Genetic profile of gliosarcomas

Evaluation and optimization of DNA delivery into gliosarcoma 9L cells by a cholesterol-based cationic liposome

This paper reports results concerning the transfection of gliosarcoma cells 9L using an original cholesterol-based cationic liposome as carrier. This cationic liposome was prepared from triethyl aminopropane carbamoyl cholesterol (TEAPC-Chol) and a helper lipid, dioleoyl phosphatidyl ethanolamine (DOPE). The used concentration of liposome was not cytotoxic as revealed by the MTT test. TEAPC-Chol/DOPE liposomes allowed the plasmids encoding reporter genes to enter the nucleus as observed both by electron microscopy and functionality tests using fluorescence detection of green fluorescent protein (GFP) and luminometric measurements of luciferase activity. By changing the cationic lipid/DNA molar charge ratio, optimal conditions were determined. Further, improvement of the transfection level has been obtained by either precondensing plasmid DNA with poly-L-lysine or by adding polyethylene glycol (PEG) in the transfection medium. The optimal conditions determined are different depending on whether the transfection is made with cells in culture or with tumors induced by subcutaneous (s.c.) injection of cells in Nude mice. For in vivo assays, a simple method to overcome the interference of haemoglobin with the chemiluminescence intensity of luciferase has been used. These results would be useful for gaining knowledge about the potential for the cationic liposome TEAPC-Chol/DOPE to transfect brain tumors efficiently.

Comprehensive analysis of genomic alterations in gliosarcoma and its two tissue components

Gliosarcoma is a variant of glioblastoma multiforme characterized by two components displaying gliomatous or sarcomatous differentiation. We investigated 38 gliosarcomas for aberrations of tumor-suppressor genes and proto-oncogenes that are commonly altered in glioblastomas. Amplification of CDK4, MDM2, EGFR, and PDGFRA were found in 11% (4/35), 8% (3/38), 8% (3/38), and 3% (1/35) of the tumors, respectively. Nine of 38 gliosarcomas (24%) carried TP53 mutations. PTEN mutations were identified in 45% (9/20) of the investigated tumors. Twenty gliosarcomas were analyzed by comparative genomic hybridization (CGH). Chromosomal imbalances commonly detected were gains on chromosomes 7 (15/20; 75%), X (4/20; 20%), 9q, and 20q (3/20, 15% each); and losses on chromosomes 10 and 9p (7/20, 35% each), and 13q (3/20, 15%). Five different high-level amplifications were mapped to 4q12-q21 (1 case), 6p21 (1 case), 7p12 (2 cases), proximal 12q (4 cases), and 14q32 (1 case) by CGH. Southern blot and/or differential PCR analyses identified amplification of PDGFRA (4q12), CCND3 (6p21), EGFR (7p12), CDK4 (12q14) and/or MDM2 (12q14.3-q15), and AKT1 (14q32.3) in the respective tumors. Separate analysis of the gliomatous and sarcomatous components of eight gliosarcomas by CGH after microdissection and universal DNA amplification revealed that both components shared 57% of the chromosomal imbalances detected. Taken together, our data indicate that the genomic changes in gliosarcomas closely resemble those found in glioblastomas. However, the number of chromosomes involved in imbalances in gliosarcomas was significantly lower than that in glioblastomas, indicating a higher genomic stability in gliosarcomas. In addition, we provide further support for the hypothesis that the gliomatous and sarcomatous components are derived from a single precursor cell clone, which progressed into subclones with distinct morphological features during tumor evolution. According to our data, gain/amplification of genes on proximal 12q may facilitate the development of a sarcomatous phenotype.

Sequential extension of proliferative lifespan in human fibroblasts induced by over-expression of CDK4 or 6 and loss of p53 function

Replicative senescence is thought to be a significant barrier to human tumorigenesis, which in human fibroblasts, and many other cell types, can be overcome experimentally by combined loss of function of p53 and Rb 'pathways'. To avoid the confounding pleiotropic effects of HPVE7 frequently used in such studies, here we have employed retroviral vectors over-expressing CDK4 or CDK6 as a more representative model of naturally-occurring mutations targeting the Rb pathway. We show that these can extend fibroblast lifespan by approximately 10 population doublings, ending in a viable senescence-like state which contrasts with the apoptotic end-stage seen with E7. Compared with 'normal' senescence, this growth arrest was, in most cases, not accompanied by any further increase in p21(Waf1) levels but with up to a 19-fold increase in p16(Ink4a). Surprisingly however, this could not explain arrest, since expression of mutant CDK4 and/or CDK6, incapable of binding p16(Ink4a), did not confer any greater lifespan extension than the wild-type CDKs. Subsequent abrogation of p53 function by a second vector, encoding HPVE6, downregulated p21(Waf1) and conferred a second lifespan extension, ending in a crisis-like state, consistent with full escape from senescence. These data: (i) point to a back-up 'senescence' mechanism distinct from induction of p21(Waf1) or p16(Ink4a); and (ii) provide an in vitro model of clonal evolution through successive dysfunction of Rb and p53 pathways in a relevant human cell context.

Gli and hedgehog in cancer: tumours, embryos and stem cells

Do tumours arise from stem cells, or are they derived from more differentiated cells that, for some reason, begin to recapitulate developmental programmes? Inappropriate activation of the Sonic hedgehog-Gli signalling pathway occurs in several types of tumour, including those of the brain and the skin. Studies in these and other systems suggest that inappropriate function of the Gli transcription factors in stem or precursor cells might lead to the onset of a tumorigenic programme and that these factors are prime targets for anticancer therapies.

PTEN mutation is rare in chondrosarcoma

Chondrosarcoma is the second most common primary malignant neoplasm of bone in adults, but the major genetic events involved in the progression of this often-fatal cancer remain to be elucidated. Loss of heterozygosity of chromosome 10q has been reported in 67% of chondrosarcoma. The tumor suppressor gene PTEN is located on chromosome 10q, specifically 10q23, raising the possibility that the loss of PTEN function is responsible for some chondrosarcomas. The authors examined 40 chondrosarcoma tumors and tumor-derived cell lines for alterations in PTEN. Only one mutation resulting in a truncated PTEN protein was detected, which was in a metastasized extraskeletal myxoid chondrosarcoma. Thus, mutated PTEN is an uncommon event in the development of chondrosarcoma. The high frequency of loss of heterozygosity on 10q suggests the presence of additional tumor suppressor genes at these loci.

Genetic and biologic progression in astrocytomas and their relation to angiogenic dysregulation

Infiltrative astrocytic neoplasms are the most common malignancies of the central nervous system. They remain clinically problematic because of their involvement of brain structures critical to proper cognitive, behavioral, and motor function; their widely invasive properties, which make them difficult to resect totally; and their nearly inevitable biologic progression in spite of adjuvant therapy. Glioblastoma multiforme (GBM, World Health Organization grade IV), the most malignant form of infiltrating astrocytoma, can present as a high-grade lesion from the outset (so-called de novo GBM) or can evolve from a lower grade precursor lesion (secondary GBM). Molecular genetic investigations suggest that GBM is best regarded as a clinicopathologic entity composed of multiple molecular genetic subsets. Molecular alterations associated with progression to GBM and that define genetic subsets include epidermal growth factor receptor amplifications, p53 mutations, retinoblastoma pathway alterations [most commonly, p16(CDKN2A) losses], and chromosome 10 alterations, including PTEN mutations. Despite the wide range of genetic events that ultimately lead to GBM, the vascular changes that evolve are remarkably similar. Microvascular hyperplasia is spatially and temporally associated with pseudopalisading necrosis in GBM and is believed to be driven by hypoxia-induced expression of proangiogenic cytokines such vascular endothelial growth factor. In addition, genetic alterations in GBM are thought to contribute directly or indirectly to angiogenic dysregulation. Both p53 mutations and genetic losses on chromosome 10 may tip the balance toward an angiogenic phenotype through upregulation of proangiogenic factors and/or downregulation of angiogenesis inhibitors. Understanding genetic events and their relation to angiogenic regulation in astrocytic neoplasms may eventually lead to therapies that are specifically directed at molecularly defined subsets of these diseases.

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.

Phase I clinical evaluation of a neutralizing monoclonal antibody against epidermal growth factor receptor in advanced brain tumor patients: preliminary study

High levels of growth factors and their receptors have been demonstrated in human tumors. Gliomas and meningiomas are characterized by overexpression of epidermal growth factor receptor (EGF-R). Ior egf/r3, is a neutralizing murine monoclonal antibody (MAb) against EGF-R, and was generated at the Cuban Institute of Oncology. The antibody recognizes EGF-R with high affinity, inhibiting tyrosine kinase activation. A clinical trial was conducted in brain tumor patients to evaluate toxicity, immunogenicity, and clinical benefit of escalating doses of the antibody. Nine patients with histologically confirmed gliomas or meningiomas, who had active or recurrent disease after receiving conventional treatment, received four intravenous doses of ior egf/r3. Total dosages ranged from 160 to 480 mg. As inclusion criteria, radioimmunoscintigraphy with the same MAb labeled with 99mTechnetium (99mTc) was performed. Immune response against the murine antibody was also evaluated. After four doses of ior egf/r3 MAb, no significant toxicity was found, except in one patient who developed a grade 4 allergic adverse event. This reaction was probably related with previous sensitization to the same MAb and the development of human anti-mouse antibodies (HAMA) response. Despite no major objective antitumor responses, eight patients had stable disease on the 6-month evaluation, and two patients remain alive after four years of MAb therapy.

Loss of heterozygosity on chromosome 10 is more extensive in primary (de novo) than in secondary glioblastomas

Glioblastomas develop de novo (primary glioblastomas) or through progression from low-grade or anaplastic astrocytoma (secondary glioblastomas). There is increasing evidence that these glioblastoma subtypes develop through different genetic pathways. Primary glioblastomas are characterized by EGFR and MDM2 amplification/overexpression, PTEN mutations, and p16 deletions, whereas secondary glioblastomas frequently contain p53 mutations. Loss of heterozygosity (LOH) on chromosome 10 (LOH#10) is the most frequent genetic alteration in glioblastomas; the involvement of tumor suppressor genes, other than PTEN, has been suggested. We carried out deletion mappings on chromosome 10, using PCR-based microsatellite analysis. LOH#10 was detected at similar frequencies in primary (8/17; 47%) and secondary glioblastomas (7/13; 54%). The majority (88%) of primary glioblastomas with LOH#10 showed LOH at all informative markers, suggesting loss of the entire chromosome 10. In contrast, secondary glioblastomas with LOH#10 showed partial or complete loss of chromosome 10q but no loss of 10p. These results are in accordance with the view that LOH on 10q is a major factor in the evolution of glioblastoma multiform as the common phenotypic end point of both genetic pathways, whereas LOH on 10p is largely restricted to the primary (de novo) glioblastoma.