Biomedical subjects

K Radig

Publications and source records attributed to K Radig.

At least 19 recordsLinked to original sources

PubMed1999

Telomeric lengths and telomerase activity in liposarcomas.

To assess the role of telomerase in the development of liposarcomas, we measured telomerase activity in 36 malignant and seven benign lipomatous neoplasias from 34 patients. A sensitive polymerase chain reaction-based telomerase assay (the telomeric repeat amplification protocol) was applied. Shortening or elongation of telomeric repeat fragment lengths, as measured by using hybridization with a telomere-specific oligonucleotide probe, was correlated with the presence of telomerase activity. The latter was demonstrable in 69% of malignant tumors. Benign tumors can be distinguished from malignant neoplasias on the basis of telomerase activity. However, telomerase expression seems to be characteristic of poorly differentiated liposarcomas. Myxoid/round cell liposarcomas exhibited a higher telomerase activity level than the classical low-grade variants. Telomerase activity was not correlated with age at the time of diagnosis or with sex. In most cases, telomerase-positive tumors showed higher proliferation indices than did neoplasias lacking telomerase. All eight recurrences expressed telomerase activity, reflecting a close association of telomerase with the biological behavior of liposarcomas. Our findings suggest that telomerase may play a key role in the establishment and progression of malignant lipomatous tumors.

Adult↗

PubMed1999

Protease expression in dedifferentiated parosteal osteosarcoma.

BACKGROUND: Parosteal osteosarcoma with dedifferentiation provides a useful model to study tumor progression from an indolent locally aggressive neoplasm to highly lethal metastasizing malignancy. Up-regulation of the proteolytic enzymes participating in stromal degradation is known to promote invasive growth and metastasis of several human and experimental tumors. METHODS: The expression patterns of urokinasase plasminogen activator (u-PA), its cell-surface receptor (u-PAR), and cathepsin B were analyzed by immunohistochemical techniques in 11 cases of parosteal osteosarcoma and in 4 cases of dedifferentiated parosteal osteosarcoma. RESULTS: Both enzymes and the receptor were coexpressed in most tumor cells of parosteal and dedifferentiated parosteal osteosarcoma. Their expression was strikingly enhanced in the dedifferentiated high-grade component of the tumors. Tumor cells involved in bone production (ie, those adjacent to tumor produced bone trabeculae) exhibited equally strong expression of u-PA, u-PAR, and cathepsin B, regardless of their histologic grade. Expression of u-PA, u-PAR, and cathepsin B was undetectable in the "normalized" cells embedded in the well-developed tumor bone trabeculae. CONCLUSION: These data indicate that u-PA and its interacting molecules, such as u-PAR and cathepsin B, may have some contributory effects on the metastatic potential of tumor cells in dedifferentiated parosteal osteosarcoma.

Bone Neoplasms↗

PubMed1998

No correlation of c-myc overexpression and p53 mutations in liposarcomas.

Although it is well known that oncogenesis is a multistep process involving the activation of normal cellular genes to become oncogenes and/or the inactivation of tumor suppressor genes, this process has seldom been investigated in soft tissue tumours. We screened a group of 36 liposarcomas for genetic abnormalities in the p53 tumour suppressor gene and c-myc oncogene. Altered c-myc gene expression was examined by differential RT-PCR assay. p53 Gene mutations in exons 4-8 were analysed by using PCR-SSCP analysis and direct sequencing. Elevated c-myc expression was found in 6 of 31 liposarcomas (19.4%). p53 Gene mutations were observed in 5 of 36 liposarcomas (13.9%). Both genetic alterations were associated with the histological subtype of liposarcomas. Whereas c-myc gene expression was a characteristic of myxoid/round cell liposarcomas, p53 gene mutations were found more frequently in pleomorphic variants. Liposarcomas of the well-differentiated subtype showed neither p53 gene mutations nor altered c-myc gene expression. Our results indicate that the c-myc oncogene and the p53 tumor suppressor gene do not seem to cooperate in the oncogenesis of liposarcomas.

Adult↗

PubMed1998

On telomere shortening in soft-tissue tumors.

PURPOSE: Specific simple DNA repeats occur at the telomeric ends of mammalian chromosomes. Loss of (G + C)-rich repeats can result in genetic instability, associated with tumorigenesis. So far, data on telomere shortening have not been available for different types of soft-tissue tumors. METHODS: Using tumor material and the blood of the corresponding patient, high-molecular-mass DNA was prepared by digestion with proteinase K and extraction with phenol/chloroform. A 10-microg sample of DNA was digested with the restriction enzyme HinfI. DNA fragments were separated in a 0.7% agarose gel, and in-gel hybridization was performed with the telomere-specific repeat probe (TTAGGG)3. RESULTS: Shortening of the telomere repeat was observed in 14/30 soft-tissue tumors; 5 tumors showed elongated telomere repeats, whereas the telomeres appeared unchanged in 11 tumors. Decreased telomere repeat length correlated with advanced age, DNA ploidy, and a higher proliferation index. There was no association between telomere repeat length and tumor grade. Interestingly, in contrast to other entities, all malignant schwannomas and leiomyosarcomas showed significantly reduced telomere lengths. An explanation for the telomere heterogeneity in liposarcomas may include differential telomerase reactivation in well and poorly differentiated tumors. CONCLUSIONS: Telomere shortening is frequent but not a uniform phenomenon in different types of soft-tissue tumor. Studies on telomerase activity should be performed in the same cohort of sarcomas.

Adult↗

PubMed1998

MDM2 amplification and loss of heterozygosity at Rb and p53 genes: no simultaneous alterations in the oncogenesis of liposarcomas.

PURPOSE: The present study aimed to investigate the status of alterations of the MDM2, Rb and p53 genes in a series of 45 liposarcomas. Furthermore, the possible correlation with histological and clinical parameters was studied. METHODS: MDM2 amplification was examined by non-radioactive Southern blot hybridization with a human MDM2 cDNA probe. Mutations in the p53 gene were screened by polymerase chain reaction/single-strand conformation polymorphism analysis and direct sequencing. To study loss of heterozygosity (LOH) at the tumor-suppressor genes Rb and p53, we used four polymorphic intragenic Rb markers (introns 1, 17, 20, and 25) and two p53 markers (intron 1 and exon 4). RESULTS: MDM2 amplification was found in 19 of 45 liposarcomas (42.2%). The frequency of LOH in Rb and p53 was nearly identical (22%). In 4 of 9 tumors (44.4%) with LOH, allelic loss was a concurrent event in both genes. Of 45 liposarcomas, 6 (13.3%) showed p53 mutations. Overall, alterations of the p53/MDM2/Rb pathway occurred in 30 of 45 liposarcomas (66.6%). In contrast to myxoid and pleomorphic variants, well-differentiated liposarcomas were characterized by a high frequency of MDM2 amplification, a lack of LOH of Rb and p53, and p53 mutations. CONCLUSIONS: Obviously MDM2 amplification and LOH at the Rh and p53 genes do not occur simultaneously in the oncogenesis of liposarcomas, as is the case for MDM2 amplification and p53 gene mutations (with one exception). We suggest that well-differentiated, myxoid and pleomorphic liposarcomas are characterized by a different pattern of molecular alterations.

Adult↗

PubMed1998

p53 gene mutations in osteosarcomas of low-grade malignancy.

Alterations in tumor suppressor gene p53, localized on chromosome 17p13, are considered to play a significant role in the initiation and, to some extent, even in the progression of various malignant tumors. In this respect, investigations on conventional highly malignant osteosarcomas have shown a mutation rate of approximately 20%. However, currently, data on the mutation rate in the group of variant histology osteosarcomas of low-grade malignancy do not exist. Therefore, we investigated a panel of low malignant entities (five low malignant intramedullary osteosarcomas grade 1; one intramedullary osteosarcoma grade 2; eight parosteal osteosarcomas, including one local recurrence grades 1 and 2, and five periosteal osteosarcomas grade 2) with polymerase chain reaction/single-strand conformation polymorphism (PCR-SSCP) analysis focusing on exons 4 to 8 of the p53 gene followed by direct sequencing. Point mutations were found in one low-grade osteoblastoma-like osteosarcoma and in two periosteal osteosarcomas grade 2 (one missense, one silent, and one nonsense mutation). This mutation rate of 15.7% (3 of 19) is comparable to that determined in highly malignant osteosarcomas. Moreover, the analysis of clinical data did not show any difference in the behavior of tumors with p53 mutations compared with those without. Therefore, we suggest that alterations in p53 gene are an early event in the tumorigenesis of malignant osteoblastic tumors without impact on progression of these tumors.

Adolescent↗

PubMed1998

Alveolar soft part sarcoma of the uterine corpus. Report of two cases and review of the literature.

Alveolar soft-part sarcoma (ASPS) is a rare tumor of uncertain histogenesis, mainly localized in the extremities and less frequently found in the head, neck and trunk. The present report describes two cases of ASPS localized in the uterus. In general, this entity is very rarely encountered in the female genital tract. Including the two cases presented here, 27 patients have been described in the literature. Whereas the prognosis for ASPS in soft tissues is usually poor (most of the patients died of lung metastases), those localized in the female genital tract are associated with a much better survival. This could be explained by the fact that their diameter seldom exceeds 5 cm, the size which is regarded as being the critical prognostic limit. Histologically, both tumors showed the same characteristics as known for ASPS in other localizations: organoid or nest-like arrangement of tumor cells; rounded or polygonal cells with cytoplasm of varying density; thin-walled, sinusoidal vascular spaces between tumor cell nests. Immunohistochemically, we found positivity for desmin and, to a lesser extent, for vimentin. Cytokeratin was negative, which is important in differential diagnosis to other rare uterine neoplasias like clear cell (mesonephroid) adenocarcinomas or metastases.

Adult↗

PubMed1998

p53 and ras mutations in Ewing's sarcoma.

The role of tumor suppressor genes and oncogenes in the development of Ewing's sarcoma has not yet been fully clarified. In this study, we analyzed the frequency of p53 tumor suppressor gene mutation in exons 4-8 by PCR-SSCP and direct sequencing, and the expression of p53-protein in Ewing's sarcoma (ES) by using immunohistochemistry. The overexpression of MDM2, which acts as a functional inactivator of p53, was studied by immunohistochemistry. In addition, a screening for point mutations in the hot spot regions codon 12 and 13 of exon 1 and codon 61 of exon 2 of ras-genes (H-ras, N-ras, K-ras) was performed. In one case, a p53 gene mutation could be confirmed in codon 238 of exon 7 (1/24). Overexpression of MDM2 was found in five cases; in ras-genes, no mutations were detected. Compared with other highly malignant mesenchymal pediatric tumors such as osteosarcomas, mutations of p53 and ras in Ewing's sarcomas are an extraordinarily rare event. However, their frequency is comparable to that of PNET, suggesting that the low incidence of these mutations in ES and PNET could be group-specific for tumors of neuroectodermal genesis.

Adolescent↗

PubMed1998

Clinicopathologic implications of MDM2, p53 and K-ras gene alterations in osteosarcomas: MDM2 amplification and p53 mutations found in progressive tumors.

It is widely recognized that various oncogenes and tumor suppressor genes contribute to tumorigenesis and progression of osteosarcomas. However, whether genetic alternations enable us to predict the prognosis of patients with osteosarcomas is unclear. Southern blotting and polymerase chain reaction/single strand conformation polymorphism (PCR-SSCP) analyses were performed to search for MDM2, ras family and p53 gene alterations in 17 patients with high-grade osteosarcomas. Amplification of the MDM2 gene was found in three tumors, two of which were obtained from a regional lymph node metastasis and the other from a locally advanced lesion. Point mutations of the p53 gene were found in exons 4 and 5 in two tumors each. One of the four tumors with p53 mutations was obtained from a lymph node metastasis, one from a recurrent tumor and another from the primary tumor of a patient who developed lung metastases. Coexistence of MDM2 amplification with point mutation of the p53 gene was observed in two tumors. A point mutation of the K-ras oncogene was detected at codon 13 in two tumors. MDM2 amplification and p53 mutation may reflect tumor progression, although no correlation between alteration and response to chemotherapy or patient survival was demonstrated.

Adolescent↗

PubMed1998

Genetic instability in osteoblastic tumors of the skeletal system.

At the histological level, the differential diagnosis of osteoblastic bone tumors is characterized by several problems that cannot be solved by conventional histological methods including immunohistology. Differentiating aneurysmal bone cyst from telangiectatic osteosarcoma or giant cell tumor from giant cell-containing highly malignant osteosarcoma are only two examples reflecting the complexity of this field. To develop a new approach to these diagnostic problems, we analyzed the genetic instability in a large number of bone-forming tumor-like lesions as well as in benign and malignant osteoblastic tumors. Our research concentrated on genetic alterations in cell cycle regulator genes: mutations in the p53 gene and ras gene, loss of heterozygosity at the p53, p16 and Rb-locus, and amplification of the mdm2-gene and the c-myc-gene. In addition to cell cycle regulators, the telomerase activity has also been analyzed. The results show that the number of genetic alterations increases with the malignancy of the tumors. The highest number of genetic alterations could thus be found in conventional intraosseous osteosarcoma. In tumor-like lesions, genetic alterations have rarely been observed. The results of this study show that analyzing the genetic instability probably contributes to an improvement in the differential diagnosis of osteoblastic tumors.

Bone Neoplasms↗

PubMed1998

Gene alterations at the CDKN2A (p16/MTS1) locus in soft tissue tumors.

The CDKN2A gene (p16/MTS1) is a tumor suppressor that is frequently deleted, mutated, or inactivated by transcriptional silencing in certain tumor types and many tumor cell lines. We analyzed CDKN2A gene mutations and the frequency of loss of heterozygosity (LOH) at the CDKN2A locus in 135 soft tissue sarcomas. PCR-SSCP analysis of exons 1 and 2 of CDKN2A gene revealed only one missense mutation in codon 15 in a rhabdomyosarcoma. LOH-analysis was performed with two polymorphic markers in the surrounding regions of the CDKN2A gene (D9S171, D9S162) and the sequence-tagged-site marker c5.1. An allelic loss was found in 7/135 cases (5.1%) and was a characteristic of poorly differentiated sarcomas. We observed a high frequency of microsatellite instability expressed as allelic imbalances (25%). Presumably, alterations of the CDKN2A gene do not contribute to the oncogenesis in the majority of soft tissue tumors.

Alleles↗

PubMed1998

[Genetic instability in osteoblastic tumors of the skeletal system].

In the histological differential diagnosis of osteoblastic bone tumors, several problems could not have been solved by conventional histological methods including immunohistology. Some well-known examples are the differential diagnosis between aneurysmal bone cyst and telangiectatic osteosarcoma and giant cell tumor versus giant cell-containing highly malignant osteosarcoma. As a new approach to these diagnostic problems, we analyzed the genetic instability in a larger number of bone-forming tumor-like lesions, benign and malignant osteoblastic tumors. Analysis focused on genetic alterations in cell cycle regulator genes: Mutations in the p53 gene and ras gene, loss of heterozygosity at the p53, p16 and Rb-locus, and amplification of the mdm2 gene and the c-myc-gene. In addition to cell cycle regulators, the telomerase activity has also been analyzed. The results show that the number of genetic alterations increases with the malignancy of the tumors. The highest number of genetic alterations could thus be found in conventional intraosseous osteosarcoma. In tumor-like lesions, genetic alterations have rarely been observed. The results of this study show that the analysis of genetic instability will probably contribute to an improved differential diagnosis of osteoblastic tumors.

Bone Neoplasms↗

PubMed1998

[Telomere lengths and telomerase activity in liposarcomas].

We measured telomerase activity in 36 malignant and seven benign lipomatous neoplasias from 34 patients to assess the role of telomerase in the development of liposarcoma. The sensitive PCR-based telomerase assay (telomeric repeat amplification protocol-TRAP) was applied. We correlated telomerase activity with the shortening or elongation of telomeric repeat fragment length (TRF), measured by using hybridization with a telomere specific oligonucleotide probe. Telomerase activity was demonstrated in 69% of malignant tumors. This information may be helpful in distinguishing benign tumors from malignant neoplasias. Telomerase expression, however, seems to be characteristic of poorly differentiated liposarcomas. Telomerase activity was not correlated with age at the time of diagnosis or with sex. We observed that telomerase expressing tumors had higher proliferation indices than neoplasias lacking telomerase. Telomerase activity was observed in all eight recurrences, suggesting a close association of telomerase with the biologic behavior of liposarcomas. Therefore, we assume that telomerase plays a key role in the establishment and progression of lipomatous tumors.

Humans↗

PubMed1997

Expression of plasminogen activators and plasminogen activator inhibitor 1 in dedifferentiated chondrosarcoma.

BACKGROUND: The plasminogen activator system plays an important role in different malignant tumors. These enzymes participate in the destruction of intercellular matrices and basement membranes and/or can modulate the growth potency of tumor cells and may even promote metastases. In this study, the expression of three glycoproteins that play a role in the plasminogen activator system as activators of proteolysis-urokinase type plasminogen activator (u-PA), tissue type plasminogen activator (t-PA), and plasminogen activator inhibitor type 1 (PAI-1) were studied in various components of dedifferentiated chondrosarcomas of bone. METHODS: The expression of u-PA, t-PA, and PAI-1 was investigated in 10 dedifferentiated chondrosarcomas and 14 conventional chondrosarcomas. The plasminogen activator/inhibitor glycoproteins were visualized immunohistochemically on paraffin sections and the levels of expression were assessed semiquantitatively. RESULTS: In dedifferentiated chondrosarcoma, high grade dedifferentiated components displayed strong, diffuse coexpression of u-PA, t-PA, and PAI-1. For all glycoproteins studied, the immunoreactivity was significantly increased compared with the reactions in the low grade cartilaginous component of the same tumor and conventional chondrosarcoma. In the latter, u-PA, t-PA, and PAI-1 expression was found to be enhanced at invasive foci and in regions of endochondral ossification. CONCLUSIONS: The current study documents the overexpression of u-PA, t-PA, and PAI-1 in dedifferentiated chondrosarcoma and suggests involvement of the plasminogen activator system in the biology of these tumors.

Bone Neoplasms↗

PubMed1997

Loss of heterozygosity on chromosome 9q21 (p16 gene) uncommon in soft-tissue sarcomas.

Chromosome region 9p21 contains a tumor suppressor locus (p16) that may be involved in the genesis of several kinds of malignant tumors. To characterize the role of this gene in the development of soft-tissue tumors (STTs), we investigated the frequency of loss of heterozygosity (LOH) at this locus. DNA was obtained from 77 tumors and the peripheral blood of 23 of the patients with the tumors. Using one microsatellite marker distal to p16(D9S171) and one intragenic sequence-tagged site (STS) marker (c5.1), we observed LOH in only one liposarcoma and one malignant schwannoma (2.6%). Homozygous deletions of the p16 markers were not found. The osteosarcoma cell line MG-63 was used as a control for loss of the p16 gene. Because of the low LOH frequency, we hypothesize that the p16 gene is not essential for STT oncogenesis.

Chromosomes, Human, Pair 9↗

PubMed1997

Improved detection of p53 mutations in soft tissue tumors using new gel composition for automated nonradioactive analysis of single-strand conformation polymorphism.

We report a new nonradioactive method to detect sequence changes, including single-base substitutions through shifts in electrophoretic mobility using an automated fluorescence sequencer (ALFexpress, Pharmacia, Biotech) connected to external cooling equipment. Single strands were identified by incorporation of fluorescein-labeled primers during amplification and subsequent laser detection at the bottom of the gel. The amplified polymerase chain reaction (PCR) products were heat-denatured and loaded onto a polyacrylamide gel under nondenaturing conditions and strict control of constant low temperature. Peak shifts in the fluorogram indicated mutations. A novel gel composition improved the detection rate for mutations considerably. Automatic analysis of single-strand conformation polymorphism (SSCP) gels saves time and costs, and is highly reproducible. The method was applied for mutation screening in exon 7 of the p53 tumor suppressor gene in DNA of freshly frozen soft tissue tumors. The mutation spectrum and frequency in exon 7 of the p53 gene are discussed with respect to oncogenesis in soft tissue sarcomas.

Autoanalysis↗

PubMed1997

Expression of MDR1/p-glycoprotein and multidrug resistance-associated protein in childhood solid tumours.

We evaluated the expression of MDR1/p-glycoprotein in paediatric tumours using reverse transcriptase polymerase chain reaction (RT-PCR), RNA dot blot analysis, and immunohistochemistry on formalin fixed paraffin-embedded material with JSB-1 and C-219 monoclonal antibodies, and compared these three techniques. The expression of multidrug resistance-associated protein (MRP) gene was examined by RT-PCR assay. We studied MDR1/p-glycoprotein and MRP expression in 13 samples from 10 neuroblastoma patients, 11 samples from 10 nephroblastoma patients, 2 rhabdomyosarcomas, 1 adrenocortical carcinoma and 10 benign tumours or tumour-like lesions. Eleven of 13 neuroblastomas, 7 of 11 nephroblastomas, 2 rhabdomyosarcomas, 1 adrenocortical carcinoma, and 7 of 10 benign tumours or tumour-like lesions showed MDR1 PCR products. By RNA dot blot analysis, MDR1 transcripts were detectable in 11 of 34 specimens. Immunohistochemically, we detected positive reaction products for JSB-1 in 26 of 36 samples. There was a significant correlation between the immunoreactivity for JSB-1 and the expression of MDR1 mRNA expression by RT-PCR (P = 0.0001). However, the presence of p-glycoprotein immunostaining does not correlate with the MDR1 expression shown by RT-PCR in every case. As for MRP mRNA expression, 9 of 13 neuroblastomas and 10 of 11 nephroblastomas revealed PCR products.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1997

p53 gene mutations in soft-tissue sarcomas--correlations with p53 immunohistochemistry and DNA ploidy.

The significance of p53 mutations in a group of 67 soft-tissue tumors was examined using single-strand conformation polymorphism and direct sequencing analysis. Molecular findings were correlated with immunohistochemical detection of the p53 protein and DNA ploidy status. Mutations of the p53 gene were detected in 13 (19.5%) out of 67 cases of soft-tissue tumors. Only three were localized outside the conservative regions of the p53 gene. Six mutations were described for the first time in these tumors. Most of the mutations were point mutations in exons 5-8 and, in one case, a deletion at the 3'-splice site of exon 5 could be demonstrated. There was no significant correlation between the occurrence of p53 mutations and the histological grade, although a high number of mutations were defined in poorly differentiated tumors (grade 3). Molecular finding of a p53 gene mutation and immunohistochemical detection of p53 expression did not correlate, which may be due to the high percentage of nonsense mutations in our study (50%). We confirm that only DNA sequencing allows a unique identification and differentiation of mutations in the p53 gene. Other factors may be responsible for the detection of p53 protein in many cases. Histological grade correlated with aneuploidy. The frequency of mutations observed was in accordance with values quoted in the literature. Generally, p53 mutations and p53 overexpression are more likely to represent a late event in the oncogenesis of soft-tissue tumors.

Adult↗