Isolation and expression analysis of a novel human homologue of the Drosophila glial cells missing (gcm) gene

A novel human homologue (GCMB) of the Drosophila glial cells missing gene (dGCM) was isolated using RACE. GCMB contained a gcm motif sequence and a nuclear targeting sequence similar to that of dGCM and mouse GCMb. Homology searches indicated that GCMB was located within chromosome 6p24.2. Transcripts of GCMB were detected by means of RT-PCR in fetal brain, normal adult kidney, 3/3 medulloblastomas, 1/3 gliomas and 4/8 non-neuroepithelial tumor cell lines. Our data suggest that humans have two homologues of gcm like mice and that human gcm genes form a novel family which may function not only during fetal development but also in the postnatal or pathological stage.

Rapid growth of cutaneous metastases after surgical resection of thrombospondin-secreting small blue round cell tumor of childhood

In animal models, the importance of tumor-derived antiangiogenic factors in controlling metastases has been demonstrated by the growth acceleration of distant metastases after surgical excision of a primary tumor mass. We report the case of an infant who developed rapidly growing cutaneous metastases after surgical resection of a neoplasm of an upper extremity. The tumor was undifferentiated, with some morphological features of primitive neuroectodermal tumor. To test the possibility that the primary tumor was secreting an angiogenic inhibitor, cells from the primary tumor were grown in culture, and the culture medium was tested with an in vitro endothelial cell migration assay and Western blot. The cultured cells secreted sufficiently high levels of an angiogenic inhibitor to overcome the inducing ability of vascular endothelial growth factor and basic fibroblast growth factor. One of the secreted proteins was thrombospondin-1, a potent antiangiogenic glycoprotein. The rapid dissemination of distant metastases after resection of the primary tumor in this case suggests that tumor-derived angiogenic inhibitors are important in maintaining the local net balance of angiogenic mediators controlling the growth of micrometastasis.

Platelet-derived growth factor (PDGF) in primary brain tumours of neuroglial origin

It has become clear that disruptions in the genome of somatic cells play a causative role in tumour development. We know that the ultimate formation of a malignancy is the result of a multistep process in which the functional loss and/or the altered or increased expression of genes play important roles. One such family of genes are the oncogenes, encoding protein products with mainly growth stimulating effects. Platelet-derived growth factor (PDGF) belongs to the family of oncogenes. It is likely that PDGF plays an essential role in the development of at least a subgroup of malignant astrocytic tumours that do not contain amplification of the EGF-receptor. The expression of PDGF alpha-receptors is related to tumour progression in these tumours, and some of the most malignant tumours were shown to contain amplification of the PDGF alpha-receptor. It is also clear now from several experimental studies that PDGF can drive the transformed phenotype, and that PDGF antagonists, by blocking the PDGF autocrine pathway revert the transformed phenotype of certain tumour cells. Because of the findings that receptor protein tyrosine kinases such as the EGF- and the PDGF-receptor play a crucial role in the development of gliomas, it is possible that inhibitors of the phosphorylation of the protein tyrosine kinases will be future candidates for glioma therapy. They might be able to at least delay the development of a fully malignant glioma. The role of PDGF in other tumours of neuroglial origin in the central nervous system has not been studied as extensively as its role in gliomas. Recent data suggest that also for the primitive neuroectodermal tumours overexpression of the PDGF alpha-receptor is related to malignancy of the tumours. For other tumours, such as neuroblastomas, PDGF exerts a differentiating rather than a mitogenic function and is an important survival factor. Further studies are needed to elucidate the role of PDGF in these non-glial primary brain tumours. Moreover, for a complete understanding of the role of PDGF in malignancies of the CNS, it is important to explore its function in the development of the normal CNS further.

Immunohistochemistry of medulloepithelioma and neural tube

Immunohistochemistry profiles of medulloepithelioma (from two 2 1/2-year-old girls who had cerebral medulloepitheliomas and a 35-week postconceptional female infant with congenital posterior fossa tumor) and neural tube are compared. Microscopically, the tumors contained a medulloepitheliomatous component, manifested as tubular epithelial structures lined by pseudostratified columnar epithelium delineated by well-defined basement membranes. In all cases, glial and neuronal differentiation were noted to differing extents. The medulloepitheliomatous components did not exhibit glial fibrillary acidic protein, neuron-specific enolase, or S-100 protein reactivity. Neurofilament, cytokeratin, and epithelial membrane antigen were focally present in one case. Extensive nestin immunopositivity was confined to the basal cell layer of the epithelium, leaving the luminal surface unreactive or slightly reactive. These cells also displayed a reactivity to vimentin and to microtubule-associated protein type 5 similar to that of cells of the primitive neural tube. The similarity between the immunohistochemical profile of medulloepithelioma and that of neural tube epithelium suggests a possible reexpression of that component of the genome responsible for neural tube growth and differentiation in medulloepithelioma.

CD24, a glycosylphosphatidylinositol-anchored molecules is transiently expressed during the development of human central nervous system and is a marker of human neural cell lineage tumors

CD24 is a glycoprotein with an unusual structure consisting of a small protein core extensively glycosylated and linked to the outer surface of the plasma membrane by a glycosylphosphatidylinositol (GPI) lipid anchor. Its murine homolog mCD24 is transiently expressed during the development and differentiation of the hematopoietic and neural cell lineages. We have searched for the expression of CD24 in the developing and in the mature human brain as well as in a wide range of neuroectodermal tumors. Neuroblastomas, a subgroup of tumors able to maturate from undifferentiated features towards mature ganglioneuromas, were more extensively studied. Immunohistochemical studies demonstrated that CD24 is transiently expressed by neurons during human brain development. In neuroectodermal tumors, CD24 is a marker of neuronal tumors. Furthermore, in neuroblastomas, CD24 expression decreases as tumors differentiate. In non-neuronal neuroectodermal tumors, CD24 expression is mostly absent. When present, it correlates with the emergence of anaplastic histological features. Reverse transcriptase -polymerase chain reaction (RT-PCR) demonstrated the presence of an unique transcript identical in both hematopoietic, developing and tumoral nervous tissue. RT-PCR and in situ hydridization techniques showed that CD24 expression is transcriptionally regulated. Interestingly, Western blot analysis demonstrated differential CD24 isoforms according to the tissue (hematopoietic versus nervous), the differentiation status, and the origin of neuroblastomas likely reflecting variations in the extent of glycosylation. This indicates an additional level of regulation of CD24 involving post-translational modifications.