Immunohistochemical detection of p140trkA and p75LNGFR neurotrophin receptors in neuroblastoma

A distinct gene expression signature characterizes human neuroblastoma cancer stem cells

Neuroblastoma, a malignancy of multipotent embryonic neural crest cells, is the most common extracranial solid cancer in childhood and most common cancer in infancy. Cellular phenotype has been shown to be an important determinant of the malignant potential in human neuroblastoma cells and tumors. Whereas neuroblastic (N-type) are moderately malignant and nonneuronal (S-type) cells are nonmalignant, I-type stem cells are highly tumorigenic, irrespective of N-myc amplification status. In the present study, we sought to determine which genes were overexpressed in the I-type cells which might characterize and maintain the stem cell state and/or malignancy of human neuroblastoma cancer stem cells. We used a microarray platform to compare the steady-state expression levels of mRNAs from 13 human neuroblastoma cell lines representing the three cellular phenotypes. Using qRT-PCR and Western blot analyses, we identified seven genes whose expression is consistently elevated exclusively in neuroblastoma cancer stem cells: CD133, KIT, NOTCH1, GPRC5C, PIGF2, TRKB, and LNGFR. Moreover, we show that the genes are phenotype specific, as differentiation of I-type BE(2)-C cells to either an N- or S-type morphology results in significantly reduced mRNA expression. Finally, we show that NOTCH1 plays an important role in maintaining the stem cell phenotype. The identification and characterization of these genes, elevated in highly malignant neuroblastoma stem cells, could provide the basis for developing novel therapies for treatment of this lethal childhood cancer.

The role of nerve growth factor in caspase-dependent apoptosis in human BE(2)C neuroblastoma

PURPOSE

The purpose of the study was to determine if nerve growth factor (NGF) stimulation induces apoptosis in the BE(2)C neuroblastoma cell line in vitro.

METHODS

The LPCX retroviral vector was used to achieve stable transduction of NGF complementary DNA into BE(2)C neuroblastoma cells. Wild-type and NGF-transduced cells were then incubated with varying concentrations of NGF for varying periods. A laddering assay was performed to determine the presence of DNA fragments characteristic of apoptosis. The expression of various cleaved and total caspases was determined by Western immunoblotting.

RESULTS

p75 receptor expression in the NGF-transduced cell line was equivalent to that in the wild-type cell line, but Trk A receptor expression was significantly decreased in BE(2)C-NGF cells. DNA laddering assay demonstrated that only BE(2)C-NGF cells underwent apoptosis after stimulation with exogenous NGF. BE(2)C-NGF cells have increased expression of cleaved caspase-3 when compared with wild-type cells. Cleaved caspase-3 expression is further increased with exogenous NGF stimulation in the transduced cells.

CONCLUSION

This study confirms that NGF stimulation of BE(2)C neuroblastoma cells can induce apoptosis through activation of the caspase cascade in vitro. The differential expression of the receptors Trk A and p75 between the wild-type and NGF-transduced cell lines may explain the differing effects observed.

Tumor Suppressor Proteins are Differentially Affected in Human Ependymoblastoma and Medulloblastoma Cells Exposed to Nerve Growth Factor

The aim of our study was to investigate the role of nerve growth factor (NGF) on the expression of the p73 protein in human ependymoblastoma (EP) and medulloblastoma (MB) cells. It was found that NGF exposure on MB cells blocks proliferation, as well as on EP cells and induces overexpression of p73. NGF reduces the number of cells and promotes the expression of TrkA of these neoplastic cells. Moreover, NGF plus cisplatin treatment reduces the cytotoxic effect of cisplatin. These observations indicate that NGF by interfering with mechanisms associated with cells proliferation and survival might induce the differentiation event through TrkA pathways.

Expression of the neurotrophin receptors Trk A and Trk B in adult human astrocytoma and glioblastoma

Neurotrophins and their receptors of the Trk family play a critical role in proliferation, differentiation and survival of the developing neurons. There are reports on their expression in neoplasms too, namely, the primitive neuroectodermal tumours of childhood, and in adult astrocytic gliomas. The involvement of Trk receptors in tumour pathogenesis, if any, is not known. With this end in view, the present study has examined 10 tumour biopsy samples (identified as astrocytoma, pilocytic astrocytoma and glioblastoma) and peritumoral brain tissue of adult patients, for the presence of Trk A and Trk B receptors, by immunohistochemistry. The nature of the tumour samples was also confirmed by their immunoreactivity (IR) to glial fibrillary acidic protein. In the peritumoral brain tissue, only neurons showed IR for Trk A and Trk B. On the contrary, in the tumour sections, the IR to both receptors was localized in the vast majority of glia and capillary endothelium. There was an obvious pattern of IR in these gliomas: high levels of IR were present in the low-grade (type I and II) astrocytoma; whereas in the advanced malignant forms (WHO grade IV giant cell glioblastoma and glioblastoma multiforme) the IR was very weak. These findings suggest that Trk A and Trk B are involved in tumour pathogenesis, especially in the early stage, and may respond to signals that elicit glial proliferation, and thus contribute to progression towards malignancy.