 mutations were identified in both cell types, indicating that gemistocytes are indeed neoplastic cells. Their lack of proliferative activity may indicate terminal differentiation.

Adult↗
PubMed2001

Invasiveness in vitro and biological markers in human primary glioblastomas.

Invasion of spheroids from 20 human primary glioblastomas into precultured fetal rat brain tissue in culture has been studied and quantified. Between 30 and 98 percent of the normal brain tissue was destroyed by invading glioma cells within 4 days. The degree of invasion did not correlate with patient survival. A slightly higher invasiveness and shorter survival was seen in tumors with EGF receptor overexpression, and the opposite pattern was found for tumors with a TP53 mutation. The degree of invasiveness in vitro was far higher than would be expected from the dynamics of clinically observed tumor spread. This suggests that mechanisms suppressing invasion may be operative in the normal brain; alternatively the differences may be due to a higher permissiveness of the fetal brain tissue for invasion in vitro.

Adult↗
PubMed2001

Promoter hypermethylation of the RB1 gene in glioblastomas.

Loss of expression of the retinoblastoma gene (RB1) has been shown to occur in up to 25% of glioblastomas (WHO Grade IV). To elucidate the underlying mechanism, we assessed RB1 promoter hypermethylation using methylation-specific polymerase chain reaction and RB1 expression by immunohistochemistry in 35 primary (de novo) glioblastomas and in 21 secondary glioblastomas that had progressed from low-grade diffuse astrocytoma (WHO Grade II) or anaplastic astrocytoma (WHO Grade III). Promoter hypermethylation was significantly more frequent in secondary (9 of 21, 43%) than in primary glioblastomas (5 of 35, 14%; p = 0.0258). There was a clear correlation between loss of RB1 expression and promoter hypermethylation. In the majority of glioblastomas with loss of RB1 expression, there was promoter hypermethylation (11 of 13, 85%), whereas 93% of tumors with RB1 expression had a normal RB1 gene status (p < 0.0001). In three glioblastomas, areas with and without RB1 expression were microdissected; promoter hypermethylation was detected only in areas lacking RB1 expression. In patients with multiple biopsies, methylation of the RB1 promoter was not detectable in the less malignant precursor lesions, ie, low-grade diffuse and anaplastic astrocytoma. These results indicate that promoter hypermethylation is a late event during astrocytoma progression and is the major mechanism underlying loss of RB1 expression in glioblastomas.

Adult↗
PubMed2001

Promoter methylation of the DNA repair gene MGMT in astrocytomas is frequently associated with G:C --> A:T mutations of the TP53 tumor suppressor gene.

O(6)-Methylguanine-DNA methyltransferase (MGMT) is a repair protein that specifically removes promutagenic alkyl groups from the O(6) position of guanine in DNA. Repair of O(6)-alkylguanine adducts by tumour cells has been implicated in drug resistance since it reduces the cytotoxicity of alkylating chemotherapeutic agents. We assessed promoter methylation of the MGMT gene in astrocytic brain tumours by methylation-specific PCR. MGMT promoter methylation was detected in 26 of 54 (48%) low-grade diffuse astrocytomas (WHO grade II) and in 12 of 16 (75%) of secondary glioblastomas (WHO grade IV) that had progressed from low-grade astrocytomas. The frequency of MGMT methylation was significantly lower in primary (de novo) glioblastomas (13 of 36, 36%, P = 0.0155). The majority of low-grade astrocytomas with MGMT methylation (24/26, 92%) contained a TP53 mutation, whereas only 11 out of 28 (39%) cases without MGMT methylation carried a TP53 mutation (P < 0.0001). Furthermore, G:C --> A:T transition mutations at CpG sites were significantly more frequent in low-grade astrocytomas with MGMT methylation (15/26, 58%) than in those without (3/28, 11%, P = 0.0004). These results suggest that loss of MGMT expression as a result of promoter methylation, which frequently occurs at an early stage in the pathway leading to secondary glioblastomas, appears to be associated with increased frequency of TP53 mutations, in particular G:C --> A:T transitions.

Adult↗
PubMed2001

Concurrent inactivation of RB1 and TP53 pathways in anaplastic oligodendrogliomas.

Oligodendrogliomas are characterized by frequent loss of heterozygosity (LOH) on chromosomes 1p and 19q, but additional genetic alterations are likely to be involved. In this study, we screened 28 oligodendrogliomas (WHO grade II) and 20 anaplastic oligodendrogliomas (WHO grade III) for alterations in the RB1/CDK4/p16INK4a/p15INK4b and TP53/p14ARF/MDM2 pathways. In oligodendrogliomas, hypermethylation of RB1 (1 case) and p14ARF (6 cases) were the only detectable genetic changes (7/28, 25%). In anaplastic oligodendrogliomas, the RB1/CDK4/p16INK4a/p15INK4b signaling pathway regulating the G1 -->3 S transition of the cell cycle was altered in 13/20 (65%) cases, by either RBI alteration, CDK4 amplification, or p16IN4a/p15INK4b homozygous deletion or promoter hypermethylation. Further, 50% (10/20) of anaplastic oligodendrogliomas showed alterations in the TP53 pathway through promoter hypermethylation or homozygous deletion of the p14ARF gene and, less frequently, through TP53 mutation or MDM2 amplification. Of 13 anaplastic astrocytomas with an altered RB1 pathway, 9 (69%) also showed a dysregulated TP53 pathway. Thus, simultaneous disruption of the RB1/CDK4/p16INK4a/p15INK4b and the TP53/p14ARF/MDM2 pathways occurs in 45% (9/20) of anaplastic oligodendrogliomas, suggesting that these phenomena contribute to their malignant phenotype.

Gene Deletion↗
PubMed2001

Second primary glioblastoma.

Although characterized by a highly variable phenotype and multiple genetic alterations, glioblastomas are considered monoclonal in origin. We here report on a 64-yr-old patient who developed a second glioblastoma in the left frontal lobe 10 yr after surgical resection of a glioblastoma of right frontal lobe. The first tumor contained 2 p53 mutations, in codon 213 (CGA-->TGA, Arg-->stop) and codon 306 (CGA-->TGA, Arg-->stop), further, 1 missense PTEN mutation (codon 257, TTC-->TTA, Phe-->Leu) and a silent PTEN mutation (codon 154, TTC-->TTT, Phe-->Phe). The second glioblastoma also contained multiple, but different mutations: p53 mutations in codons 158 (CGC-->CAC, Arg-->His) and 273 (CGT-->TGT, Arg-->Cys), and a PTEN mutation in codon 233 (CGA-->TGA, Arg-->Stop). Both neoplasms had a homozygous p16 deletion. The discordant pattern of mutations indicates that the second glioblastoma was not a recurrence but an independent second glioblastoma. The presence in these neoplasms of multiple mutations in tumor suppressor genes suggests the involvement of a novel disease mechanism but there was no indication of a DNA mismatch repair deficiency or of an inherited tumor syndrome.

Chromosomes, Human, Pair 10↗
PubMed2001

p14ARF deletion and methylation in genetic pathways to glioblastomas.

The CDKN2A locus on chromosome 9p21 contains the p14ARF and p16INK4a genes, and is frequently deleted in human neoplasms, including brain tumors. In this study, we screened 34 primary (de novo) glioblastomas and 16 secondary glioblastomas that had progressed from low-grade diffuse astrocytomas for alterations of the p14ARF and p16INK4a genes, including homozygous deletion by differential PCR, promoter hypermethylation by methylation-specific PCR, and protein expression by immunohistochemistry. A total of 29 glioblastomas (58%) had a p14ARF homozygous deletion or methylation, and 17 (34%) showed p16INK4a homozygous deletion or methylation. Thirteen glioblastomas showed both p14ARF and p16INK4a homozygous deletion, while nine showed only a p14ARF deletion. Immunohistochemistry revealed loss of p14ARF expression in the majority of glioblastomas (38/50, 76%), and this correlated with the gene status, i.e. homozygous deletion or promoter hypermethylation. There was no significant difference in the overall frequency of p14ARF and p16INK4a alterations between primary and secondary glioblastomas. The analysis of multiple biopsies from the same patients revealed hypermethylation of p14ARF (5/15 cases) and p16INK4a (1/15 cases) already at the stage of low-grade diffuse astrocytoma but consistent absence of homozygous deletions. These results suggest that aberrant p14ARF expression due to homozygous deletion or promoter hypermethylation is associated with the evolution of both primary and secondary glioblastomas, and that p14ARF promoter methylation is an early event in subset of astrocytomas that undergo malignant progression to secondary glioblastoma.

Brain Neoplasms↗
PubMed2000

Gene expression profiling of low-grade diffuse astrocytomas by cDNA arrays.

Diffuse astrocytoma WHO grade II is a well-differentiated, slowly growing tumor that has an inherent tendency to progress to anaplastic astrocytoma (WHO grade III) and, eventually, to glioblastoma (WHO grade IV). Little is known about its molecular basis, except for p53 mutations that are found in >60% of cases. In a search for additional genetic alterations, we carried out gene expression profiling of 11 diffuse astrocytomas using cDNA expression arrays. Expression of six genes (TIMP3, c-myc, EGFR, DR-nm23, nm23-H4, and GDNPF) was detected in 64-100% of diffuse astrocytomas, but not in nontumorous brain tissue. Seven genes (AAD14, SPARC, LRP, PDGFR-alpha, 60S ribosomal protein L5, PTN, and hBAP) were found to be up-regulated more than 2-fold in 20-60% of cases, whereas 11 genes (IFI 9-27, protein kinase CLK, TDGF1, BIN1, GAB1, TYRO3, LDH-A, adducin 3, GUK1, CDC10, and KRT8) were down-regulated to less than 50% of normal levels in 64-100% of cases. Semiquantitative conventional reverse transcription-PCR was performed for 11 genes, 9 of which showed an expression profile similar to that obtained with cDNA expression arrays. Immunohistochemical staining for SPARC showed cytoplasmic immunoreactivity of neoplastic cells in all diffuse astrocytomas analyzed. These results indicate significant changes in gene expression in diffuse astrocytomas, but it remains to be shown which of these are causally related to the transformation of glial cells.

Adult↗
PubMed2000

APO2L/TRAIL expression in human brain tumors.

APO2 ligand (APO2L)/TRAIL is a novel member of the tumor necrosis factor cytokine family and a potent inducer of apoptosis in tumor cell lines. We recently reported that APO2L is consistently expressed in low-grade astrocytomas, anaplastic astrocytomas, glioblastomas, and cell lines derived thereof, and that malignant glioma cell lines are susceptible to APO2L-induced apoptosis. In this study, we investigated whether APO2L is expressed in medulloblastoma or neuroblastoma cell lines and whether these cells are sensitive to APO2L-induced apoptosis. Immunoblot analyses revealed full-length APO2L protein expression in one (DAOY) of three medulloblastoma cell lines but not in two neuroblastoma cell lines (SKN-BE and SKN-LE). Viability assay performed after exposure to soluble APO2L for 16 h showed that DAOY medulloblastoma cells were the most sensitive and that apoptosis induced by APO2L was greatly enhanced when protein synthesis was inhibited by cycloheximide. Neuroblastoma cell lines were almost completely resistant to APO2L-induced apoptosis. We also carried out APO2L immunohistochemistry in a total of 115 tumors of the nervous system with different histogenesis and biological behavior. In all 9 pilocytic astrocytomas, the areas of dense fibrillary network showed diffuse and strong APO2L expression. In oligodendrogliomas, APO2L expression was observed in areas with a significant admixture of astrocytic cells, but was absent in neoplastic oligodendrocytes. In 13 of 14 ependymomas, APO2L was expressed in perivascular pseudorosettes. In all 12 medulloblastomas, strong APO2L expression was observed in intra-tumoral-reactive astrocytes, but neoplastic cells did not show APO2L immunoreactivity. Thus, the pattern of APO2L expression was largely similar to that of glial fibrillary acidic protein (GFAP), except for choroid plexus tumors and 3 of 8 anaplastic meningiomas, in which APO2L was focally expressed without concomitant GFAP expression. APO2L expression was absent in meningiomas, neurocytomas, and schwannomas. Thus, there is considerable heterogeneity of APO2L expression and susceptibility to APO2L-induced apoptosis among human brain tumors.

Apoptosis↗
PubMed2000

Genetic profile of gliosarcomas.

There are distinct genetic pathways leading to the glioblastoma, the most malignant astrocytic brain tumor. Primary (de novo) glioblastomas develop in older patients and are characterized by epidermal growth factor (EGF) receptor amplification/overexpression, p16 deletion, and PTEN mutations, whereas secondary glioblastomas that progressed from low-grade or anaplastic astrocytoma develop in younger patients and frequently contain p53 mutations. In this study, we assessed the genetic profile of gliosarcoma, a rare glioblastoma variant characterized by a biphasic tissue pattern with alternating areas displaying glial and mesenchymal differentiation. Single-strand conformation polymorphism followed by direct DNA sequencing revealed p53 mutations in five of 19 gliosarcomas (26%) and PTEN mutations in seven cases (37%). Homozygous p16 deletion was detected by differential polymerase chain reaction in seven (37%) gliosarcomas. The overall incidence of alterations in the Rb pathway (p16 deletion, CDK4 amplification, or loss of pRb immunoreactivity) was 53%, and these changes were mutually exclusive. Coamplification of CDK4 and MDM2 was detected in one gliosarcoma. None of the gliosarcomas showed amplification or overexpression of the EGF receptor. Thus gliosarcomas exhibit a genetic profile similar to that of primary (de novo) glioblastomas, except for the absence of EGFR amplification/overexpression. Identical PTEN mutations in the gliomatous and sarcomatous tumor components were found in two cases. Other biopsies contained p16 deletions, an identical p53 mutation, or coamplification of MDM2 and CDK4 in both tumor areas. This strongly supports the concept of a monoclonal origin of gliosarcomas and an evolution of the sarcomatous component due to aberrant mesenchymal differentiation in a highly malignant astrocytic neoplasm.

Adult↗