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Biomedical subjects

T Pietsch

Publications and source records attributed to T Pietsch.

At least 55 records · Page 3Linked to original sources
PubMed1999

Betulinic acid: a new cytotoxic agent against malignant brain-tumor cells.

Malignant brain tumors are the most common solid tumors in children. The overall prognosis for this group of patients is still poor, emphasizing the importance of more effective therapies. Betulinic acid (Bet A) has been described as a novel cytotoxic compound active against melanoma and neuroblastoma cells. Here we report that Bet A was active against medulloblastoma and glioblastoma cell lines. In addition, Bet A exerted cytotoxic activity against primary tumor cells cultured from patients in 4 of 4 medulloblastoma-tumor samples tested and in 20 of 24 glioblastoma-tumor samples. Since a small percentage of primary-glioblastoma-tumor cells (4/24) did not respond to Bet-A treatment, resistance to Bet A might occur. Induction of apoptosis by Bet A involved mitochondrial perturbations, since inhibition of the mitochondrial permeability transition by the mitochondrion-specific inhibitor bongkrekic acid (BA) reduced Bet-A-induced apoptosis. In addition, mitochondria undergoing Bet-A-induced permeability transition triggered DNA fragmentation in isolated nuclei. Cytochrome c was released from mitochondria of Bet-A-treated cells, and might be involved in activation of caspases. Following treatment with Bet A, caspase-8, caspase-3 and PARP were proteolytically processed. Inhibition of caspase cleavage by the broad-range caspase inhibitor zVAD.fmk strongly reduced Bet-A-induced apoptosis, indicating that apoptosis was mediated by activation of caspases. Since Bet A did not exhibit cytotoxicity against murine neuronal cells in vitro, these findings suggest that Bet A may be a promising new agent for the treatment of medulloblastoma and glioblastoma cells that clearly warrants further pre-clinical and clinical evaluation.

Antineoplastic Agents, Phytogenic↗
PubMed1999

Vasoactive intestinal peptide (VIP) and VIP receptors: gene expression and growth modulation in medulloblastoma and other central primitive neuroectodermal tumors of childhood.

Vasoactive intestinal peptide (VIP) is a neuromodulator and growth regulator in the developing nervous system. We analyzed 10 primitive neuroectodermal tumor (PNET) cell lines, 29 central PNET (cPNET) and 17 tumors of the Ewing's sarcoma/peripheral PNET family (ESFT) using reverse transcriptase-polymerase chain reaction (RT-PCR) and Southern hybridization. Each of the 10 cell lines and 86.2% of cPNET expressed mRNA for VIP receptor 1 (VIPR1) compared to 52.9% of ESFT. VIPR2 was expressed in 75.8% of cPNET, in 28.6% of ESFT and in all 10 cell lines. cPNET demonstrated high-affinity binding of 125I-VIP on quantitative autoradiography and in competitive binding assays. VIP inhibited tumor cell proliferation in a dose-dependent manner in 5 of 7 PNET cell lines. We conclude that VIPR1 and VIPR2 are highly expressed in cPNET and demonstrate that VIP is a growth modulator in these tumors.

Autoradiography↗
PubMed1999

Expression of granulocyte colony-stimulating factor in recurrent glial tumors is inversely correlated with tumor progression.

We have previously reported that in vivo-expression of granulocyte colony-stimulating factor (G-CSF) is a characteristic feature of reactive and neoplastic astrocytes. The aim of the present study was to analyze the expression of G-CSF protein in primary and recurrent astroglial, oligodendroglial and mixed glial-differentiated tumors. G-CSF expression was present in all GFAP-positive tumors excepting glioblastomas. G-CSF expression was significantly reduced in recurrent tumors more dedifferentiated than their primary counterparts. G-CSF expression was absent in all GFAP-negative tumors such as oligodendrogliomas. Our results demonstrate that G-CSF is a highly sensitive differentiation marker of neoplastic astrocytes, which is lost during tumor progression.

Adolescent↗
PubMed1999

Childhood hepatoblastomas frequently carry a mutated degradation targeting box of the beta-catenin gene.

Hepatoblastomas (HBs) are embryonal tumors affecting young children and representing the most frequent malignant liver tumors in childhood. The molecular pathogenesis of HB is poorly understood. Although most cases are sporadic, the incidence is highly elevated in patients with familial adenomatous polyposis coli. These patients carry germline mutations of the APC tumor suppressor gene. APC controls the degradation of the oncogene product beta-catenin after its NH2-terminal phosphorylation on serine/threonine residues. APC, as well as beta-catenin, has been found to be a central effector of the growth promoting wingless signaling pathway in development. To find out if this pathway is involved in the pathogenesis of sporadic HBs, we examined 52 biopsies and three cell lines from sporadic HBs for mutations in the APC and beta-catenin genes. Using single-strand conformational polymorphism analysis, deletion screening by PCR, and direct sequencing, we found a high frequency of beta-catenin mutations in sporadic HBs (48%). The mutations affected exon 3 encoding the degradation targeting box of beta-catenin leading to accumulation of intracytoplasmic and nuclear beta-catenin protein. The high frequency of activating mutations in the beta-catenin gene indicates an important role in the pathogenesis of HB.

Adolescent↗
PubMed1999

The CD34 epitope is expressed in neoplastic and malformative lesions associated with chronic, focal epilepsies.

The etiology and pathogenesis of complex focal lesions associated with chronic, intractable epilepsy are largely unknown. Some data indicate that malformative changes of the central nervous system may precede the development of gangliogliomas and other epilepsy-associated neoplasms. In the present immunhistochemical study, we have examined epilepsy-associated lesions for CD34, a stem cell marker transiently expressed during early neurulation. Surprisingly, most tissue samples from patients with chronic epilepsy (n = 262) revealed neural cells immunoreactive for CD34. Prominent immunoreactivity was detected in gangliogliomas (74%), low-grade astrocytomas (62%) and oligodendrogliomas (59%). Only 52% of non-neoplastic, malformative pathologies, such as glio-neuronal hamartias or hamartomas showed solitary or small clusters of CD34-immunoreactive cells. None of the adult control tissues (n = 22), none of the specimens obtained from the developing human brain (n = 44) and none of those tumor samples from patients without epilepsy (n = 63) contained CD34-immunoreactive neural cells. However, a malignant teratoma with microscopic features of early neural differentiation displayed a focal CD34-immunoreactive staining pattern. The majority of CD34-immunoreactive cells co-localized with S-100 protein and a small subpopulation was also immunoreactive for neuronal antigens. CD34 may, thus, represent a valuable marker for the diagnostic evaluation of neoplastic and/or malformative pathological changes in epilepsy patients. The CD34 immunoreactivity of these lesions indicates an origin from dysplastic or atypically differentiated neural precursors. Further studies may elucidate the functional significance of CD34 expression during the pathogenesis of epilepsy-related focal lesions as well as during neurogenesis.

Adolescent↗
PubMed1999

Stability of RNA transcripts in post-mortem psychiatric brains.

RNA isolated from frozen human post-mortem brain tissue was used for analysis of five gene products with a recently developed sensitive and competitive RT-PCR technique. Samples varying in post-mortem intervals up to four days from controls, schizophrenics and alcoholics were analyzed. Evaluation of three housekeeping genes, as well as Trk B and Trk C demonstrated that the levels of mRNA transcripts were stable in brain samples at all time periods (one to four days) examined. This observation demonstrates that this RT-PCR protocol is a sensitive and reliable method to study relative amounts of mRNAs. The overall stability of housekeeping transcripts implicates the value of post-mortem brain samples for differential gene expression studies.

Actins↗
PubMed1999

Molecular genetic analysis of ependymal tumors. NF2 mutations and chromosome 22q loss occur preferentially in intramedullary spinal ependymomas.

Ependymal tumors are heterogeneous with regard to morphology, localization, age at first clinical manifestation, and prognosis. Several molecular alterations have been reported in these tumors, including allelic losses on chromosomes 10, 17, and 22 and mutations in the NF2 gene. However, in contrast to astrocytic gliomas, no consistent molecular alterations have been associated with distinct types of ependymal tumors. To evaluate whether morphological subsets of ependymomas are characterized by specific genetic lesions, we analyzed a series of 62 ependymal tumors, including myxopapillary ependymomas, subependymomas, ependymomas, and anaplastic ependymomas, for allelic losses on chromosome arms 10q and 22q and mutations in the PTEN and NF2 genes. Allelic losses on 10q and 22q were detected in 5 of 56 and 12 of 54 tumors, respectively. Six ependymomas carried somatic NF2 mutations, whereas no mutations were detected in the PTEN gene. All six of the NF2 mutations occurred in ependymomas of WHO grade II and were exclusively observed in tumors with a spinal localization (P = 0.0063). These findings suggest that a considerable fraction of spinal ependymomas are associated with molecular events involving chromosome 22 and that mutations in the NF2 gene may be of primary importance for their genesis. Furthermore, our data suggest that the more favorable clinical course of spinal ependymomas may relate to a distinct pattern of genetic alterations different from that of intracerebral ependymomas.

Adolescent↗
PubMed1999

Expression of different extracellular matrix components in human brain tumor and melanoma cells in respect to variant culture conditions.

Local tumor invasion into the surrounding brain tissue is a major characteristic of malignant gliomas. These processes critically depend on the interaction of tumor cells with various extracellular matrix (ECM) components. Because only little quantitative information about expression of ECM gene products in general and expression in response to alterations of the surrounding environment is available, the present study was designed. Four human glioblastoma cell lines (U373MG, U138MG, U251MG, GaMG) as well as four human melanoma cell lines (MV3, BLM, 530, IF6) were tested with semiquantitative RT-PCR for their ability to express mRNA of different human ECM components (fibronectin, decorin, tenascin, collagen I, collagen IV, versican). In addition, two human medulloblastoma (MHH-Med 1, MHH-Med 4) and two fibrosarcoma (HT1080, U2OS) cell lines were analyzed. Cells which were grown in DMEM medium containing 10% FCS expressed most of the analyzed protein components. When the same medium, but depleted of ECM proteins by filtrating through a membrane with cut-off at > 100 kD was used, basal mRNA expression of the ECM proteins was changed in most of the examined cell lines. Using serum free conditions, most of the cell lines again showed a variation in the expression pattern of mRNA encoding for the different ECM proteins compared to the other medium conditions. Comparing different cell lines from one tumor entity or different tumor groups, ECM expression was heterogeneous with regard to the different tumor entities as well as within the entities themselves. Migration assays revealed heterogeneous responses between the different cell lines, ECM components and culture conditions, making it difficult to correlate ECM expression patterns and migratory behavior. Our results revealed that all examined cell lines are able to produce ECM proteins in vitro. This suggests that tumor cells can modulate their microenvironment in vitro which has to be taken into consideration for studies related to migration and invasion.

Brain Neoplasms↗
PubMed1999

Vascular endothelial growth factor (VEGF) in astrocytic gliomas--a prognostic factor?

Survival in astrocytic gliomas is closely related to WHO tumor grade. Within one tumor grade, especially in grade II and III tumors, the clinical course is variable and can hardly be predicted by histological criteria. Neovascularization is a neuropathological hallmark in high grade gliomas and angiogenic factors may play an important role in malignant tumor progression. Therefore, 162 primary astrocytic gliomas (57 astrocytomas WHO grade II, 27 astrocytomas WHO grade III and 78 glioblastomas WHO grade IV) were investigated immunohistochemically for expression of vascular endothelial growth factor (VEGF), which is considered to represent the main angiogenic factor in astrocytic gliomas. Clinical data known to influence prognosis were documented. VEGF expression was found in 21 of 57 astrocytomas WHO grade II (36.8%), in 18 of 27 astrocytomas WHO grade III (66.7%) and in 50 of 78 glioblastomas (64.1%). A strong correlation between VEGF expression and survival was found within the whole study group, however, within one tumor grade no such correlation was obvious. In a multifactorial analysis VEGF expression was not found to be an independent prognostic factor in astrocytic gliomas.

Adult↗
PubMed1999

Chromosomal imbalances and DNA amplifications in SV40 large T antigen-induced primitive neuroectodermal tumor cell lines of the rat.

Comparative genomic in situ hybridization analysis of four cell lines derived from SV40 large T antigen-induced primitive neuroectodermal tumors of the rat revealed non-recurrent chromosomal copy number changes and DNA amplifications at chromosomal bands 2q34, 4q43qter and 15q12qter in cell lines TZ102, TZ103 and TZ107, respectively. Semi-quantitative PCR and western blot analysis demonstrated amplification and over-expression of the rat N-ras proto-oncogene in TZ102. Furthermore, all cell lines displayed aneuploid cell populations and variable chromosome numbers as assessed by flow cytometry and cytogenetics. These findings suggest that DNA amplification as well as genomic instability may contribute to the pathogenesis of SV40 large T antigen-induced primitive neuroectodermal tumors of the rat.

Aneuploidy↗
PubMed1999

Isolation and characterization of human patched 2 (PTCH2), a putative tumour suppressor gene inbasal cell carcinoma and medulloblastoma on chromosome 1p32.

Mutations of the human Patched gene ( PTCH ) have been identified in individuals with the nevoid basal cell carcinoma syndrome (NBCCS) as well as in sporadic basal cell carcinomas and medulloblastomas. We have isolated a homologue of this tumour suppressor gene and localized it to the short arm of chromosome 1 (1p32.1-32.3). Patched 2 ( PTCH2 ) comprises 22 coding exons and spans approximately 15 kb of genomic DNA. The gene encodes a 1203 amino acid putative transmembrane protein which is highly homologous to the PTCH product. We have characterized the genomic structure of PTCH2 and have used single-stranded conformational polymorphism analysis to search for mutations in PTCH2 in NBCCS patients, basal cell carcinomas and in medulloblastomas. To date, we have identified one truncating mutation in a medulloblastoma and a change in a splice donor site in a basal cell carcinoma, suggesting that the gene plays a role in the development of some tumours.

Amino Acid Sequence↗
PubMed1999

High expression of somatostatin receptor subtype 2 (sst2) in medulloblastoma: implications for diagnosis and therapy.

Medulloblastoma is a pediatric malignancy, which arises in cerebellum. The neuropeptide somatostatin (SS-14) is a neuromodulator and growth regulator in the developing cerebellum. SS-14 has previously been demonstrated in medulloblastomas with immunohistochemical techniques, but somatostatin receptor (sst) expression is less well understood. We analyzed somatostatin and sst subtype expression (sst1-5) in central primitive neuroectodermal tumors (cPNET), including 23 medulloblastomas, 6 supratentorial PNET, and 10 cPNET cell lines. The expression of SS-14 and sst genes in cPNET was compared with expression of these genes in 17 tumors of the Ewing's sarcoma family of tumors using reverse transcriptase-PCR, Southern hybridization, quantitative in vitro receptor autoradiography, and competitive membrane binding assays. The sst1 subtype was expressed in similar frequency in cPNET (83%) and Ewing's sarcoma family of tumors (71%). Nine of the 10 cell lines and 76% of the cPNET expressed mRNA for sst2 compared with 35% of the Ewing's sarcoma family of tumors. High-affinity binding of SS-14 was demonstrated in cPNET by quantitative autoradiography as well as by competitive binding assays. The cPNET cell line D283 Med bound SS-14 and octreotide with high affinity; SS-14 inhibited proliferation of D283 Med cells as measured by a decrease in [3H]thymidine uptake. We conclude that both sst1 and sst2 are highly expressed in cPNET and suggest that somatostatin may regulate proliferation and differentiation in these developmental tumors.

Adolescent↗
PubMed1998

CD95 ligand-induced apoptosis of human medulloblastoma cells.

CD95 ligand (CD95L) is a cytotoxic cytokine that induces apoptosis in susceptible target cells. Medulloblastoma is the most common non-glial intrinsic malignancy of the brain. In this study, we have studied CD95-mediated apoptosis of human medulloblastoma cell lines. We found that DAOY, MED-1 and D-283 cells are susceptible to CD95L-induced apoptosis when RNA and protein synthesis are inhibited. Preexposure of D-283, but not DAOY or MED-1 cells, to interferon-gamma or tumor necrosis factor-alpha enhances CD95 expression and primes these cells for CD95-mediated apoptosis. Inhibitors of interleukin 1-converting enzyme (ICE)-like protease (caspase) activity block CD95L-induced cytotoxicity, suggesting that caspases mediate the death signal induced by CD95L in human medulloblastoma cells. Interestingly, medulloblastoma cells belong to an increasing number of tumor cell types that coexpress CD95 and CD95L. We conclude that CD95 may be a promising target of immunochemotherapy for human medulloblastoma.

Animals↗
PubMed1998

A highly conserved processed PTEN pseudogene is located on chromosome band 9p21.

PTEN/MMAC1/TEP1, encoding a dual-specificity phosphatase, is a tumor suppressor gene which has recently been cloned and mapped to chromosome 10q23.3. We have shown that germline mutations of PTEN are present in individuals with two hamartoma syndromes: Cowden Syndrome, associated with a predisposition to breast and thyroid cancers, and Bannayan-Zonana syndrome. Somatic mutations of PTEN have been reported in a variety of human cancer cell lines, suggesting a potential role for this gene in the pathogenesis of human malignancies. We report the identification of a highly conserved PTEN processed pseudogene, psiPTEN, which shares over 98% homology with the coding region of functional PTEN, and its localisation to chromosome 9p21. The high sequence homology of psiPTEN with the PTEN transcript may potentially lead to misinterpretation when performing mutation analyses based on cDNA templates. Caution should be exerted when using such screening approaches.

Amino Acid Sequence↗
PubMed1998

No evidence for the H133Y mutation in SONIC HEDGEHOG in a collection of common tumour types.

The human homologue of the Drosophila segment polarity gene patched is mutated in the cancer predisposition syndrome naevoid basal cell carcinoma syndrome (NBCCS), as well as in several types of tumour associated with the disorder. It was recently reported that a single recurrent mutation in the SONIC HEDGEHOG gene, which encodes the PATCHED ligand, was found in one of 43 basal cell carcinomas (BCCs), one of 14 medulloblastomas and one of six breast carcinomas analysed (Oro et al., 1997). We have searched extensively for this same mutation in a large collection of BCCs, medulloblastomas and carcinomas of the breast, ovary and colorectum and have failed to detect the mutation in any sample analysed.

Adolescent↗
PubMed1998

Expression of the c-Kit receptor and its ligand SCF in non-small-cell lung carcinomas.

Increasing experimental evidence indicates that stem-cell factor (SCF) and its cognate receptor c-Kit may participate in the growth control of various solid human malignancies. In the present study, we have extended this analysis to non-small-cell lung carcinomas (NSCLC). The results of an immunohistochemical analysis demonstrated that c-Kit/SCF are expressed by 30%/58% of adenocarcinomas, 15%/37% of squamous-cell carcinomas and by 40%/30% of undifferentiated carcinomas respectively. In 15% of primary and 18% of metastatic tumors, co-expression of the receptor and its ligand was documented. Western-blot assays of tumor extracts demonstrated that both molecules exhibit features of the normal receptor and ligand. Since biologically active SCF is physiologically present in the bloodstream, our data indicate that SCF is available to c-kit-expressing NSCLC cells via autocrine, paracrine or endocrine mechanisms. Thus activation of c-Kit in these tumors may contribute critically to their progression.

Carcinoma, Non-Small-Cell Lung↗