Comparative molecular genetic profiles of anaplastic astrocytomas/glioblastomas multiforme and their subsequent recurrences.
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Malignant glial tumors (anaplastic astrocytomas and glioblastomas multiforme) arise mostly either from the progression of low grade precursor lesions or rapidly in a de novo fashion and contain distinct genetic alterations. There is, however, a third subset of malignant gliomas in which genetic lesions remain to be identified. Following surgical resection, all gliomas appear to have an inherent tendency to recur. Comparative molecular analysis of ten primary malignant gliomas (three anaplastic astrocytomas and seven glioblastomas multiforme) with their recurrences identified two distinct subgroups of recurrent tumors. In one group, primary tumors harbored genetic aberrations frequently associated with linear progression or de novo formation pathways of glial tumorigenesis and maintained their genetic profiles upon recurrence. In the other subset with no detectable known genetic mutations at first presentation, the recurrent tumors sustained specific abnormalities associated with pathways of linear progression or de novo formation. These included loss of genes on chromosomes 17 and 10, mutations in the p53 gene, homozygous deletion of the DMBTA1 and p16 and/ or p15 genes and amplification and/or overexpression of CDK4 and alpha form of the PDGF receptor. Recurrent tumors from both groups also displayed an abnormal expression profile of the metalloproteinase, gel A, and its inhibitor, TIMP-2, consistent with their highly invasive behavior. Delineation of the molecular differences between malignant glioblastomas and their subsequent recurrences may have important implications for the development of rational clinical approaches for this neoplasm that remains refractory to existing therapeutic modalities. (+info)
Leukemia translocation protein PLZF inhibits cell growth and expression of cyclin A.
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The PLZF gene was identified by its fusion with the RARalpha locus in a therapy resistant form of acute promyelocytic leukemia (APL) associated with the t(11;17)(q23;q21) translocation. Here we describe PLZF as a negative regulator of cell cycle progression ultimately leading to growth suppression. PLZF can bind and repress the cyclin A2 promoter while expression of cyclin A2 reverts the growth suppressed phenotype of myeloid cells expressing PLZF. In contrast RARalpha-PLZF, a fusion protein generated in t(11;17)(q23;q21)-APL activates cyclin A2 transcription and allows expression of cyclin A in anchorage-deprived NIH3T3 cells. Therefore, cyclin A2 is a candidate target gene for PLZF and inhibition of cyclin A expression may contribute to the growth suppressive properties of PLZF. Deregulation of cyclin A2 by RARalpha-PLZF may represent an oncogenic mechanism of this chimeric protein and contribute to the aggressive clinical phenotype of t(11;17)(q23;q21)-associated APL. (+info)
Multiple target sites of allelic imbalance on chromosome 17 in Barrett's oesophageal cancer.
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Twelve Barrett's adenocarcinomas have been analysed for the occurrence of allelic imbalance (LOH) on chromosome 17 using 41 microsatellite markers. This study provides evidence for 13 minimal regions of LOH, six on 17p and seven on 17q. Four of these centre in the vicinity of the known tumour suppressor genes (TSGs) TP53 (17p13.1), NFI (17q11.2), BRCA1 (17q21.1), and a putative TSG (17p13.3). The tumours all displayed relatively small regions of LOH (1-10 cM), and in several tumours extensive regions of LOH were detected. One tumour displayed only two very small regions of LOH; 17p11.2 and 17p13.1. The frequency of allelic imbalance has been calculated based on the LOH encompassing only one minimal region, and based on all the LOH observations. By both evaluations the highest LOH frequencies were found for regions II (p53), III (17p13.1 centromeric to p53), IV (17p12), V (17p11.2) and VII (NF1, 17q11.2). Our data supports the existence of multiple TSGs on chromosome 17 and challenges the view that p53 is the sole target of LOH on 17p in Barrett's adenocarcinoma. (+info)
Correlation between the status of the p53 gene and survival in patients with stage I non-small cell lung carcinoma.
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The association of p53 abnormalities with the prognosis of patients with non-small cell lung carcinoma (NSCLC) has been extensively investigated to date, however, this association is still controversial. Therefore, we investigated the prognostic significance of p53 mutations through exons 2 to 11 and p53 protein expression in 103 cases of stage I NSCLC. p53 mutations were detected in 49 of 103 (48%) tumors. Two separate mutations were detected in four tumors giving a total of 53 unique mutations in 49 tumors. Ten (19%) of mutations occurred outside exons 5-8. Positive immunohistochemical staining of p53 protein was detected in 41 of 103 (40%) tumors. The concordance rate between mutations and protein overexpression was only 69%. p53 mutations, but not expression, were significantly associated with a shortened survival of patients (P<0.001). Furthermore, we investigated the correlation between the types of p53 mutations and prognosis. p53 missense mutations rather than null mutations were associated with poor prognosis (P < 0.001 in missense mutations and P=0.243 in null mutations). These results indicated that p53 mutations, in particular missense mutations, rather than p53 expression could be a useful molecular marker for the prognosis of patients with surgically resected stage I NSCLC. (+info)
Retinoic acid, but not arsenic trioxide, degrades the PLZF/RARalpha fusion protein, without inducing terminal differentiation or apoptosis, in a RA-therapy resistant t(11;17)(q23;q21) APL patient.
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Primary blasts of a t(11;17)(q23;q21) acute promyelocytic leukaemia (APL) patient were analysed with respect to retinoic acid (RA) and arsenic trioxide (As2O3) sensitivity as well as PLZF/RARalpha status. Although RA induced partial monocytic differentiation ex vivo, but not in vivo, As203 failed to induce apoptosis in culture, contrasting with t(15;17) APL and arguing against the clinical use of As203 in t(11;17)(q23;q21) APL. Prior to cell culture, PLZF/RARalpha was found to exactly co-localize with PML onto PML nuclear bodies. However upon cell culture, it quickly shifted towards microspeckles, its localization found in transfection experiments. Arsenic trioxide, known to induce aggregation of PML nuclear bodies, left the microspeckled PLZF/RARalpha localization completely unaffected. RA treatment led to PLZF/RARalpha degradation. However, this complete PLZF/RARalpha degradation was not accompanied by differentiation or apoptosis, which could suggest a contribution of the reciprocal RARalpha/PLZF fusion product in leukaemogenesis or the existence of irreversible changes induced by the chimera. (+info)
High-resolution physical and genetic mapping of the critical region for Meckel syndrome and Mulibrey Nanism on chromosome 17q22-q23.
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Previously, we assigned the genes for two autosomal recessive disorders, Meckel syndrome (MKS; MIM 249000) and Mulibrey Nanism [MUL (muscle-liver-brain-eye Nanism); MIM 253250] that are enriched in the Finnish population, to overlapping genomic regions on chromosome 17q. Now, we report the construction of a bacterial clone contig over the critical region for both disorders. Several novel CA-repeat markers were isolated from these clones, which allowed refined mapping of the MKS and MUL loci using haplotype and linkage disequilibrium analysis. The localization of the MKS locus was narrowed to <1 cM between markers D17S1290 and 132-CA, within an approximately 800-kb region. The MUL locus was refined into an approximately 1400-kb interval between markers D17S1290 and 52-CA. The whole MKS region falls within the MUL region. In the common critical region, the conserved haplotypes were different in MKS and MUL patients. A trancript map was constructed by assigning expressed sequence tags (ESTs) and genes, derived from the human gene map, to the bacterial clone contig. Altogether, four genes and a total of 20 ESTs were precisely localized. These data provide the molecular tools for the final identification of the MKS and the MUL genes. (+info)
A susceptibility locus for epidermodysplasia verruciformis, an abnormal predisposition to infection with the oncogenic human papillomavirus type 5, maps to chromosome 17qter in a region containing a psoriasis locus.
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Epidermodysplasia verruciformis (EV) is a rare genodermatosis characterized by an abnormal susceptibility to infection with a specific group of related human papillomavirus (HPV) genotypes, including the oncogenic HPV5 associated with the skin carcinomas developing in about half of EV patients. EV is usually considered as an autosomal recessive condition. Taking EV as a model to identify a locus underlying the susceptibility to HPV infections, we performed a genome-wide search for linkage with 255 microsatellite genetic markers in three consanguineous EV families comprising six patients, using the homozygosity mapping approach. Homozygosity restricted to affected individuals was observed for a marker of chromosome 17q (D17S784) in two families and a marker about 17 centiMorgan (cM) distal (D17S1807) in the third family. Ten additional microsatellite markers spanning 29 cM in this region were analyzed. Two-point lod score values greater than 3 were obtained for four markers and multipoint linkage analysis yielded a maximum lod score of 10.17 between markers D17S939 and D17S802. Recombination events observed in two families allowed a candidate region for the EV susceptibility locus to be mapped to the 1 cM region defined by these two markers. The EV locus (named EV1) is included in the 17qter region recently found to contain a dominant locus for the susceptibility to familial psoriasis. It has been shown that patients suffering from psoriasis are likely to constitute the reservoir of HPV5. It is thus tempting to speculate that distinct defects affecting the same gene may be involved in the two skin conditions. (+info)
Localization of PS6K to chromosomal region 17q23 and determination of its amplification in breast cancer.
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The application of comparative genomic hybridization to the analysis of genetic abnormalities in breast carcinoma has consistently revealed that chromosome region 17q22-24 is a frequent site of gene amplification in this type of cancer. As part of an examination of expressed sequence tags for novel amplified genes in this region, we identified PS6K amplifications in both breast tumor tissues and cell lines. PS6K was localized to 17q23 and encodes a serine-threonine kinase whose activation is thought to regulate a wide array of cellular processes involved in the mitogenic response including protein synthesis, translation of specific mRNA species, and cell cycle progression from G1 to S phase. Northern and Western analyses revealed that amplification of this gene was accompanied by corresponding increases in mRNA and protein expression, respectively. These data represent the first determination of a gene amplification within 17q22-24 in breast cancer and suggest an oncogenic activity for PS6K. (+info)